Self-regulated underwater phototaxis of a photoresponsive hydrogel-based phototactic vehicle

• Published in: Nature nanotechnology Vol. 19; no. 1; pp. 77 - 84
• Main Authors: Hou, Guodong, Zhang, Xu, Du, Feihong, Wu, Yadong, Zhang, Xing, Lei, Zhijie, Lu, Wei, Zhang, Feiyu, Yang, Guang, Wang, Huamiao, Liu, Zhenyu, Wang, Rong, Ge, Qi, Chen, Jiangping, Meng, Guang, Fang, Nicholas X., Qian, Xiaoshi
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.01.2024; Nature Publishing Group
• Subjects: 639/166/988; 639/301/1005; Barriers; Chemistry and Materials Science; Closed loops; Control theory; Feedback loops; Graphene; Hydrogels; Illumination; Maneuvers; Materials Science; Nanoparticles; Nanotechnology; Nanotechnology and Microengineering; Negative feedback; Phototaxis; Poly(N-isopropylacrylamide); Polyisopropyl acrylamide; Sunlight; Underwater
• ISSN: 1748-3387; 1748-3395
• DOI: 10.1038/s41565-023-01490-4

Incorporating a negative feedback loop in a synthetic material to enable complex self-regulative behaviours akin to living organisms remains a design challenge. Here we show that a hydrogel-based vehicle can follow the directions of photonic illumination with directional regulation inside a constraint-free, fluidic space. By manipulating the customized photothermal nanoparticles and the microscale pores in the polymeric matrix, we achieved strong chemomechanical deformation of the soft material. The vehicle swiftly assumes an optimal pose and creates directional flow around itself, which it follows to achieve robust full-space phototaxis. In addition, this phototaxis enables a series of complex underwater locomotions. We demonstrate that this versatility is generated by the synergy of photothermofluidic interactions resulting in closed-loop self-control and fast reconfigurability. The untethered, electronics-free, ambient-powered hydrogel vehicle manoeuvres through obstacles agilely, following illumination cues of moderate intensities, similar to that of natural sunlight. An untethered phototactic soft machine composed of poly( N -isopropylacrylamide) hydrogel blended with graphene oxide and gold nanoparticles demonstrates underwater full-space artificial phototaxis and manoeuvres around obstacles in natural sunlight.