Printable hydrogels based on starch and natural rubber latex with high toughness and self-healing capability

Fully bio-based hydrogels with printability, high toughness, self-healing, robust mechanical property and conductivity are highly desired but now remain a huge challenge. In this work, inspired by preparation of "Liangpi" (cold noodles, a traditional Chinese food), a satisfactory hydrogel was constructed using starch and natural rubber latex through a simple heating process. Benefitting from the physical dual cross-linked network, the resultant composite hydrogels exhibited high mechanical properties (ultimate tensile stress of 1.01 MPa with a failure strain of 1500 %, high toughness of 6.28 MJ m^-3), good self-healing ability and 3D printability. Moreover, a conductive hydrogel can be easily obtained by in-situ silver mirror reaction during the heating process, which enable the hydrogel to be used as a wearable sensor to monitor human motions with high gauge factor of 2.027 and good durability (1000 cycles). Taking the advantage of its printability, electronic glove (E-glove) has been easily prepared by printing the precursor sol directly on the glove and successfully used to detect the hand motions exactly. This work provides a new route for the fabrication of multifunctional hydrogels with high performance and opens a new road for designing complex wearable sensors to monitor human motions.