Rapid Microfluidic Mixer Based on Ferrofluid and Integrated Microscale NdFeB-PDMS Magnet

Abstract

Ferrofluid-based micromixers have been widely used for a myriad of microfluidic industrial applications in biochemical engineering, food processing, and detection/analytical processes. However, complete mixing in micromixers is extremely time-consuming and requires very long microchannels due to laminar flow. In this paper, we developed an effective and low-cost microfluidic device integrated with microscale magnets manufactured with neodymium (NdFeB) powders and polydimethylsiloxane (PDMS) to achieve rapid micromixing between ferrofluid and buffer flow. Experiments were conducted systematically to investigate the effect of flow rate, concentration of the ferrofluid, and micromagnet NdFeB:PDMS mass ratio on the mixing performance. It was found that mixing is more efficient with lower total flow rates and higher ferrofluid concentration, which generate greater magnetic forces acting on both streamwise and lateral directions to increase the intermixing of the fluids within a longer residence time. Numerical models were also developed to simulate the mixing process in the microchannel under the same conditions and the simulation results indicated excellent agreements with the experimental data on mixing performance. Combining experimental measurements and numerical simulations, this study demonstrates a simple yet effective method to realize rapid mixing for lab-on-chip systems.

Magnetic Polymers for Magnetophoretic Separation in Microfluidic Devices

“…The schematic of the microsystem with the soft composite microstructure adjacent to the microfluidic channel is presented in Figure 1d, as well as micro-photographies of three different shapes for the composite microstructure. They studied the deviation operated on magnetic beads, performed the separation of yeast and magnetic beads at flow rates of few µL/min, and rapidly mixed ferrofluids and distilled water [46].…”

“…Magnetic PDMS is the most commonly encountered due to the microfabrication properties of PDMS by soft lithography and the massive use of the latter for the realization of microfluidic systems. Thus, a large panel of microfluidic functionalities for fluid sample handling has emerged employing composite polymers, such as micro-valves, micro-pumps, or micro-mixers for microfluidic flow control [36,40,[42][43][44][45][46][47]; dynamic artificial cilia [41,[48][49][50]; and reversible microchannel bonding [51]. Ferrofluids were also explored for actuation in microfluidic systems [52][53][54][55].…”

An explicit dissipative model for isotropic hard magnetorheological elastomers

“…Rare earth-based, hard (permanent) magnetic NdFeB particle-filled magnetorheological elastomers (MREs) have been recently explored towards their potential applications in magnetic soft robots (Kim et al, 2018;Zhao et al, 2019;Ren et al, 2019;Alapan et al, 2020), microfluidic separators (Hilber and Jakoby, 2012;Royet et al, 2017;Zhou et al, 2020), and bio-inspired magnetic sensors (Kaidarova et al, 2018) among other innovative applications. In contrast to traditional soft magnetic iron particle-filled MREs, denoted henceforth as s-MREs, (Danas et al, 2012;Bodelot et al, 2017), NdFeB particle-filled hard MREs, denoted as h-MREs, exhibit remanent magnetization.…”

Dynamic analysis and active control of hard-magnetic soft materials

“…Combined with 3D printing technology, the hard-magnetic soft materials structures can achieve more complex deformation and adapt to the complex working environment [4]. It can be seen that the hard-magnetic soft materials will play an important role in the fields of flexible electronics, biomedical devices, and soft robotics [19][20][21][22].…”