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.
Keywords: durability; flexible sensors; liquid film; self-healing; superlyophilic.