PEDOT:PSS (mixed conductor of electrons and ions)

If I read this correctly, the big selling point for UBC’s flexible, wearable display screen is energy efficiency. From a July 10, 2023 University of British Columbia (UBC) news release on EurekAlert,

Imagine a wearable patch that tracks your vital signs through changes in the colour display, or shipping labels that light up to indicate changes in temperature or sterility of food items.
These are among the potential uses for a new flexible display created by UBC researchers and announced recently in ACS Applied Materials and Interfaces.
“This device is capable of fast, realtime and reversible colour change,” says researcher Claire Preston, who developed the device as part of her master’s in electrical and computer engineering at UBC. “It can stretch up to 30 per cent without losing performance. It uses a colour-changing technology that can be used for visual monitoring. And it is relatively cheap to manufacture.”
Previous attempts at creating stretchable displays have involved complex designs and materials, limiting their stretchability and optical quality. In this new research, scientists leaned on electrochromic displays—which are able to reversibly change colour, while requiring low power consumption—to overcome these limitations. [emphasis mine]
“We used PEDOT:PSS, an electrochromic material that consists of a conductive polymer combined with an ionic liquid, resulting in a stretchable electrode that acts as both the electrochromic element and the ion storage layer. This simplifies the device’s architecture and eliminates the need for a separate stretchable conductor,” says Ms. Preston.
The display is transparent and feels like a stiff rubber band. To support the thin layers of PEDOT and allow them to elongate without breaking, the team added a solid polymer electrolyte and a stretchable encapsulation material called styrene-ethylene-butylene-styrene (SEBS).
“The potential uses for this stretchable display are significant. It could be integrated into wearable devices for biometric monitoring, allowing for real-time visual feedback on vital signs. The displays could also be used in robotic skin, enabling robots to display information and interact more intuitively with humans,” noted senior author Dr. John Madden, a professor of electrical and computer engineering who supervised the work.
Additionally, the low power consumption and cost-effectiveness of this technology make it attractive for use in disposable applications such as indicator patches for medical purposes or smart packaging labels for sensitive shipments. It could also be used to actively change the colour of jackets, hats and other garments.
“While there is need for more work to integrate this device into everyday devices, this breakthrough brings us one step closer to a future where flexible and stretchable displays are a common part of our daily lives,” Dr. Madden added.

Here’s a link to and a citation for the paper,

Intrinsically Stretchable Integrated Passive Matrix Electrochromic Display Using PEDOT:PSS Ionic Liquid Composite by Claire Preston, Yuta Dobashi, Ngoc Tan Nguyen, Mirza Saquib Sarwar, Daniel Jun, Cédric Plesse, Xavier Sallenave, Frédéric Vidal, Pierre-Henri Aubert, and John D. W. Madden. ACS Appl. Mater. Interfaces 2023, 15, 23, 28288–28299 DOI: https://doi.org/10.1021/acsami.3c02902 Publication Date: June 5, 2023 Copyright © 2023 The Authors. Published by American Chemical Society

This paper is open access.

A July 1, 2020 news item on ScienceDaily announces work which researchers are hopeful will allow them exert more control over neuromorphic devices’ speed of response,

“Neuromorphic” refers to mimicking the behavior of brain neural cells. When one speaks of neuromorphic computers, they are talking about making computers think and process more like human brains-operating at high-speed with low energy consumption.
Despite a growing interest in polymer-based neuromorphic devices, researchers have yet to establish an effective method for controlling the response speed of devices. Researchers from Tohoku University and the University of Cambridge, however, have overcome this obstacle through mixing the polymers PSS-Na and PEDOT:PSS, discovering that adding an ion conducting polymer enhances neuromorphic device response time.
…

A June 24, 2020 Tohoku University press release (also on EurekAlert), which originated the news item, provides a few more technical details,

Polymers are materials composed of long molecular chains and play a fundamental aspect in modern life from the rubber in tires, to water bottles, to polystyrene. Mixing polymers together results in the creation of new materials with their own distinct physical properties.
Most studies on neuromorphic devices based on polymer focus exclusively on the application of PEDOT: PSS, a mixed conductor that transports both electrons and ions. PSS-Na, on the other hand, transports ions only. By blending these two polymers, the researchers could enhance the ion diffusivity in the active layer of the device. Their measurements confirmed an increase in device response time, achieving a 5-time shorting at maximum. The results also proved how closely related response time is to the diffusivity of ions in the active layer.
“Our study paves the way for a deeper understanding behind the science of conducting polymers.” explains co-author Shunsuke Yamamoto from the Department of Biomolecular Engineering at Tohoku University’s Graduate School of Engineering. “Moving forward, it may be possible to create artificial neural networks composed of multiple neuromorphic devices,” he adds.

Here’s a link to and a citation for the paper,

Controlling the Neuromorphic Behavior of Organic Electrochemical Transistors by Blending Mixed and Ion Conductors by Shunsuke Yamamoto and George G. Malliaras. ACS [American Chemical Society] Appl. Electron. Mater. 2020, XXXX, XXX, XXX-XXX DOI: https://doi.org/10.1021/acsaelm.0c00203 Publication Date:June 15, 2020 Copyright © 2020 American Chemical Society

This paper is behind a paywall.

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Tag Archives: PEDOT:PSS (mixed conductor of electrons and ions)

Wearable screen (flexible display) from the University of British Columbia (UBC)

Improving neuromorphic devices with ion conducting polymer