Analyse du procédé et des paramètres de fabrication par écriture-direct assistée par lumière ultraviolet pour des applications d'emmagasinage d'énergie mécanique

Technological applications in the field of micro- and nano-technologies are evolving rapidly and are ever more demanding in their energy storage requirements for operation over long periods of time in a variety of environments. Chemical batteries are generally the preferred option due to their ease of use and high energy storage capacity. Mechanical energy storage devices (e.g., mechanical springs) provide a better resistance to extreme temperatures, more charge cycles before failure, a rapid release of energy and less leakage of stored energy compared to chemical batteries. Developments in advanced materials and nanotechnologies have led to materials with strengths that far exceed that of conventional materials and could be used to fabricate mechanical energy storage devices which compete with the chemical batteries in the specific energy (i.e., energy per unit mass). Here we used the Ultraviolet-Assisted Direct-Write (UV-DW) manufacturing process to produce three-dimensional (3D) micro-coils with filament diameters around 100 microns. By reducing the size of the filaments, the structures can be more compact and have higher energy densities (i.e., energy per unit volume). The UV-DW procedure involves the extrusion of 3D freeform filaments polymerized by immediate exposure to UV light. Helical and square spiral tower (SST) microcoil geometries and two modes of loading (tension and torsion) were analyzed in this study. A process-structure property relationship map was determined by fabricating multiple structures while varying the main process parameters. Parameter combinations leading to the desired structure configurations were determined. Helical and SST microcoils were fabricated and their mechanical responses were tested using a mechanical testing apparatus. For helical microcoils loaded in tension, a spring stiffness of 7.7 N m-1 was measured leading to a total energy storage of 34.2 μJ, an energy density of 4.15 kJ m-3 and a specific energy of 0.041 kJ kg-1.