high frequency screen printers

custom t shirt printing, high-quality screen printing - threadbird

We're a custom t-shirt printing & apparel company, specializing in high-quality discharge , waterbase and plastisol screen printing for brands, clothing companies, businesses and more. Take a look around our website to get a feel for what we're all about!

Our customers come in all shapes and sizes, but regardless of where you're headed or where you've been, Threadbird can help you achieve your goals through high-quality custom t-shirt printing, screen printing, embroidery and other custom merchandise.

sweet screens are made of this | flexotech

The most technical part of the entire flexo process is the production of screens, pulling knowhow from the worlds of physics, chemistry and engineering, to create structures invisible to the naked eye. By Michal Lodej

With the evolution of the flexo printing process, platemaking has moved from film-to-plate to direct-to-plate, but this change brought an unintended consequence; dots became roundtopped rather than flat-topped due to the loss of the oxygen inhibiting film which is inherent only with film-toplate. Eventually plate technology providers solved the problems of oxygen exposure by effectively putting a film layer over the plate. Plate makers could again generate polymer plates with flat-top dots, and the screening of smaller halftone dots too became possible, allowing screening to become more sophisticated.

Each screen uses a slightly different dot size, shape, and spacing in each colour that ensures that they do not interfere with each other. The dot algorithm further interleaves the dots in one colour with the dots in another producing what is called a stochastic rosette. This eliminates screen angles and angle clashes, as well as moir between the dots in the different colours.

Bellissima is a set of Digitally Modulated Screens (DMS) developed by Hamillroad explicitly for flexography. These screens are imaged at 4000dpi and provide a high level of image reproduction (greater than 300lpi equivalent). There are two primary DMS screens: a Standard screen with 300400lpi resolution, and an eXtended screen of 350450lpi resolution. The eXtended screen uses slightly smaller dots that are a little closer together, thereby enhancing fidelity, while the Standard screen has dots that are more robust.

The Standard screen uses dots designed for wide web printing and offers flexible packaging printers the ability to print at resolutions of 300400lpi. Some printers may be concerned that the dots employed to produce such high fidelity may not be durable enough for use with longrun jobs. The root cause of durability problems is unstable dots on a plate, and not small dots per se. Unstable dots can break off the plate, or they fatten up on press, causing dirty or muddy looking print. Bellissima DMS plates are capable of extremely long runs by creating dots that are stable and durable.

Bellissimas eXtended screen is helping flexo trade shops and converters win business from offset. A label printer, based in Germany, was producing offset labels for a large European pharmacy brand. The printer was struggling to cope with increasing costs, in part due to 800 metres of offset make-ready waste each time he went on press with a particular job. The printer discussed his concerns with its trade shop, who suggested using flexo with Bellissima DMS screen plates instead. The printer agreed, put the job on press, ran the job, and got to colour much more quickly, reducing his makeready waste down to 150 metres. The brand owner was more than happy and signed off on the labels. The label printer is now converting more of his offset work over to flexo with Bellissima, which is now his screening of choice.

One particular wide-web flexibles printer has reported using a single set of Bellissima plates, imaged on MacDermid ITP60 material, for a job that ran at 300m/min for 1.6 million linear metres. The print results from the first pull to the last remained stable, consistent, and repeatable.

Using a combination of the Standard and eXtended screens, Bellissima is effective for fixed palette/extended gamut printing. Taking the CMY from the eXtended screen for CMY, and the CMY from the Standard screen for OGV and the K from either screen, printers can run seven-colour prints on narrow and wide-web easily.

Bellissimas stochastic rosette stops interference between the dots in any of the colours and, therefore, no moir. It also delivers flat tints that are as smooth and sharp tinted, and reverse tinted text.

The technology has helped make one of FGSs clients fixed palette vision a reality. Flexographic Solutions S.L. (FGS) is a flexographic trade shop based in Barcelona, Spain. Specialising in the production and manufacture of photopolymers, ITR sleeves, and engraved elastomer plates, FGS has offered its pre-press services to printers of the flexible packaging market for more than 20 years.

One specific customer of FGS, a wide-web flexibles printer, was initially reluctant to print using more than four colours on its wide-web press and communicated its concerns to FGS regarding colour stability when printing with fixed palette inks. FGS discussed the benefits of Bellissima with the printer, who agreed to begin a test print. Joan Rodriguez Cosano, technical director at FGS, commented, The print test helped our customer to realise the results quickly, and after the test, he transitioned to running fixed palette jobs on the press full-time.

Using Bellissima, the client has reduced the time on press by an hour per job due to the elimination of press wash-ups, shorter makeready times, and reduced waste from misregistration issues. The printer has quantified this to be a 30% reduction in costs per job. This is excellent for the printer and FGS as it means that we can retain and grow the client. The printer is currently converting all its other printing presses to Bellissima DMS.

We all thought we knew about screening in flexo or dot-screens conventional (AM), stochastic (FM), hybrid (AM/FM) combinations, object based and even dynamically modulated varieties, said Doug Mawdsley, product manager Xeikon pre-press, These gave us great scope to reproduce tones in print getting towards photograph quality. We were just getting the hang of it and then someone comes along and puts another screen on top!

Surface screens, or surface microstructures are not a particularly new phenomenon in flexo. Earlier photopolymer suffered an unflattering comparison in terms of solid-ink laydown against the molded rubber plates they were replacing. It was noticed that sometimes, the 90% screened area was actually printing a higher density (SID) than the full solid 100%. Thus the first surface screens were born, an extra screen of around 400lpi with a 90% tint was applied in solid areas to assist the ink-transfer. This was not well known and can hardly be described as successful.

The event of Flat-Top-Dot technology, reducing oxygen inhibition during main exposure by lamination, oxygen replacement (by gas), layers built into the plate or out-running by fast and powerful LED exposures, made very effective high-frequency surface micro-structures possible.

These fine structures enable a noticeable increase in solid ink density, with a far smoother appearance and increased quality of ink laydown, fine details with reduced edge effects and cleaner dots with less bridging.

Mr Mawdsley added, The ThermoFlexX approach to screening for tonal reproduction is very simple. We are laser system experts and dont make workflow or RIP systems. So, ThermoFlexX imaging systems are totally open to facilitate the very best screening methods available. All industry resolutions, 2400, 2540, 4000, 4800 and 5080, and custom options, are supported. This ensures that the systems fit comfortably into any workflow and reproduce any chosen screen, perfectly.

Mr Mawdsley continued, For the new variety of screen, surface micro-structures, a fresh approach was needed. Woodpecker SuS was developed to take advantage of ThermoFlexX higher resolution optics. If a client workflow produces files at 4000dpi with the common MCWSI pattern built in, then Woodpecker T01/Replay mode can reproduce these faithfully with the single pixels automatically detected in the file and boosted to a pre-defined laser power level to ensure sufficient UV light for good exposure. More interestingly, files of standard resolution, 2400 or 2540dpi, using 5080dpi optics for output, can output a finer (than MCWSI at 4000dpi) surface pattern at the imaging stage. In other words, standard legacy image files can be imaged onto digital flexo plates with greatly enhanced printing capabilities.

Finally the Woodpecker Nano was developed. This operates with standard resolution image files, 2000, 2400 or 2540dpi but has the highest frequency pattern available with digital flexo (LAMs) plates. Higher resolution output optics are essential for this peck-per-pixel technique. The closer, perfectly symmetrical patterns can be applied to a variety of tone screens with less chance of interference than the lower frequency options.

Most RIPs now provide surface screening options. All competitive imager manufacturers have solutions or wish to develop them. ThermoFlexX, as part of Flint Group, has the advantage of close co-operation with Flint Group Flexographic to develop, provide and support full equipment and plate packages. ThermoFlexX imagers, Catena-E UV LED exposure and Flint Group nyloflex plates are vital parts of this comprehensive solution.

Paul Bates, sales manager UK, Ireland & Global Accounts at Hybrid Software said, The flexo market is always looking for the next big technology to help improve the print quality. The trend over recent years has been print at 4000dpi combined with a high definition modulated screening algorithm, which has solved many problems but also introduced instability on press and reduced platemaking imaging speeds, locking customers into one system.

We worked with our RIP partner Global Graphics to developed Harlequin Cross Modulated (HXM) this is hybrid AM/FM screening for flexo that allows higher screen rulings than provided by AM screens alone, unlike other systems we have designed HXM to work with any output device and flexo plate manufacture. HXM screening combines the advantages of both AM and FM screening and is therefore able to limit the loss of small printed structures and detail at high line screen rulings by controlling the dot size in the highlight and shadow. It limits the smallest structure produced to be that which can reliably be printed on the target system. Once this point is reached within a given HXM screen, structures are removed completely rather than continuing to be reduced in size to create the required tonal range. Therefore, it does not disappear in the light areas or merge in the dark areas, which improves the print quality with smoother tones, flat tints and gradient transitions.

