Flexible Pressure Sensor Based on Gradient Porosity Sponge for Morse Code Communication and Human Motion Detection

Abstract Flexible pressure sensors have garnered significant attention due to their widespread applications in wearable electronics and health monitoring. Porous conductive composites have emerged as highly attractive materials for such sensors, which enable wide-range and high-sensitivity pressure detection. In this study, a flexible pressure sensor based on gradient porosity sponge is fabricated by introducing a three-dimensional interconnected porous structure into a polydimethylsiloxane-based conductive composite, using sugar particles as a sacrificial template. This natural templating strategy facilitates simple, low-cost, and environmentally friendly fabrication, while enabling tunable gradient porosity along the thickness direction by adjusting the sugar content. The resulting sensor integrates regions of large pores for high compressibility and small pores for enhanced mechanical stability, delivering outstanding overall performance with a high sensitivity of 5.6 kPa–1, broad detection range of 0–350 kPa, and a large strain tolerance of 70%. The sensor demonstrates reliable performance in practical applications, including human motion detection, Morse code communication via pressure encoding, and foot pressure distribution mapping. These results highlight its strong potential for diverse real-world applications in flexible and wearable sensing.