From wearable device to patch – electronic nano-adhesive plaster capable of measuring muscular activityWed, Dec 2, 2015
On November 16 at a press conference held by the Public Relations Committee of the Society of Polymer Science, a group comprised of Professor Shinji Takeoka, Assistant Professor Toshinori Fujie, graduate student Kento Yamagishi and others from the Graduate School of Advanced Science and Engineering announced that they have developed an ultrathin electrode (an electronic nano-adhesive plaster) that can be attached to a person’s skin to measure bioelectric signals. The ultrathin electrode was developed in collaboration with a research group from the Italian Institute of Technology comprised of researchers Alessandra Zucca and Francesco Greco, Senior Researcher Virgilio Mattoli, and others. Further details about their research were revealed at the 24th Polymer Material Forum at Tower Hall Funabori on November 26-27.
The electronic nano-adhesive plaster made from electricity-conducting plastic (an electro-conductive polymer) is so thin and flexible at 240 nanometers (1 nanometer = millionth of a millimeter) that it can be attached to the skin without the use of adhesives. By attaching the nano-adhesive plaster to a person’s arm, the device can instantaneously measure the action potential of muscles (surface muscle potential) in response to flexing and extension movements. The electronic nano-adhesive plaster can also be produced in large quantities through roll to roll printing technology1) which will contribute significantly to the development of next-generation wearable devices.
Wearable devices that can be attached to the body and measure various biological information (body temperature, pH, heart rate, muscle potential, etc.) are becoming increasingly important not only in daily life but also in sports and medicine. In recent years, as electronic circuits are printed on soft polymer thin film, there are reports of devices that can be attached to the body like a sticker. The time is coming when more and more devices will be stuck to rather than worn on the body. However, for a device to be attached onto soft body tissue such as skin without causing discomfort, the hard metal parts that make up its electronic circuitry (wires, electrodes, etc.) need to be made from softer materials such as plastic. In addition, to minimize production time and costs, it is important to establish new mass production techniques that employ printing technology rather than relying on existing microfabrication technology.
The Waseda University research team has previously developed medical polymer nanosheets (nano-adhesive plasters) with sufficient adhesiveness and flexibility for skin and organs. In this latest collaborative research with the Italian Institute of Technology (IIT), which specializes in robots, the team has developed a new electronic nano-adhesive plaster using the electro-conductive polymer, poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). This electronic nano-adhesive plaster exhibits high flexibility and adhesiveness, and is ultrathin at 10-100 nanometers. When the plaster is attached to the skin, it acts as an electrode that can detect bioelectric signals (such as surface muscle potential). By utilizing roll to roll processing, the technique of continuous printing that was refined during the development of nano-adhesive plasters, the team has established new techniques for increasing area size from square centimeters to square meters.
As the electronic nano-adhesive plaster sticks to and moves with the skin on a nano-level without the use of glue or adhesive gel, it can stay secure without breaking or peeling off from sweat or skin expansion that occurs during sports such as futsal. The team also found that when using the electronic nano-adhesive plaster, they were able to detect surface muscle potential with nearly the same signal-to-noise ratio as with metallic electrode pads (with adhesive gel) currently used in hospitals.
By measuring surface muscle potential, this research has confirmed that the electronic nano-adhesive plaster can be used as a skin patch electrode. The flexibility and adhesiveness of its ultrathin structure allows it to gently attach to the skin without noticeable discomfort. The lack of an additional adhesive agent minimizes damage to the skin (such as from the peeling away of keratin) upon removal of the plaster and the device is expected to be used for various purposes such as motion measurement for athletes to health care for infants, the elderly, and the disabled. In the field of biorobotics, the electronic nano-adhesive plaster will dramatically advance the design of wearable devices that use biosignals, and is expected to be implemented in artificial arms and legs, and wearable robots. The various types of printing technology are accelerating the development of biometric devices with increasingly elaborate electronic circuits.
In the future, the electronic nano-adhesive plaster is expected to have applications in the fields of wearable devices, flexible electronics, health care devices, biosensors, human-machine and brain-machine interfaces, artificial limbs, and wearable robots.
1) Reference: Zucca, A.†, Yamagishi, K.†, Fujie, T.*, Takeoka, S., Mattoli, V.*, and Greco, F.* “Roll to Roll Processing of Ultraconformable Conducting Polymer Nanosheets”, J. Mater. Chem. C., 3, 6539-6548 (2015). (*Corresponding authors, †Equal contribution) DOI: 10.1039/C5TC00750J.