Dynamic self-assembly and control of microfluidic particle crystals

Abstract

Engineered two-phase microfluidic systems have recently shown promise for computation, encryption, and biological processing. For many of these systems, complex control of dispersed-phase frequency and switching is enabled by nonlinearities associated with interfacial stresses. Introducing nonlinearity associated with fluid inertia has recently been identified as an easy to implement strategy to control two-phase (solid-liquid) microscale flows. By taking advantage of inertial effects we demonstrate controllable self-assembling particle systems, uncover dynamics suggesting a unique mechanism of dynamic self-assembly, and establish a framework for engineering microfluidic structures with the possibility of spatial frequency filtering. Focusing on the dynamics of the particleparticle interactions reveals a mechanism for the dynamic selfassembly process; inertial lift forces and a parabolic flow field act together to stabilize interparticle spacings that otherwise would diverge to infinity due to viscous disturbance flows. The interplay of the repulsive viscous interaction and inertial lift also allow us to design and implement microfluidic structures that irreversibly change interparticle spacing, similar to a low-pass filter. Although often not considered at the microscale, nonlinearity due to inertia can provide a platform for high-throughput passive control of particle positions in all directions, which will be useful for applications in flow cytometry, tissue engineering, and metamaterial synthesis.inertial ordering | hydrodynamic interaction | particle-laden flow | defocusing | microfluidics

Particle Focusing in Curved Microfluidic Channels

“…This type of high quality focusing is important for both high precision positional focusing and due to the correlation between this single point focusing and consistent longitudinal ordering between particles 23,36 . It is also of note that single point particle focusing is possible in simple curved channels not requiring the more complicated structures required for the other known techniques for sheathless alignment of particles 26,37,38 .…”

Hydrodynamic mechanisms of cell and particle trapping in microfluidics

“…These applications including but not limited to cell and particle focusing, [61][62][63] sorting, 64 separation, [65][66][67] self-assembly, 68 filtration, [69][70][71] and enrichment and trapping 72 are poised to be high-throughput due to their operation under high flow rates. Recent progress and potential future directions in the area of inertial microfluidics are discussed in a recent review article by Di Carlo.…”

Dynamics of particle migration in channel flow of viscoelastic fluids

“…Depending on the flow conditions, inertial effects, proximity of the channel wall, fluid elasticity, shear-thinning, particle deformability, and particle-particle interactions may affect the dynamics of the particle motion and the flow field. Interplay between these effects result in various interesting phenomena, such as cross-streamline particle migration (Segré & Silberberg 1961), particle focusing at the channel centreline Lim et al 2014a), wall-surface accumulation of particles Gauthier et al 1971), self-assembly of two particles (Lee et al 2010) and the particleinduced lateral transport of the fluid (Amini et al 2012). These phenomena have been successfully used for the manipulation of cells and particles suspended in microfluidic platforms.…”