- The novel hydrogel can sustain a chemical reaction for four weeks after exposure to near-infrared light.
- The research draws inspiration from the shape-shifting abilities of organisms such as the sensitive plant and chameleon.
- The STERS system combines liquid metal particles with vinyl monomers to drive the reaction.
- Clinical applications face multiple challenges, including tissue matching and external stimulus control.
A novel shape-shifting hydrogel developed by Chinese researchers can trigger a chemical reaction lasting up to four weeks after a single exposure to near-infrared light. The team created the material to mimic slow biological transformation processes, including wound healing and embryonic development. Known as STERS, the system uses gallium-based liquid metal particles to sustain the reaction, gradually altering the gel's shape and providing a potential platform for adaptive tissue scaffolds, brain-machine interfaces, and soft robotics. The study includes laboratory demonstrations involving stem cells and electrodes used to monitor electrical signals during rat embryonic development.
Study author Du Xuemin, a professor at the Shenzhen Institute of Advanced Technology of the Chinese Academy of Sciences, said his research on intelligent materials was inspired by organisms such as the sensitive plant and chameleon. He noted that progress in shape-shifting materials has been rapid, with some changes now occurring in milliseconds. However, slower biological processes present a different challenge. "I realized that while organisms deform rapidly, they also undergo slow, long-term evolutionary transformations," he said, citing processes such as wound healing and embryonic development. Tissue engineering scaffolds typically carry active substances to support healing. Du pointed out that existing materials either change too quickly or cannot deform at all.
Mimicking nature's shape-shifting processes
"That made me wonder whether we could mimic these slower morphological transformation processes in nature to build slowly shape-shifting materials," he said.
STERS stands for Spatiotemporal Evolution Reaction Species. The system combines gallium-based liquid metal particles with vinyl monomers, which helps drive reactant generation and hydrogel polymerization. Near-infrared light initiates the process, while the liquid metal continuously generates reactants through repeated surface oxidation and oxide layer removal. Once the layer is removed, the metal is exposed again, allowing the reaction to continue. This provides the chemical activity needed for the hydrogel structure to evolve over time. "This novel approach enables programmable, anthropomorphic morphological evolution of hydrogels, spanning microscopic to macroscopic scales, minutes to weeks in duration, and single to multiple transformation cycles," the research team wrote in their paper.
Potential clinical applications and challenges
The researchers also created a hydrogel that gradually changes color, demonstrating its potential as a long-term visual indicator. The team used the hydrogel to guide stem cell differentiation into bone cells and neuron-like cells. "Additionally, we used this material to modify the surface of brain-machine interface electrodes to monitor the evolution of electrical signals during rat embryonic development," Du said. According to the researchers, the material's rate and magnitude of change can be tuned to match changes in the developing embryonic brain. Because liquid metal may damage tissue, biosafety remains a concern. Du noted that the team used a sandwich structure to encapsulate the material and prevent it from leaking into surrounding tissue.
Clinical application still faces multiple challenges, including matching the transformation to specific tissues, achieving slow shape changes, and controlling the process through external stimuli. For now, Du said the system is suited for sensing and laboratory demonstrations in tissue engineering and brain-machine interfaces. The study was published in the journal Matter.
Impact of hydrogel technology on biomedicine
This research demonstrates the potential of hydrogels in simulating biological processes, particularly in wound healing and embryonic development. By mimicking nature's shape-shifting processes, researchers have developed materials with adjustable rates of change, which has significant implications for applications in tissue engineering and brain-machine interfaces. However, the biosafety concerns of liquid metal remain to be resolved, which may affect the feasibility of clinical applications. Advances in this technology will contribute to the development of smarter medical materials in the future.