Artificial muscles have the potential to fill inherent gaps left behind by large, hard, complex traditional actuators. One such emerging category of artificial muscles which is showing potential in filling these gaps is composite yarn hydrogel actuators. Hydrogels are soft, potentially biocompatible, polymer materials which can be tuned to have varying swelling ratios to produce the desired mechanical response.
Composite yarn hydrogel actuators function by an embedded hydrogel swelling within the confined fibrous structure of a twisted yarn. This hydrogel swelling exerts pressure on the yarn which, in turn, drives either torsional or linear actuation, depending on the twisted structure of the composite yarn.
The focus of this research is to develop techniques to produce, test and model this new class of actuator. We will endeavor to garner a deeper understanding of the effects of hydrogel swelling ratio, applied yarn-twist, and the complex structure of the composite actuator.
Composite yarn hydrogel actuators comprising of niobium nanowire/hydrogel twisted composites have been produced that can generate large and fast torsional stroke as high as 300 deg/mm over 15 seconds when stimulated by water. Simple cotton/hydrogel coiled composites have demonstrated large repeatable linear stroke lengths of 30% contraction upon hydration. A new class of composite actuator (hydrogel composite tube actuators) can show combined linear and torsional actuation within the same device.