Hydrogels are highly absorbent gels in which the swelling agent is water. They’re used in a wide range of biomedical and commercial applications, such as tissue engineering, wound healing, cell culture, contact lenses, and disposable diapers.

This invention is the first hydrogel that is fully functional below freezing. This new class of materials are synthesized by adding salt with the hydrogel. The temperature range at which the hydrogels are partially or non-frozen can be easily modified by adjusting the salt concentration, and these are capable of remaining strong and flexible in a wide range of temperatures. For example, a polyacrylamide-alginate hydrogel, prepared at room temperature and containing a 30wt% Calcium Chloride, can maintain its mechanical properties without freezing at a temperature of -500C.

A broad set of applications are possible, including partially-frozen hydrogel packs for cooling applications and non-freezing hydrogels for soft robotic and ionic sensors that must operate at low temperatures.