Category Archives: Flexible Displays

The global active-matrix organic light-emitting diode (AMOLED) panel market is forecast to surge 63 percent in 2017 from a year ago to $25.2 billion on growing demand for AMOLED panels in the smartphone and TV industries, according to IHS Markit (Nasdaq: INFO).

“Growing use of AMOLED panels in smartphones and rising sales of AMOLED TVs will mainly drive the growth of the AMOLED panel market,” said Ricky Park, director of display research at IHS Markit. “A steady rise in demand from head-mount displays and mobile PCs would also prop up the market.”

AMOLED_shipment_revenue_forecast_2

The demand for AMOLED displays has rapidly risen in the smartphone market in particular as the flexible substrate allows phones to be produced in various designs with a lighter and slimmer bodies. This year, leading smartphone makers have competitively rolled out premium phones that boast a very narrow bezel or nearly bezel-less designs.

“The AMOLED display market is also expected to get a boost from Apple’s decision to use an AMOLED screen in its iPhone series to be released later this year, and Chinese smartphone makers’ moving to newer applications of AMOLED panels,” Park said. “To meet the burgeoning demand, South Korean and Chinese display makers have been heavily investing in Generation 6 AMOLED fabs.”

According to Display Long-term Demand Forecast Tracker from IHS Markit, the TV industry, the second biggest market for AMOLED panels, will also play a major role in fostering the growth of the AMOLED panel market this year. LG Display, which currently dominates the AMOLED TV panel market, is set to embark on the operation of its second AMOLED TV panel line E4-2 with an aim to mass produce panels in the latter half of this year.

Bumped up by an increase in output, the AMOLED TV panel market is forecast to grow from 890,000 units last year to 1.5 million units this year. By 2021, the AMOLED panel market is projected to expand at a compound annual growth rate of 22 percent to exceed $40 billion.

As active-matrix organic light-emitting diode (AMOLED) displays quickly displace liquid crystal displays (LCDs) in smartphones, panel makers are rapidly adding new production capacity, accelerating the demand for the fine metal mask (FMM), a critical production component used to manufacture red-green-blue (RGB) AMOLEDs. The FMM market is forecast to grow at a compound annual growth rate (CAGR) of 38 percent from $234 million in 2017 to $1.2 billion in 2022, according to IHS Markit (Nasdaq: INFO).

 

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In the AMOLED manufacturing process, FMM is a production component used to pattern individual red, green and blue subpixels. A heating source evaporates organic light-emitting materials, but vapor deposition can only be controlled precisely with the use of a physical mask. FMM — a metal sheet, only tens of microns thick, with millions of very small holes per panel — is the only production-proven method of accurately depositing RGB color components in high-resolution displays.

“FMM has become a bottleneck in the supply of AMOLED panels due to the manufacturing technology challenges posed by increasing resolutions and a limited supply base. As pixels per inch (PPI) increase, thinner FMMs with finer dimensions are required, which reduce mask production yield and useable lifetime,” said Jerry Kang, senior principal analyst of display research at IHS Markit.

Dai Nippon Printing (DNP) is the dominant FMM supplier, owing to its proprietary etching technology for very thin metal foils and mass production experience. Currently, DNP’s FMMs are used to fabricate the vast majority of AMOLED smartphone panels, and exclusively for high-end quad high definition (QHD) resolutions. “Most panel makers are now trying to procure DNP’s FMM in hopes of being able to quickly ramp new fabs to high yields,” Kang said.

The critical nature of FMM and rapid demand growth are encouraging a number of companies to develop alternative FMM technologies and enter the market. Panel makers are also encouraging new players as a second source to mitigate supply chain risk and create price competition. As the supply of FMM is a determinant factor in the AMOLED display market to meet its projected growth rates, and with the FMM market forecast to grow five times its current size by 2022, FMM is garnering intense interest from both set and panel makers alike and creating new opportunities for suppliers.

The AMOLED Shadow Mask Technology & Market – 2017 report from IHS Markit provides a comprehensive analysis of the latest technology and market trends for FMMs and open masks, as well as mask and panel supplier status updates, including forecasts of revenues, units, area and prices from 2014 to 2022.

