Flexible Sweat Sensors: From Films to Textiles

Abstract

Flexible sweat sensors have found widespread potential applications for long-term wear and tracking and real-time monitoring of human health. However, the main substrate currently used in common flexible sweat sensors is thin film, which has disadvantages such as poor air permeability and the need for additional wearables. In this Review, the recent progress of sweat sensors has been systematically summarized by the types of monitoring methods of sweat sensors. In addition, this Review introduces and compares the performance of sweat sensors based on thin film and textile substrates such as fiber/yarn. Finally, opportunities and suggestions for the development of flexible sweat sensors are presented by summarizing the integration methods of sensors and human body monitoring sites.

Sweat Sensor Based on Wearable Janus Textiles for Sweat Collection and Microstructured Optical Fiber for Surface-Enhanced Raman Scattering Analysis

“…Surface-enhanced Raman scattering (SERS) is a powerful nondestructive testing technology with fingerprint recognition capabilities, widely used in detecting trace substances. − Traditional SERS substrates were constructed on rigid substrates such as glass slides and silicon wafers. The advent of flexible materials has sparked interest in developing flexible SERS substrates that can conform to curved surfaces for noninvasive detection. − In particular, wearable SERS sensors have been proposed and developed. Similar to the development of wearable electronics, multifunctionality has been integrated into the wearable SERS substrate, − such as autonomous sweat extraction, accurate quantification of sweat loss and sweat rate.…”

Flexible Wearable Plasmonic Paper-Based Microfluidics with Expandable Channel and Adjustable Flow Rate for Portable Surface-Enhanced Raman Scattering Sweat Sensing

“…The research on wearable sensors has achieved significant advancements in the field of human sweat-based health monitoring. − Currently, wearable sensors based on various detection methods, such as colorimetric, fluorescence, electrochemical, and surface-enhanced Raman scattering (SERS) techniques, have been developed for instant, continuous, noninvasive, and accurate detection of analytes in biological fluids. − By harnessing the noninvasive sweat transmission method, these sensors can reflect the physiological and pathological conditions of the human body. For instance, colorimetric and fluorescence methods, when combined with smartphones and applications, enable in situ sensing of various sweat components (lactate, glucose, chloride, and pH). , Wireless wearable electrochemical monitoring platforms have been developed for the long-term continuous analysis of multiple sweat biomarkers such as lactate, pH, vitamin, and tyrosine, which provide insights into the metabolic stressors and physiological responses to exercise. − However, colorimetric and fluorescence techniques exhibit significant limitations in long-term continuous monitoring, , while electrochemical techniques not only require intricate electrode design and complex circuitry , but also exhibit less composition information and poor anti-interference ability. , On the contrary, SERS can provide plentiful compositional information by virtue of the inherent molecular fingerprints of analytes and is basically insusceptible to external factors. , However, its application in human sensing has been less studied.…”

A new algorithm to generate randomly distributed fibers within the fiber bundle and numerical investigation of bundle cross-sectional performances in transverse compression

“…[1][2][3] Although staple yarns and filament yarns are the main yarn forms in yarn-based materials, 4 filament yarns with great continuity and stability 5,6 are more popular and have been widely used in various fields. Parallel fiber bundles which are composed of long fibers (filaments) have been applied in rope, 7 composites, 8,9 flexible sensors, [10][11][12] etc. During the preparation and use of bundle-based materials in various applied situations, a common and typical type of load applied to the bundle is the transverse compression, which leads to the bundle cross-sectional deformation directly.…”