We have been thinking outside the box to bring to market a totally new concept, Intelligent Flexo Mr Bates continued, Intelligent Flexo, brings new workflow functionality to Hybrid Softwares CLOUDFLOW, which can apply screening modifications intelligently to post-ripped files. Working on post-rip data we have more control and better tools to identify problem areas in the images that warrant intervention. The intention of Intelligent Flexo is to help overcome issues that are inherent with high speed flexographic printing processes which are consistent in an automated and repeatable process.

Released last year, Print Control Wizard was designed to improve the flexo plate making process and flexographic print quality via Crystal Screens. It offers a simplified, standardised approach to take several process parameters such as ink, printing press, substrate and anilox into consideration for screen and curve creation. It then outputs a set of Crystal Screens and dot gain compensation curves used for plate exposure on a CDI Crystal XPS.

Print Control Wizard was developed in response to industry calls to simplify the implementation of screens and dot gain curves, and we wanted to build on our immediate success of the wizardstyle user experience with additional functionality, said Robert Bruce, RIP & screening product manager, at Esko. Thats why weve added integrated colour management tools and optimised the implementation process. For example, while global standards call for three press trials to define a flexo print condition, from optimisation with single screen testing, through characterisation with colour management and a fingerprint for dot gain, Print Control Wizard 20.0 users can now go straight to fingerprinting. This offers a significant reduction in time, cost and press downtime too.

Our goal was to provide flexographic pre-press experts with the tools to standardise and simplify screening and dot gain curve creation, enabling them to achieve the best quality results without additional steps and checks being added to the process, Mr Bruce finished, After Print Control Wizard was honoured with a number of top industry awards, we have been working tirelessly to develop these new enhancements.

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founder electronics - eaglerip

Founder began research on RIP technology since 1975. Founders EagleRIP Flexo is a native PDF interpreter, with high speed performance, advanced screening technology and good layout application compatibility. EagleRIP Flexo not only supports flexo printing, but also supports offset printing.

Founders EagleRIP creates superb quality PDF and PostScript jobs. Complex documents, vivid colors, transparent objects, files with embedded ICC profiles and smooth shading are consistently processed to meet the high standards of the most demanding customer. EagleRIP provides support for features within PDF 1.7 and PostScript 3.

Ensure the output is accurate by digitally previewing color and dot shape prior to committing to physical output. EagleRIP lets you preview color separations and composites, and includes preview functions such as Zoom, Negative, Mirror, Rotate and Screen preview of the bitmap dot.

EagleRIP screen dot shapes allow users to select the dot that ensures maximum printing quality. Nine standard screenings include Euclidean Round, Rhomb, Ellipse, Diamond, Pure Round, Sharp Ellipse, Square, Cross and FM screening. Optional screenings such as EagleAM, EagleFM, EagleFAM (AM & FM hybrid printing) and EagleAGS (gravure printing) are available as plug-ins.

EagleAM screening optionAdopts new screen angle technology (+/- 7.5) comparing to the traditional AM screening angle (15, 45, 90, 75). a. Improves the rosette pattern, gray level is exquisite and smooth.b. More accurate angles produces higher quality.c. Better reproduction of gradient shading and overprint effect of tints and skin color.d. Suitable for printing high frequency images on CTP (greater than 300LPI).

a. Control the randomicity of dots, ensuring the smooth middle tone.b. Smooth transition at continuous tones, keeping details at overlapped colors.c. Light area and shadow area can use different dot size for easy press and expanding the color gamut.

3. Supports to overlap page bitmaps in manual ganging function, supports to arrange up and down relationship of the overlapped bitmaps. (bitmap should be generated by 1 Bit TIFF template and separated)

5. RealDot Viewer is an option of EagleRIP Flexo 5.1 license code, you needn't a separated license code for RealDot Viewer if the code of EagleRIP Flexo 5.1 contains this option. RealDot Viewer needs to be installed on the same computer as EagleRIP Flexo 5.1.

4. Support optional FlexoRound Balance screening:On highlight, based on AM screening technology, we adopt dots with different sizes small, medium and large, increase gray level. This special technology can break the limitation of highlight dots in flexo printing and reproduce 1% or smaller dot.

6. On shadow, based on FM screening technology, adds extract tiny dots in the shadow, this special technology greatly improves the shortage of insufficient solid ink of flexoprinting, and get a excellent print quality.

7. Support Real dot preview tool: RealDot Viewer, an essential checking tool. By browsing all the details of the real doton the monitor, to do the final check before printing, so as to secure the output file on flexo CTP plate is perfect without any error.

FlexoRound Balance: On highlight, we adopt dots with different sizes small, medium and large, increase gray level. This special technology breaks the limitation of highlight dots in flexo printing, reproduce 1% or smaller dot.

RealDot Viewer, an essential checking tool. By browsing all the details of the real dot on the monitor, to do the final check before printing, so as to secure the output file on flexo CTP plate is perfect without any error.

FlexoRound Balance: On highlight, we adopt dots with different sizes - small, medium and large, increase gray level. This special technology breaks the limitation of highlight dots in flexo printing, reproduce 1% or smaller dot.

screen printing | hackaday

This build is a long, long, time in the making first beginning in 2015 when Fran started investigating the DSKY of the Apollo Guidance Computer. At the time, there were reproductions, but honesty they were all terrible. The reproductions used off-the-shelf seven-segment LEDs or light pipes. Thereal DSKY was a work of art and at the time probably the most complex electroluminescent display ever created. This led [Fran] to a very special trip to the annex of the Air and Space Museum where she was allowed to inspect a real DSKY display. She got all the measurements, and with some non-destructive investigation, she was able to piece together how this very special display was put together.

With that information, [Fran] was able to figure out that this display was a fairly complex series of silk screens. If its silk screen, you can put it on a t-shirt, so thats exactly what [Fran] did. This used a DIY silk screen jig with phosphorescent inks. Its not an electroluminescent display, but itdoes glow in the dark.

While this DSKY t-shirt does glow in the dark, that means its not an electroluminescent display like the original DSKY. That said, screen printed electroluminescent displays on a t-shirt arent unheard of. Several years ago, a screen printing company did a few experiments with EL displays on wearables. Of course, if you want a real electroluminescent DSKY display, [Ben Krasnow] has a very modern reproduction of the screen printed display. The electronics of [Ben]s project do not resemble what flew to the moon in any way whatsoever; the original DSKY hadrelays. That said, weve never been closer to a modern recreation of the display from an Apollo Guidance Computer, and we have [Fran] and [Ben]s work to point us forward.

The lottery is to some a potential bonanza, to others a tax on the poor and the stupid. The only sure-fire way to win a huge fortune in the lottery does remain to start with an even bigger fortune. Nevertheless, scratch-off tickets are the entertainment that keep our roads paved or something. [Emily] over on Instructables came up with a way to create your own scratch-off cards, and the process is fascinating.

For [Emily]s scratchers, there are five layers of printing on the front of the card. From back to front, they are the gray security confusion layer printed with a letterpress, black printing for the symbols and prize amounts, also printed on a letterpress, a scratch-off surface placed onto the card with a Silhouette cutter, the actual graphics on the card, printed in blue with a letterpress, and a final layer of clear varnish applied via screen printing. Theres a lot that goes into this, but the most interesting (and unique) layer is the actual scratch-off layer. You can just buy that, ready to cut on a desktop vinyl cutter. Who knew.

After several days worth of work, [Emily] had a custom-made scratcher, ready to sent out in the mail as a Christmas card. Its great work, and from the video below we can see this is remarkably similar to a real scratch-off lottery ticket. Not that any of us would know what scratching a lottery ticket would actually be like; of course thats only for the gullible out there, and of course none of us are like that, oh no. You can check out a video of the scratch-off being scratched off below.

There is a technology that will allow you to add inks, resins, and paints to any flat surface. Screen printing has been around since forever, and although most of the tutorials and guides out there will tell you how to screen print onto t-shirts, [Ben Krasnow] had the idea of putting patterns of paint on acrylic, metal, or even ITO glass for electroluminescent displays. With screen printing, the devil is in the details, but lucky enough for all of us, [Ben] figured everything out and is sharing his knowledge with us.

The ten thousand foot view of screen printing is simple enough put some ink on a screen that has some photoemulsion, and squeegee it through onto a t-shirt. While this isnt wrong, theres a lot of technique, and things will go wrong if this is your first time doing it. Screens are easy, and the best way to get those is by buying a pre-stretched frame. The photoemulsion is a bit different. The old way of applying a photoemulsion is by squeegeeing it on with a bizarre tool. Its almost impossible to get a thin consistent layer with this technique, so [Ben] recommends just buying some photoemulsion film.

Once the photoemulsion is on the screen and dry, you need to put an image on this. The photoemulsion cures hard with UV, so the traditional technique is using transparency (actually, the real old-school way is using a camera obscura). Transparency sheets for laser printers work, but30-lb vellum is actually more transparent to UV light than clear acetate sheets. This is then applied print side down to the dry screen, and believe me when I say this is the most important part. You will not get a good screen print if there is not direct contact between your photomask and your photoemulsion. This is so important, it may be worth considering some experiments in vinyl cutting to create the photomask.

