Self-compounded, tough biohydrogels for robust self-adhesive biointerfaces

Bio-friendly and sustainable hydrogels of natural origins are attractive alternatives to their synthetic counterparts, offering imaginative opportunities for applications in bioelectronics and biomedical fields. Most biopolymers, however, are intractable and inherently fragile, incapable of proper operation without blending or modifications. Here we report that highly stable and robust pure biohydrogels can be engineered with tissue-like mechanical and electrical properties. By harnessing and controlling the natural gelation process of starches, a strong association between the microstructural evolution and the macroscopic properties of bulk hydrogels is established. Accordingly, tough pure starch hydrogels with a unique self-compounded heterostructure are constructed, showing anti-fatigue properties originating from the dynamic noncovalent hydrogen bonding. Such biohydrogels exhibit instant and reversible self-adhesiveness to assorted materials, securing seamless and reliable interfacing with dynamic wet skins. Wearable strain sensors and epidermal bioelectrodes are successfully demonstrated, exhibiting high sensitivity over a wide strain range and superior biosignal quality with long-term reliability. The multifunctional pure starch hydrogels are completely biodegradable, offering a green and sustainable solution for intimate human-machine interfaces.