Flexible sensor detects different types of touch

Researchers from the University of British Columbia have developed a bendable, stretchable, transparent sensor that could have a wide range of applications in wearable electronics.

Described in the journal Science Advances, the flexible device is able to recognise proximity, touch and pressure, combining multiple sensing functions from some of the leading smartphones. It is made using a layer of ionically conductive hydrogel electrodes, sandwiched between two layers of stretchable silicone. The polyacrylamide electrodes project an electric field above the sensor, which can detect a hovering finger as well as swiping and tapping.

“There are sensors that can detect pressure, such as the iPhone’s 3D Touch, and some that can detect a hovering finger, like Samsung’s AirView,” said researcher Mirza Saquib Sarwar, a PhD student in electrical and computer engineering at UBC.

“There are also sensors that are foldable, transparent and stretchable. Our contribution is a device that combines all those functions in one compact package.”

According to the team, the materials used in the manufacture of the sensor are cheap, and the process is relatively simple and scalable. A 5cm x 5cm prototype film was made using a simple moulding technique. Light touch on the sensor produced a localised decrease in capacitance of 15 per cent, and the device was also able to detect the location of multiple fingers. Furthermore, touch could be detected while the device was bent or stretched, something the team says has not been done before. Some of the potential uses include disposable wearables for monitoring health and soft-touch robotic skins.

“Currently, machines are kept separate from humans in the workplace because of the possibility that they could injure humans,” said John Madden, Sarwar’s supervisor and a professor in UBC’s faculty of applied science.

“If a robot could detect our presence and be ‘soft’ enough that they don’t damage us during an interaction, we can safely exchange tools with them, they can pick up objects without damaging them, and they can safely probe their environment."