With the screen developed, its simply a matter of globbing on some ink and pressing it onto a piece of acrylic. [Ben] used regular oil paints, an unmixed artists oil paint, and the professional solution, epoxy-based screenprinting paint. By far, the epoxy paint gave the best finish, but its a stinky mess that is nearly impossible to clean.

With a somewhat successful screenprinting setup, what will [Ben] be able to do? Well, hes been working on electroluminescent displays, and the first EL displays were screenprinted anyway. More than that, you could use screen printing to create a resist for copper etching for creating your own PCBs. Theres a lot you can do when you can put epoxy down in a thin layer, like make a blockchain of Tide pods, and this is the best tutorial weve ever seen on using photoemulsions.

Travel around to enough security conferences, faires, and festivals, and youll see some crazy wearable electronics. Most of them blink, and most of them use LEDs. Electroluminescent panels are used for wearables, but thats a niche the panels are a little expensive, and you have to deal with high frequency AC instead of the much simpler, plug in a LiPo here circuit LED-based wearables have to contend with.

Still, electroluminescent panels are cool, and thanks to how EL panels are made, you can screen print EL displays. Thats what some of the guys at AMBRO Manufacturing did recently: screen printing electroluminescent lights directly onto garments. Its t-shirts from Tron made real.

EL panels and EL wire are really only three separate parts: a conductor of some sort, a phosphor, and another conductor. Pass a high-frequency AC current through the conductors, and the phosphor lights up. With EL wire, its a thick copper wire clad in phosphor and wrapped in a very fine copper wire. EL displays are made with conductive ITO-coated glass or plastic. Its a relatively simple construction, and one that is perfectly suited for screen printing. In fact, one of the first EL displays the DSKY, the user interface for the Apollo Guidance Computer used screen printed seven-segment EL displays.

The folks at AMBRO only have a proof of concept right now, but it is a completely screen printed electroluminescent design on fabric. To light it up, the t-shirt will need an inverter, but this is the beginnings of t-shirts from Tron.

mev screener - midwestern industries, inc

The high-frequency screens manufactured by Midwestern can be utilized in many screening applications from rugged quarry and rock sizing to sand and gravel processing and high volume fine mesh screening. With a variety of sizes and screening decks, the versatile MEV Screener can fit numerous applications.

The MEV High-Frequency Screener is a rectangular screener that utilizes an elliptical motion to convey material across itsscreening surface. Available in sizes three-foot by five-foot (3 x 5), four-foot by eight-foot (4 x 8), and five-foot by ten-foot (5 x 10) with the availability of one to five screening decks gives the MEV Screener the versatility to meet your screening needs.

The MEV Screener is designed to retain material at the feed end for a longer period of time and then gently slops the material near the discharge end, assisting itoff the screening deck and into production. This is achieved by the screeners unique parallel-arc configuration. Crossbars support the end-tensioned screens tocreate a flat screening surface, thus maximizing the screening area.

The end-tensioned screens used in the high-frequency screener simplify changing screen panels. End-tensioning permits the use of square-opening and slotted screens and is accurately maintained by a spring-loaded drawbar. Users can make screen changes in 1015 minutes.

Midwesterns commitment to providing our customers with outstanding screening products continues with our full line of replacement rectangular screens. Our screens are manufactured to fit all makes and models of screeners.

vibrating screen, multi deck high frequency screen | h-screening

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Vibrating screensare the most important screening machines primarily utilised in the mineral processing industry. They are used to separate slurry feeds containing solid and crushed ores down to approximately 200m in size, and are applicable to both perfectly wetted and dried feed. H-Screening offers high frequency fine screen stakck sizer, linear vibrating screens for fine screening and wet processing, dewatering screens, PLC controlled electromagnetic vibrating fine screen.

screening machines & screeners

Super phosphate (SP), triple super phosphate (TSP) or double super phosphate (DSP) as well as diammonium phosphate (DAP) and monoammonium phosphate (MAP) are mainly used as fertilizers and are subject to strict quality requirements. Since phosphate fertilisers are produced in large quantities of several hundred tonnes per hour, even small efficiency deficits lead to high product losses. The aim of the screening process is to achieve high product purities at maximum throughput - and this can only be achieved by preventing clogging of the screen meshes.

The screening tasks in the processing of nitrogenous fertilizers such as ammonium sulphate (AS), ammonium nitrate (AN), calcium nitrate (CN), potassium nitrate (KN), calcium ammonium nitrate (KAS) and urea range from lump separation to the demanding separation of product fractions as well as dust removal. Screening nitrogen fertilizer with high efficiency and throughput requires precise adjustment of all machine parts as well as a well-functioning self-cleaning system, since urea and co. tend to bind air humidity in the dust fraction and thus clog the screen cloth.

To properly separate sugar requires the application of a high frequency directly to the material. The reason is, that sugar can become sticky even at low humidity levels and also tends to clog the sieve mesh, due to its crystalline grain shape. Screening machines with direct excitation of the screen mesh have therefore proven to be not only energy efficient, but also extremely precise. Thanks to the high accelerations, they reliably separate even finest sugars into several fractions simultaneously.

Efficient separation of metal powdersHigh-alloyed metal powders for 3D printing (additive manufacturing/ rapid technology) should be extremely pure to guarantee a high-quality end product. Dust and agglomerates must therefore be reliably removed from the extremely fine powder during production and recycling. A suitable screening machine should not only be highly precise, but also reduce the loss of valuable product and machine downtime to a minimum.

When processing dry mortar into different fractions, the fluctuating grain size distribution of the crushed limestone, as well as its tendency to clog up the screen mesh, lead to great challenges during screening. Efficient and flexible screening equipment can prevent these negative effects. On the one hand, it must be possible to individually adjust the oscillation amplitudes on each screen deck, and on the other hand, an automatic cleaning system is required to keep the screen surface open and thereby ensure throughput and product quality.

In this particular type of drive, two unbalance motors with different speeds are used. Upstream, a large oscillation amplitude ensures the loosening and removal of the material, while downstream, a small oscillation amplitude at higher acceleration ensures that even difficult to screen products are classified accurately.

Linear and circular vibrating screens are a cost-effective alternative to directly excited screening machines. They can be supplied with several screen decks on request and are available in tailor-made special designs. Their low-maintenance unbalance motors and good accessibility through large inspection openings simplify maintenance tasks.

By overcoming cohesion forces, our high-performance dewatering screens achieve maximum dewatering of solid particles from suspensions with optimized residual moisture content for particles down to less than 1 mm. In wet processing, the precise screening technology ensures efficient disagglomeration of the material and thus optimum separation of coarse and fine material.

Believe it or not for over 70 years it has been our objective to manufacture the best screening machines in the world! For our customers, we always aim to deliver the most effective screening machines for their specific task. Of course, we consider our customers technical and commercial constraints, and adjust each screening machine exactly to their wishes and requirements.

RHEWUM screening machines are Made in Germany or more precisely Made in Remscheid for this reason it is no surprise that we are not the cheapest manufacturer of screening machines, but our sophisticated clientele appreciates our established quality. Still not convinced? We will test your material in our technical center and demonstrate to you the performance of our screening machines, live on site! Clear, committed answers instead of cryptic promises are what you can expect from RHEWUM.

high frequency screening: from piles to profit - quarry

The underlaying features of high frequency screens have remained constant, that is, their highly efficient ability to separate particles from around 25mm down to 0.425mm and the capability to handle wetter, stickier materials. What has now developed is the means at which this capability is deployed.

Astec has now produced three track-mounted systems, to be used for a variety of applications. The FT2618VM is the system with the most runs on the board, as it typically runs in-line with Astecs FT2650 tracked jaw crusher and FT300 tracked cone crusher as a final screen for producers wanting to screen for a specific manufactured sand profile. Recently, the high frequency range has increased to include the GT205 multi-frequency tracked screen and the GT165 multi-frequency tracked screen.

{{image2-a:r-w:300}}The GT205 is a direct feed screen with a conventional top deck to screen off top size overs but also includes high frequency technology on the second and third decks to allow a more efficient product cut.

Recent use cases have seen the GT205 being fed recycled gypsum, recycled glass and topsoil. The most intriguing use case has been the processing of otherwise waste material to produce low grade road base that meets local council specifications.

Astec has recently launched the GT165. In this configuration, the multi-frequency screen with its mix of conventional screening on top deck and high frequency lower deck has been arranged for scalping. The benefits of using the multi-frequency configuration in the scalping function is that raw feed (larger rock) can be handled on the top side deck, while the second deck can run a much finer screen cloth that can handle a stickier type of materials often found in scalping applications.

Apart from mobile track-mounted applications, Astec has also sold different sized high frequency screens that have been mounted in a modular frame. With minimal dynamic loading, the structures are modest, robust and can be used for a wide variety of applications. The most common use cases for high frequency screens in static applications include operations processing crusher run of dust into manufactured sand.

