Ultrastrong Ionotronic Films Showing Electrochemical Osmotic Actuation

Abstract

A multifunctional soft material with high ionic and electrical conductivity, combined with high mechanical properties and the ability to change shape can enable bioinspired responsive devices and systems. The incorporation of all these characteristics in a single material is very challenging, as the improvement of one property tends to reduce other properties. Here, a nanocomposite film based on charged, high‐aspect‐ratio 1D flexible nanocellulose fibrils, and 2D Ti3C2Tx MXene is presented. The self‐assembly process results in a stratified structure with the nanoparticles aligned in‐plane, providing high ionotronic conductivity and mechanical strength, as well as large water uptake. In hydrogel form with 20 wt% liquid, the electrical conductivity is over 200 S cm−1 and the in‐plane tensile strength is close to 100 MPa. This multifunctional performance results from the uniquely layered composite structure at nano‐ and mesoscales. A new type of electrical soft actuator is assembled where voltage as low as ±1 V resulted in osmotic effects and giant reversible out‐of‐plane swelling, reaching 85% strain.

Electrochemically Controlled Hydrogels with Electrotunable Permeability and Uniaxial Actuation

“…To stimulate the ECO hydrogel, we connect it directly to an electric cable and apply a low voltage of ±1 V to capacitively charge/discharge the CNTs in the bulk of the hydrogel (Figure 1e). We note that the main electrochemical reaction here is non‐faradaic, but these systems also work with pseudocapacitive charging as we have shown with MXene in a parallel work [ 27 ] and may also work with faradaic processes. Inserted electrons are compensated by Na + from the solution, resulting in a flux of ions into the bulk of the hydrogel, transducing the ECO pressure into uniaxial expansion.…”

“…[35] Two-way actuation (reversibility) without a spring-back is also a desirable feature, which we show is possible using the ECO principle in MXene-based nanocomposite hydrogels. [27] To increase the actuation rate, we envision tuning the type of electrolyte and its concentration, reduce the cohesion in the network, or design of advanced structures with channels or holes to provide faster access to the electrolyte locally, which has been shown to improve the actuation rate of CNF sheets. [14] Thanks to the abundance of CNFs and bulk electroactive nanomaterials, our multifunctional hydrogels can be easily produced in any lab and at scale.…”

“…Two‐way actuation (reversibility) without a spring‐back is also a desirable feature, which we show is possible using the ECO principle in MXene‐based nanocomposite hydrogels. [ 27 ]…”

Multifunctional Conductive Hydrogel Composites with Nickel Nanowires and Liquid Metal Conductive Highways

“…Conductivity was first measured by a four-probe tester (RTS-8, 4Probes Tech Ltd., China), and the thickness of hydrogels was measured by a digital thickness gauge. , Four-probe tests can minimize contact resistance; for the conductivity tests of hydrogels incorporating aligned NiNWs, the direction of the current was placed along their long axis.…”

A personalized electronic textile for ultrasensitive pressure sensing enabled by biocompatible MXene/PEDOT:PSS composite

“…The rapid advancement of 5G information technology and the Internet of Things has sparked a heightened demand for intelligent sensing devices 1–8 . The convergence of sensing technologies with textiles has the potential to accelerate the development of next‐generation wearable electronics, catering to a diverse range of applications such as human‐machine interfaces, human motion detection, health monitoring, artificial electronic skin (E‐skin), and so forth 9–15 .…”