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Thursday, May 31, 2012

Express yourself: Wear flexible, organic electronics

June 4, 2012
by Mark Ollig

Creating flexible, “wearable electronics” is the goal of Professor Ana Claudia Arias.

Professor Arias joined the University of California, Berkeley in January 2011.

“Flexible electronics are thin, lightweight, and conformal, and can allow new form factors not currently available with established technologies,” she explained.

Professor Arias hopes to soon have information-providing flexible, electronic displays woven into our clothing.

Before coming to Berkeley, Professor Arias led the semiconductor group at Plastic Logic in Cambridge, UK, where she focused her research on the development and use of flexible, printed organic electronic materials.

Professor Arias also spent eight years at the Palo Alto Research Center (PARC), where she used inkjet-printing techniques to produce organic, active-matrix display backplanes for paper-thin displays and flexible sensors.

Professor Arias Berkeley lab group is working on finding a way to use printed electronics for flexible displays, wearable memory, and electronic sensors as thin as a piece of tape.

Using organic electronic materials has its advantages: They can be produced at a low cost, and require minimal power to operate.

Professor Arias is working to directly “print” the organic electronics onto various substrates which would produce the desired chemical reaction – and then layer them onto surface materials such as clothing.

Developing systems to directly print electronics is formidable, from an engineering perspective.

Today, we have a variety of flexible electronics; from ultra-lightweight, flexible, plastic color displays as thin as a sheet of paper, to disposable electronic Radio Frequency Identification (RFID) tags.

Professor Arias group at Berkeley has developed an organic, inkjet-printing technique to produce flexible, small-area electronic displays that make use of positively-and negatively-charged electrical particles suspended in a liquid somewhat similar to e-ink technology.

Most electronic circuits contain a transistor component, which is a solid-state switching device, containing three electrical contacts (base, collector, and emitter), that controls the electrical current passing through it. A negative or positive voltage can trigger this component.

Creation of complex circuitry was achieved by Arias’s group by combining both positive and negative voltage-enabled switching components.

Arias research produced special sensors which are able to detect surrounding ambient light through photosensitive inks and pressure.

These special sensors use a slice of an organic polymer (molecule compound) between two electrical conductors, which change their electrical characteristics when various pressures are applied to the said organic polymer. Similar sensors can be found in car airbags.

Altering the thickness of the polymers and the materials used, changes pressure sensitivity. One use for this type of sensor is a wearable electronic device that detects shocks and stores its informational data; it is called a blast dosimeter.

The PARC website describes the military use of a blast dosimeter as a printable, polymer pressure sensor. PARC went on to say the blast dosimeter senses “. . . blast events due to improvised explosive devices (IEDs) [which] are a major cause of traumatic brain injury (TBI) in the battlefield. The tape-like blast dosimeter is designed to measure and record the severity and the number of [blast] events during one week in order to enable early administration of medical care.”

Recognizing the power of these blasts provides a much better understanding of the causes of TBI, and allows for earlier diagnosis and treatment.

Printed with electronic memory processors, sensors, and thin-film batteries, the disposable blast dosimeter can be affixed (like tape) to a soldier’s helmet.

Professor Arias group was able to construct a type of flexible electrophoretic informational display that creates visible images.

Electrophoretic displays are regarded as examples under the electronic paper classification because of their low power consumption, and thin, paper-like look.
High-resolution, active-matrix displays used in today’s popular e-book readers are a type of electrophoretic display.

These special displays need memory to store their information, and so, Arias lab created a special processing technique to hold their non-volatile memory.

As with most computers, a continuous trickle of electricity is needed to keep its current memory state constant. However, Professor Arias organic material maintains previous memory states, using no power. This is achieved by using components that rely on magnetism (not electricity) to store its data. Although the memory is retained for just eight hours using this method, the technology could be used in applications which require intermittent changes on a display screen.

Professor Arias is currently in the process of adapting wearable electronics to include a variety of uses – such as wearable medical sensors.

“This is just the beginning; wearable sensors that measure environmental and biological signals can open up many applications for people who play sports, are in the hospital, or just want to monitor their daily health,” said Professor Arias.

In addition to her current project, biosensors and wearable medical devices, Professor Arias is also involved with flexible photovoltaics, and printed flexible magnetic resonance Imaging (MRI) Coils.

In the not-too-distant future, many of us may be sporting a personal health monitoring sensor, or an environmental measuring device, or an entertainment or social media interface, or some other type of application on a flexible, organic, electronic video display screen – wearable or interwoven onto our clothing.