 

Taiwan is the world’s largest consumer of semiconductor materials for the seventh consecutive year, bringing new opportunities in this increasingly critical sector.  SEMICON Taiwan (13-15 September), held at Taipei’s Nangang Exhibition Center, will feature over 1,700 booths and 700 exhibitors, and more than 45,000 attendees from the global electronics manufacturing supply chain. This year, in addition to the much-anticipated Executive Summit, themed “Transformation: A Key to Solution,” 27 international forums will be held, exploring major issues. Speakers from TSMC, UMC, Powerchip, NVIDIA, Micron and Amkor will share their insights on trends and strategies of the next-generation electronics industry.

According to the SEMI Material Market Data Report, Taiwan’s semiconductor materials consumption was US$9.8 billion in 2016 − the world’s largest. Global semiconductor manufacturing equipment billings reached US$13.1 billion in Q1 2017, exceeding the record quarterly high set in Q3 2000. These figures signal that application drivers will continue to drive the development of a supply chain feeding their manufacturing processes, equipment and materials.

“As SEMICON Taiwan celebrates its 22nd year, the exhibition area will be expanded to closely align with the four major trends of applications in the market, which include Internet of Things (IoT), Smart Manufacturing, Smart Transportation, and Smart Medtech,” said Terry Tsao, president of SEMI Taiwan. “This year, SEMICON Taiwan aims to increasingly connect the entire manufacturing ecosystem vertically and horizontally. In addition, it will provide an overview of market trends and leading technologies in the industry, with forums and business matching activities which will enable collaboration and new opportunities.”

Theme Pavilions and Region Pavilions Focus on Opportunities

In addition to the eight customary theme pavilions, five new pavilions are featured this year, and to promote cross-border collaboration, eight regional pavilions are offered. The 21 pavilions include:

Theme Pavilions
  • Automated Optical Inspection (AOI)
  • Chemical Mechanical Planarization (CMP)
  • High-Tech Facility
  • Materials
  • Precision Machinery
  • Secondary Market
  • Smart Manufacturing & Automation
  • Taiwan Localization

 
New Theme Pavilions
  • Circular Economy
  • Compound Semiconductor
  • Flexible Hybrid Electronics/Micro-LED
  • Laser
  • Opto Semiconductor

 
Regional Pavilions
  • Cross-Strait
  • German
  • Holland High-Tech
  • Korean
  • Kyushu (Japan)
  • Okinawa (Japan)
  • Silicon Europe
  • Singapore

Co-located with SEMICON Taiwan 2017, the SiP Global Summit will discuss three key system-in-package topics:

  • Package Innovation in Automotive
  • 3D IC, 3D interconnection for AI and High-end Computing
  • Innovative Embedded Substrate and Fan-Out Technology to Enable 3D-SiP Devices

Participants will share trends on 2.5D/3D IC technologies, and the evolution and challenges of embedded technologies and wafer level packaging.

This is the first year that the International Test Conference (ITC) will be co-located with SEMICON Taiwan 2017, also marking the first time that ITC is held in Asia. The conference will focus on the rapid growth of emerging applications like IoT and automotive electronics, and how testing technologies are challenged by rapid advancements of manufacturing processes, 3D stacking and SiP.

For more information about SEMICON Taiwan 2017, please visit www.semicontaiwan.org or follow us on Facebook.

A new type of semiconductor may be coming to a high-definition display near you. Scientists at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) have shown that a class of semiconductor called halide perovskites is capable of emitting multiple, bright colors from a single nanowire at resolutions as small as 500 nanometers.

A 2-D plate showing alternating cesium lead chloride (blue) and cesium lead bromide (green) segments. Credit: Letian Dou/Berkeley Lab and Connor G. Bischak/UC Berkeley

A 2-D plate showing alternating cesium lead chloride (blue) and cesium lead bromide (green) segments. Credit: Letian Dou/Berkeley Lab and Connor G. Bischak/UC Berkeley

The findings, published online this week in the early edition of the Proceedings of the National Academy of Sciences, represent a clear challenge to quantum dot displays that rely upon traditional semiconductor nanocrystals to emit light. It could also influence the development of new applications in optoelectronics, photovoltaics, nanoscopic lasers, and ultrasensitive photodetectors, among others.

The researchers used electron beam lithography to fabricate halide perovskite nanowire heterojunctions, the junction of two different semiconductors. In device applications, heterojunctions determine the energy level and bandgap characteristics, and are therefore considered a key building block of modern electronics and photovoltaics.

