fantastic plastic

Acreo, in collaboration with Linköping University, are developing low-cost electronics printed on paper. Their focus is on electrochemical devices, such as electrochromic displays. The change between bright and dark state is based on the difference in absorbtion of a polymer, e.g. PEDOT:PSS, in the oxidised versus the reduced state. Switching occurs at low voltages (0.6 to 0.9V), but is inherently slow (~1s).
The difference in conductivity of polymers, such as PEDOT:PSS, PANI, Polypyrrole and Polyhexylthiophene, between different redox states can be used to fabricate electrochemical transistors.

Other applications exploiting a change in material properties upon oxidation/reduction are a wettability switch and and a switchable polariser.

Acreo is using different printing techniques (e.g. screen- and offset-printing) to deposit layers such as the conducting polymer and polymer electrolyte layers.

The New Scientist is reporting on flexible electrochromic displays developed by Siemens:

The display consists of a layer of electrochromic material sandwiched between two electrode layers. The material changes from one colour to another when stimulated by an electric current. The top electrode layer is made from transparent plastic, so the display can be seen clearly through it.
The electrochromic mixture used by Siemens, which enables the screen to work so rapidly, has not been disclosed, but commonly used electrochromic substances include conductive polymers such as polyaniline. […]
The display is controlled by a printed circuit and can be powered by a very thin printable battery or a photovoltaic cell. The goal is to be able to create the entire device – the display and its power source - using the same printing method, so that manufacturing costs would be as low as possible. Siemens expects to achieve this by 2007.

Aveso, Inc. [formerly known as Commotion solutions], a recent spin-out from The Dow Chemical Company, announced today its entry into the $50-billion electronic display market. Aveso is developing paper-thin microelectronic devices that feature the company’s proprietary printed electronic display technology integrated with electronic components including microprocessors, power, radio frequency (RF) antenna and user interface. The integrated devices, typically less than half the thickness of a standard credit card, are produced using existing, readily available high-speed print processes and capacity. They can be rapidly scaled using cost-effective, mature manufacturing processes, making it possible for the first time to integrate electronic displays into printed high volume products like credit cards and labels. Integrated Aveso displays are expected to enable original equipment manufacturers (OEMs) and brand owners in these markets grow revenue, reduce fraud and theft, and improve safety and security. […]

Aveso is actively developing solutions for a variety of card and label applications, including:
• Display-enabled credit cards that generate a one-time password to support secure Internet-based transactions. Integrating a display into a financial credit card eliminates the need for a separate hardware token, providing card issuers with a simple, cost-effective strong authentication tool for broad customer deployment.
• Display-enabled stored value, loyalty or gift cards that provide immediate access to balance, usage or expiration information. Added display functionality represents a natural product extension for the exploding gift card market.
• Product labels that allow brand owners and consumers to verify product authenticity directly on the package through touch or radio frequency (RF) activation. The display-based “covert-to-overt” label represents a cost-effective, novel technology to guard against product counterfeiting in markets such as software and pharmaceuticals.

In related news, Aveso announced

its membership in the Smart Card Alliance (SCA), a not-for-profit organization formed in 2000 for the purpose of educating business and the public about smart card technology and its many uses.

A few more details on their display technology can be found on their website:

Traditional electrochromic materials rely on a “redox dye” that must serve as both the redox material and the color-changing agent, resulting in an unsatisfactory tradeoff between contrast, lifetime (number of cycles), and available color sets.
In contrast to traditional electrochromic systems, the Aveso system separates the function of the redox material from the dye. The Aveso system is based on the following electrochemical-chemical principle:
• A reversible oxidation-reduction (redox) material is used to create a pH gradient
• A pH sensitive dye responds to the change in pH, resulting in the formation of a high contrast, reflective image
By separating the function of the redox material and the dye, Aveso inks provide a novel family of high contrast materials that are inherently stable, processable, and versatile. Further, by requiring only one redox couple for producing the pH change, color selection flexibility and long life are achieved compared to systems that require a new redox couple for each color.

This article by IDTechEX on low-cost display technologies talks about Ntera’s NanoChromic Display (NCD):

At the heart of this NCD is an electrochromic material, which is normally transparent but turns blue when a negative charge is applied. It requires no moving parts, making NCDs unique among other electronic paper technologies, such as electrophoretic displays. […]
In Ntera’s display, an array of transparent electrodes made of metal oxide semiconductor, mounted on a transparent film, allows it to produce images with a resolution of about 0.25 millimeters or 100 dots per inch. Adding an opaque white layer of titanium dioxide behind the electrochromic layer creates a white background to the monochromatic images that makes them more readable. The company is also planning eventually to develop a colour display.