Highly Conductive, Photolithographically Patternable Ionogels for Flexible and Stretchable Electrochemical Devices.

Yong Zhong,Cédric Plesse,Frédéric Vidal,Giao T M Nguyen,Edwin W H Jager

doi:10.1021/acsami.8b03537

Yong Zhong, Cédric Plesse + Show 3 more

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https://doi.org/10.1021/acsami.8b03537

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Abstract

An ionic conducting membrane is an essential part in various electrochemical devices including ionic actuators. To miniaturize these devices, micropatterns of ionic conducting membrane are desired. Here, we present a novel type of ionogel that can be patterned using standard photolithography and soft imprinting lithography. The ionogel is prepared in situ by UV-initiated free-radical polymerization of thiol acrylate precursors in the presence of ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. The resultant ionogel is very flexible with a low Young's modulus (as low as 0.23 MPa) and shows a very high ionic conductivity (up to 2.4 × 10-3 S/cm with 75 wt % ionic liquid incorporated) and has a reactive surface due to the excess thiol groups. Micropatterns of ionogel are obtained by using the thiol acrylate ionogel solution as an ionic conducting photoresist with standard photolithography. Water, a solvent immiscible with ionic liquid, is used as the photoresist developer to avoid complete removal of ionic liquid from thin micropatterns of the ionogel. By taking advantage of the reactive surface of ionogels and the photopatternability, ionogels with complex three-dimensional microstructure are developed. The surface of the ionogels can also be easily patterned using UV-assisted soft imprinting lithography. This new type of ionogels may open up for building high-performance flexible electrochemical microdevices.

Highlights

The increasing demand for wearable and flexible electrochemical devices has emphasized a need for soft and flexible ionic conducting membranes with high ionic conductivities[1,2,3,4,5]
A ionic conducting membrane such as a solid polymer electrolyte and an ionogel is a type of material which has been widely used as an ion reservoir and electronic insulator in numerous applications including supercapacitors[6], ionic actuators[7], electrolyte-gated transistors[8], electrochromic devices[9], solar cells[10] and electrochemical sensors[11]
The polymer gel network for ionogel preparation in this study was synthesized by the photopolymerization of a mixture of trifunctional thiol, PEG diacrylate and monofunctional PEG methacrylate in the presence of the photoinitiator benzoin methyl ether

Summary

Introduction

The increasing demand for wearable and flexible electrochemical devices has emphasized a need for soft and flexible ionic conducting membranes with high ionic conductivities[1,2,3,4,5]. A ionic conducting membrane such as a solid polymer electrolyte and an ionogel is a type of material which has been widely used as an ion reservoir and electronic insulator in numerous applications including supercapacitors[6], ionic actuators[7], electrolyte-gated transistors[8], electrochromic devices[9], solar cells[10] and electrochemical sensors[11]. An ABA-triblock copolymer based ionogel was utilized to prepare high-capacitance thin ionic conducting micropatterns for electrolyte-gated transistors[8]. These studies show that conventional standard photolithography is a convenient technique to obtain micropatterns of ionic conducting membrane and incorporate them into various microdevices. Microscale patterned ionic conducting membrane is possible by using soft imprinting lithographic or micromoulding techniques[20]

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