The researchers pointed out that the lattice in halide perovskites is held together by ionic instead of covalent bonds. In ionic bonds, atoms of opposite charges are attracted to each other and transfer electrons to each other. Covalent bonds, in contrast, occur when atoms share their electrons with each other.

“With inorganic halide perovskite, we can easily swap the anions in the ionic bonds while maintaining the single crystalline nature of the materials,” said study principal investigator Peidong Yang, senior faculty scientist at Berkeley Lab’s Materials Sciences Division. “This allows us to easily reconfigure the structure and composition of the material. That’s why halide perovskites are considered soft lattice semiconductors. Covalent bonds, in contrast, are relatively robust and require more energy to change. Our study basically showed that we can pretty much change the composition of any segment of this soft semiconductor.”

In this case, the researchers tested cesium lead halide perovskite, and then they used a common nanofabrication technique combined with anion exchange chemistry to swap out the halide ions to create cesium lead iodide, bromide, and chloride perovskites.

Each variation resulted in a different color emitted. Moreover, the researchers showed that multiple heterojunctions could be engineered on a single nanowire. They were able to achieve a pixel size down to 500 nanometers, and they determined that the color of the material was tunable throughout the entire range of visible light.

The researchers said that the chemical solution-processing technique used to treat this class of soft, ionic-bonded semiconductors is far simpler than methods used to manufacture traditional colloidal semiconductors.

“For conventional semiconductors, fabricating the junction is quite complicated and expensive,” said study co-lead author Letian Dou, who conducted the work as a postdoctoral fellow in Yang’s lab. “High temperatures and vacuum conditions are usually involved to control the materials’ growth and doping. Precisely controlling the materials composition and property is also challenging because conventional semiconductors are ‘hard’ due to strong covalent bonding.”

To swap the anions in a soft semiconductor, the material is soaked in a special chemical solution at room temperature.

“It’s a simple process, and it is very easy to scale up,” said Yang, who is also a professor of chemistry at UC Berkeley. “You don’t need to spend long hours in a clean room, and you don’t need high temperatures.”

The researchers are continuing to improve the resolution of these soft semiconductors, and are working to integrate them into an electric circuit.

The problem is a fundamental incompatibility in communication styles.

That conclusion might crop up during divorce proceedings, or describe a diplomatic row. But scientists designing polymers that can bridge the biological and electronic divide must also deal with incompatible messaging styles. Electronics rely on racing streams of electrons, but the same is not true for our brains.

“Most of our technology relies on electronic currents, but biology transduces signals with ions, which are charged atoms or molecules,” said David Ginger, professor of chemistry at the University of Washington and chief scientist at the UW’s Clean Energy Institute. “If you want to interface electronics and biology, you need a material that effectively communicates across those two realms.”

Lead author Rajiv Giridharagopal, left, and co-author Lucas Flagg, right, standing next to an atomic force microscope. Credit: Dane deQuilettes

Lead author Rajiv Giridharagopal, left, and co-author Lucas Flagg, right, standing next to an atomic force microscope. Credit: Dane deQuilettes

Ginger is lead author of a paper published online June 19 in Nature Materials in which UW researchers directly measured a thin film made of a single type of conjugated polymer — a conducting plastic — as it interacted with ions and electrons. They show how variations in the polymer layout yielded rigid and non-rigid regions of the film, and that these regions could accommodate electrons or ions – but not both equally. The softer, non-rigid areas were poor electron conductors but could subtly swell to take in ions, while the opposite was true for rigid regions.

Organic semiconducting polymers are complex matrices made from repeating units of a carbon-rich molecule. An organic polymer that can accommodate both types of conduction — ion and electrons — is the key to creating new biosensors, flexible bioelectronic implants and better batteries. But differences in size and behavior between tiny electrons and bulky ions have made this no easy task. Their results demonstrate how critical the polymer synthesis and layout process is to the film’s electronic and ionic conductance properties. Their findings may even point the way forward in creating polymer devices that can balance the demands of electronic transport and ion transport.

“We now understand the design principles to make polymers that can transport both ions and electrons more effectively,” said Ginger. “We even demonstrate by microscopy how to see the locations in these soft polymer films where the ions are transporting effectively and where they aren’t.”

