ABSTRACT
Manipulation of particles in a microfluidic system is an important research subject in biomedical engineering. However, most conventional passive techniques for particle control have difficulties in integrating other functions into microfluidic channels. A unique microfluidic valve was proposed in this study for switchable particle control by employing a shape memory polymer (SMP). A microfluidic logic device can be programmed based on deformation of the SMP microchannel constructed on a poly(dimethylsiloxane) (PDMS) film. Particles in a viscoelastic flow were focused at preferred equilibrium locations by the competition between inertia and elastic forces. The channel shape played an important role in determining those forces in the channel. Hydrodynamic behavior and shape recovery behavior of the SMP microchannel were modeled theoretically. It was confirmed that the particle valve prepared with the SMP implemented a programmable binary logic operation in the microfluidic channel.
Subject(s)
Dimethylpolysiloxanes , Lab-On-A-Chip Devices , Logic , Elasticity , Equipment Design , ViscosityABSTRACT
Particles in a viscoelastic fluid are typically focused at the center and four corners of a rectangular channel because of the combination of fluid elasticity and inertia forces. In this study, we observe the transition between single-line and multiple-line particle focusing in a microfluidic device induced by the synergetic effect of inertia and viscoelasticity. The elastic and inertial forces acting on suspended particles are manipulated by controlling the concentration of dilute polymer solution and the flow rate of a fluid. The finding shows that the confinement effects determined by the channel aspect ratio and the inlet geometry lead to the multiple-line focusing of particles in the microfluidic channel due to the fluid elasticity and hydrodynamic behavior of the fluid. A microfluidic channel with high channel aspect ratio possesses broad minimal region of the elastic force across the channel, which generates a wide particle focusing band rather than a single particle focusing at the center. The multiple-line particle focusing occurs as the inertial force outweighs the elastic force, resulting in the particle migration toward the channel sidewalls.
