# NIR-Mediated Deformation from a CNT-Based Bilayer Hydrogel

## TL;DR

A new hydrogel system that responds to near-infrared light was developed, enabling shape-shifting with strong mechanical properties and complex deformation.

## Contribution

A novel NIR-responsive bilayer hydrogel with high mechanical strength and deformation capability was created using CNTs and P-DN hydrogels.

## Key findings

- The hydrogel achieved a fracture strength of 312 kPa and a fracture strain of 357%.
- The bilayer hydrogel bent 0°–110° within 10 minutes under NIR irradiation.
- The system enables complex deformation movements suitable for soft actuators.

## Abstract

Shape-shifting polymers are widely used in various fields such as intelligent switches, soft robots and sensors, which require both multiple stimulus-response functions and qualified mechanical strength. In this study, a novel near-infrared-light (NIR)-responsible shape-shifting hydrogel system was designed and fabricated through embedding vinylsilane-modified carbon nanotubes (CNTs) into particle double-network (P-DN) hydrogels by micellar copolymerisation. The dispersed brittle Poly(sodium 2-acrylamido-2-methylpropane-1-sulfonate) (PNaAMPS) network of the microgels can serve as sacrificial bonds to toughen the hydrogels, and the CNTs endow it with NIR photothermal conversion ability. The results show that the CNTs embedded in the P-DN hydrogels present excellent mechanical strength, i.e., a fracture strength of 312 kPa and a fracture strain of 357%. Moreover, an asymmetric bilayer hydrogel, where the active layer contains CNTs, can achieve 0°–110° bending deformation within 10 min under NIR irradiation and can realise complex deformation movement. This study provides a theoretical and experimental basis for the design and manufacture of photoresponsive soft actuators.