A loofah skeleton reinforced interpenetrating hydrogel for flexible wearable sensors.

Flexible hydrogel sensors are crucial wearable electronic devices, but their practical use is limited by poor mechanical strength, structural instability, and single sensing capability. A high-performance interpenetrating network composite hydrogel has been developed through the in situ copolymerization of acrylamide and acrylic acid monomers based on a carbonized loofah skeleton (LS). The LS is obtained from natural loofah sponge by a continuous process of in situ delignification, microfibril dissociation, and carbonization. The modified loofah skeleton constructs a continuous and interconnected conductive network, while tightly integrating with synthetic polymers to form a robust three-dimensional interpenetrating structure. Benefiting from the unique biomass framework optimization, the internal microstructure of the hydrogel is effectively regulated, achieving significantly enhanced mechanical strength and structural stability. The optimized LS/P(AM-co-AA) hydrogel demonstrates a high compressive strength of 2 MPa at 70% strain and a tensile strength of 256 kPa, which exhibits remarkable mechanical improvement compared with the pure P(AM-co-AA) hydrogel. Due to the combined impact of the conductive loofah network and flexible polymer matrix, the hydrogel sensor exhibits remarkable dual tensile and compressive sensing abilities. These properties allow for accurate monitoring of human motion and reliable encoding and transmission of information. This research presents a straightforward and environmentally friendly method for the deliberate design and regulated manufacture of functional hydrogels derived from biomass.