To accommodate unique site requirements, static applications of high frequency screens can be configured with multiple decks and differing lengths and widths. One of the strengths of running the high frequency screen is the ability to change the screen angle, frequency and stroke of the individual screen decks. This control allows tuning of the screen to the properties and size of the material being screened, giving precise stratification and optimal screening outcomes.

To date the high frequency screen has been successfully used in manufactured sand, concrete stone, agricultural lime, recycled materials and topsoil. To assist producers in scoping the high frequency screen for their application, Astec offers a complimentary material testing service where customers can test their specific materials on a demo screen at the Astec head office in Brisbane, Queensland.

screen-printed flexible bandstop filter on polyethylene terephthalate substrate based on ag nanoparticles

Rajendra Dhakal, Younsu Jung, Hyejin Park, Gyoujin Cho, Nam Young Kim, "Screen-Printed Flexible Bandstop Filter on Polyethylene Terephthalate Substrate Based on Ag Nanoparticles", Journal of Nanomaterials, vol. 2015, Article ID 978562, 8 pages, 2015. https://doi.org/10.1155/2015/978562

We present a low-power, cost-effective, highly reproducible, and disposable bandstop filter by employing high-throughput screen-printing technology. We apply large-scale printing strategies using silver-nanoparticle-based ink for the metallization of conductive wires to fabricate a bandstop filter on a polyethylene terephthalate (PET) substrate. The filter exhibits an attenuation pole at 4.35GHz with excellent in-and-out band characteristics. These characteristics reflect a rejection depth that is better than 25dB with a return loss of 0.75dB at the normal orientation of the PET substrate. In addition, the filter characteristics are observed at various bending angles (0, 10, and 20) of the PET substrate with an excellent relative standard deviation of less than 0.5%. These results confirm the accuracy, reproducibility, and independence of the resonance frequency. This screen-printing technology for well-defined nanostructures is more favorable than other complex photolithographic processes because it overcomes signal losses due to uneven surface distributions and thereby reveals a homogeneous distribution. Moreover, the proposed methodology enables incremental steps in the process of producing highly flexible and cost-effective printed-electronic radio devices.

Flexible cost-effective devices, such as radiofrequency identification (RFID), antennas, and filters, are needed for enabling realization of high-performance devices for operation in frequency bands of the monolithic microwave integrated circuit (MMIC) and radiofrequency integrated circuit (RFIC). Recently, more sophisticated processes have been used for printing various types of electronic devices and systems. These printing processes are critical for replacing the more complicated, time-consuming, and expensive photolithographic process. One of the most powerful device fabrication methods, photolithography, is widely used for miniaturized microwave devices composed of metallic lines of only a few microns wide. However, photolithography is a rather complicated process, even for creating a few samples with simple structural designs [1, 2].

The screen-printing technique produces electronics devices on paper as well as on plastic foil with different thicknesses and dielectric constants, which can be tailored to design requirements [3]. High-performance, low-cost, and flexible narrowband bandstop (NBBS) filters with a minimum size and weight, high-frequency selectivity, and excellent pass-band insertion and return losses are important for C-band applications in modern communication systems. These parameters are the key factors for the development of demanding, miniature, and multifunctional communication systems for wireless sensor networks and smart electronic devices. The deposition of suitable metal ink on the prescribed flexible substrate for the fabrication of highly desirable electronic devices is a major challenge [4, 5]. This metallization itself presents the challenge of the formulation of suitable silver (Ag) nanoparticle ink. The metal precursor ink must provide a sufficiently high resolution and good adhesion to the surface with good morphological structure within the Ag nanoparticles. Accordingly, signal loss due to the skin effect can be easily studied and minimized [6, 7].

However, no technology exists that is sufficiently advanced for building a flexible, high-throughput, cost-effective, and highly reproducible bandstop filter (BSF). The design of flexible single-band BSF on a PET substrate with high stopband attenuation and low return loss has not yet been reported. The imprecise formulation of the Ag-nanoparticle-based ink has resulted in design complexity for uniform width and thickness of the transmission-line. Furthermore, it has degraded the results in the return loss and rejection depth [8]. Various processes and strategies have been previously proposed for bandstop filter design. These studies have focused on fabrication using flame retardant 4 (FR4), low-temperature cofired ceramic (LTCC), coplanar waveguide, and metamaterials, with complex and expensive photolithography being the most common method of fabrication [914]. Screen-printing is a promising approach for large-scale fabrication with minimal radial loss by the skin effect at high frequency with even surface characterization electroplated by Ag nanoparticles. This approach has surpassed the aforementioned complex photolithography process.

To address the above limitations, we propose a simple and cost-effective method to manufacture a highly reproducible BSF on a PET substrate by employing high-throughput screen-printing technology with an attenuation pole at 4.35GHz. Excellent performance of transmission parameters in the stop band with a good morphological characterization of the Ag nanoparticles justifies the operational characteristics of BSF. Through experiments, we demonstrate the relative standard deviation (RSD) for five consecutive experiments in each bending angle of the substrate. The result of an RSD value of less than 0.5% confirms the accuracy, reproducibility, and independence of the resonance frequency despite the flexibility of the substrate.

The schematic structure of the proposed BSF was realized on a PET substrate. The Ag nanoparticles applied for the metallization of the conductive lines served as a signal carrier at high frequency. The concept of folded signal lines toward the input was implemented with capacitance in between the C-shaped stubs. The connection of folded meander-line with multiple bends can generate a specific resonance frequency. However, the rejection depth degrades and the topology will be too complex to bend the signal line. Furthermore, the complexity of the junction discontinuity effects will increase, such that an accurate value of the return loss cannot be obtained [15, 16]. The proposed structure was therefore designed on a PET substrate with a thickness of 180m, a dielectric constant of 3.0, and a loss tangent of 2.5. Screen-printing technology was introduced along with Ag nanoparticles for the metallization of the BSF. To minimize the effective area of the filter, the length of the high-impedance section of the resonator was modified by bending it along the width. The filter can be used to suppress the resonance frequency () by 25.88dB in the stopbands and simultaneously achieve a narrowband bandwidth with a 10dB fractional bandwidth (FBW) of 6.44%. The layout of the proposed filter with detailed dimensions is mm, mm, mm, mm, mm, mm, mm, mm, mm, and mm, as shown in Figure 1.

The use of Ag for metallization on the polymer PET substrate has gained considerable research interest. The deposition of Ag nanoparticles during metallization has been deemed favorable over other metals on account of its unique properties, such as chemical inertness, excellent electrical conductivity, and ease of ink formulation. A PET film (width of 200mm and thickness of 180m, purchased from SKC, Korea) was used along with Ag-nanoparticle-based conducting ink (PG-007 BB type, Paru Co., Korea). The silver ink was further formulated to meet the viscosity of 500cp and surface tension of 47mN/m using ethylene glycol (Sigma-Aldrich) and dipropylene glycol methyl ether (Sigma-Aldrich), respectively.

For fabrication of the screen-printed bandstop filter, we used a single-step printing process through a screen printer (Sun Mechanix Co., Korea). With its ease of use for designing flexible devices, screen-printing is a remarkable technique, especially for printing on flexible substrate; moreover, the process is relatively simple, cost-effective, and versatile [17, 18]. The screen plate above the substrate was used to make the pattern. The screen plate was made with a stretchy fine lattice structure of 200 mesh. Ag ink was placed on top of the screen with a squeegee bar to fill it with ink, as shown in Figures 2(a) and 2(b). The movement of the squeegee with pressure enabled the Ag ink to pass through the pattern to create the Ag pattern designed on the PET substrate. The Ag ink was printed on PET film with a printing speed of 5mm/s and a pressure of 5. The resulting Ag printed films were dried at 150C for 10min. To provide the ground for the signal line of the bandstop filter, the Ag ink was reprinted on the backside of the PET substrate with a printing speed of 5mm/s and a pressure of 5. It was additionally treated at 150C for 10min, as represented in supplementary FigureS1 in Supplementary Material available online at http://dx.doi.org/10.1155/2015/978562. For the final testing of the BSF, it was encapsulated in printed circuit board (PCB) with a 50 port connected to the input and output sides of the transmission-line. The necessary transmission parameters were then obtained by connecting the input and output ports to an Agilent 8510C vector network analyser (VNA), as shown in Figure 2(c).

The design of the filter was implemented by the concept of the folded meander-line structure to generate the BSF with an attenuation pole at 4.35GHz with good selectivity, as demonstrated in Figure 3(a). The C-stub along the meander-line was folded to generate the stopband characteristics. Each bend of the meander-line represents a series inductor connected to a parallel capacitor for generation of the stopband characteristics of the proposed filter. The tank circuits , and , represent the equivalent inductance and capacitance for the bends and , respectively, as represented in Figure 3(b). Figure 3(c) depicts a magnified view of the gap between the C-shaped stubs with gap capacitance (, ). The equivalent circuit representation of the transmission-line on the input and output sides was modeled by the inductor () and capacitor (), as represented in Figure 3(d). and represent the impedances of the transmission-line and are assumed to be 50. The distance between the C-stubs could be varied to generate variation in gap capacitance and ultimately the resonance frequency of the filter during the design analysis. The rejection depth is reflected by , while generate the return loss for the BSF, as mentioned in Figure 3(d) [19, 20].

