Biocompatible Dielectric-Conductive Microsystems Monolithically 3-D Printed Via Polymer Extrusion

Additive manufacturing (AM), i.e., the layer-by-layer construction of devices using a computer-aided design (CAD) file, has been recently explored as a manufactur- ing toolbox for MEMS. The demonstration of monolithic multi-material devices in 3-D printed MEMS has the potential to implement better, more complex, and more capable microsystems at a small fraction of the time and cost typically associated with semiconductor cleanroom microfabrication. Fused filament fabrication (FFF) is an AM technique based on extrusion of thermoplastic polymers that is arguably the simplest and cheapest commercial 3-D printing technology available.

Here,wereportadditivelymanufacturedmonolithic microsystems composed of conductive and dielectric layers using an FFF dual extruder 3-D printer. The base material is a biocompatible polymer, polylactic acid (PLA), which can be doped with micro/nanoparticles to becomeelectricallyconductive.Characterizationofthe printing technology demonstrates close resemblance between CAD files and printed objects, generation of watertight microchannels, high-vacuum compatibility, and non-cytotoxicity. A large (~23) piezoresistive gauge factor was measured for a certain graphite-doped conductive PLA, suggesting its utility to implement 3-D printed strain transducers via FFF. Multiplexed electrohydrodynamic liquid ionizers with integrated extractor electrode and threaded microfluidic port were also demonstrated. The per-emitter current vs. per-emitter flowrate characteristic shows a power dependence with 0.6 coefficient, close to the square-root dependence predicted by de la Mora’s law for the cone-jet emission mode.