Highly Electrically Conductive Flexible Ionogels by Drop‐Casting Ionic Liquid/PEDOT:PSS Composite Liquids onto Hydrogel Networks

Abstract

Ionogels have been extensively studied as ideal flexible and stretchable materials by virtue of the unique properties of ionic liquids, such as non-volatility, non-flammability, and negligible vapor pressure. However, the generally low ionic conductivity of the current ionogels limits their applications in the market of highly conductive, flexible, and stretchable electrical devices. Here, the fabrication of highly electrically conductive ionogels is reported by combining composite liquids consisting of 1-ethyl-3-methylimidazolium dicyanamide ([EMIM][DCA]) and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) with flexible negative-charged poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPS) hydrogel. The generated composite film exhibits high electrical conductivity up to about 38 S cm −1 with the maximum tensile strain of 45% and fracture stress of 27 kPa. In addition, it is demonstrated that the composite film can maintain conductivity in a high level under different mechanical deformations, and can also be used as flexible sensors in a wide temperature range from −58 to 120 °C. It is believed that the designed composite film would expand the applications of flexible conductive materials where both high conductivity and robust mechanical flexibility are required.

Manipulation of cross-linking in PEDOT:PSS hydrogels for biointerfacing

“…This trend is similar to that reported of PEDOT:PSS thin films where ionic liquid is used as an additive to increase conductivity. 36 The conductivity values of these conducting hydrogels are comparable to other reports of pure PEDOT:PSS hydrogels made with mixing and casting techniques (10–20 S m −1 ). 15,17,37 With more extensive preparation and/or post-fabrication processing steps such as annealing, acid or solvent treatment, conductivity and modulus of PEDOT:PSS hydrogels have been reported to be 2–3 orders magnitude higher than the hydrogels here (∼2 MPa and ∼4000 S m −1 ), 20,38,39 and additionally, display lower water fractions (∼70–89%).…”

Boosting the Performance of PEDOT:PSS Based Electronics Via Ionic Liquids

“…In addition, Yang et al selected a non-volatile IL (EMIM:DCA) as the modifier and measured the conductivity of PEDOT:PSS/IL composite material with a four-point-probe (4PP), which reached as high as 1200 S cm −1 . [51] Given PEDOT:PSS's distinctive mixed ion/electron conductivity characteristics, IL incorporating can also significantly enhance its ionic conductivity. In contrast to the method of testing electronic conductivity, ionic conductivity is usually measured by electrochemical impedance spectroscopy (EIS).…”

“…Reproduced with permission. [ 51 ] Copyright 2021, Wiley‐VCH GmbH. “Printability”: Reproduced with permission.…”

Recent Progress in Mechanically Robust and Conductive‐Hydrogel‐Based Sensors

“…[49,71] Common electronic conductive materials include metal (e.g., gold, silver, and copper) NPs/nanowires, [72][73][74] carbon-based materials (e.g., carbon NPs/carbon nanowires, graphene, and graphene oxide [GO]), [75,76] and conductive polymers (e.g., polyaniline [PANI], polypyrrole [PPy], poly(3,4-ethylene dioxythiophene):polystyrene sulfonate [PEDOT:PSS]). [77][78][79] Introducing electronic conductive materials provides conductivity to hydrogels and improves their tensile and mechanical properties. The direct addition of metal materials to hydrogels affects their elasticity and tensile properties.…”