Near-Zero Hysteresis Ionic Conductive Elastomers with Long-Term Stability for Sensing Applications

Abstract

Soft conductive elastomers with low hysteresis over a wide range of stretchability are desirable in various applications. Such applications include soft sensors with a long measurement range, motion recognition, and electronic skin, just to name a few. Even though the measurement capability of the sensors based on soft materials has been greatly improved compared to the traditional ones in recent years, hysteresis in the loading and unloading states has limited the applications of these sensors, thereby negatively affecting their accuracy and reliability. In this work, conductive elastomers with near-zero hysteresis have been formulated and fabricated using 3D printing. These elastomers are made by combining highly stretchable dielectric elastomer formulations with a polar hydrophobic ionic liquid and polymerizing under ultraviolet light. High-performance piezoresistive sensors have been fabricated and characterized, with a 10-fold stretchability and low hysteresis (1.2%) over long-term stability (more than 10 000 cycles under cyclic stress) with a 20 ms response time. Additionally, the current elastomers displayed fast mechanical and electrical self-healing properties. Using 3D printing in conjunction with some of our structural innovations, we have fabricated smart gloves to show this material's wide range of applications in soft robots, motion detection, wearable devices, and medical care.

Printed Low-Hysteresis Stretchable Strain Sensor Based on a Self-Segregating Conductive Composite

“…The sensitivity, i.e., the gauge factor (GF), can be calculated by eq : where ΔR is the change in resistance under applied strain, R 0 is the resistance at 0% strain, and ε is the applied strain. Our SSCC sensor shows a gauge factor (GF) of 13.8 with a low hysteresis of 6.2%, as well as a linear response to stretching ( R 2 ≈ 0.996) and release ( R 2 ≈ 0.988), which is an excellent property compared to those of the recently reported strain sensors. ,,− When the sensor is stretched to 80% with a stepwise strain of 20%, and a holding time of 65 s, the resistance response follows the applied strain promptly and completely recovers to its initial value after sequential release (Figure c). The SSCC sensor shows excellent response reliability compared to that of random PDMS/CB, as shown in Figure d, Figure S7, and Video S1; upon application of cyclic strain to the sensor with different values of 60%, 80%, and 100%, the sensor shows relatively stable resistance response characteristics.…”

3D Printing of High Viscosity UV‐Curable Resin for Highly Stretchable and Resilient Elastomer

“…The disappearance of the characteristic absorption ─NCO peak (2270 cm −1 ) further proved that the PU-NCO and TBEMA completely reacted and formed the HUBs structure of PUB oligomers. Furthermore, the structure of PUB is characterized by 1 H NMR (Figure S3, Supporting Information). The characteristic peaks of (H 1 ) and (H 2 ) are related to ─C═CH 2 at 5.5-6.0 ppm, and the peaks at 1.0-1.5 ppm (H 5 ) belong to the ─CH 3 bond in the tert-butyl group.…”

“…Elastomers produced through additive manufacturing (AM, also known as 3D printing), have found broad applications in a wide variety of fields, including flexible sensors, soft robotics, and DOI: 10.1002/adma.202304430 bioengineering. [1] These applications often call for the creation of intricate, highprecision 3D structures. For instance, constructing designed cavity channels in flexible actuators can lead to complex actions.…”

A Mechanically Robust, Self‐Healing, and Adhesive Biomimetic Camouflage Ionic Conductor for Aquatic Environments

“…However, the presence of fillers in the composite causes it to become opaque and may result in breaks in the electronic pathways under large strains due to the mismatch between the modulus of the elastomer and the filler. [ 11 ] Additionally, electrical leakage can occur when the composite is structurally damaged underwater. [ 12 ] Ion‐conductive hydrogels are obtained through the introduction of electrolytes.…”