Materials capable of shape‐morphing and/or fluorescence imaging have practical significances in the fields of anti‐counterfeiting, information display, and information protection. However, it's challenging to realize these functions in hydrogels due to the poor mechanical properties and lack of tunable fluorescence. A tough hydrogel with good shape‐memory ability and phototunable fluorescence is reported here, which affords reprogrammable shape designing and information encoding for dual‐encryption. This hydrogel is prepared by incorporating donor–acceptor chromophore units into a poly(1‐vinylimidazole‐co‐methacrylic acid) network, in which the dense intra‐ and interchain hydrogen bonds lead to desirable features including high stiffness, high toughness, and temperature‐mediated shape‐memory property. Additionally, the hydrogel shows photomediated tunable fluorescence through a unimer‐to‐dimer transformation of the chromophores. By combining photolithography and origami/kirigami designs, hydrogel sheets encoded with fluorescent patterns can deform into specific 3D configurations. The geometrically encrypted fluorescent information in the architected hydrogels is readable only after sequential shape recovery and UV light irradiation. As demonstrated by proof‐of‐concept experiments, both the fluorescent pattern and the 3D configuration are reprogrammable, facilitating repeated information protection and display. The design of tough hydrogels with rewritable fluorescent patterns and reconfigurable shapes should guide the future development of smart materials with improved security and wider applications in aqueous environments.
because it can afford remote and precise control over the properties of hydrogels. [5] In recent years, a series of photo responsive hydrogel-based functional materials have been developed that show a number of emerging features, such as fluorescent, mechanical, and adhesive properties. [6][7][8][9][10] However, changing the conductivity of hydrogels by illuminationmediated ionic migration represents a promising yet challenging photoconductive property [11][12][13][14][15][16] that could be applied in many fields, including photo detectors, [17] the simulation of biophotoelectric signals, [18] and light control circuits. [19] Because of the difficulty of modulating the free movement of ions, it seems impossible to achieve photo controlled ionic conductivity in hydrogels by using a chemical strategy. In a few research studies, [20][21][22][23] the photo conductivity of hydrogels was realized through the introduction of traditional photo conductive electronic materials into the systems via a physical approach. For example, Zhu and co-workers successfully fabricated a 3D hydrogel network of titanium dioxide (TiO 2 )-graphene using a simple one-pot method; this network exhibited enriched adsorption-photoelectro catalytic degradation of low-concentration bisphenol A. [21] Ray and co-workers A novel ion-conducting supramolecular hydrogel with reversible photoconductive properties in which the azobenzene motif, α-cyclodextrin (α-CD), and ionic liquid are grafted onto the gel matrix is reported. Hostguest interactions with different association constants between α-CD and azobenzene or the anionic part of the ionic liquid can be readily tuned by photoinduced trans-cis isomerization of the azobenzene unit. When irradiated by 365 nm light, α-CD prefers to form a complex with the anionic part of the ionic liquid, resulting in decreased ionic mobility and thus high resistance of the hydrogel. However, under 420 nm light irradiation, a more stable complex is again formed between α-CD and trans-azobenzene, thereby releasing the bound anions to regenerate the low-resistive hydrogel. As such, remote control of the ionic conductivity of the hydrogel is realized by simple host-guest chemistry. With the incorporation of a logic gate, this hydrogel is able to reversibly switch an electric circuit on and off by light irradiation with certain wavelengths. The concept of photoswitchable ionic conductivity of a hydrogel mediated by competitive molecular recognition is potentially promising toward the fabrication of optoelectronic devices and applications in bioelectronic technology. HydrogelsThe ORCID identification number(s) for the author(s) of this article can be found under https://doi.Photoresponsive hydrogels have attracted broad interest as functional materials to enable drug delivery systems, [1] cell culture substrates, [2] permeable membranes, [3] and microactuators. [4] Compared with other stimuli-responsive mechanisms, light irradiation has particular advantages and promising applications
In periodically patterned gels, buckled domains mutually interact and cooperatively deform to minimize total elastic energy.
Composite hydrogels with both in-plane and out-of-plane structural gradient are fabricated by multi-step photolithography and exhibit programmed deformations and shape transformations under stimulation.
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