Nanofiber-assisted construction of flexible sponge sensors with engineered biomimetic structures for wearable devices and gesture recognition.

Porous flexible piezoresistive sensors are commonly used in wearable devices. To achieve excellent deformation capability, sensitive resistance changes, and stable signal input, such sensors must possess a robust skeletal structure and abundant pores. This not only effectively distributes external stress but also provides a larger contact area for conductive fillers. Inspired by leaf veins and natural concrete structures, this study developed a flexible sponge sensor with a “column-plate” architecture. This sponge utilizes sodium alginate and polyvinyl alcohol as “mortar” for its skeletal framework. Electrospun nanofibers and cellulose nanofibers are incorporated into the substrate as “rebars” or “leaf veins”. respectively, to enhance the framework’s mechanical properties and to form a cross-linked network. Conductive MXene and MWCNTs serve as “bricks and mortar,” forming abundant hydrogen-bond networks with the polymer substrate to densify the crosslinked interpenetrating network. Crucially, horizontal freeze-drying technology controls ice crystal growth horizontally, yielding a sponge with parallel-aligned pores and a “lamellar” structure. The assembled piezoresistive sensor exhibits excellent sensing performance, demonstrating high responsiveness to various external strains (2.07, -4.97 kPa− 1, -0.83 for stretching, pressure, and bending stimuli). It maintains stable responsiveness after 8,000 compression cycles with a short response time (0.1 s). These excellent properties enable the sensor to monitor human motion states in real time and allow individuals with speech impairments to communicate via Morse code. It is also integrated into smart gloves, enabling gesture recognition and AI-assisted wireless control of robotic grippers. This demonstrates its broad application potential in human-machine interaction, remote object grasping, and flexible wearable electronics.