title: Numerical Simulations of the Digital Microfluidic Manipulation of Single Microparticles.
abstract: Single-cell analysis techniques have been developed as a valuable bioanalytical tool for elucidating cellular heterogeneity at genomic, proteomic, and cellular levels. Cell manipulation is an indispensable process for single-cell analysis. Digital microfluidics (DMF) is an important platform for conducting cell manipulation and single-cell analysis in a high-throughput fashion. However, the manipulation of single cells in DMF has not been quantitatively studied so far. In this article, we investigate the interaction of a single microparticle with a liquid droplet on a flat substrate using numerical simulations. The droplet is driven by capillary force generated from the wettability gradient of the substrate. Considering the Brownian motion of microparticles, we utilize many-body dissipative particle dynamics (MDPD), an off-lattice mesoscopic simulation technique, in this numerical study. The manipulation processes (including pickup, transport, and drop-off) of a single microparticle with a liquid droplet are simulated. Parametric studies are conducted to investigate the effects on the manipulation processes from the droplet size, wettability gradient, wetting properties of the microparticle, and particle-substrate friction coefficients. The numerical results show that the pickup, transport, and drop-off processes can be precisely controlled by these parameters. On the basis of the numerical results, a trap-free delivery of a hydrophobic microparticle to a destination on the substrate is demonstrated in the numerical simulations. The numerical results not only provide a fundamental understanding of interactions among the microparticle, the droplet, and the substrate but also demonstrate a new technique for the trap-free immobilization of single hydrophobic microparticles in the DMF design. Finally, our numerical method also provides a powerful design and optimization tool for the manipulation of microparticles in DMF systems.
authors.affiliation: School of Engineering, University of California-Merced , Merced, California 95343, United States.
authors.forename: Chuanjin
authors.initials: C
authors.lastname: Lan
authors.affiliation: School of Engineering, University of California-Merced , Merced, California 95343, United States.
authors.forename: Souvik
authors.initials: S
authors.lastname: Pal
authors.affiliation: Division of Applied Mathematics, Brown University , Providence, Rhode Island 02912, United States.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Li
authors.affiliation: School of Engineering, University of California-Merced , Merced, California 95343, United States.
authors.forename: Yanbao
authors.initials: Y
authors.lastname: Ma
mesh_terms: D000465:Algorithms; D046210:Microfluidic Analytical Techniques; D056004:Molecular Dynamics Simulation; D010316:Particle Size; D059010:Single-Cell Analysis; D017155:Wettability