Polypyrrole/Polydimethylsiloxane Sponge-Based Flexible Pressure Sensors with Enhanced Sensitivity and a Wide Detection Range Using Programmable Gradient Pore Density

Flexible pressure sensors are in the spotlight for various fields, such as human–machine interfaces and intelligent robotics. In this study, we designed a gradient pore density (GPD) based polypyrrole (Ppy)/polydimethylsiloxane (PDMS) sponge for a flexible pressure sensor by using a fused deposition modeling type three-dimensional printer. The GPD PDMS sponge was fabricated by using an acrylonitrile butadiene styrene filament mold with gradient infill density. PDMS was then cast and cured, and the mold was dissolved in acetone. In situ polymerization was used to coat the Ppy onto the GPD PDMS sponge and produced the GPD Ppy/PDMS sponge pressure sensor (GPPS). GPPS showed a wide sensing range of 0–1500 kPa, a maximum sensitivity of 2.26 kPa –1, and a low limit of detection of 17 Pa. It also proved excellent sensing stability across loading rates of 0.1–30 mm/min, and cyclic durability after 2000 repeated compression-recovery tests at two different pressure levels. Additionally, GPPS was confirmed to be applicable as a wearable sensor across a range from low to high pressure. The spatial resolution of the sensor was demonstrated through various tests using a 3 × 3 sensor array, which confirms its applicability in multi-information sensing fields.