Strong and crack-resistant hydrogel derived from pomelo peel for highly sensitive wearable sensors

Hydrogel sensors have great potentials in the fields, like bioelectronics and wearable electronics, owing to their high water content, high flexibility and biocompatibility. However, it remains challenging to endow a hydrogel sensor with proper mechanical properties, stability and a high sensitivity. Herein, a hydrogel sensor possessing enhanced mechanical properties, high defect-resistance and high sensitivity is developed by anchoring silver nanowires in the composite hydrogel (PPH) composed of 3D network of delignified pomelo peel (DPP) and polyacrylamide (PAM). With only ~ 1.3% mass ratio of DPP, PPH has a compressive strength around 2.5 times of PAM hydrogel. Moreover, the compressive strength of PPH with 10 pre-defined cracks is as good as the PPH without any cracks, showing a high tolerance to defects. The gradient modulus of PPH endows the sensor with a high sensitivity to static pressure, bending and impact. The sensitivity of the PPH sensor reaches 2.033 kPa(-1) under a pressure in the range of 0-0.6 kPa. The current work not only provides a hydrogel sensor with high stability and high sensitivity, but also proposes a sustainable strategy to utilize food residues for high-tech materials.