GALCIT Colloquium

Several recent discoveries show that hydrogels can achieve properties and applications well beyond previously imagined.  A hydrogel mixes a polymer network and water at molecular scalar. The polymer network makes the hydrogel a soft elastic solid, and water makes the hydrogel a fast ionic conductor.  Most existing hydrogels are fragile and dry out in open air.  We have recently made hydrogels as tough as rubber, and made hydrogels retain water in low-humidity environment. We have used hydrogels to mimic the function of axons, transmitting electrical signals over long distances, at high speeds.  We show that a high-speed ionic cable transmits signals with a diffusivity 16 orders of magnitude higher than the diffusivity of ions in water. We have made a fully transparent loudspeaker capable of playing music over entire audible range.  We have also made stretchable, transparent, large-area sheet of distributed sensors. This talk describes the mechanics and chemistry of these materials and devices.