Hydrogel-driven carbon nanotube microtransducers

We demonstrate the fabrication and integration of active microstructures based on composites of 3D carbon nanotube (CNT) frameworks and hydrogels. The alignment of the CNTs within the microstructures converts the isotropic expansion of the gel into a directed anisotropic motion. Actuation by a moisture-responsive gel is observed by changing the ambient humidity, and is predicted by a finite element model of the composite system. These shape changes are rapid and can be transduced electrically within a microfluidic channel, by measuring the resistance change across a CNT microstructure during expansion of the gel. Our results suggest that combinations of gels with aligned CNTs can be a platform for directing the actuation of gels and measuring their response to stimuli.