Ginger’s team measured the physical and electrochemical properties of a film made out of poly(3-hexylthiophene), or P3HT, which is a relatively common organic semiconductor material. Lead author Rajiv Giridharagopal, a research scientist in the UW Department of Chemistry, probed the P3HT film’s electrochemical properties in part by borrowing a technique originally developed to measure electrodes in lithium-ion batteries.

The approach, electrochemical strain microscopy, uses a needle-like probe suspended by a mechanical arm to measure changes in the physical size of an object with atomic-level precision. Giridharagopal discovered that, when a P3HT film was placed in an ion solution, certain regions of the film could subtly swell to let ions flow into the film.

“This was an almost imperceptible swelling — just 1 percent of the film’s total thickness,” said Giridharagopal. “And using other methods, we discovered that the regions of the film that could swell to accommodate ion entry also had a less rigid structure and polymer arrangement.”

More rigid and crystalline regions of the film could not swell to let in ions. But the rigid areas were ideal patches for conducting electrons.

Ginger and his team wanted to confirm that structural variations in the polymer were the cause of these variations in electrochemical properties of the film. Co-author Christine Luscombe, a UW associate professor of materials science and engineering and member of the Clean Energy Institute, and her team made new P3HT films that had different levels of rigidity based on variations in polymer arrangement.

By subjecting these new films to the same array of tests, Giridharagopal showed a clear correlation between polymer arrangement and electrochemical properties. The less rigid and more amorphous polymer layouts yielded films that could swell to let in ions, but were poor conductors of electrons. More crystalline polymer arrangements yielded more rigid films that could easily conduct electrons. These measurements demonstrate for the first time that small structural differences in how organic polymers are processed and assembled can have major consequences for how the film accommodates ions or electrons. It may also mean that this tradeoff between the needs of ion and electrons is unavoidable. But these results give Ginger hope that another solution is possible.

“The implication of these findings is that you could conceivably embed a crystalline material — which could transport electrons — within a material that is more amorphous and could transport ions,” said Ginger. “Imagine that you could harness the best of both worlds, so that you could have a material that is able to effectively transport electrons and swell with ion uptake — and then couple the two with one another.”

UPV/EHU-University of the Basque Country’s researchers have explored superelasticity properties on a nanometric scale based on shearing an alloy’s pillars down to nanometric size. In the article published by the prestigious scientific journal Nature Nanotechnology, the researchers have found that below one micron in diameter the material behaves differently and requires much higher stress for it to be deformed. This superelastic behaviour is opening up new channels in the application of microsystems involving flexible electronics and microsystems that can be implanted into the human body.

Superelasticity is a physical property by which it is possible to deform a material to a considerable extent, up to 10%, which is much higher than that of elasticity. So when stress is applied to a straight rod, the rod can form a U-shape and when the stress applied is removed, the rod fully regains its original shape. Although this has been amply proven in macroscopic materials, “until now no one had been able to explore these superelasticity properties in micrometric and nanometric sizes,” explained José María San Juan, lead researcher of the article published by Nature Nanotechnology and a UPV/EHU professor.

Researchers in the UPV/EHU’s Department of Condensed Matter Physics and Applied Physics II have managed to see that “the superelastic effect is maintained in really small devices in a copper-aluminium-nickel alloy”. It is an alloy with shape memory on which the research team has been working for over 20 years on a macroscopic level: Cu-14Al-4Ni, an alloy that displays superelasticity in ambient temperature.

Pillars were built using the Cu-Al-Ni alloy, each one with a diameter measuring about 500 nm (half a micrometre). Credit: José María San Juan / UPV/EHU

Pillars were built using the Cu-Al-Ni alloy, each one with a diameter measuring about 500 nm (half a micrometre). Credit: José María San Juan / UPV/EHU

By using a piece of equipment known as a Focused Ion Beam, “an ion cannon that acts as a kind of atomic knife that shears the material”, explained San Juan, they built micropillars and nanopillars of this alloy with diameters ranging between 2 μm and 260 nm –a micrometre is one millionth of a metre and a nanometre one thousand-millionth of a metre–. And to them they applied a stress using a sophisticated instrument known as a nanoindenter, which “allows extremely small forces to be applied,” and then they measured their behaviour.

