Environmentally Compatible Wearable Electronics Based on Ionically Conductive Organohydrogels for Health Monitoring with Thermal Compatibility, Anti‐Dehydration, and Underwater Adhesion

• Published in: Small (Weinheim an der Bergstrasse, Germany) Vol. 17; no. 24; pp. e2101151 - n/a
• Main Authors: Niu, Yan, Liu, Hao, He, Rongyan, Luo, Meiqing, Shu, Maoguo, Xu, Feng
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01.06.2021
• Subjects: Acrylic acid; Adhesive strength; antifreezing; anti‐dehydration; Biocompatibility; Covalent bonds; Dehydration; Electronics; Freezing; Gelatin; Glycerol-Water; High temperature; Human performance; Hydrogels; Lithium chloride; Nanotechnology; skin electronics; Softness; Structural failure; thermal compatibility; Underwater; underwater adhesion; Wearable technology; wet adhesion; anti-dehydration; thermal compatibility; antifreezing; underwater adhesion; skin electronics; wet adhesion
• ISSN: 1613-6810; 1613-6829
• DOI: 10.1002/smll.202101151

Hydrogel‐based electronics have found widespread applications in soft sensing and health monitoring because of their remarkable biocompatibility and mechanical features similar to human skin. However, they are subjected to potential challenges like structural failure, functional degradation, and device delamination in practical applications, especially facing extreme environmental conditions (e.g., abnormal temperature and humidity). To address these, ionically conductive organohydrogel‐based soft electronics are developed, which can perform at subzero and elevated temperatures (thermal compatibility) as well as at dehydrated and hydrated environments (hydration compatibility) for extended applications. More specifically, gelatin/poly(acrylic acid–N‐hydrosuccinimide ester) (PAA–NHS ester)‐based ionic‐conductive organohydrogel is synthesized. By introducing a glycerol–water binary solvent system, the gel can maintain mechanical softness in a wide temperature range (from −80 to 60 °C). Besides, excellent conductivity is achieved under various conditions by soaking the gel into lithium chloride anhydrous (LiCl) solution. Strong adhesion with skin, even under water, can be realized by covalent bonds between NHS ester from gel and amino groups from human skin. The excellent performances of LiCl‐loaded PAA‐based organohydrogel (L‐PAA‐OH)‐based electronics are further demonstrated under freezing and high temperatures as well as underwater conditions, unveiling their promising prospects in wearable health monitoring in various conditions. An environmentally compatible organohydrogel is developed, showing excellent conductivity, stretchability, and strong adhesion in a wide temperature range and wet environment. Such advantageous features ensure the reliable electromechanical performance and robust integration to skin and thus pave the way for next‐generation wearable sensors.