A compact, elastomeric multimodal sensor for tactile softness discrimination

Abstract

Replicating the natural ability to perceive softness in skin-inspired tactile sensors is vital for the advancement of robotic manipulation and object classification. Humans sense softness through the activation of specific skin receptors, which are sensitive to pressure and lateral strain. Current electronic skins (eSkin) mimic this dual functionality by detecting both normal pressure and lateral strain. However, these sensors are challenging to fabricate and often have large spatial footprints, limiting their integration into high-density arrays. To overcome these challenges, this work presents an all-elastomer sensor for tactile detection of softness, combining a parallel-plate capacitor structure with a serpentine piezoresistive strain sensor in a vertically stacked design. Conductive carbon structures, digitally laser patterned and embedded in a styrene-ethylene-butylene-styrene (SEBS) thermoplastic elastomer, serve as robust and modifiable electrodes. The device displays the ability to differentiate moduli between 74 kPa and 1.49 MPa. We conduct a parametric study to evaluate the effects of object dimensions, materials choices, and design parameters on sensor performance. Importantly, we investigate the sensor performance when mounted onto a soft substrate, analogous to the human fingertip or robotic digit. Overall, this work highlights the potential of z-directionally stacked sensing components with tunable properties to realize compact, multimodal devices.