Bioinspired Self-Healing Liquid Films for Ultradurable Electronics

Abstract

Resistive strain sensors play a crucial role in the development of flexible and stretchable electronics because of their excellent sensitivity and conformability. However, such sensors suffer from poor durability because of the low adhesion strength between the solid conductive layer and polymer and the irreparable dry friction inside the conventional solid conductive layers. Here, inspired from the structures and excellent abrasion resistance of tear films on animal corneas, we demonstrate ultradurable strain sensors based on uniform self-healing wear-free liquid films formed on biomimetic microvilli made from modified polydimethylsiloxane (PDMS). Ethanol solutions containing ionic liquids (ILs) are added to PDMS microvilli, which are superlyophilic due to the surface chemistry and special structures. During evaporation, ILs are driven upward by Laplace pressure and join into continuous conductive films. As the sensing layer, when repeatedly stretched and released, the capillary-stabilized liquid film is lossless because of wet friction, and the cracks will recover completely after release due to the capillary-force-induced self-healing capability, allowing the strain sensors to exhibit high durability of over 22 500 loading–unloading cycles. This work presents an approach for the construction of ultradurable electronics.

Facile Fabrication of Robust and Reusable PDMS Supported Graphene Dry Electrodes for Wearable Electrocardiogram Monitoring

“…To endow LIG electrodes with better adhesivity, the mixture of the silicone base and crosslinker of the PDMS‐based elastomer along with a trace of ethoxylated polyethylenimine (PEIE) is painted on the area outside of LIG, which has been previously reported to improve the stretchability, softness, and adhesion of PDMS. [ 25–28 ] The compliant surface and dangling bounds enhance the adhesion of PDMS/PEIE. [ 25 ] Eventually, the sample is cured at 90 °C for 1 h, forming single‐sided adhesive epidermal electrodes.…”

“…Till now, PEIE‐modified PDMS has been used to prepare adhensive flexible electronics. [ 9,26–28 ] Although no skin irritation was reported, the toxicity and biocompatibility of PEIE‐modified PDMS are still under research and it has not been concluded. This issue should be confirmed by a larger number of subjects and a series of cell incubation before practical use.…”

Flourishing Self‐Healing Surface Materials: Recent Progresses and Challenges

“…As a numerous source of inspiration, creatures in nature have evolved over millions of years, creating and achieving many special futures and properties, which provide unique structure and material sources for researchers to imitate . Thus, recently, the bioinspired self‐healing surface materials have become a hotspot owing to its widely recognized advantages . Up to date, some works have made obvious progresses by miming vascular systems and plant leaf surfaces .…”

Advances in Materials for Soft Stretchable Conductors and Their Behavior under Mechanical Deformation

“…The self-healing mechanism behind these materials have been largely categorized as extrinsic or intrinsic self-healing with extrinsic self-healing mechanism relying on dispersed healing agents to help repair damage. For electrical self-healing, examples of extrinsic self-healing sensors are those that involve liquid metals and ionic liquid-based active components which reflow to allow intermixing of materials at the reconnected interface [ 194 , 195 ]. This extrinsic mechanism is reliable but limited in the number of times it can be healed whereas intrinsic self-healing is dependent upon dynamic reversible covalent or non-covalent bonds which can allow the system to heal repeatedly through reorganization of the polymer matrix and often pertains to mechanical self-healing.…”