Multi-mode strain and curvature sensors for soft robotic applications

In this paper we describe the fabrication and testing of elastomer-based sensors capable of measuring both uniaxial strain and curvature. These sensors were fabricated from Sylgard 184, which is a transparent silicone elastomer. We created microchannels directly in silicone elastomer substrates using a laser to ablate material. The sensing element was an alloy of gallium and indium, which is liquid at room temperature, contained within the laser-created microchannels. As the substrate deformed, the microchannel deformed within it, resulting in a measurable change in electrical resistance. By fabricating two matching resistive strain-sensing elements on opposite sides of the sensor, we were able to unambiguously measure uniaxial strain and curvature by observing the common mode and differential mode changes in resistance, respectively. There was very little coupling between modes, demonstrating the utility of the differential sensor design. We characterized the sensor in terms of its response to strain and curvature, its noise, and its stability over time. We believe that this type of sensor has application in soft sensory skins and can observe pose in soft robotic systems.