Soft Pneumatic Tactile Pressure Sensor Matrix

Abstract

The use of fluidics in soft devices has gained popularity in recent years, particularly in actuators and logic circuits. However, most tactile pressure sensors in the literature output an electrical or optical signal increasing the complexity of soft devices as the electrical or optical signals are transduced from the sensors to fluidic logic, and electrical power is needed just for the purposes of sensors and transducers. Including electrical and optical materials into a soft device also complicates the fabrication of the device. To address these drawbacks, we propose a soft pneumatic tactile pressure sensor matrix consisting of four sensors and operating on fluidic principles. Each sensor contains a meandering microchannel fabricated only from the same elastomer typically used in soft devices. When compressed, the pressure drop of the channel changes, which is measured as a sensor output signal. Our sensors can detect forces ranging from under 0.1 N to 4 N, with a maximum sensitivity of 50.5 N−1. They have a hysteresis of 3.9% and the sensor signal drifts 16.4% in 12 hours under static compression. By using multiple sensors in a matrix, we can detect the point of contact and the magnitude of the applied force. Furthermore, we demonstrate that by attaching a protruding post to the matrix, we can infer forces acting on the post in three axes. This work paves the way toward electronics-free, entirely fluidic soft devices and soft robots that can detect not only the magnitudes of the contact forces but also their locations.