Junjun Ding1
Alfred University1
Material extrusion 3D printing (ME3DP) processes including fused filament fabrication (FFF), direct ink writing (DIW), and robocasting are versatile to construct three-dimensional structures layer by layer by patterning a wide variety of materials. This is especially useful for printing multiple functional materials for controlled electromechanical properties. To employ multiple materials in composites in the material extrusion 3D printing processes, different approaches have been reported, including using multiple nozzles or designing a feedstock with different desired materials. I will introduce our approaches to design and fabricate functional composites for sensing and energy storage applications.<br/>The compressive strain sensor is an extensively used flexible electronic device because of its capability to convert mechanical deformation to an electrical signal. However, the difficulty in tuning the performance of the strain sensor limits its further applications. Herein, we present the approach of fabricating a carbon nanotube (CNT)/ polydimethylsiloxane (PDMS) compressive strain sensor, which has both tunable mechanical and electrical performance. We use the ME3DP method to fabricate the composites, due to its advantages of design flexibility and compatibility with liquid-based materials. The foam microstructure formed by removing sodium chloride provides a large-scale deformation of at least 50% compressive strain and excellent elasticity. The strain sensor works durably over 1000 cycles, with a gauge factor of 2.35.<br/>Energy storage devices in a flexible form have a spreading application in various fields, such as soft robotics, human motion monitoring, and smart textiles. Fiber shaped supercapacitors are especially attractive as an energy storage unit in these applications due to their excellent flexibility. Here we prepare flexible core-shell fibers via a modified material extrusion 3D printer. The extrusion system with a custom-designed core-shell nozzle is used to extrude slurries from inner core and outer shell at the same time. Carboxymethylcellulose sodium salt (CMC) slurry with controlled rheological properties is extruded from the shell channel, while the graphene oxide (GO) slurry is extruded from the core channel simultaneously. The formed GO-CMC fiber is then reduced to achieve a conductive inner rGO core with CMC sheath as a separator to avoid short circuits between two electrodes. The resulted core-shell fiber supercapacitor lays a foundation for a robust and flexible 3D supercapacitor constructed by the fibers.