Soft sensor material could make clothes smarter

Wiring-free sensor material can add electronic functionality to objects and be used in medical devices

Researchers from Purdue University in Lafeyette, Indiana are to unveil a new material for flexible sensors, along with a method for processing the signals they produce, at an upcoming conference in Canada.

The material has applications in sport, smart clothing, medical sensing and prosthetics, they claim, and can sense in real time, without any delays, and with no need for wiring.

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

The material, called iSoft, is made of carbon-filled silicon rubber, which has piezoresistive properties; that is, its electrical resistance changes when it is deformed. Because these properties are intrinsic to the material, it does not need any wiring or electronics within the sensor itself; just a series of electrodes around the edge of the rubbery sheet.

Carbon-filled silicon rubber has been investigated for soft sensor applications before, but the sticking-point has previously been rebound elasticity, which causes a signal delay while the material returns to its original shape. The Purdue team has developed an algorithm called dynamic baseline update (DBU) that compensates for this.

“The platform provides the ability to create and customise soft sensors,” said research leader Karthik Ramani, a mechanical engineer and director of Purdue’s C Design laboratory. “Even if you have no professional knowledge of electronics you can modify any object with it, including objects with complex shapes.”

Unlike some soft sensors developed previously, iSoft can handle continuous contact and also can be easily modified for custom purposes after manufacture. “By continuous, we mean moving on the surface and also pressing all the time such as drawing with a pen, which is difficult to achieve,” Ramani said.

The iSoft system could be used as a skin for robots, and to sense, measure and track body motion, and as an interface to control other electronics, for example in clothing that could interface with smartphones. It is easily customisable, and suitable for use by novices in electronics and signal processing, Ramani said.

“We also provide a software toolkit for users to design and deploy personalised interfaces with a customised look. This customisation toolkit allows users to perform interactions instantly after deployment without any extra training processes.”

Ramani’s team is to present a paper on iSoft at the ACM Symposium on User Interface Software and Technology (UIST) in Quebec City, Canada on 25 October.