Diagram of Molecular Structure (image) Harvard University Caption By themselves, polyacrylamide gels (a) and alginate gels (b) are brittle. The new hydrogel (c), however, has a more complex molecular structure that helps to dissipate stress across a wide area. The red circles represent calcium ions, and the blue triangles and green squares represent covalent crosslinks between chains. Credit Image courtesy of Jeong-Yun Sun and Widusha R. K. Illeperuma Usage Restrictions None 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.