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Kinetics of Light-Responsive CNT / PNIPAM Hydrogel Microactuators
Aoife Gregg1,2, Michael De Volder2, Jeremy J Baumberg1
1Cavendish Laboratory, Department of Physics, University of Cambridge, J.J. Thomson Avenue, Cambridge, CB3 0HE, UK.
Small (Weinheim an Der Bergstrasse, Germany)
|October 22, 2023
Summary
Light-responsive carbon nanotube (CNT) and poly(N-isopropylacrylamide) (PNIPAM) hydrogel composites offer fast microactuation. Polymer diffusion limits the deswelling dynamics, enabling applications like microswimmers.
Area of Science:
- Materials Science
- Nanotechnology
- Polymer Science
Background:
- Vertically aligned carbon nanotube (CNT) forests offer efficient light absorption.
- Poly(N-isopropylacrylamide) (PNIPAM) hydrogels exhibit temperature-dependent volume phase transitions.
- Combining CNTs and PNIPAM creates light-responsive composite microactuators.
Purpose of the Study:
- To investigate the light-responsive behavior and kinetics of CNT-PNIPAM composite microactuators.
- To analyze the deswelling dynamics and identify rate-limiting factors.
- To explore potential applications of these microactuators, such as microswimmers.
Main Methods:
- Fabrication of CNT-PNIPAM composite microactuators using lithography.
- Characterization of microactuator response to light irradiation using high-speed videography.
- Development and application of a theoretical model combining thermal convection and polymer diffusion to analyze deswelling kinetics.
Main Results:
- CNT-PNIPAM composites demonstrate rapid response times as fast as 15 ms.
- CNTs efficiently convert light into heat, triggering PNIPAM contraction.
- Theoretical modeling indicates that polymer diffusion is the rate-limiting step in the deswelling process.
- Demonstrated over 1500 actuation cycles in micro-jellyfish designs.
Conclusions:
- CNT-PNIPAM composites are effective light-responsive microactuators with tunable properties.
- Understanding the deswelling kinetics is crucial for optimizing microactuator performance.
- These microactuators show promise for applications in micro-robotics and microfluidics, including light-actuated microswimmers.
