Ultrastretchable, Tough, Underwater-Adhesive, Self-Healing, and Environment-Tolerant Conductive Protein-Based Gel for Amphibious Sensing Applications

With the rapid development of flexible wearable electronic devices, various conductive gels have been developed and displayed great application potential in health monitoring, intelligent manufacturing, sensing, and other scenarios. However, their poor underwater adhesion and intrinsic swelling remain the main defects that usually limit their applications in wet and underwater environments. As such, an eco-friendly and cost-effective plant protein-based conductive gel is developed by using the gliadin of wheat gluten, tannic acid (TA), and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) as raw materials. Due to the delicate balance of hydrophilic hydroxyl groups and hydrophobic backbones of gliadin, the resultant gliadin/TA/PEDOT:PSS gels demonstrated excellent ultrahigh stretchability (≥2200%), instantaneous and robust underwater adhesion ability, excellent antiswelling (42% after 7 days), and underwater adhesion stability (≥100 days). Meanwhile, various dynamic hydrogen bonds endowed the gels with excellent underwater self-adhesive properties under different aquatic environments and underwater self-healing ability. In addition, the gliadin/TA/PEDOT:PSS gel-based sensors demonstrated significant potential for continuous human motion monitoring both in air and underwater and enabled information transmission through the Morse code underwater. The potential applications in biomedical sensing have been approved by constructing the gliadin/TA/PEDOT:PSS gel-based electrodes for ECG health monitoring. Consequently, this eco-friendly, sustainable, and scalable production plant protein-based gel holds significant potential as flexible electronics for amphibious sensing applications.