Piezoresistive elastomer-based composites play a critical role in dielectric elastomer switches (DESs) for soft robotics, enabling mechanical strain-driven switching. While conventional liquid-based DES materials suffer from signal instability and poor long-term stability, particle-filled silicone composites offer greater signal stability and are durable but lack a strong piezoresistive response. The present article aims to enhance piezoresistivity by the alignment of graphite flakes in soft and stretchable silicone-based composites by using thin films. The electromechanical behavior was characterized through uniaxial tensile testing with in situ electrical resistance measurements. It is shown that films with thicknesses below 20μm exhibit significantly stronger piezoresistive responses than bulk composites, with increases in resistance of up to four orders of magnitude at 40% strain at voltages up to 3 kV. Wide-angle X-ray scattering measurements elucidated that graphite flake alignment, resulting from the shear and physical confinement of flakes within thin films, plays a major role in enhancing the strain sensitivity. These findings indicate that graphite flakes/elastomer composites are promising materials for high-sensitivity DES applications. The ability to control piezoresistivity by the film thickness opens new possibilities for fully autonomous soft robotic systems with integrated sensing and actuation.
Advanced Robotics Research , 2025, xxx e202500053.