Direct ink writing of reinforced polydimethylsiloxane elastomer composites for flexure sensors

Flexible materials with ideally designed structures and properties through direct ink writing (DIW) offer vast potential for flexible wearable devices, sensors, soft robots, and so on. Despite its common use as a flexible material, Sylgard-184's poor rheological properties restrict its ability of printing precision models by DIW. Herein, we have improved the viscosity of Sylgard-184 by adding suitable crosslinkers and silica, which produce inks with high printing quality and a low slump rate (3.75%). In addition, the DIW printing process was investigated, and a theoretical model relating to the basic printing parameters was developed. With the model, it is possible to predict printing parameters for various elastomers. To further demonstrate the application of this strategy to flexible wearable devices, a sensor was printed. The sensor allowed real-time monitoring of bending angles through bending angle tests. A change from 0 to 135° was detected using this bending sensor. We believe that the results of this research will provide ideas for the high-quality printing of silicone elastomers.