3d Printing a Tear-Resistance Conductive Organogel Used for Wearable Sensor

Abstract

In recent years, ion conductive hydrogels based on photocurable 3D printing technology have attracted wide attention in the application of wearable sensors, which greatly simplifies the manufacturing process of devices, while making devices with high sensitivity and high fidelity. However, the current ionic hydrogel network via photocuring 3D printing is mainly cross-linked by covalent bonds. Due to the lack of sufficient energy dissipation and high-functionality cross-links within the network, the gel cannot withstand large deformation, and the toughness and tear resistance are poor, so the hydrogel will inevitably crack after continuous dynamic loading. Here, we designed an organic gel that is completely constructed by physical crosslinking network and can be realized by photocurable 3D printing. The precursor of the organic gel is mainly composed of N-methylol acrylamide (NAM), nano-clays, photoinitiator, and water-glycerol binary solvent system. After the photocuring reaction, through forming strong hydrogen bonds with the poly-NAM molecular chains, the nano-clays containing a large number of hydroxyl functional groups constructed nanoscale high-functionality cross-links, which greatly improved the tear resistance of the gel. In addition, thanks to the Na+ ions released by nano clays, the gel had better ionic conductivity. In addition, the gel prepared with binary water-glycerol solvent system can still maintain good mechanical stability at -20°C. What's more, combining skin-like organic gels and 3D printing technology enables the manufacture of highly sensitive sensors much easier and more designable. This study not only provides a method for the preparation of high-precision ionic conductors with complex structures and good mechanical stability, but also clears the way for developing a new class of wearable devices and intelligent electronics.

Keywords: Wearable sensor, Photocurable 3D printing, Ionic conductor, organogel, Tear resistance