We envision implementing direct ink writing for 3-D printing while aligning microfibers in the resin using standingwave ultrasonics; the aligned fibers would control desired mechanical properties such as strength and ductility, and 3-Dprinting would match the mechanical properties to the particular part geometry. At this time we work with highviscosityfluids as a physical simulant of representative resins, and spherical polystyrene microparticles or glass microrodsinstead of microfibers. In this paper we show experimental results using square glass capillaries (with interiordimensions ranging from 0.4 to 1.0 mm) as our microfluidic systems, which are inherently well-suited by their geometryto act as print nozzles, sandwiched between two piezoceramic plates that generate the ultrasonic standing waves. Wereport experimental data for particle alignment as we change from our initial test fluid, water, to high-viscosity fluids.Similarly, we report experimental data of the fluid behavior pertinent to direct ink writing; we enforce controlledvolumetric flow rates (which correspond to print speeds) for high-viscosity fluids under pressurized flow through glasscapillaries of varying cross-sectional areas and varying lengths, observing and measuring the approximate ink line widthand height. Our use of commercially available square glass capillaries (sandwiched between piezoceramic transducersthat are driven at frequencies away from transducer resonance) is novel and distinguishes our approach from that ofother research groups; the underlying physics of our devices differs from that of Lund-type acoustic resonators.
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