The samples on PET substrates were characterized using X-ray diffraction (XRD), atomic force microscopy (AFM), and scanning electron microscopy (SEM). The surface characterization of the filter with respect to XRD and AFM was presented. A typical XRD pattern of the PET film is illustrated in Figure 4, where different peaks are assigned to represent the different structures and compositions of the PET film and Ag nanoparticles. For the tested PET film, a peak is observed at 2 = 25.87 and at 38.13, corresponding to Ag (111), which reveals the preferentially oriented growth of the Ag nanoparticles. The data obtained from the XRD measurement indicate the high-quality Ag metallization on the PET substrate as a promising candidate for the application to flexible radio devices.

In addition, three peaks are observed for the 2 angle, which correspond with planes (111), (200), and (220), with the highest diffraction intensity being for plane (111). Additionally, diffraction with lower intensity peaks is observed at a 2 angle of 44.34 (200) and 64.49 (220) for the Ag nanoparticles on the PET substrate. The XRD measurement further verifies that the peak intensity obtained for the Ag nanoparticles contains no lattice strain. Moreover, the particle size of Ag deposited on the PET film calculated by Scherrers equation is 79.2nm. The tolerable discrepancy in the particle size of 50~130nm generated from the SEM image is comparable to that obtained from the XRD measurement. During the deposition process, the original particles crashed into smaller grains, as confirmed by the XRD measurement, to form the flatter or homogeneous surface profile. It is observed that the metallization of the Ag nanoparticles on the PET substrate depends on the process and orientation of the metallization, as demonstrated by the XRD representation.

The easiest and most effective way to investigate the impact of screen-printed Ag nanoparticles on PET film is by using atomic force microscopic (AFM) analysis. AFM images of the screen-printed Ag nanoparticles are shown in Figures 5(a) and 5(b). From analysis of the AFM measurement, we can conclude that the Ag nanoparticles are not completely homogenous over the surface of the substrate; rather, there exist some evenly distributed peaks and valleys. In other words, the surface of the screen-printed Ag nanoparticles appears comparatively flatter, representing an evenly distributed topographical structure [21]. The root mean square (RMS) value of 20.93nm from its surface area of 108.82m2 is sufficient for the simple and cost-effective screen-printing technique. In addition, the histogram and line graph also represent this surface topology with evenly distributed peaks and valleys. The maximum and minimum peaks and valleys created with screen-printing were approximately 50nm peak-to-peak, as represented by Figures 5(c) and 5(d). We confirmed the Ag nanoparticle sizes using both SEM and transmission electron microscopy (TEM) images, which show a similar result. The size distribution of these particles was 50~130nm with a thickness of 12.20m. Detailed information on the Ag nanoparticles is provided in Figures 6(a) and 6(b). The size of these nanoparticles does not significantly influenced the resistance unless they were less than 5nm. From printing with the proposed Ag ink, there was no considerable difference in the resistance.

Good adhesion was obtained between the substrate and Ag nanoparticles, which verifies that the fabricated device is flexible and mechanically robust. Figure 6(a) clearly illustrates the cross-sectional view of the Ag metal layer with a thickness of 12.20m with excellent adhesion with the PET substrate. Here, Figure 6(b) demonstrates that there is no aggregation among the particles with homogeneous surface profiles. The morphological characterization of the pattern suggests the RMS value of approximately 20.93nm. Additionally, the AFM analysis suggests that the peaks and valleys formed by the nanoparticles are homogeneous. This homogeneous distribution of particle size minimizes the roughness of the surface along with the radial loss of the signal at high frequency. This result is on account of the skin effect, as shown in supplementary FigureS2. The minimization of radial losses by maintaining the homogeneous surface profile helps to improve the return loss and attenuation depth of the signal [22, 23].

A flexible NBBS filter was designed and fabricated on the PET substrate with Ag nanoparticles as the conductive material for the transmission-line oriented at the normal condition (0) to the surface, with the maximum signal attenuation level of 25.88dB and an attenuation pole at 4.35GHz, as shown in Figures 7(a) and 7(b). The device response for the various bending angles showed a small amount of deterioration of the performance parameters; however, this was considered within tolerable limits. The obtained results verify that the proposed device demonstrates consistent measurement results despite exposure to a different strain, as illustrated in supplementary FigureS3. For the device orientation of 10 and 20 to the horizontal surface, where 10 and 20 are the absolute values of the downward bending angle, it produced an attenuation level of 24.79dB and 24.10dB at a resonance frequency of 4.31GHz and 4.34GHz, respectively, as shown in Figures 7(b) and 7(c). The experimental data obtained from the first measurement of the multiple iterations has been considered for necessary illustration and analysis.

From the results of this experiment, we conclude that the device characteristics remain consistent despite its flexibility in various bending angles. The reproducibility of BSF was characterized by measuring the resonance frequency at various bending angles of the substrate. We carried out five different sets of experiments for each of the bending angles to observe the resonance frequency for each iteration of the experiment. Fifteen different experiments were performed in total. No device performance deterioration was observed over these numerous iterations of the measurement process. As a result, the relative standard deviation of less than 0.5% was observed for each bending angle of the substrate, as illustrated in Table 1. These findings validate the reproducibility capability of the proposed flexible BSF.

In addition, a full-wave electromagnetic simulation of the filter by Sonnet is illustrated. It closely resembles the measurement result obtained from the VNA. A compact geometry was chosen for the compact size of an approximate range between 4mm and 3.49mm. The maximum attenuation level of 25.88dB at the stopband exhibits a lower cut-off frequency of 4.18GHz and an upper cut-off frequency of 4.46GHz results, which results in an FBW (10dB) of 6.44%. The stopband bandwidth and resonance frequency of the fabricated filter are closely matched with the simulated bandwidth and resonance frequency, as represented in Figure 7(d). The proposed method highlights a narrow stopband with sharp skirt selectivity, a higher rejection depth of 25.88dB, and a lower return loss of 0.75dB. The NBBS filter produced an excellent radio frequency (RF) phenomenon in the flexible PET substrate. It is therefore proved to be a suitable candidate for evolving technologies in the development of flexible radio devices and systems.

In this paper, we demonstrated the feasibility of realizing a bandstop filter at 4.35GHz through the injection of ink made from Ag nanoparticles on a commercially available PET substrate. This cost-effective screen-printing technology on a PET substrate is highly suitable for the realization of BSF filters with excellent in-and-out band performance at normal and bending conditions. The reproducibility of the device performance for various bending angles (0, 10, and 20) of the substrate was explored. The results showed an excellent RSD of less than 0.5%, which confirms its flexibility as the BSF. Thus, the proposed printing method would facilitate the implementation of a simple, flexible, and reproducible bandstop filter with a homogeneous surface profile as a suitable candidate for C-band applications.

This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT and Future Planning (no. 2011-0030079) and a grant supported by the Korean Government (MEST) (no. 2012R1A1A2004366). This work was also supported by a Research Grant from Kwangwoon University in 2015. Additionally, the authors appreciate the financial support provided by the Ministry of Education in Korea through the Basic Science Research Program at Sunchon National University and by the Global Leading Technology Program of the Office of Strategic R&D Planning (OSP) through the Ministry of Commerce, Industry and Energy, Republic of Korea (10042537, Printed Electronics Total Solution Development).

The sheet resistance for the curing time with different heat treatment produced the minimum sheet resistance at a treatment temperature of 150C. The sheet resistance sharply decreases for all treatment temperatures up to the curing time of around 1 min. For the curing time above 1 min, the sheet resistance is somehow constant. The treatment temperature of 150C produces constant sheet resistance as compared to other heat treatment temperature.

Copyright 2015 Rajendra Dhakal et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

screen printed passive components for flexible power electronics | scientific reports

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Additive and low-temperature printing processes enable the integration of diverse electronic devices, both power-supplying and power-consuming, on flexible substrates at low cost. Production of a complete electronic system from these devices, however, often requires power electronics to convert between the various operating voltages of the devices. Passive componentsinductors, capacitors and resistorsperform functions such as filtering, short-term energy storage and voltage measurement, which are vital in power electronics and many other applications. In this paper, we present screen-printed inductors, capacitors, resistors and an RLC circuit on flexible plastic substrates and report on the design process for minimization of inductor series resistance that enables their use in power electronics. Printed inductors and resistors are then incorporated into a step-up voltage regulator circuit. Organic light-emitting diodes and a flexible lithium ion battery are fabricated and the voltage regulator is used to power the diodes from the battery, demonstrating the potential of printed passive components to replace conventional surface-mount components in a DC-DC converter application.

