Tough and Transparent Photonic Hydrogel Nanocomposites for Display, Sensing, and Actuation Applications

Thermosensitive hydrogels with periodic dielectric structures displaying tunable structural color by temperature stimuli have attracted much research interest recently. However, reported thermosensitive photonic hydrogels either using the poly(N-isopropylacrylamide) (PNIPAM) bulk hydrogel as the responsive matrix or using PNIPAM microgels as the photonic building blocks have poor mechanical strength. Moreover, the expensive and time-consuming preparation process also limits their further application. In this work, a different strategy for preparing PNIPAM-based photonic hydrogel nanocomposite films with strong mechanical strength is proposed by incorporating a PNIPAM microgel film with the polyacrylamide (PAM) hydrogel. The preparation process is simple but efficient, and the obtained nanocomposite films have tunable mechanical strength by changing the crosslinking degree of the PAM hydrogels. More interestingly, the structural color of the nanocomposite films can be retained up to 80 °C (at least), much higher than those of previously reported PNIPAM-based photonic materials. In addition to being thermochromic, the film is sensitive to humidity, and the structural color-changing process is similar to the molting process of cicadas. Furthermore, the nanocomposite films have synchronous shape deformations and color changes and can be used as color-tunable soft actuators. The microgel film-capped photonic hydrogels provide a new strategy for the preparation of thermoresponsive photonic hydrogels and structural color-tunable actuators

Self-Healing Chameleon Skin Functioning in the Air Environments

Chameleons are famous for their uncommon ability to change skin colors rapidly by tuning the lattice distance of guanine nanocrystals within the dermal iridophores. This mechanism has inspired various artificial photonic crystal (PC) films with tunable structural colors. However, the structural colors of most reported films are facile to be destroyed by external factors such as friction, impact, or water evaporation. Herein, an artificial intelligent skin, which has an elastomer–colloidal photonic crystal–hydrogel sandwich structure, is presented in this work. The outer modified polydimethylsiloxane layer acts as the cuticle to protect the hydrogel layer from water evaporation and endows the skin with self-healing ability. The inner hydrophilic hydrogel layer embedded with the colloidal photonic crystals acts as the dermis layer, and the polystyrene colloids layer plays the role of the guanine nanocrystals. A programmed color change can be easily controlled by varying the elongation of the artificial skin, covering the full visible spectrum range. Moreover, skin with patterned stripes, which is similar to the panther chameleon skin that can manipulate multiple colors, has also been achieved. The present artificial skin will offer fresh perspectives on the preparation of artificial chameleon skin similar to the real dynamic flexible skin, which would promote the application of PCs in optical devices

Self-Healing Chameleon Skin Functioning in the Air Environments

Chameleons are famous for their uncommon ability to change skin colors rapidly by tuning the lattice distance of guanine nanocrystals within the dermal iridophores. This mechanism has inspired various artificial photonic crystal (PC) films with tunable structural colors. However, the structural colors of most reported films are facile to be destroyed by external factors such as friction, impact, or water evaporation. Herein, an artificial intelligent skin, which has an elastomer–colloidal photonic crystal–hydrogel sandwich structure, is presented in this work. The outer modified polydimethylsiloxane layer acts as the cuticle to protect the hydrogel layer from water evaporation and endows the skin with self-healing ability. The inner hydrophilic hydrogel layer embedded with the colloidal photonic crystals acts as the dermis layer, and the polystyrene colloids layer plays the role of the guanine nanocrystals. A programmed color change can be easily controlled by varying the elongation of the artificial skin, covering the full visible spectrum range. Moreover, skin with patterned stripes, which is similar to the panther chameleon skin that can manipulate multiple colors, has also been achieved. The present artificial skin will offer fresh perspectives on the preparation of artificial chameleon skin similar to the real dynamic flexible skin, which would promote the application of PCs in optical devices

Self-Healing Chameleon Skin Functioning in the Air Environments

Chameleons are famous for their uncommon ability to change skin colors rapidly by tuning the lattice distance of guanine nanocrystals within the dermal iridophores. This mechanism has inspired various artificial photonic crystal (PC) films with tunable structural colors. However, the structural colors of most reported films are facile to be destroyed by external factors such as friction, impact, or water evaporation. Herein, an artificial intelligent skin, which has an elastomer–colloidal photonic crystal–hydrogel sandwich structure, is presented in this work. The outer modified polydimethylsiloxane layer acts as the cuticle to protect the hydrogel layer from water evaporation and endows the skin with self-healing ability. The inner hydrophilic hydrogel layer embedded with the colloidal photonic crystals acts as the dermis layer, and the polystyrene colloids layer plays the role of the guanine nanocrystals. A programmed color change can be easily controlled by varying the elongation of the artificial skin, covering the full visible spectrum range. Moreover, skin with patterned stripes, which is similar to the panther chameleon skin that can manipulate multiple colors, has also been achieved. The present artificial skin will offer fresh perspectives on the preparation of artificial chameleon skin similar to the real dynamic flexible skin, which would promote the application of PCs in optical devices