Magnetophoresis ‘meets’ viscoelasticity: deterministic separation of magnetic particles in a modular microfluidic device

Abstract

The deflection of magnetic beads in a microfluidic channel through magnetophoresis can be improved if the particles are somehow focused along the same streamline in the device. We design and fabricate a microfluidic device made of two modules, each one performing a unit operation. A suspension of magnetic beads in a viscoelastic medium is fed to the first module, which is a straight rectangular-shaped channel. Here, the magnetic particles are focused by exploiting fluid viscoelasticity. Such a channel is one inlet of the second module, which is a H-shaped channel, where a buffer stream is injected in the second inlet. A permanent magnet is used to displace the magnetic beads from the original to the buffer stream. Experiments with a Newtonian suspending fluid, where no focusing occurs, are carried out for comparison. When viscoelastic focusing and magnetophoresis are combined, magnetic particles can be deterministically separated from the original streamflow to the buffer, thus leading to a high deflection efficiency (up to ~96%) in a wide range of flow rates. The effect of the focusing length on the deflection of particles is also investigated. Finally, the proposed modular device is tested to separate magnetic and non-magnetic beads.

Particle manipulations in non-Newtonian microfluidics: A review

“…The flow-induced elasto-inertial effect in viscoelastic fluids has been utilized to pre-focus particles for a continuous sheath-free [132] first demonstrated such a hybrid separation in an H-shaped microchannel (Fig. 12a, top), where the buffer in the top branch is a particle-free solution for collecting the sorted magnetic particles.…”

Sheathless Dean-flow-coupled elasto-inertial particle focusing and separation in viscoelastic fluid

“…Therefore, sheath ow or specic channel geometry to induce particles to one side of the wall can be applied initially, then separation can be realized downstream. This has been demonstrated in several studies: with the aid of sheath ow to pinch all the particles along one sidewall at the inlet, Nam et al 32 realized particle separation with high purity using elasto-inertial effect of PEO solution in a square channel; Lu and Xuan 33 presented the "elasto-inertial pinched ow fractionation" (eiPFF) method to achieve continuous particle separation in PEO solutions; Kang et al 34 achieved particle separation by size in DNA solution; Del Giudice and his coworkers 35 integrated magnetophoresis with viscoelasticity in polyacrylamide (PAM) solution in a H-shaped channel to achieve separation of magnetic and non-magnetic beads. However, sheath ow is not benecial for channel parallelization design and high-throughput processing.…”

Is microrheometry affected by channel deformation?

“…9,28 The channel height H for both the devices is H ¼ 100 lm. Some clarifications need to be done for the PDMS device bonded on a glass coverslip (see Fig.…”