Ultra precision screening of hollow glass microspheres under the synergistic effect of airflow field and ultrasonic vibration

To meet the strict particle size requirements of hollow glass microspheres (HGMs) for high-precision assembly of augmented reality (AR) diffractive optical waveguide lenses, this study proposes a high-precision screening method for HGMs. A vibration-airflow screening device combining oscillatory vibration, ultrasonic vibration, and airflow field is designed and manufactured. Using the coupled computational fluid dynamics and discrete element method (CFD-DEM), the effects of the top blower, bottom induced draft fan, and double-layer annular air outlet on the airflow distribution over the screen surface are systematically analyzed, and the optimal wind speed combination for a uniform airflow field on three-layer screens is obtained. Screening efficiencies under different synergistic conditions are evaluated via EDEM simulations, with the maximum average screening efficiency reaching 76.1%. Key process parameters including amplitude, frequency, ultrasonic frequency, and wind speed are optimized using single-factor experiments and response surface methodology (RSM). Under the optimal parameters, the particle size standard deviation of the screened HGMs is 1.12 μm, which fully satisfies the high-precision requirements for spacer materials in AR diffractive optical waveguide lens assembly.