title: Microfluidic magnetic self-assembly at liquid-liquid interfaces.
abstract: We present a microfluidic method that controllably self-assembles microparticles into clusters at an aqueous two-phase liquid-liquid interface. The liquid-liquid interface is formed between converging flows of aqueous dextran and polyethylene glycol, in a microfluidic cross-slot device. We control the size of the self-assembled particle clusters as they pass through the liquid-liquid interface, by systematically varying the applied magnetic field gradient, and the interfacial tension of the liquid-liquid interface. We find that upon penetration through the interface, the number of particles within a cluster increases with increasing interfacial tension, and decreasing magnetic field gradient. We also develop a scaling model of the number of particles within a cluster, and observe an inverse scaling of the number of particles within a cluster with the dimensionless magnetic Bond number. Upon cluster penetration across the liquid-liquid interface, we find magnetic Bond number regimes where the fluid coating drains away from the surface of the cluster, and where the clusters are encapsulated inside a thin film coating layer. This self-assembly technique may find application in controlling the size of microscale self-assemblies, and coating such assemblies; for example, in clustering and coating of cells for immunoisolated cell transplants.
authors: Ryerson University, Mechanical and Industrial Engineering, Toronto, Canada. scott.tsai@ryerson.ca.
authors: Steven G
authors: SG
authors: Jones
authors: Niki
authors: N
authors: Abbasi
authors: Byeong-Ui
authors: BU
authors: Moon
authors: Scott S H
authors: SS
authors: Tsai