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 (μapp > 3700 Pa s at shear rates γ˙ = 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, 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.