Fully 3D Printed Multi-Material Soft Bio-Inspired Whisker Sensor for Underwater-Induced Vortex Detection

Bio-mimicking the underwater sensors has tremendous potential in soft robotics, under water exploration and human interfaces. Pinniped are semiaquatic carnivores that use their whiskers to sense food by tracking the vortices left by potential prey. To detect and track the vortices inside the water, a fully 3D printed pinniped inspired multi-material whisker sensor is fabricated and characterized. The fabricated whisker is composed of a polyurethane rod with a length-to-diameter ratio (L/d) of 20:1 with four graphene patterns (lengthxdiameter: 60x0.3mm) perpendicular to each other. The graphene patterns are further connected with output signal wires via copper tape. The displacement (approximate to 5mm) of the whisker rod in any direction (0-360 degrees) causes the change in resistance because of generated tensile. The analog signals (resistance change) are digitalized by using analog to digital modules and fed to a microcontroller to detect the vortex. A virtual environment is designed such that it consists of a 3D printed fish fin, a water tank, a camera, and data loggers to study the response of fabricated whisker. The underwater sensitivity of the whisker sensor in any direction is detectable and remarkably high ((Lambda R/R-0)% similar to 1180). The mechanical reliability of the whisker sensor is tested by bending it up to 2000 cycles. The fabricated whisker's structure and material are unique, and no one has fabricated them by using cost-effective 3D printing methods earlier. This fully 3D printable flexible whisker sensor should be applicable to a wide range of soft robotic applications.