Recent years have seen the development of a wide variety of flexible devices for applications in wearable and large-area electronics and the Internet of Things1,2. These include energy harvesting devices such as photovoltaics3, piezoelectrics4 and thermoelectrics5; energy storage devices such as batteries6,7; and power-consuming devices such as sensors8,9,10,11,12 and light sources13. While a great deal of progress has been made on the individual energy sources and loads, combining these components together into a complete electronic system typically also requires power electronics to overcome any mismatch between the source behavior and the loads requirements. For example, batteries produce a variable voltage dependent on their state of charge. If a load requires a constant voltage, or a higher voltage than the battery can produce, then power electronics are necessary. Power electronics use active components, transistors, to perform switching and control functions, as well as passive componentsinductors, capacitors and resistors. In a switching voltage regulator circuit, for example, inductors are employed to store energy during each switching cycle, capacitors are used to reduce voltage ripple and the voltage measurement required for feedback control is accomplished using a resistor divider.

Power electronics appropriate for the demands of wearable devices such as the pulse oximeter9, which requires a few volts and a few milliamps, typically operate at frequencies in the range of hundreds of kHz to a few MHz and require inductance and capacitance of several H and several F, respectively14. The conventional approach for manufacturing these circuits is to solder discrete components onto a rigid printed circuit board (PCB). While the active components of a power electronic circuit are often combined into a single silicon integrated circuit (IC), the passive components are usually external, either to allow customization of the circuit or because the required inductance and capacitance values are too large to be achieved in silicon.

Fabrication of electronic devices and circuits by additive printing processes offers a number of advantages in terms of simplicity and cost when compared to the conventional PCB-based manufacturing techniques. First, since many components of a circuit require the same materials, such as metal for contacts and interconnects, printing allows multiple components to be fabricated simultaneously, with relatively few processing steps and few sources of materials15. Replacing subtractive processes such as photolithography and etching with additive processes further reduces process complexity as well as materials waste16,17,18,19. In addition, the low temperatures used in printing are compatible with flexible and inexpensive plastic substrates, allowing large areas to be covered with electronics using high-speed roll-to-roll manufacturing processes16,20. For applications that cannot be fully realized using printed components, hybrid approaches have been developed in which surface-mount technology (SMT) components are attached at low temperature to flexible substrates alongside the printed components21,22,23. In such hybrid approaches, replacing as many SMT components as possible with their printed counterparts is still desirable to reap the benefits of the additive processes and improve the overall flexibility of the circuit. To achieve flexible power electronics, we propose a combination of SMT active components and screen-printed passive components, with particular emphasis on replacing bulky SMT inductors by planar spiral inductors. Of the various technologies for fabricating printed electronics, screen printing is especially well suited for passive components because of its large film thickness (which is necessary to minimize series resistance of metallic features) and its high printing speed, even when covering centimeter-scale areas with material24.

It is essential to minimize losses in passive components for power electronics, since the efficiency of the circuit directly affects the size of the energy source that is required to power a system. This is particularly challenging for printed inductors, which consist of long coils and are therefore susceptible to high series resistance. As a result, although there has been some effort toward minimizing resistance of printed coils25,26,27,28, there remains a lack of efficient printed passive components for power electronics. To date, many reported printed passive components on flexible substrates are designed to operate in resonant circuits for radio frequency identification (RFID) or energy harvesting purposes10,12,25,27,28,29,30,31. Others focus on materials or fabrication process development and demonstrate general-purpose components that are not optimized for a particular application26,32,33,34. Power electronic circuits such as voltage regulators, by contrast, tend to utilize larger components than the typical demonstrations of printed passives and do not require resonance, thus demanding different component designs.

Here, we present the design and optimization of screen-printed inductors in the H range to achieve minimal series resistance and high performance at frequencies relevant to power electronics. Screen-printed inductors, capacitors and resistors with various component values are fabricated on flexible plastic substrates. The suitability of these components for flexible electronics is first demonstrated in a simple RLC circuit. Printed inductors and resistors are then integrated with an IC to form a step-up voltage regulator. Finally, organic light-emitting diodes (OLEDs) and a flexible lithium-ion battery are fabricated and the voltage regulator is used to power the OLEDs from the battery.

To design printed inductors for power electronics, we first predicted the inductance and DC resistance of a range of inductor geometries based on the current sheet model presented in Mohan et al.35 and fabricated inductors of different geometries to confirm the accuracy of the model. A circular shape was selected for the inductors in this work because higher inductance can be achieved with lower resistance compared to polygon geometries36. The effect of the type of ink and the number of print cycles on resistance was determined. These results were then used along with the current sheet model to design 4.7H and 7.8H inductors optimized for minimum DC resistance.

The inductance and DC resistance of a spiral inductor can be described by a few parameters: the outer diameter do, turn width w and spacing s, number of turns n and the sheet resistance Rsheet of the conductor. Fig. 1a shows a photograph of a screen-printed circular inductor with n=12, indicating the geometric parameters that determine its inductance. Inductance was calculated for a range of inductor geometries according to the current sheet model of Mohan et al.35, in which

(a) Photograph of a screen-printed inductor, indicating geometric parameters. Diameter is 3cm. Inductance (b) and DC resistance (c) for a variety of inductor geometries. Lines and markers correspond to calculated and measured values, respectively. (d,e) DC resistance of inductors L1 and L2, respectively, screen-printed from Dupont 5028 and 5064H silver inks. (f,g) SEM micrographs of films screen-printed from Dupont 5028 and 5064H, respectively.

At high frequencies, the skin effect and parasitic capacitance change an inductors resistance and inductance from their DC values. It is desirable to operate the inductor at frequencies low enough that these effects are negligible and the device behaves as a constant inductance with a constant resistance in series. Thus, in this work we analyze the relationships between the geometric parameters, inductance and DC resistance and use the results to obtain a given inductance with minimum DC resistance.

Inductance and resistance were calculated for a range of geometric parameters achievable with screen printing and expected to give inductances in the H range. Outer diameters of 3 and 5cm, line widths of 500 and 1000m and various numbers of turns were compared. The calculations were performed assuming a sheet resistance of 47m/, corresponding to a single 7m thick layer of Dupont 5028 silver microflake conductor printed using a 400-mesh screen and setting w=s. Calculated inductance and resistance values are shown in Fig. 1b,c, respectively. The model predicts that inductance and resistance both increase as the outer diameter and number of turns are increased, or as the line width is decreased.

Inductors spanning a range of geometries and inductances were fabricated on polyethylene terephthalate (PET) substrates in order to assess the accuracy of the model predictions. Measured inductance and resistance values are shown in Fig. 1b,c. While the resistances show some deviation from the expected values, mainly due to variations in thickness and uniformity of the deposited ink, the inductance shows excellent agreement with the model.

These results can be used to design inductors having a desired inductance with minimum DC resistance. For example, suppose an inductance of 2H is desired. Figure 1b shows that this inductance can be achieved using 3cm outer diameter, 500m line width and 10 turns. The same inductance can also be produced using a 5cm outer diameter, with either 500m line width and 5 turns or 1000m line width and 7 turns (also shown in the figure). Comparing the resistance of these three possible geometries in Fig. 1c reveals that the 5cm inductor with 1000m line width has the lowest resistance of 34, about 40% lower than the other two. The generalized design process to achieve a given inductance with minimum resistance is summarized as follows: first, the largest allowable outer diameter is selected based on the spatial constraints imposed by the application. Then, the line width should be made as large as possible while still allowing the desired inductance to be reached, resulting in a high fill ratio (equation (3)).

Reducing the sheet resistance of the metal films, either by increasing the thickness or by using a material with higher conductivity, can further reduce the DC resistance without impacting the inductance. Two inductors, with geometric parameters given in Table 1, referred to as L1 and L2, were fabricated with varying number of coats to evaluate the change in resistance. As the number of coats of ink was increased, the resistance decreased proportionally as expected, as shown in Fig. 1d,e for inductors L1 and L2 respectively. Figure 1d,e show that up to 6-fold reduction in resistance can be achieved, through the application of 6 coats, while the greatest reduction in resistance (5065%) occurs between 1 and 2 coats. A screen with a relatively small mesh size (400 threads per inch) was used to print these inductors because each coat of ink is relatively thin, allowing us to investigate the effect of conductor thickness on resistance. Similar thickness (and resistance) could be achieved faster by printing a smaller number of coats with a larger mesh size, as long as the patterned features remain larger than the minimum resolution of the mesh. This approach could be used to achieve the same DC resistance as the 6-coat inductors discussed here, but with higher production speed.

Figure 1d,e also show that a twofold reduction in resistance is achieved by using a higher-conductivity silver flake ink, Dupont 5064H. As seen in the SEM micrographs of films printed from the two inks, Fig. 1f,g, the lower conductivity of the 5028 ink arises from its smaller particle size and the presence of many voids between the particles in the printed film. The 5064H, on the other hand, has larger and more closely packed flakes, giving behavior closer to that of bulk silver. While this ink produced thinner films than the 5028 ink, 4m for a single coat and 22m for 6 coats, the enhancement in conductivity was substantial enough that the resistance was reduced overall.