The researchers have for the first time confirmed and quantified that in diameters of less than a micrometre there is a considerable change in the properties relating to the critical stress for superelasticity. “The material starts to behave differently and needs a much higher stress for this to take place. The alloy continues to display superelasticity but for much higher stresses”. San Juan highlights the novelty of this increase in critical stress linked to size, and also stresses that they have been able to explain the reason for this change in behaviour: “We have proposed an atomic model that allows one to understand why and how the atomic structure of these pillars changes when a stress is applied”.

Microsystems involving flexible electronics and devices that can be implanted in the human body

The UPV/EHU professor highlighted the importance of this discovery, “spectacular superelastic behaviour on a small scale”, which opens up new channels in the design of strategies for applying alloys with shape memory to develop flexible microsystems and electromechanical nanosystems. “Flexible electronics is very much present on today’s market, it is being increasingly used in garments, sports footwear, in various displays, etc.” He also affirmed that all this is of crucial importance in developing smart healthcare devices of the Lab-on-a-chip type that can be implanted into the human body. “It will be possible to build tiny micropumps or microactuators that can be implanted on a chip, and which will allow a substance to be released and regulated inside the human body for a range of medical treatments.”

It is a discovery that “is expected to have great scientific and technological repercussions and offer the potential to revolutionise various aspects in related fields,” concluded San Juan, and he welcomed the fact that “we have managed to transfer all the necessary knowledge and to acquire the working tools that the most advanced centres can avail themselves of to open up a new line of research which can be fully developed at the UPV/EHU”.

FlexTech’s annual Flexible Electronics Conference and Exhibit – 2017FLEX – is set for the Hyatt Regency Hotel & Spa in Monterey, Calif.  from June 19-22, 2017. Consistently attracting 500+registrants, the event is the premier technology conference for the emerging flexible electronics industry. Twenty-six sessions will cover the landscape of flexible hybrid electronics and printed electronics, including R&D, manufacturing and applications. Short courses and networking events round out 2017FLEX.

According to Zion Research, “global demand for the flexible electronics market was valued at $5.13 billion in 2015 and is expected to generate revenue of $16.5 billion by 2021, growing at a CAGR of slightly above 21 percent between 2016 and 2021.”  Key elements of the market include flex displays, sensors, batteries, and memory. Applications also abound in the automotive, consumer electronics, healthcare, and industrial sectors.

While technology advancement and accelerating to manufacturing are the primary themes of the FLEX Conference, applications and business trends are highlighted on the opening day:

  • Applied Materials Keynote by Brian Shieh, corporate VP and GM, Display Business Group, on the flexible display market
  • Flex, the global EMS provider, and NextFlex, America’s Flexible Hybrid Electronics Manufacturing Institute, on the challenges and solutions for manufacturing flexible and stretchable electronics
  • Libelium on how new IOT platforms that integrate sensors to monitor and control body parameters will lead to better healthcare for billions
  • Experience Co-Creation Partnership on the ten starting points for the development of flexible/hybrid sensors for agriculture and food
  • NovaCentrix on the OE-A Roadmap 2017, giving an outlook on organic and printed electronics developments and prospects
  • Gartner Group on when flexible electronics will reach critical mass

Sessions are planned for FHE manufacturing, standards and reliability, substrates, conductors, inspection, encapsulation and coating, nanoparticle inks, direct write, and 3D printing, among others. Well-known companies will present, such as Molex, Panasonic, Eastman Chemical, and Northrup Grumman, as well as leading universities, and the U.S. Army and U.S. Air Force Research Laboratories.

Among the R&D organizations presenting at 2017FLEX are CEA-LITEN (France), ETRI (South Korea), Flexible Electronics & Display Center (USA), Fraunhofer Institute (Germany), Holst Center (Netherlands), National Research Council (Canada), PARC (USA), and VTT (Finland). Topics of the presentations range from new forms of flexible substrates to TFT and OLED pilot lines to printed health monitoring sensors.

The exhibit floor, short courses and networking opportunities round out the event, as well as many member-only meetings.  FlexTech, the Nano-Bio Manufacturing Consortium (NBMC) and NextFlex hold member and planning meetings for the governing councils, technical councils and technology working groups.  Initiatives in manufacturing, mobile power, e-health, as well as project proposals will be discussed, all buoyed by the information shared during the technical conference.

