A robotic muscle made with wood cellulose (IMAGE) KTH, Royal Institute of Technology Caption The hydrogel muscle (left) and a piece of hydrogel before being combined with carbon nanotubes. Credit David Callahan Usage Restrictions No restrictions. License CC0 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.