A comparative analysis of capacitive-based flexible PDMS pressure sensors

This paper focuses on the fabrication, characterization and comparative study of flexible pressure sensors, prepared from structured polydimethylsiloxane (PDMS) as flexible dielectric. In specific, four different patterning methods on PDMS dielectric surface were investigated including inverse mold, replica mold, photolithographic and non-shaped microstructures. The different patterned dielectrics were compared to gain insight onto the effect of flexible microstructure design on pressure sensitivity. A complete material characterization was performed using optical microscopy, scanning electron microscopy and tensile testing to evaluate the physical and electrical properties of the different microstructured PDMS dielectric. Static and dynamic pressure measurements were also performed to determine pressure sensitivities. Our results showed a strong dependence of the pressure sensitivity versus the microstructure patterning method utilized. Dielectric patterned from a simple tape molding procedure showed increased sensitivity at higher-pressure regimes (p > 3 kPa) compared to the photolithographic structured dielectric. The inverse dielectric structures produced a higher sensitivity at pressures less than 3 kPa. This work gives new tools to achieve desired pressure sensitivities in flexible polymer-based sensors, especially for pressures ranging several kPa. The comparative analysis presented in this paper will aid further development of flexible sensors with various tactile sensitivities.