Standard and inverse microscale Chladni figures in liquid for dynamic patterning of microparticles on chip

We report on experimental demonstrations of the first sub-100 μm scale standard and inverse Chladni figures in both one- (1D) and two-dimensional (2D) fashions in liquid, and on exploiting these micro-Chladni figures for patterning microparticles on chip, via engineering multimode micromechanical resonators with rich, reconfigurable 1D and 2D mode shapes. Silica microparticles (1–8 μm in diameter) dispersed on top of resonating doubly-clamped beams (100 × 10 × 0.4 μm3) are observed to aggregate at antinodal points, forming 1D inverse Chladni figures, while microbeads atop square trampoline resonators (50 × 50 × 0.2 μm3) cluster at nodal lines/circles, creating 2D standard Chladni figures such as “,” “○,” “×,” and “\.” These observations suggest two distinct micro-Chladni figure patterning mechanisms in liquid. Combining analytical and computational modeling, we elucidate that streaming flow dominates the inverse Chladni pattern formation in the 1D beam experiments, while vibrational acceleration dictates ...