New Hydrogel Actuator Allows Soft Robots to Move Over Rough Terrain

The adaptive evolution and all-terrain locomotion of the PNIPAm sponge. Credit: NIMTE

Researchers at the Ningbo Institute of Materials Technology and Engineering (NIMTE) of the Chinese Academy of Sciences (CAS) have developed a new hydrogel-based soft robot that can adapt to and move over rough terrain. The team, led by Prof. Chen Tao, in cooperation with Prof. Zheng Yinfei at Zhejiang University, published their work in the journal Research.

Hydrogel's Potential as a Biomimetic Material

Organisms have evolved to move in various ways, such as walking, crawling and swimming, to adapt to changes in their environment. Hydrogel, a biomimetic material, has the potential to replicate these diverse forms due to its self-deformation and mechanical properties similar to soft tissue. However, activating this self-deformation to achieve autonomous movement and perform multiple tasks has been a challenge.

Photothermal Hydrogel Layer

Inspired by the self-growth and evolution of living organisms such as inchworms, the researchers developed a photothermal hydrogel layer containing Fe3O4 nanoparticles that were grown on the surface of an isotropic poly(N-isopropyl acrylamide) (PNIPAm) sponge. This formed an anisotropic bilayer structure via interfacial diffusion polymerization.

Adaptive Deformation

When exposed to programmed near-infrared light irradiation, the anisotropic configurations of the bilayer hydrogel were reconfigured and reassembled to adapt to changes in external environments. This allows for multiple degrees of deformation and various forms.

Mortise-and-Tenon Interlock

By virtue of spatially programmed deformation, a mortise-and-tenon interlock was dynamically formed via the interaction between self-deformation and rough terrains. The hydrogel actuator can imitate the crawling of inchworms to generate periodic propulsion, allowing for off-road locomotion on various artificial rough substrates and natural sandy terrains.

Adapting to Complex Terrains

Benefiting from the adaptive deformation, the crawlable hydrogel actuator can change its volume and crawling mode with the synergy of every tentacle, thus adapting to complex terrains including a mountain pass, a valley, and a ridge.

Potential Applications

This strategy is a step forward for the design and development of soft robots, deformable materials, and biomimetic devices. Assembling several hydrogel motors can even activate a static cargo and allow it to crawl on a 2D rough substrate or overstep complex sandy terrains.

In conclusion, the new hydrogel actuator developed by researchers at NIMTE and Zhejiang University allows for soft robots to adapt to and move over rough terrain. The potential applications for this technology are vast and could be used in the development of soft robots, deformable materials, and biomimetic devices.

Journal Information: Baoyi Wu et al, The Dynamic Mortise-and-Tenon Interlock Assists Hydrated Soft Robots Toward Off-Road Locomotion, Research (2022). DOI: 10.34133/research.0015