Soft Normal and Shear Force Sensor for Underwater Robotic Applications

Tactile perception is a fundamental requirement to perceive and control the manipulation of an object via physical interaction. However, contemporary sensing technologies have some shortcomings in terms of directional force recognition such as inflexibility, intricate design, expensive fabrication methodology, and most importantly incompatibility with underwater applications. In this work, we report a facile and cost-effective methodology to build a soft and multi-directional force sensor especially focusing on its applicability in the underwater environment. The sensor consists of a silicone cover, a 3D printed pyramidal shape, piezo-resistive sensor nodes, and a silicone base. Whenever there is any force applied normal to the sensor, the pyramid shape would distribute the force equally to all the nodes and provide similar outputs from them whereas any other directional force would result in putting differential forces on the nodes and generate distinctive output patterns. The developed sensor was characterized experimentally and tested successfully for underwater demonstrations.