Study of Humanoid Robot’s E-Skin with Piezoresistive Nanocomposite Based Tactile Sensors Modelling

Piezoresistive nanocomposites are often used as the active layer in the tactile sensors of Electronic Skin (E-skin) for humanoid robots, mostly for static measurements. This study describes the modelling and simulation of three distinct piezoresistive polymer composite materials: Conductive PDMS (CPDMS, a combination of carbon black and PDMS), Polydimethylsiloxane with Multi-Wall Carbon Nano Tubes (PDMS + MWCNT), and MWCNT + Styrene-Butadiene-Styrene (MWCNT + SBS). A generic template of a pressure sensor is modelled on a polyimide substrate and the aforementioned composite materials with optimum weight (wt.) ratios of the CNT as the sensory layer. The mechanical and electrical characteristics of these flexible pressure sensors are simulated, considering real-time environmental conditions. In our study, modelling of the PDMS+MWCNT active layer resulted in a linear response over a wide range of upto 12N of applied tension, while MWCNT + SBS (4% wt.), with a Young's Modulus(E) of 60.4MPa resulted the most conformable sensor, with a maximum displacement of 8.601 x 1013 for 100Pa load. Additional physical aspects that are simulated include the influence of substrate thickness on sensor sensitivity, as well as the validation of the sensor response by putting the active material on both the surface and subsurface layers of an Ecoflex substrate. The resistance changes of the MWCNT + PDMS nanocomposite were simulated and compared to a real-time sensor with a similar physical design, demonstrating consistency between the two. The simulated research of the physical and electrical characteristics yielded a comprehensive comprehension of the sensor's behavior prior to the fabrication of an actual sensor in real time.