Stretching and Contracting Hydrogel (video) RIKEN Share Print E-Mail Loading video... Caption The hydrogel stretches and contracts as the temperature goes up and down, but does not change in volume. Credit Kim et al. Nature Materials Usage Restrictions Kim et al. Nature Materials Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.