An Autofluorescent Hydrogel with Water‐Dependent Emission for Dehydration‐Visualizable Smart Wearable Electronics

Abstract

Wearable flexible electronics that are derived from hydrogels inevitably undergo dehydration, and the sensing performance is highly affected because the stretchability and conductivity weaken. Monitoring the water retention rate of hydrogels as they operate without dismantling the assembled sensing device is vital for evaluating sensing performances and intervening in a timely manner to address the problem. However, relevant research is still lacking. Herein, an autofluorescent hydrogel is engineered based on clusterization‐triggered emission (CTE) for wearable strain‐sensing electronics that can undergo self‐visualizing dehydration. The fluorescence intensity of the CTE‐type autofluorescent hydrogel depends on the aggregation level of molecule clusters that are dangled on the gel networks, which is dominated by the water retention rate of the hydrogel. Thus, the dehydration process can be reflected by the fluorescent images taken in a scenario of long‐term strain‐sensing. This strategy helps the operator evaluate the water retention rate of the hydrogel without removing it from the assembled electronics and then quickly address the problem. In addition, this strategy is also applicable for dehydration‐tolerant systems, demonstrating the versatility of the autofluorescent hydrogel. Overall, the CTE‐type autofluorescent hydrogel will promote the development of high‐performance and smart wearable electronics.

Recent progress in low‐swellable polymer‐based smart photonic crystal sensors

“…In the case of water, the interaction mechanism between solvent and polymer chain can be further understood by the real-time FTIR spectra of wetted polymer samples. [181][182][183] Due to the characteristic peaks of some functional groups overlapping each other, it is difficult to interpret spectroscopic intensity fluctuations of copolymers under various external conditions such as pressure, temperature, concentration, time, electric field intensity, etc. As a comprehensive method proposed by Noda, [184,185] 2D correlational analysis can intuitively identify overlapping peaks in the original spectra by spreading the spectral bands along a second dimension, which improves the spectral resolution.…”

Stimuli‐responsive fluorescent hydrogels: Strategies and applications

“…They have broad application prospects in the fields of tissue engineering, [44] biomedicine, [45] and sensing. [46,47] Here, we attempt to provide a comprehensive overview that summarizes the recent advances in stimuliresponsive fluorescent hydrogels, with a special focus on diverse construction methods and important demonstration applications. We hope that this review can stimulate new ideas and attract like-minded researchers in the field of stimuli-responsive fluorescent materials.…”

Biodegradable Shape‐Memory Ionogels as Green and Adaptive Wearable Electronics Toward Physical Rehabilitation

“…[2,3] Recently, emerging wearable electronics have been proposed as good candidates for extracting real-time physical or psychological signals that reflect the health status of the human body. [4][5][6][7][8] This has considerable potential for physical rehabilitation. However, most existing wearable electronics are not shape-programmable, so it remains a challenge to achieve geometryadaptive skin-device interfaces.…”