Bamboo-inspired mechanically flexible and electrically conductive polydimethylsiloxane foam materials with designed hierarchical pore structures for ultra-sensitive and reliable piezoresistive pressure sensor

Flexible pressure-sensing materials with high sensitivity and good mechanical reliability are highly required to meet the long-time and accurate detecting requirement for wide-stress motions. Herein, we describe a bamboo-inspired design approach to fabricate mechanically flexible and electrically conductive carbon nanofiber/polydimethylsiloxane foam composites with unique and designed hierarchical pore structures. The optimized multi-level pore structures not only show outstanding mechanical flexibility and reliability, but also possess high sensitivity at a relatively wide stress range. Typically, the hierarchical pore structures (i.e. large-size pore structure of several hundreds of micrometers, hollow structure of several micrometers, micro-/nano-irregular pores on the hollow skeleton) are sensitive to tiny pressures to construct additional conductive paths and thus achieve high sensitivity of ~0.6 kPa−1 at 0–1 kPa. Further, such hierarchical structures easily form highly interconnected conductive network induced by the serious deformation of large pores and sinking of hollow-structure, thus providing the extremely sensitive sensing behavior for a relatively large pressure level as large as 20 kPa. Moreover, the optimized sensor presents good repeatability and excellent reliability after 10000 compressive cycles, which can satisfactorily meet the critical requirements of subtle vital signs, human motions monitoring and so on. Clearly, this work offers a route to design and development of the multifunctional advanced pressure-sensor for potential artificial intelligence application.