Quasi‐Homogeneous and Hierarchical Electronic Textiles with Porosity‐Hydrophilicity Dual‐Gradient for Unidirectional Sweat Transport, Electrophysiological Monitoring, and Body‐Temperature Visualization

Abstract

On‐skin electronics based on impermeable elastomers and stacking structures often suffer from inferior sweat‐repelling capabilities and severe mechanical mismatch between sub‐layers employed, which significantly impedes their lengthy wearing comfort and functionality. Herein, inspired by the transpiration system of vascular plants and the water diode phenomenon, a hierarchical nonwoven electronic textile (E‐textile) with multi‐branching microfibers and robust interlayer adhesion is rationally developed. The layer‐by‐layer electro‐airflow spinning method and selective oxygen plasma treatment are utilized to yield a porosity‐hydrophilicity dual‐gradient. The resulting E‐textile shows unidirectional, nonreversible, and anti‐gravity water transporting performance even upon large‐scale stretching (250%), excellent mechanical matching between sub‐layers, as well as a reversible color‐switching ability to visualize body temperature. More importantly, the conducting and skin‐conformal E‐textile demonstrates accurate and stable detecting capability for biomechanical and bioelectrical signals when applied as an on‐skin bioelectrode, including different human activities, electrocardiography, electromyogram, and electrodermal activity signals. Further, the E‐textile can be efficiently implemented in human‐machine interfaces to build a gesture‐controlled dustbin and a smart acousto‐optic alarm. Hence, this hierarchically‐designed E‐textile with integrated functionalities offers a practical and innovative method for designing comfortable and daily applicable on‐skin electronics.

Recent Advances in Stretchable and Permeable Electrodes for Epidermal Electronics

“…Many efforts have adopted this strategy to develop permeable multilayered electronics. [ 18,21,59–64 ] For example, Ma et al fabricated multilayer and permeable electronics by alternatively printing liquid metal layers and depositing electrospun SEBS fiber mats, which allowed for physiological signal monitoring and electrothermal therapy (Figure 2b). [ 64 ] Zheng et al developed a permeable and moisture‐wicking electronic skin in the form of a trilayer structure with wettability gradients (Figure 2c).…”

“…In addition, recent studies have introduced a new generation of epidermal electrodes featuring directional water transport that actively pumps sweat away from the skin. [ 18,21,59–63 ] Xu et al created a permeable electrode in a trilayer architecture consisting of an active Au layer, a hydrophobic TPU nanofiber mat, and a hydrophilic cellulose nanofiber mat (see Figure a,b). Due to its porous microstructure and wettability gradients, the resulting electrode can unidirectionally pump sweat away from the skin.…”

Quantification of Fundamental Textile Properties of Electronic Textiles Fabricated Using Different Techniques

“…An MMT was also employed by Zhao et al [6] who explored the thermal properties of their fabric; here, they applied heat and observed the spread of the heat with a thermal camera. Work by Dong et al [7] showed both the moisture and air permeability taken using commercially available testing equipment; these measurements were compared to standard commercial textiles (however, full details of these textiles were not provided). It should be noted that the water vapor transmission rate was measured, not moisture absorbency.…”

Full‐Color “Off–On” Thermochromic Fluorescent Fibers for Customizable Smart Wearable Displays in Personal Health Monitoring

“…[ 7–10 ] In modern materials science, considerable effort has been devoted to exploring conductive nanomaterials with thermocouples and their utilization in electronic‐based digital sensors for body‐temperature monitoring. [ 11–19 ] Such electronic temperature sensors are capable of accurately and quickly determining body temperatures; however, they are also susceptible to electromagnetic interference and subject to electrical safety issues. More importantly, the miniaturization of electronic temperature sensors is difficult to realize for autonomous health monitoring applications in real‐time.…”