Design of a Simple and Rugged Soft Polydimethylsiloxane-Carbon Nanotube-Graphene-Based Composite Sensor

Many applications in human health screening, soft robotics, and structural health monitoring require sensors that can accommodate large deformations and highly curved geometries, while providing reliable measurements across a range of frequencies. Ideally, such sensors will also be low cost and easy to manufacture. While prior studies achieve some of these goals, it is rare to achieve them all in a holistic manner. Here, a soft sensor that is easy to manufacture, affordable, and water compatible is presented. The sensor is made of a combination of carbon nanotubes and few-layer graphene dispersed in a polydimethylsiloxane elastomer. The sensor's ability to detect a broad range of frequencies under both uniaxial stretch and bending is demonstrated. The sensor is effective in multiple configurations, including directly stretching the sensor, adhering the sensor to a deforming compliant substrate, and operating under water. Specifically, the sensor can accurately detect vibrational frequencies with amplitudes as small as 0.1% strain and excitation frequencies covering a broad range of 50–600 Hz with an average root mean square error (RMSE) of 0.16%. Even in the presence of large (≈ 20%) deformations and aqueous environments the sensor can recover the fundamental and higher order vibrational modes within less than 2% error.