Dynamics simulation of positioning and assembling multi-microparticles utilizing optoelectronic tweezers

Abstract

Optoelectronic tweezer (OET) has become a powerful and versatile technique for manipulating microparticles and cells using real-time reconfigurable optical patterns. However, detailed research in the dynamics of particles in an OET device is still scarce, and the multipleparticle interactions still need further quantitative investigation. In this study, a dynamics simulation model coupling optically induced dielectrophoretic force, interaction forces between particles, and hydrodynamic and sedimentary forces is established and numerically solved by utilizing a finite element method and a dynamics simulation frame for multi-microparticles' positioning and assembling in a typical OET device. The spatial distributions of particles in the energized OET device before optically projecting are simulated first and the condition for particle chain formation is discussed. Then, the most representative ring-shaped optical pattern is applied, and the influences of optical-ring tweezer' dimensions of inner radius R e and width d e on positioning and assembling effect are dynamically simulated and discussed for 5-and 2-lm radius particles. The simulation results indicate the particles inside and outside optical ring both undergo negative DEP and are distributed centre-symmetrically under the action of ring virtual tweezers. Average distance between the particle and center of ring (ADPC) at equilibrium and the system equilibrium time characterizing particle positioning effect dramatically increase for both 5-and 2-lm radius particles while R e increases from 35 to 55 lm. Specially, the captured particles will pile up and immediately form a three-dimensional micropyramid structure when R e approximately equals 25 lm for the 5-lm radius particle. Moreover, ADPC decreases very slowly for both two particle-sizes and the system equilibrium time of 2-lm radius particle vary more obviously than that of 5-lm radius particle with d e increasing from 10 to 30 lm. And the system equilibrium time for 2-lm radius particle is always larger than that for 5-lm radius particle. The primary simulation results are in good agreement with experimental observations; hence this dynamics simulation model can truly predict the particlemoving trajectory and equilibrium positions in an OET device. Moreover, this dynamics simulation holds promise for designing and optimizing optical patterns for accuracy in assembling particles in order to form a specific microstructure.

Mixing Mechanism of Microfluidic Mixer with Staggered Virtual Electrode Based on Light-Actuated AC Electroosmosis

“…In general, the conductivity of the photoconductive layer was approximately σ D = 6.7 × 10 –5 S/m, and when light was projected onto the photoconductive layer, the conductivity of the illuminated area increased sharply to σ L = 0.2 S/m [ 48 ]. This means that a specific nonuniform electric field was generated in the microchannel when a specific optical pattern was projected onto the photoconductive layer.…”

Expanding the flexibility of dynamics simulation on different size particle–particle interactions by dielectrophoresis

“…As far as the effective dipole moment is concerned, the mutual DEP force between two particles can be expressed in Eq. (1) [24] as:…”

Microscopic Particle Manipulation via Optoelectronic Devices

“…The ODEP (also called optoelectronic tweezers, OETs) has showed the ability to parallelly position colloidal particles without any template [18,35]. The microparticles can be trapped and driven by the DEP forces induced by the optical micropatterns in optoelectronic devices [36,37]. However, the rotation of assembled microparticle chains by OETs has rarely been investigated, and the degree of freedom for varying the postures, positions or orientations of the microparticle chains still has limitations.…”