For more information on 2017FLEX, please visit:  www.semi.org/en/2017-flex

Today FlexTech, A SEMI Strategic Association Partner, announced the full agenda for the inaugural flexible hybrid electronics (FHE) conference coming up on May 31-June 1 in Seoul at COEX Exhibition Center.  The new conference, 2017FLEX Korea, focusing on the theme “A Practical Path to Flexible Hybrid Electronics,” is brought to action with a market-focused agenda and presentations on Displays, Wearables, Sensors, OLED, Quantum Dot, Micro LED, Head Up Display, Roll-to-Roll and 3D Printing by experts from both the industry and academia.

2017FLEX Korea features a technical conference, a Short Course, and networking opportunities. The two-day technical conference includes four sessions on critical areas for FHE success. The four sessions will feature 14 technology experts from Korea, America, Asia and Europe representing organizations active in the FHE area, including:

  • Display Applications: KIMM and UIN3D
  • Wearables and Sensors Applications: KT and KITECH
  • Emerging Markets Applications: EyeDis, KOPTI, and KITECH
  • Core Technology Applications: Coatema Coating Machinery GmbH, Daelim Chemical, Dankook University, DuPont, Kolon Industries, Nanosys, and Universal Display Corporation

Three keynotes will set the stage for all of the other topics, including:

  • LG Display: “Flexible Display Changes Your Life” by Joon Young Yang, head of OLED Advanced Research Division
  • FlexTech: “Emerging Product Opportunities and the Worldwide Ecosystem of FHE” by Melissa Grupen-Shemansky, Chief Technology Officer
  • Samsung Advanced Institute of Technology: “Quantum Dot Display” by Shinae Jun, research master

Combining traditional IC manufacturing with printed electronics, FHE is the leading technical approach to design and manufacture devices for fast-growth markets. Flexible and printed electronics applications have the potential to create business opportunities in growing market opportunities such as wearables, health care, flexible displays and other advanced applications. A 3-hour Short Course is intended for individuals and organizations seeking a comprehensive overview on the Printed Electronics industry.

“We are pleased to hold the 2017FLEX Korea conference,” said Hyun-Dae CHO, president of SEMI Korea. “We hope the conference will provide you with the insights into the FHE industry and you will also find networking opportunities at the event.”

Register by May 26 to reserve your spot with a discounted price: http://www.semi.org/ko/flex-korea-register

Orbotech Ltd., a provider of process innovation technologies, solutions and equipment that are enabling the transformation of the global electronics manufacturing industry, announced today that Tianma Micro-electronics Co. Ltd. (“Tianma”), a producer of display solutions with over three decades of experience in the Flat Panel Display (FPD) field, has selected Orbotech’s ArrayChecker and Automated Optical Inspection (AOI) solutions for its production line upgrade to flexible AMOLED technology.

Tianma has invested approximately $1.8 billion to extend its Gen 6 AMOLED fab in Wuhan, China. The Wuhan fab is designed for the production of flexible AMOLED display panels which are rapidly gaining popularity in consumer electronics devices.  When the new line ramps up to mass production during the second half of 2017, Tianma expects to achieve capacity of 30,000 panels per month, with an additional 30,000 per month capacity increase in 2018.

According to the IHS Display Long-Term Demand Forecast Tracker Q4 2016, “AMOLED’s share of overall FPD revenue will increase to almost 30% in 2023. Revenue from AMOLED displays is expected to grow from $15 billion in 2016 to $36 billion in 2023 for a CAGR of 17%.”

“We are delighted that Tianma has selected our solutions for their flex AMOLED fabrication line,” stated Mr. Edu Meytal, President of Orbotech Pacific Display.  “These solutions, which were designed to enable the new manufacturing processes required to produce flex AMOLED displays, will enable our customers to produce the most advanced FPD products available with high yields.  This deal builds upon past successful implementations of Orbotech’s inspection, testing and repair solutions.”

As electronics become increasingly pervasive in our lives – from smart phones to wearable sensors – so too does the ever rising amount of electronic waste they create. A United Nations Environment Program report found that almost 50 million tons of electronic waste were thrown out in 2017–more than 20 percent higher than waste in 2015.