Finally, while the inductance (equation (1)) depends on the period of the turns (w+s), the resistance (equation (5)) depends only on the line width w. Therefore, by increasing w relative to s, the resistance can be reduced even further. Two additional inductors, L3 and L4, were designed with w=2s and large outer diameter, as shown in Table 1. These inductors were fabricated using 6 coats of Dupont 5064H, shown previously to give the highest performance. L3 had inductance of 4.720 0.002H with resistance of 4.9 0.1, while L4 had 7.839 0.005H and 6.9 0.1, in good agreement with the model predictions. This represents an improvement in the L/R ratio of more than an order of magnitude relative to the values in Fig. 1, due to the enhancements in thickness, conductivity and w/s.

Although a low DC resistance is promising, assessing the suitability of the inductors for power electronics operating in the kHz-MHz range requires characterization at AC frequencies. Figure 2a shows the dependence of resistance and reactance of L3 and L4 on frequency. For frequencies below 10MHz, the resistance stays roughly constant at its DC value and the reactance increases linearly with frequency, implying a constant inductance as expected. The self-resonant frequency, defined as the frequency at which the impedance transitions from inductive to capacitive, occurs at 35.6 0.3MHz for L3 and 24.3 0.6MHz for L4. The dependence of the quality factor Q, equal to L/R, on frequency is shown in Fig. 2b. L3 and L4 reach their maximum quality factors of 35 1 and 33 1 at frequencies of 11 and 16MHz respectively. The inductance of several H and relatively high Q in the MHz frequencies make these inductors adequate replacements for conventional surface-mount inductors in low-power DC-DC converters.

To minimize the required footprint for a given capacitance, it is desirable to use a capacitor technology with a large specific capacitance, equal to the dielectric permittivity divided by the thickness of the dielectric. In this work, we chose a barium titanate composite for the dielectric, because it presents higher than other solution processed organic dielectrics. The dielectric layer was screen-printed between two layers of the silver conductor to form a metal-dielectric-metal structure. Capacitors with various dimensions on the centimeter scale, as shown in Fig. 3a, were fabricated using either two or three coats of dielectric ink, to maintain good yield. Figure 3b shows cross-sectional SEM micrographs of a representative capacitor fabricated with two coats of dielectric, for a total dielectric thickness of 21m. The top and bottom electrodes are one and six coats of 5064H, respectively. The micron-scale barium titanate particles are visible in the SEM image as brighter areas surrounded by the darker organic binder. The dielectric ink wets the bottom electrode well forming a clear interface with the printed metal film, as shown in the higher-magnification inset figure.

(a) Photographs of the capacitors with five different areas. (b) Cross-sectional SEM micrographs of a capacitor with two coats of dielectric, showing the barium titanate dielectric and silver electrodes. (c) Capacitance of capacitors with 2 and 3 coats of barium titanate dielectric and varying area, measured at 1MHz. (d) Capacitance, ESR and dissipation factor of a 2.25cm2 capacitor with 2 coats of dielectric, vs. frequency.

The capacitance scales proportionally with area as expected, as shown in Fig. 3c, with a specific capacitance of 0.53nF/cm2 for two coats of dielectric and 0.33nF/cm2 for three coats. These values correspond to a permittivity of 13. Capacitance and dissipation factor (DF) were also measured at varying frequency, as shown in Fig. 3d for a 2.25cm2 capacitor with two coats of dielectric. We found that capacitance is relatively flat over the frequency range of interest, increasing by 20% from 1 to 10MHz, while the DF increases from 0.013 to 0.023 over that same range. As the dissipation factor is a ratio of energy lost to energy stored per AC cycle, a DF of 0.02 signifies that 2% of the power handled by the capacitor is dissipated. This loss is also often expressed as a frequency-dependent equivalent series resistance (ESR), equal to DF/C, in series with the capacitor. As shown in Fig. 3d, the ESR is below 1.5 for frequencies greater than 1MHz and below 0.5 for frequencies greater than 4MHz. While the F-scale capacitances needed for DC-DC converters would require prohibitively large areas using this capacitor technology, the 100pF - nF capacitance range and low loss of these capacitors makes them suitable for other applications, such as filters and resonant circuits. A number of approaches could be used to increase the capacitance. A higher dielectric constant would increase the specific capacitance37; this can be achieved by increasing the concentration of barium titanate particles in the ink, for example. A smaller dielectric thickness could be used, although this would require a bottom electrode with lower roughness than the screen printed silver flakes. Thinner, lower roughness layers for capacitors can be deposited by inkjet printing31 or gravure printing10, which could be integrated with the screen printing process. Finally, multiple alternating layers of metal and dielectric could be printed in a stack and connected in parallel, increasing the capacitance per unit area34.

Voltage dividers, consisting of a pair of resistors, are typically used to perform the voltage measurement necessary for feedback control of a voltage regulator. For this type of application, printed resistors should present resistances in the range of k-M and low variation from device to device. Here, a single coat of screen-printed carbon ink was found to have a sheet resistance of 900/. This information was used to design two straight-line resistors (R1 and R2) and one serpentine resistor (R3) with nominal resistances of 10k, 100k and 1.5M, respectively. Resistances in between the nominal values were achieved by printing two or three coats of ink, as shown in Fig. 4 alongside photographs of the three resistors. 812 samples of each type were fabricated; in all cases, the standard deviation of the resistances was 10% or less. Samples with two or three coats tended to have slightly less variation in resistance than those with one coat. The small variation in measured resistance and close agreement with the nominal values suggests that other resistances in this range can be obtained straightforwardly by modifying the resistor geometry.

An RLC circuit, a classic textbook example of the combination of resistor, inductor and capacitor, was fabricated to demonstrate and verify the behavior of the passive components integrated into a truly printed circuit. In this circuit, an 8H inductor and a 0.8nF capacitor were connected in series and a 25k resistor was placed in parallel with them. A photograph of the flexible circuit is shown in Fig. 5a. This particular series-parallel combination was selected because its behavior is dominated by each of the three components at different frequencies, allowing the performance of each one to be highlighted and assessed. The expected frequency response of the circuit was calculated, taking into account the 7 series resistance of the inductor and the 1.3 ESR of the capacitor. The circuit diagram is shown in Fig. 5b and the calculated impedance magnitude and phase are shown in Fig. 5c and d along with measured values. At low frequency, the high impedance of the capacitor means that the behavior of the circuit is dominated by the 25k resistor. As the frequency increases, the impedance of the LC path decreases; the overall circuit behavior is capacitive until the resonant frequency of 2.0MHz. Above the resonant frequency, the inductor impedance dominates. Figure 5 clearly shows the excellent agreement between the calculated and measured values over the entire frequency range. This signifies that the model used here, where the inductors and capacitors are ideal components with series resistances, is accurate for predicting circuit behavior at these frequencies.

(a) Photograph of screen-printed RLC circuit using a series combination of 8H inductor and 0.8nF capacitor, in parallel with a 25k resistor. (b) Model of the circuit including inductor and capacitor series resistances. (c,d) Impedance magnitude (c) and phase (d) of the circuit.

Finally, the printed inductors and resistors were implemented in a step-up voltage regulator. The IC used in this demonstration was the Microchip MCP1640B14, a PWM-based synchronous boost regulator operating at 500kHz. The circuit diagram is shown in Fig. 6a. A 4.7H inductor and two capacitors (4.7F and 10F) are used as the energy storage elements and a pair of resistors is used to measure the output voltage for the feedback control. The resistor values were chosen to regulate the output voltage to 5V. The circuit was fabricated on a PCB and its performance was measured over a range of load resistances and input voltages between 3 and 4V, simulating the voltages of a lithium ion battery at various states of charge. The efficiency with printed inductors and resistors was compared to that with SMT inductor and resistors. SMT capacitors were used in all cases, because the capacitances required for this application were too large to accomplish using the printed capacitors.

(a) Diagram of voltage regulator circuit. (bd) Waveforms of (b) Vout, (c) Vsw and (d) current into the inductor, with 4.0V input voltage and 1k load resistance, measured using printed inductor. Surface-mount resistors and capacitors were used for this measurement. (e) Efficiency of a voltage regulator circuit using all surface-mount components vs. one with printed inductor and resistors, for various load resistances and input voltages. (f) Ratio of efficiencies of the surface-mount and printed circuits shown in (e).

Waveforms measured using a printed inductor are shown in Fig. 6bd, for a 4.0V input voltage and 1000 load resistance. Figure 6c shows the voltage at the Vsw terminal of the IC; inductor voltage is Vin-Vsw. Figure 6d shows current into the inductor. Efficiency of the circuits with SMT and printed components is shown as a function of input voltage and load resistance in Fig. 6e, Fig. 6f shows the ratio of efficiency with printed components to that with SMT components. The measured efficiencies with the SMT components are similar to the expected values given in the manufacturers data sheet14. At high input currents (low load resistance and low input voltage), the efficiency is substantially lower with the printed inductor than the SMT inductor due to the higher series resistance. However, with higher input voltage and higher output current the resistive losses become less significant and the performance with the printed inductor begins to approach that of the SMT inductor. For load resistances >500 with Vin=4.0V, or >750 with Vin=3.5V, the efficiency with the printed inductor is >85% of the SMT inductor.

