Soft, Stretchable Sensor Eyed for Wearable Tech, Prosthetics

Researchers at Purdue University have developed a new type of soft sensor that is multi-functional and doesn’t need wiring or electronics within the material.

Researchers have been trying different approaches for how to integrate sensors into wearable technology to expand their functionality and make them more comfortable for users.

Some of the latest research is from Purdue University, where researchers have developed a new type of soft and stretchable sensor, called iSoft, which has a wide range of functionality and is unique because it doesn’t need wiring or electronics within the material, said Karthik Ramani, a professor of mechanical engineering at the university and director of the C Design Lab.

iSoft also is user-friendly, allowing even those with limited engineering expertise to work with the system to customize soft sensors for various applications, he said.

“Even if you have no professional knowledge of electronics you can modify any object with it, including objects with complex shapes,” he said.


iSoft soft sensor

A new type of soft sensor developed at Purdue University can be attached to every-day objects, including clothing. The sensor is unique in that it doesn’t need wiring or electronics within the material, making it a good platform for creating and customizing soft sensors. (Source: Purdue University image/C Design Lab)


iSoft is a thin, rubbery sheet--made from carbon-filled silicone rubber, a non-toxic piezoresistive material--that features electrodes around the periphery.

The technology has a number of capabilities, including the ability to sense in real time or without delay. It also can perform multi-modal sensing, which means it can sense a variety of stimuli such as continuous contact and stretching in all directions, Ramani said.

“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,” he said.

Researchers demonstrate iSoft in a video (below) and presented a research paper about the technology at the ACM Symposium on User Interface Software and Technology in Canada. They envision iSoft for use in myriad applications ranging from fitness- and health-monitoring wearables, to prosthetics and virtual reality.





Key to the functionality of iSoft is an electrical impedance tomography (EIT) technique that estimates changes of resistance distribution on the sensor caused by fingertip contact, Ramani said.

The system also uses an algorithm the team developed called a dynamic baseline update for EIT--triggered by fingertip contact and movement detections--that compensates for what’s called “rebound elasticity,” he said. This normally causes a signal delay while the elastomer returns to its original shape.

“Further, we support unidirectional stretching sensing using a model-based approach that works separately with continuous contact sensing,” he added.

To help researchers develop personalized interfaces and customized looks for iSoft, the team also is providing a software toolkit that allows users to perform interactions instantly after deployment without any extra training, Ramani said.

The Purdue Research Foundation’s Office of Technology has filed a patent for the iSoft technology to help take the sensor from the lab into the commercial market.

Elizabeth Montalbano is a freelance writer who has written about technology and culture for more than 15 years.



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