Acoustophoretic Liquefaction for 3D Printing Ultrahigh-Viscosity Nanoparticle Suspensions.

Liu, Zheng; Pan, Wenyang; Wang, Kaiyang; Matia, Yoav; Xu, Artemis; Barreiros, Jose A; Darkes-Burkey, Cameron; Giannelis, Emmanuel P et al. · Adv Mater · 2022

basic_science · Level V

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Abstract

An acoustic liquefaction approach to enhance the flow of yield stress fluids during Digital Light Processing (DLP)-based 3D printing is reported. This enhanced flow enables processing of ultrahigh-viscosity resins (μ<sub>app</sub>  > 3700 Pa s at shear rates <math xmlns="http://www.w3.org/1998/Math/MathML"><mover><mi>γ</mi> <mo>˙</mo></mover> </math>  = 0.01 s<sup>-1</sup> ) based on silica particles in a silicone photopolymer. Numerical simulations of the acousto-mechanical coupling in the DLP resin feed system at different agitation frequencies predict local resin flow velocities exceeding 100 mm s<sup>-1</sup> at acoustic transduction frequencies of 110 s<sup>-1</sup> . Under these conditions, highly loaded particle suspensions (weight fractions, ϕ = 0.23) can be printed successfully in complex geometries. Such mechanically reinforced composites possess a tensile toughness 2000% greater than the neat photopolymer. Beyond an increase in processible viscosities, acoustophoretic liquefaction DLP (AL-DLP) creates a transient reduction in apparent viscosity that promotes resin recirculation and decreases viscous adhesion. As a result, acoustophoretic liquefaction Digital Light Processing (AL-DLP) improves the printed feature resolution by more than 25%, increases printable object sizes by over 50 times, and can build parts >3 × faster when compared to conventional methodologies.