Highly Stretchable Additively Manufactured Capacitive Proximity and Tactile Sensors for Soft Robotic Systems

Soft robotics are considered one of the most promising approaches toward fully collaborative robotic devices. Soft robotic systems are intrinsically safe due to their compliant nature. Using additive fabrication for the development of soft capacitive sensors enables high flexibility and individualization capabilities in terms of design and material properties. In this work, we outline the sensorization of stretchable capacitive sensors for proximity and tactile detection. This sensor will represent an essential component of a soft robotic finger in future work. While the functional principle has already been shown previously, here we explore the design space further and perform more in depth test of the influences of the strain on the tactile measurements. The capacitive pad's sensitivity is evaluated by applying normal force on each sensor, where the applied force is ranged between 1 and 16 N, with resultant capacitive change of the four tactile sensors between 1 and 60 pF. The capacitive pad's proximity sensor is tested using five different materials, with proximity range of 20 mm, with change in capacitance between 0.1 and 2.4 pF. An essential aspect of soft robotics is that the sensor may also be subject to substantial deformations. We demonstrate that our proposed sensor design can withstand large strains of more than 35%, while the sensitivity toward sensing normal forces does not significantly change. This demonstrates that the proposed sensor design will be suitable for various soft robotics applications, where large deformations may occur.