Collaboration between Harvard University and the University of Tokyo has resulted in a set of pressure sensors so thin and flexible that they can be worn on a human’s hands. According to the universities, healthcare professionals may one day be able to physically screen for breast cancer using pressure-sensitive rubber gloves that can detect tumors.
While traditional pressure sensors are flexible enough to form to soft surfaces like human skin, they cannot measure pressure changes accurately once they are twisted or wrinkled, so they are not ideal candidates for use on complex and moving surfaces. In addition, they suffer from size limitation as it is difficult to reduce their thickness to lower than 100 micrometers. However, the Japanese and American engineering teams have developed a new transparent, bendable and sensitive pressure sensor that addresses these issues.
The nanofiber-type pressure sensor can measure pressure distribution of rounded surfaces such as an inflated balloon and maintain its sensing accuracy even when bent over a radius of 80 micrometers (about twice the width of a human hair). The sensor is about 8 micrometers thick and can measure the pressure in 144 locations at once.
The device is comprised of organic transistors, electronic switches made from carbon and oxygen based organic materials, and a pressure sensitive nanofiber structure. The team also added carbon nanotubes and graphene to an elastic polymer to create nanofibers with a diameter of 300 to 700 nanometers. These were then intertwined to form a transparent, thin and light porous structure.
The team has tested the pressure sensor on an artificial blood vessel and found that it could detect small pressure changes. "Flexible electronics have great potential for implantable and wearable devices. I realized that many groups are developing flexible sensors that can measure pressure but none of them are suitable for measuring real objects since they are sensitive to distortion. That was my main motivation and I think we have proposed an effective solution to this problem,” says Dr. Sungwon Lee of the University of Tokyo's Graduate School of Engineering.
The team’s journal article, "A Transparent, Bending Insensitive Pressure Sensor," was published in Nature Nanotechnology.