Troubled by this mounting waste, Stanford engineer Zhenan Bao and her team are rethinking electronics. “In my group, we have been trying to mimic the function of human skin to think about how to develop future electronic devices,” Bao said. She described how skin is stretchable, self-healable and also biodegradable – an attractive list of characteristics for electronics. “We have achieved the first two [flexible and self-healing], so the biodegradability was something we wanted to tackle.”

The team created a flexible electronic device that can easily degrade just by adding a weak acid like vinegar. The results were published May 1 in the Proceedings of the National Academy of Sciences.

A newly developed flexible, biodegradable semiconductor developed by Stanford engineers shown on a human hair. Credit: Bao Lab

A newly developed flexible, biodegradable semiconductor developed by Stanford engineers shown on a human hair. Credit: Bao Lab

“This is the first example of a semiconductive polymer that can decompose,” said lead author Ting Lei, a postdoctoral fellow working with Bao.

In addition to the polymer – essentially a flexible, conductive plastic – the team developed a degradable electronic circuit and a new biodegradable substrate material for mounting the electrical components. This substrate supports the electrical components, flexing and molding to rough and smooth surfaces alike. When the electronic device is no longer needed, the whole thing can biodegrade into nontoxic components.

Biodegradable bits

Bao, a professor of chemical engineering and materials science and engineering, had previously created a stretchable electrode modeled on human skin. That material could bend and twist in a way that could allow it to interface with the skin or brain, but it couldn’t degrade. That limited its application for implantable devices and – important to Bao – contributed to waste.

Bao said that creating a robust material that is both a good electrical conductor and biodegradable was a challenge, considering traditional polymer chemistry. “We have been trying to think how we can achieve both great electronic property but also have the biodegradability,” Bao said.

Eventually, the team found that by tweaking the chemical structure of the flexible material it would break apart under mild stressors. “We came up with an idea of making these molecules using a special type of chemical linkage that can retain the ability for the electron to smoothly transport along the molecule,” Bao said. “But also this chemical bond is sensitive to weak acid – even weaker than pure vinegar.” The result was a material that could carry an electronic signal but break down without requiring extreme measures.

In addition to the biodegradable polymer, the team developed a new type of electrical component and a substrate material that attaches to the entire electronic component. Electronic components are usually made of gold. But for this device, the researchers crafted components from iron. Bao noted that iron is a very environmentally friendly product and is nontoxic to humans.

The researchers created the substrate, which carries the electronic circuit and the polymer, from cellulose. Cellulose is the same substance that makes up paper. But unlike paper, the team altered cellulose fibers so the “paper” is transparent and flexible, while still breaking down easily. The thin film substrate allows the electronics to be worn on the skin or even implanted inside the body.

From implants to plants

The combination of a biodegradable conductive polymer and substrate makes the electronic device useful in a plethora of settings – from wearable electronics to large-scale environmental surveys with sensor dusts.

“We envision these soft patches that are very thin and conformable to the skin that can measure blood pressure, glucose value, sweat content,” Bao said. A person could wear a specifically designed patch for a day or week, then download the data. According to Bao, this short-term use of disposable electronics seems a perfect fit for a degradable, flexible design.

And it’s not just for skin surveys: the biodegradable substrate, polymers and iron electrodes make the entire component compatible with insertion into the human body. The polymer breaks down to product concentrations much lower than the published acceptable levels found in drinking water. Although the polymer was found to be biocompatible, Bao said that more studies would need to be done before implants are a regular occurrence.

Biodegradable electronics have the potential to go far beyond collecting heart disease and glucose data. These components could be used in places where surveys cover large areas in remote locations. Lei described a research scenario where biodegradable electronics are dropped by airplane over a forest to survey the landscape. “It’s a very large area and very hard for people to spread the sensors,” he said. “Also, if you spread the sensors, it’s very hard to gather them back. You don’t want to contaminate the environment so we need something that can be decomposed.” Instead of plastic littering the forest floor, the sensors would biodegrade away.

As the number of electronics increase, biodegradability will become more important. Lei is excited by their advancements and wants to keep improving performance of biodegradable electronics. “We currently have computers and cell phones and we generate millions and billions of cell phones, and it’s hard to decompose,” he said. “We hope we can develop some materials that can be decomposed so there is less waste.”