Gradual Electrical‐Double‐Layer Modulation in Ion‐Polymer Networks for Flexible Pressure Sensors with Wide Dynamic Range

To realize flexible pressure sensors with high sensitivity, surface‐textured soft films have often been adopted and the contact area can vary significantly depending on the applied pressure. However, the contact area modulation realized in such a way is subject to a limited dynamic range, and its infinitesimal zero‐pressure contact area raises concerns regarding durability. Herein, a flexible pressure sensor made of a texturing‐free piezocapacitive layer based on ion‐polymer networks is proposed. In this scheme, ion infiltration leads to electrical‐double‐layer modulation that gradually varies over a wide range of applied pressures. The proposed flexible pressure sensors with the optimal ion concentration are shown to exhibit both excellent mechanical durability and linear responses with high sensitivity over a wide pressure range up to 1 MPa. With the simple fabrication route, high performance, and reliability, the proposed approach may open up a new avenue for skin‐like pressure sensors ideal for many emerging applications. A piezocapacitive film with huge capacitance variation of 3000 times is achieved using a mechanism of electrical‐double‐layer modulation, that is enabled by a change of relative concentration of ionic liquid in a polymer network film according to thickness reduction. This planar, texture‐free, and very thin film shows superlinear response to a wide range of pressure up to 1 MPa.