A bulge-induced dehydration failure mode of nanocomposite hydrogel

Since hydrogels are very soft and usually weak in swollen state, they pose unique challenges to traditional mechanical experiments. The mechanical property of nanocomposite poly(N-isopropylacrylamide) hydrogel was characterized by the bulge test in this investigation. A dehydration failure phenomenon of the hydrogel was found and the failure mechanism was presented. A criterion is proposed that when strain reaches the threshold, water molecules migrate out of the polymer networks and the dehydration failure occurs. The critical strain keeps constant for orifices with different diameters. This failure mode can be applied in the controllable release of drugs. (C) 2013 AIP Publishing LLC.