Materials Selection and Characterization of Fabric Membrane in Tactile Sensoring

Tactile sensors are devices that are able to sense physical properties through direct contact. In this paper, we investigate on material selection for tactile sensors that mainly uses conductivity information to infer deformation. Hence, flexible and conductive materials are required to allow deformation over complex 3D surfaces and to allow the flow of electric current. Conductive fabrics have gained interest in research as membranes in tactile sensors. The main advantages of employing fabric materials are an improvement in signal hysteresis and an increase in detection sensitivity through employing multi-layered fabric structures. However, this adds on the cost of fabrication and the complexity of the design. In this contribution, a technical review is provided on various types of membranes in the context of large contact area tactile sensors. Moreover, two commercially available silver-plated knitted fabrics coated with silicone and the other with nitrile rubber are investigated as single layered membranes. The experimental results demonstrate that both the weft and warp directions of the fabric and material coating have a significant effect on the materials' mechanical and electrical performance. The elastic modulus of the nitrile rubber coated fabric is in the range of 0.14 MPa and 0.30 MPa, while that of the silicone-coated is in the range of 1.36 MPa and 1.87 MPa respectively for the weft and warp directions.