2021-037

Short Description

Sulfonate-based, water-soluble spiropyran photoswitches can be covalently incorporated into hydrogel networks to trigger light-driven volumetric expansion, with reversible contraction under dark conditions. The technology enables photoresponsive hydrogels and soft materials with tunable actuation behavior using light, pH, and polymer-network design.

Background

Stimuli-responsive hydrogels are attractive for biomaterials, soft robotics, sensing, microfluidics, and controlled delivery because they can convert external signals into mechanical or structural changes. Existing spiropyran hydrogel systems typically use water-insoluble spiropyrans and are associated with light-driven contraction, which can limit aqueous processing and the range of programmable mechanical responses. There remains a need for water-compatible photoswitches that can be chemically incorporated into hydrogels and provide reversible, spatially controlled expansion under light exposure.

Abstract

This technology provides polymerizable, sulfonate-based water-soluble spiropyran molecules that can be incorporated into crosslinked hydrogel networks. Unlike conventional spiropyran-containing hydrogels that contract upon irradiation, these sulfonated spiropyrans increase net charge upon light exposure, promoting water uptake and hydrogel expansion. The patent demonstrates that photoexpansion can be tuned through spiropyran structure, environmental pH, photoswitch loading, and polymer backbone composition, including lower critical solution temperature (LCST)-controlled networks. The platform also enables reversible bending in light-activated artificial muscle constructs, including negative phototactic behavior where hydrogel rods bend away from the light source. This approach may support development of programmable soft materials for biomedical devices, microfluidic systems, smart actuators, and responsive hydrogel platforms.

Applications of the Technology

• Light-activated soft robots, actuators and artificial muscles.  

Advantages of the Technology

• Light-driven expansion rather than conventional contraction, enabling a distinct actuation mode for spiropyran hydrogels. 
• Water-soluble and polymerizable photoswitch chemistry, supporting covalent incorporation into hydrogel networks using aqueous polymerization approaches. 
• Tunable response through material design, including sulfonation pattern, pH, photoswitch content, and LCST-adjusted polymer backbones. 
• Reversible light/dark actuation, including reproducible bending-unbending behavior demonstrated in hydrogel artificial muscle constructs. 

U.S. Patent No. 12,466,836