Gradient pore structured Ppy/PDMS conductive sponge for flexible pressure sensor

Flexible pressure sensors based on porous conductive composites have potential applications in electronic skin, healthcare due to their pressure-responsive electrical conductivity. However, simultaneously enhancing sensitivity and expanding the working range remains a formidable challenge. In this work, we propose a bioinspired polypyrrole (Ppy)/polydimethylsiloxane (PDMS) sponge, which was fabricated using a one-step emulsion ice template process. This approach allows for the creation of a gradient pore structure along the thickness direction by adjusting the solid content of the latex solution and incorporating renewable carboxymethyl cellulose (CMC) additive. The technique effectively eliminates the issues associated with template residues, chemical pollutants, and multiple processes, thereby meeting the requirements for the sustainable development of flexible electronics in the future. The as-prepared Ppy/PDMS sponge exhibits a gradient modulus from top to bottom due to its gradient pore structure, thereby resulting in a combination of enhanced compressibility arising from larger pores and excellent stress adaptation characteristics originating from smaller pores. The Ppy/PDMS sponge based sensor exhibits a remarkable strain sensitivity of 31.4, a broad strain range from 0 % to 70 % and exceptional durability even after undergoing ∼ 10000 compression-release cycles. Additionally, the sensor can be utilized for health monitoring, human motion detection, and human–machine interfaces. Furthermore, an array of our sensors possesses the capability to collect spatiotemporally resolved signals for the purpose of monitoring and analyzing intricate actions. These advantages make our Ppy/PDMS sponge a highly promising candidate for flexible pressure sensor.