Acoustophoretic Liquefaction for 3D Printing Ultrahigh-Viscosity Nanoparticle Suspensions

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 (mu(app) > 3700 Pa s at shear rates gamma = 0.01 s(-1)) 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(-1) at acoustic transduction frequencies of 110 s(-1). Under these conditions, highly loaded particle suspensions (weight fractions, phi = 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 x faster when compared to conventional methodologies.