Strong, stretchy hydrogels could deliver drugs, heal wounds and replace springy tissues
Hydrogels are already being developed for use as scaffolds for tissue engineering, vehicles for drug delivery, actuators for optics and fluidics, and models for biological studies of tissue-supporting material called the extracellular matrix. But these water-rich polymer gels are weak; they rupture if stretched just a little, and they break easily compared with resilient biological materials such as cartilage or natural rubber. A robust hydrogel developed at the Wyss Institute is highly biocompatible and has unparalleled flexibility, shape memory and strength. It could be used to build soft robotic actuators or to repair soft tissue wounds such as hernias and skin repair, which until now have had limited treatment options.
The tough hydrogel is as thin as a nickel but can rebound a stainless steel ball bearing dropped from more than seven feet above. The gel combines two different types of polymers: a seaweed extract called alginate that is used to thicken food, and polyacrylamide, which is the main material in soft contact lenses. Each of these polymers alone form a soft, weak gel, but when combined they become entangled, creating a molecular network – and therefore a gel – that is superiorly strong and resilient.
When combined with an adhesive layer containing positively-charged polymer molecules, the hydrogel’s exceptional ability to dissipate energy creates a flexible “tough adhesive” that is capable of durable bonding to biological tissues in situ, and displays none of the toxic side effects of currently used commercial adhesives.
This technology is available for licensing.