A Flexible Piezoresistive Sponge Sensor with a Dual-Scale Porous Structure for Ultra-Wide-Range and High-Sensitivity Pressure Detection

The rapid advancement of wearable electronic technologies has positioned flexible piezoresistive sensors as a prominent research frontier. However, a critical challenge persists in simultaneously achieving both high sensitivity and a wide sensing range in such devices. Addressing this challenge, we present an innovative flexible piezoresistive sponge sensor featuring a rationally designed dual-scale porous structure, which integrates a macroscale porous multiwalled carbon nanotubes (MWCNTs)/polydimethylsiloxane (PDMS) sponge matrix containing submillimeter-scale pores fabricated via an NaCl sacrificial template and a microscale porous MWCNTs/carboxymethyl cellulose (CMC) conductive coating with micrometer-scale pores formed on the sponge skeleton through CMC's viscosity and hygroscopic expansion properties. This hierarchical porous structure endows the sensor with exceptional performance characteristics that surpass most existing porous piezoresistive sensors, including an ultrawide sensing range (10 Pa to 4.3 MPa), a high peak sensitivity of 33.890 kPa^-1 (10 Pa-40 kPa, <i>R</i>²= 99.81%), and outstanding durability (4100 cycles at 1 MPa with only 5% degradation in current variation). The MC/MP sponge sensor demonstrated remarkable multimodal sensing capabilities, spanning from subtle physiological signals (Pa-level) to extreme mechanical stresses caused by automobile rear wheels (MPa-level). Human-machine interaction system composed of five flexible piezoresistive sponge sensors and a robotic hand is also developed, and real-time manipulation of the robotic hand gesture is achieved by manually pressing the sensor array. We think the dual-scale structure not only provides a universal design strategy for overcoming the sensitivity-detection range trade-off in flexible piezoresistive sensors and redefining their capabilities but also highlights their immense potential for applications in human-motion monitoring and interactive human-machine systems.