Preparation of MPASP‐PAA/Fe³⁺ Composite Conductive Hydrogel with Physical and Chemical Double Crosslinking Structure and Its Application in Flexible Strain Sensors

Abstract

Conductive hydrogels show broad prospects in wearable electronic devices. However, the conductive hydrogel cross‐linked only by chemical bonds has the shortcomings of being hard and brittle, easy to break under pressure. In order to solve these problems, the MPASP‐PAA/Fe3+ composite conductive hydrogel is prepared by the method of physical and chemical double crosslinking using modified polyaspartic acid (MPASP) as the chemical crosslinking agent and FeCl3 as the physical crosslinking agent. Compared with traditional chemical crosslinking agents such as N′N‐methylene bisacrylamide, the MPASP can not only increase mechanical properties of the conductive hydrogel, but also improve the biodegradability and biocompatibility. At the same time, FeCl3 as a physical crosslinking agent can also enhance the conductivity and toughness of the conductive hydrogel. When MPASP and Fe3+ content are 2.5 wt% and 0.75 mol%, respectively, the MPASP‐PAA/Fe3+ composite conductive hydrogel exhibits high conductivity (0.12 S m−1), sensitivity (4.93), and stretchability (329%). In addition, its compressive strength is as high as 1081.39 KPa. The flexible strain sensor assembled by the MPASP‐PAA/Fe3+ composite conductive hydrogel can not only monitor human joint movements such as elbow and wrist bending, but also detect subtle vibrations such as vocalization and swallowing.

A robust and sensitive flexible strain sensor based on polyurethane cross-linked composite hydrogels for the detection of human motion

“…MXenes are a type of two-dimensional inorganic compound and consist of transition metal carbides, nitrides or carbonitrides of several atomic layers in thickness. 33,34 The abundant surface terminations of MXenes can form physical connections ( e.g. , hydrogen bonds) with hydrogels.…”