Overcoming Water Diffusion Limitations in Hydrogels via Microtubular Graphene Networks for Soft Actuators
Margarethe Hauck, Lena M. Saure, Berit Zeller‐Plumhoff, Sören Kaps, Jörg U. Hammel, Caprice Mohr, Lena Rieck, Ali Shaygan Nia, Xinliang Feng, Nicola M. Pugno, Rainer Adelung, Fabian Schütt
Abstract
Hydrogel-based soft actuators can operate in sensitive environments, bridging the gap of rigid machines interacting with soft matter. However, while stimuli-responsive hydrogels can undergo extreme reversible volume changes of up to ≈90%, water transport in hydrogel actuators is in general limited by their poroelastic behavior. For poly(N-isopropylacrylamide) (PNIPAM) the actuation performance is even further compromised by the formation of a dense skin layer. Here it is shown, that incorporating a bioinspired microtube graphene network into a PNIPAM matrix with a total porosity of only 5.4% dramatically enhances actuation dynamics by up to ≈400% and actuation stress by ≈4000% without sacrificing the mechanical stability, overcoming the water transport limitations. The graphene network provides both untethered light-controlled and electrically powered actuation. It is anticipated that the concept provides a versatile platform for enhancing the functionality of soft matter by combining responsive and 2D materials, paving the way toward designing soft intelligent matter.