A new type of soft and stretchable sensor could find uses in applications ranging from athletics and health monitoring to prosthetics and virtual reality. The technology, called iSoft, is capable of sensing in real-time, or without delay, and can perform “multimodal” sensing, or sensing a variety of stimuli such as continuous contact and stretching in all directions.

A new type of soft sensor developed can be attached to everyday objects including clothing.
(Purdue University image/C Design Lab)

The sensor uses a “piezoresistive elastomer,” which when touched changes electrical resistance that provides sensing data. The researchers are proposing a low-cost, easy way to fabricate such piezoresistive-elastomer-based soft sensors for instant interactions.

The technology features an electrical impedance tomography (EIT) technique to estimate changes of resistance distribution on the sensor caused by fingertip contact. The system also uses an algorithm the team developed called a dynamic baseline update for EIT that compensates for “rebound elasticity,” which normally causes a signal delay. These baseline updates are triggered by fingertip contact and movement detections.

The sensor is a thin, rubbery sheet with electrodes around the periphery. It harnesses a material called carbon-filled silicone rubber, a non-toxic piezoresistive material that has been widely explored in research for various types of low-cost sensors.

The dynamic baseline update process solves the problem, while the electrical impedance tomography technique makes it possible to fabricate sensors in a “single-volume manner.”