Polymerization of moldable self-healing hydrogel with liquid metal nanodroplets for flexible strain-sensing devices

Incorporation of nanoscale colloidal objects into three-dimensional (3D) hydrogel networks can not only reinforce the hydrogels as “colloidal cross-linkers”, but also add many extra functionalities for diverse applications. For the first time, deformable droplets of liquid metal (LM) in combination with sonication were suggested to be able to initiate and gel acrylic acid (AA) via a facile sonication procedure, with comparison to many inert rigid solid nanofillers. The LM droplets were also stabilized by the resultant hydrogel shells. Besides softness, stretchability, and notch-insensitive toughness, the LM droplets also offered moldability as well as an exceptional self-healing property by releasing active radicals and ionic cross-linkers of Ga3+ cations. Thus the combination of LM and polymerizable monomers not only poses an unprecedented opportunity of incorporating LM into polymeric systems in a facile one-step procedure, but also offers a new type of hydrogels applicable in tissue engineering, wearable devices and solid electrolyte in energy storage devices.