Comparing the current waveform in Fig. 6d with the measured power loss shows that resistive losses in the inductor are primarily responsible for the difference in efficiency between the printed and SMT circuits, as expected. The measured input and output power for 4.0V input voltage and 1000 load resistance were 30.4mW and 25.8mW for the circuit with SMT components and 33.1mW and 25.2mW for the circuit with printed components, respectively. The loss in the printed circuit is therefore 7.9mW, which is 3.4mW higher than the circuit with SMT components. The RMS inductor current calculated from the waveform in Fig. 6d is 25.6mA, giving an expected power loss of 3.2mW due to its series resistance of 4.9. This is 96% of the measured 3.4mW difference in DC power. Additionally, circuits were fabricated with a printed inductor and printed resistors as well as a printed inductor and SMT resistors and no significant difference in efficiency was observed between them.

A voltage regulator was then fabricated on a flex-PCB (performance of this circuit with printed vs. SMT components is given in Supplementary Fig. S1) and connected between a flexible lithium-ion battery as the source and an array of OLEDs as the load. The OLEDs were fabricated according to Lochner et al.9 and each OLED pixel drew 0.6mA at 5V. The battery employed lithium cobalt oxide and graphite respectively as the cathode and anode and was fabricated by blade coating, the most common battery printing method.7 The capacity of the battery was 16mAh and its voltage was 4.0V at the time of testing. Figure 7 shows a photograph of the circuit on a flex-PCB, powering three OLED pixels connected in parallel. This demonstration shows the potential of the printed power components to be integrated with other flexible and organic devices to form more complex electronic systems.

We have demonstrated screen-printed inductors, capacitors and resistors with a range of values on flexible PET substrates, with the goal of replacing surface-mount components in power electronics. We have shown that the resistance of the inductors, which is of great concern for power electronics, can be reduced by more than an order of magnitude by designing the spiral with large diameter, fill ratio and line width-space width ratio and by using a thick layer of low resistivity ink. The components were integrated into a fully printed and flexible RLC circuit and show predictable electrical behavior in the kHz-MHz frequency range that is most of interest for power electronics.

A typical use case for printed power electronics would be in a wearable or product-integrated flexible electronic system powered by a flexible rechargeable battery, such as lithium ion, which produces a variable voltage depending on its state of charge. If the loads, which would include printed and organic electronic devices, require a constant voltage or one that is higher than the battery output, a voltage regulator is needed. For this reason, the printed inductor and resistors were integrated into a step-up voltage regulator alongside a conventional silicon IC, which was used to power OLEDs at a constant voltage of 5V from a variable-voltage battery source. Efficiency of the circuit surpassed 85% of that of a control circuit using surface-mount inductor and resistors over a range of load currents and input voltages. Despite the material and geometry optimization, resistive losses in the inductor remained the limiting factor of the circuit performance at high current levels (input current greater than about 10mA). At lower currents, however, the losses in the inductor were reduced and the overall performance became limited by the IC efficiency. Since many printed and organic devices require relatively low currents, such as the small OLEDs used in our demonstration, the printed power inductor can be deemed appropriate for this type of application. Higher overall converter efficiency may be achieved by utilizing an IC designed to have the highest efficiency at lower current levels.

In this work, voltage regulators were built upon conventional PCB, flex-PCB and soldering techniques for the surface-mount components and the printed components were fabricated on separate substrates. However, the low temperatures and high-viscosity inks used to produce screen-printed films should allow the passive components, as well as interconnects between devices and contact pads for surface-mount components, to be printed on arbitrary substrates. This combined with the use of existing low-temperature conductive adhesives for the surface-mount components would allow the entire circuit to be built, without subtractive processes such as PCB etching, on an inexpensive substrate such as PET. The screen-printed passive components developed in this work therefore help to pave the way for flexible electronic systems integrating energy sources and loads with high-performing power electronics, using inexpensive substrates, primarily additive processes and a minimum number of surface-mount components.

All layers of the passive components were screen printed onto flexible PET substrates, 76m in thickness, using an Asys ASP01M screen printer and stainless steel screens supplied by Dynamesh Inc. Mesh size was 400 threads per inch for the metal layers and 250 threads per inch for the dielectric and resistor layers. Screen printing was performed using a squeegee force of 55N, print speed of 60mm/s, snap-off distance of 1.5mm and Serilor squeegees with hardness of 65durometer (for metal and resistor layers) or 75durometer (for dielectric layer).

Conductive layersinductors and the contacts to the capacitors and resistorswere printed from either Dupont 5082 or Dupont 5064H silver micro-flake ink. Resistors were printed from Dupont 7082 carbon conductor. For the capacitor dielectric, Conductive Compounds BT-101 barium titanate dielectric was used. Each coat of dielectric was produced using a double pass (wet-wet) print cycle to improve uniformity of the film. For each component, the effect of multiple print cycles on component performance and variability was examined. Samples made with multiple coats of the same material were allowed to dry for 2minutes at 70C between coats. After the final coat of each material, the samples were baked at 140C for 10minutes to ensure complete drying. The screen printers automatic alignment feature was used to align subsequent layers. Contacts to the center of the inductor were made by cutting a via into the center pad and stencil printing a trace on the backside of the substrate with Dupont 5064H ink. Interconnects between printed devices were also stencil printed from Dupont 5064H. For the demonstration of printed components and SMT components together on a flex-PCB shown in Fig. 7, printed components were attached using Circuit Works CW2400 conductive epoxy and SMT components were attached using conventional soldering.

Lithium cobalt oxide (LCO) and graphite based electrodes served as the cathode and anode for the battery, respectively. Slurry for the cathode was a mixture of 80wt% LCO (MTI Corp.), 7.5wt% graphite (KS6, Timcal), 2.5wt% carbon black (Super P, Timcal) and 10wt% polyvinylidene fluoride (PVDF, Kureha Corp.) and for the anode was a mixture of 84wt% graphite, 4wt% carbon black and 13wt% PVDF. N-methyl-2-pyrrolidone (NMP, Sigma Aldrich) was used to dissolve the PVDF binder and disperse the slurry. The slurries were homogenized by stirring overnight with a vortex mixer. A 0.0005 thick stainless steel foil and 10m nickel foil served as the current collectors for the cathode and anode, respectively. The inks were printed on the current collector with a doctor blade at a print speed of 20mm/s. The electrodes were heated in an oven at 80 C for 2hr to remove the solvent. The height of the electrode after drying was ~60m resulting in theoretical capacity of 1.65mAh/cm2 based on the weight of the active material. The electrodes were cut to a dimension of 1.31.3cm2 and heated overnight in a vacuum oven at 140 C before sealing them with aluminum-laminated pouch in nitrogen filled glove box. Polypropylene based membrane separated with anode and cathode and a solution of 1M LiPF6 in EC/DEC (1:1) served as the electrolyte for the battery.

Green OLEDs were fabricated from a blend of poly(9,9-dioctylfluorene-co-n-(4-butylphenyl)-diphenylamine) (TFB) and poly((9,9-dioctylfluorene-2,7-diyl)-alt-(2,1,3-benzothiadiazole-4, 8-diyl)) (F8BT), according to the procedure outlined in Lochner et al.9.

Film thickness was measured with a Dektak stylus profilometer. The films were cut to prepare cross-sectioned samples for a study by scanning electron microscope (SEM). A FEI Quanta 3D field emission gun (FEG) SEM was used to characterize the structure of the printed films and confirm thickness measurements. SEM study was carried out under 20keV accelerating voltage and typical working distance of 10mm.

DC resistances, voltages and currents were measured with a digital multimeter. AC impedance of inductors, capacitors and circuits was measured with an Agilent E4980 LCR meter for frequencies below 1MHz and an Agilent E5061A network analyzer for frequencies above 500kHz. Voltage regulator waveforms were measured with a Tektronix TDS 5034 oscilloscope.

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This work was supported in part by the National Science Foundation under Cooperative Agreement No. ECCS-1202189. A.E.O. and C.M.L. were supported by the NSF Graduate Research Fellowship Program under Grant No. 1106400. We thank Cambridge Display Technology Limited (CDT) for supplying OLED materials and Dr. Anita Flynn, Dr. Balthazar Lechne, Joseph Corea and Yasser Khan for helpful technical discussions.

A.E.O. designed and fabricated the passive components and circuits and performed electrical characterization. I.D. performed the SEM imaging. A.M.G. fabricated the batteries. C.M.L. fabricated the OLEDs. A.E.O. wrote the manuscript, while A.C.A., I.D. and A.M.G. contributed to the experimental design and writing. All authors discussed the results and commented on the manuscript.

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