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Four-Dimensional Printing of Stimuli-Responsive Hydrogel-Based Soft Robots
Published on: January 13, 2023
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Programmable magnetic-induced functional gradient hydrogel for NIR-driven underwater soft robots.
Mengdan Yan1, Haoyang Tian1, Zhong Liu1
1School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, PR China.
Journal of Colloid and Interface Science
|December 23, 2025
Summary
A new gradient hydrogel overcomes delamination issues in soft underwater robots. This innovation enables robust, reconfigurable robots and smart optical sensors for deep-sea exploration.
Area of Science:
- Materials Science
- Robotics
- Biomimetics
Background:
- Soft underwater robots offer enhanced adaptability but suffer from interfacial delamination in multilayer designs.
- Limited drive modes and interface layering compromise structural integrity and reconfigurability.
Purpose of the Study:
- To develop a novel programmable functional gradient hydrogel for improved soft underwater robotics.
- To address interfacial failure issues and enhance reconfigurability in multilayer soft robots.
Main Methods:
- Fabrication of a gradient hydrogel incorporating magnetic Fe3O4/polydopamine hybrid nanoparticles (FPHPs) into a temperature-sensitive network.
- Utilizing 808 nm near-infrared (NIR) irradiation to induce localized heating and create a temperature gradient for actuation.
- Developing underwater smart optical sensors and jellyfish-inspired robots leveraging hydrogel properties and programmable magnetization.
Main Results:
- The gradient hydrogel demonstrated a seamless structure, avoiding interfacial failure.
- Achieved 180° bending deformation within 5 seconds, maintaining performance over 50 cycles.
- Successfully developed a hydrogel-based underwater optical sensor for tunable RGB-LED displays and a locomotion-controlled jellyfish robot.
Conclusions:
- The developed gradient hydrogel offers a stable and reconfigurable solution for soft underwater robotics.
- Pioneered hydrogel-based underwater optical sensors, enhancing deep-sea communication capabilities.
- Advanced intelligent deep-sea exploration through improved robotic design and sensing technologies.

