Research Article Highly Stretchable and Transparent Ionic Conductor with Novel Hydrophobicity and Extreme-Temperature Tolerance Lei Shi, 1 Kun Jia , 2 Yiyang Gao, 1 Hua Yang, 1 Yaming Ma, 1 Shiyao Lu, 1 Guoxin Gao, 1 Huaitian Bu , 3 Tongqing Lu , 2 and Shujiang Ding 1 1 Department of Applied Chemistry, School of Science, Xi’an Key Laboratory of Sustainable Energy Materials Chemistry, MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, State Key Laboratory of Electrical Insulation and Power Equipment, Xi’an Jiaotong University, Xi’an 710049, China 2 State Key Laboratory for Strength and Vibration of Mechanical Structure, School of Aerospace Engineering, Xi’an Jiaotong University, Xi’an 710049, China 3 SINTEF Industry, Forskningsvei 1, 0373 Oslo, Norway Correspondence should be addressed to Tongqing Lu; tongqinglu@mail.xjtu.edu.cn and Shujiang Ding; dingsj@mail.xjtu.edu.cn Received 26 January 2020; Accepted 27 February 2020; Published 19 March 2020 Copyright © 2020 Lei Shi et al. Exclusive Licensee Science and Technology Review Publishing House. Distributed under a Creative Commons Attribution License (CC BY 4.0). Highly stretchable and transparent ionic conducting materials have enabled new concepts of electronic devices denoted as iontronics, with a distinguishable working mechanism and performances from the conventional electronics. However, the existing ionic conducting materials can hardly bear the humidity and temperature change of our daily life, which has greatly hindered the development and real-world application of iontronics. Herein, we design an ion gel possessing unique traits of hydrophobicity, humidity insensitivity, wide working temperature range (exceeding 100 ° C, and the range covered our daily life temperature), high conductivity (10 -3 ~10 -5 S/cm), extensive stretchability, and high transparency, which is among the best- performing ionic conductors ever developed for flexible iontronics. Several ion gel-based iontronics have been demonstrated, including large-deformation sensors, electroluminescent devices, and ionic cables, which can serve for a long time under harsh conditions. The designed material opens new potential for the real-world application progress of iontronics. 1. Introduction Distinguished from electronics, iontronics utilize ions con- tained in electrolytes to implement functions, covering bio- logical ionic systems, electrochemical cells, electrolyte-gated transistors, and electrolyte-based flexible devices [1–5]. The gel electrolyte is a typical solid-state ionic conductor, com- posed of three-dimensional polymer networks with a large amount of saline solutions or ionic liquids swollen inside the networks [6–8]. Commonly, they are stretchable and fully transparent under visible light. Novel functions have been realized by utilizing gel electrolytes, including electroactive actuators [9–11], stretchable electroluminescent devices [12–14], soft power source [15–17], ionic sensors [18–22], ionic cable [23], and stretchable touch panels [24, 25], which are extremely difficult or even impossible to realize with con- ventional electronics. For example, Kim’s group has demon- strated an ionic touch panel with ultrahigh transparency (98%) and stretchability by using a hydrogel electrolyte [24]. Pan’s group has employed ion gels to fabricate a flexible transparent film for interfacial capacitive pressure sensing and supercapacitive nanofabric sensing, leading to ultrahigh mechanical-to-capacitive sensitivity of nF kPa -1 , which is several orders of magnitude greater than that of the tradi- tional devices [26–28]. However, it is challenging to fabricate gel electrolytes that match the requirements of real-world applications. Our daily life environment has extended humidity (10%~100% relative humidity) and temperature (-40 ° C~50 ° C) ranges. To ensure stable operation in engineering applications, devices made from gel electrolytes should bear even harsher conditions. Unfortunately, currently developed stretchable and transpar- ent gel electrolytes cannot satisfy the requirements, which hinder the development of iontronics and their widespread applications. Existing gel electrolytes show unsatisfied humidity stability and quite poor extreme-temperature AAAS Research Volume 2020, Article ID 2505619, 10 pages https://doi.org/10.34133/2020/2505619