Programmed Multiresponsive Hydrogel Assemblies with Light‐Tunable Mechanical Properties, Actuation, and Fluorescence

Abstract

Fabrication strategies for programmed hydrogels that provide precise spatial control with predetermined responses to external stimuli are highly desirable. In this study, a partially reversible light‐driven assembly (PRLDA) method is introduced to construct multiresponsive hydrogels utilizing microgel (MG) particle building blocks (swollen diameter of 107 nm). No other material is required to prepare the gels beyond the MGs themselves. Facile preparation of multiresponsive hydrogels that are reversibly responsive to light, pH, and temperature using phototriggered covalent interlinking of coumarin‐based MGs is demonstrated. The gels have phototuneable moduli and swelling ratios and show light‐assisted healing and reshaping. Remarkably, the intrinsic fluorescence of the gels undergoes a reversible light‐triggered wavelength‐shift. The emission peak blueshifted from 420 to 390 nm upon irradiation with 365 nm light. The PRLDA gels can be constructed using either positive or negative photopatterning. It is shown that the gels can be exploited for multiresponsive cytocompatible actuators, grippers, and ON/OFF circuit components as well as anticounterfeit gels. The PRLDA method provides new insight into programmed gel property control and has excellent potential for biomaterial and optoelectronic applications.

Controlling Properties and Functions of Polymer Gels Using Photochemical Reactions

“…Similarly, Saunders and colleagues prepared a hydrogel using coumarin as the photoresponsive group. [ 72 ] The [2+2] cycloaddition reaction of coumarin occurred under light irradiation at 245 nm, and the reverse reaction occurred under light irradiation at 365 nm. Similar to the [4+4] cycloaddition of anthracene, the hydrogel was repaired under irradiation at different wavelengths.…”

Dual‐Responsive Material Based on Catechol‐Modified Self‐Immolative Poly(Disulfide) Backbones

“…Lu et al. reported a multi‐responsive gel capable of actuation by virtue of a polyelectrolyte backbone, while also possessing the ability to be photocleaved and photocross‐linked through pendant coumarin groups [7] . Chen et al.…”

“…reported a multi‐responsive gel capable of actuation by virtue of a polyelectrolyte backbone, while also possessing the ability to be photocleaved and photocross‐linked through pendant coumarin groups. [7] Chen et al. presented a multi‐responsive system containing benzoxaborole ester cross‐links, responsive towards pH, ATP, fructose, and H 2 O 2 .…”

Bioinspired Stimuli‐Responsive Hydrogel with Reversible Switching and Fluorescence Behavior Served as Light‐Controlled Soft Actuators

“…However, these types of smart materials can only provide a single capability of color change or shape deformation. Although some hydrogels can show several changes, they also have some objective problems: the difficulty in controlling the simultaneous occurrence of multiple responses, [29] the harshness of the stimulus formation, [30] the long response time to the stimulus, [31] or the complicated preparation process. [32] Therefore, it is a significant challenge to integrate rapid shape deformation and color change synergistically by a simple method in the same system.…”