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

摘要

We report on experimental demonstrations of the first sub-100 mu m 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 micro-mechanical resonators with rich, reconfigurable 1D and 2D mode shapes. Silica microparticles (1-8 mu m in diameter) dispersed on top of resonating doubly-clamped beams (100 x 10 x 0.4 mu m(3)) are observed to aggregate at antinodal points, forming 1D inverse Chladni figures, while microbeads atop square trampoline resonators (50 x 50 x 0.2 mu m(3)) cluster at nodal lines/circles, creating 2D standard Chladni figures such as "(sic)," "circle," "x," 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 the standard Chladni figure generation in the 2D trampoline experiments. We further demonstrate dynamical patterning, switching, and removal of 2D micro-Chladni figures in swift succession by simply controlling the excitation frequency. These results render new understandings of Chladni patterning genuinely at the microscale, as well as a non-invasive, versatile platform for manipulating microanoparticles and biological objects in liquid, which may enable microdevices and functional device-liquid interfaces toward relevant sensing and biological applications. Published by AIP Publishing.