Light‐Actuated Anisotropic Microactuators from CNT/Hydrogel Nanocomposites

Over the past decades, functional hydrogels that respond to a variety of mechanical and chemical stimuli with a volume change of more than 100% have been developed. Despite this impressive behavior, practical applications of conventional hydrogels are limited by the need to transform their isotropic...

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Bibliographic Details
Published in:Advanced optical materials 2022-07, Vol.10 (13), p.n/a
Main Authors: Gregg, Aoife, De Volder, Michael F. L., Baumberg, Jeremy J.
Format: Article
Language:English
Subjects:
Actuation
Anisotropy
Carbon nanotubes
Electromagnetic absorption
hydrogel
Hydrogels
light actuation
Light irradiation
Materials science
Microactuators
Nanocomposites
Optics
Polyisopropyl acrylamide
soft robotics
Swelling
Thermal conductivity
vertically aligned CNTs
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Summary:Over the past decades, functional hydrogels that respond to a variety of mechanical and chemical stimuli with a volume change of more than 100% have been developed. Despite this impressive behavior, practical applications of conventional hydrogels are limited by the need to transform their isotropic swelling/contraction into useful deformations, as well as their slow response times. Here, these challenges are addressed by combining poly(N‐isopropylacrylamide) (PNIPAM), a widely used temperature‐responsive polymer, with carbon nanotubes (CNTs). To ensure strong PNIPAM−CNT cohesion, the hydrogel is synthesized directly on the CNT surfaces using in situ redox polymerization. The anisotropy of vertically‐aligned CNT forests is used to transform the isotropic (de)swelling of PNIPAM into anisotropic motion. This material combination is particularly attractive because the high optical absorption and heat conductivity of carbon nanotubes converts light irradiation into PNIPAM actuation. A wide variety of CNT‐skeleton microstructures are tested to reveal a range of actuation behaviors. The authors demonstrate fast reversible movement, active switching from low to high light absorption states, lattice shape changes, and good cycling stability. Aligned forests of carbon nanotubes are used as skeletons to guide the movement of a “muscle” hydrogel that changes volume dramatically with temperature. The shape and stiffness of the carbon nanotube forests convert this composite in a rapid shape change. The switch can also be activated with light since the carbon nanotubes absorb light strongly.
ISSN:2195-1071
2195-1071
DOI:10.1002/adom.202200180