We’re hearing more and more about “soft sensors” lately. At Purdue University, researchers have taken the technology to the next level by creating a new type of flexible sensor that does not require wiring or electronics to be encased within the material.
Called iSoft, the material stretches in all directions. It is capable of sensing in real time, without delay, and it can perform “multimodal” sensing on a variety of stimuli. It also can be easily modified for custom purposes, and can handle continuous contact – attributes lacking from some previous soft sensors.
“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,” said Karthik Ramani, mechanical engineering professor at Purdue University and director of the Purdue's C Design Lab. “Even if you have no professional knowledge of electronics you can modify any object with it, including objects with complex shapes,” he added. To that end, a software toolkit for users to design and deploy personalized interfaces has been developed.
The sensor is a thin sheet with electrodes around the periphery -- it harnesses the potential of carbon-filled silicone rubber, a non-toxic piezoresistive material, to provide data. An electrical impedance tomography (EIT) technique is used to estimate resistance distribution changes caused by ﬁngertip contact, eliminating the need for wiring inside the material. The system also uses an algorithm to compensate for signal delay that normally occurs as the elastomer returns to its original shape.
The iSoft platform has potential applications ranging from artificial skin in robotics to human prosthetics, along with health monitoring, sports medicine and tactile clothing. The team’s research points to the capacity for piezoresistive-elastomer-based soft sensors to be fabricated at a low cost.
“More immediately our work will beneﬁt human-computer interaction practitioners and novice Makers,” Ramani said. “One can develop many future applications in wearables as well as make objects interactive, or it can be used with existing consumer products as a skin.”