P. MANANDHAR, P. CALVERT, J.R. BUCK
University of Massachusetts
Dartmouth, North Dartmouth, MA, USA
Strain gauges attached to elastic fabric sleeves to monitor body motions could be used in rehabilitation from injury, training and health monitoring. This paper describes a soft hydrogel strain gauge where conduction is via salt solution in the gel. Use of AC sensing eliminates electrochemical effects.
An array of 5 sensors on a knitted sleeve around the elbow of a robot arm gives strain readings corresponding to the position of each sensor and the bend of the elbow. The single phase sensor material does not exhibit relaxation and hysteresis effects present in carbon filled elastomers and conducting polymer coated fabric sensors.
This makes the hydrogel sensor easier to use in real-time strain monitoring situations. The gauge factor of the sensor is about 2 which results in quite good signal to noise ratio when we are monitoring large strains.
The hydrogel sensor does drift due to drying, which could be greatly reduced with an encapsulating film. Connecting the sensors to flexible and stretchable wiring on a soft substrate can also be difficult.
These materials and their connections can be printed such that arrays of sensors and connectors could be developed for a disposable sleeve.