A group of researchers from the Harward University in the US has developed a soft, stretchy fabric-based Sensor that can turn any cloth into a fitness tracker. It’s a highly sensitive soft capacitive sensor composed of silicone and fabric that moves and flexes with the human body to unobtrusively and accurately detect movement.

 

“We have designed a unique batch-manufacturing process that allows us to create custom-shaped sensors that share uniform properties, making it possible to quickly fabricate them for a given application,” said Ozgur Atalay, from Wyss Institute for Biologically Inspired Engineering.

 

The technology involves a thin sheet of silicone i.e. a poorly conductive material which is flanked by two layers of silver-plated, conductive fabric i.e. a highly conductive material, forming a capacitive sensor. 

 

 

This kind of sensor registers movement by measuring the change in capacitance, or the ability to hold electric charge of the electrical field between the two electrodes. The hybrid sensor’s superior performances stem from its novel manufacturing process, in which the fabric is attached to both sides of the silicone core with an additional layer of liquid silicone that is subsequently cured.

 

To evaluate the sensor design, the team performed strain experiments in which various measurements are taken while the sensor is stretched by an electromechanical tester. Usually, when an elastic material is pulled, its length increases while the thickness and width reduce. As a result, the total area i.e. the capacitance remains constant.

 

However, the conductive area of this sensor was found to be increasing when stretched, which resulted in greater-than-expected capacitance. It was found that the hybrid sensor detected increases in capacitance within 30 milliseconds of strain application and physical changes of less than half a millimeter. This confirmed that it is capable of capturing movement on the scale of the human body.