The LUMABs concentration in the fluid chamber is 110 nM, and the AB concentration is at a 10:1 AB sensor ratio

The LUMABs concentration in the fluid chamber is 110 nM, and the AB concentration is at a 10:1 AB sensor ratio. of individual entities often seen in nature. The microparticle swarming induces high fluid velocities in initially stagnant fluids, and it can be externally controlled. The method is pilot-tested using a point-of-care test featuring a bioluminescent assay for the detection of antibodies. The mixing by the magnetic beads leads to increased assay kinetics, which indeed reduces the time to sensor readout substantially. Magnetic microparticle swarming is expected to be beneficial for a wide variety of point-of-care devices, where fast homogeneity of reagents does play a role. ? 1) microfluidics. However, active micromixers can be complex and costly to Pipequaline fabricate, particularly due to their need for external components.11 Magnetic microparticle mixing offsets complex fabrication and reduces cost because actuation is done remotely without physical connection to the device. Furthermore, magnetic microparticles are commercially available, often already used for target capturing and separation without active mixing and can be externally controlled via electromagnets. Magnetic microparticles have been studied to sort, transport, and capture targets in a microfluidic chip. Here, we exploit an additional function of these magnetic capturing elements that increase fluid kinetics and subsequently sample homogeneity via mixing. It has Pipequaline been demonstrated that an external magnetic field can induce self-assembly of suspended magnetic beads into (anisotropic) chains as a result of the dipoleCdipole interactions between the beads.12 When these chains are subjected to a rotating magnetic field, they evoke a rotational motion, which locally stirs and mixes the fluid (microstirrers).13 Under certain conditions, a phenomenon of collective motion of these microstirrers occurs, which can induce strong vortical flow in a microfluidic chamber.14 Here, we present a magnetic actuation configuration and associated protocols that lead to Pipequaline a phenomenon in a microfluidic chamber, which we call magnetic particle Rabbit Polyclonal to GJA3 swarming (MPS) due to its resemblance to bird swarming. Due to Pipequaline this phenomenon, magnetic bead chains do not only exhibit local rotational motions to cause local vortices but also a global rotational motion throughout the microchamber, which is important for reaching global sample homogeneity. The microfluidic mixing induced by the MPS shows potential for enhanced micromixing for fast PoC testing, in particular for no-flow-through systems in which mixing must be achieved in initially stagnant fluids. Therefore, we analyze the MPS in depth: we systematically study the occurrence of MPS in relation to two of the most determinant parameters for its formation, namely magnetic field rotational frequency and magnetic field strength. We study the resulting bead dynamics, quantify the induced fluid flow, as well as the resulting mixing effectiveness (i.e., the level of solution homogeneity). The Pipequaline analysis shows how the phenomenon depends on the relative importance of magnetic and viscous forces at work. Finally, we demonstrate the effect of magnetic mixing induced by MPS on a bioluminescent AB-based sensor assay for PoC applications in terms of time to readout. Magnetic Bead Behavior in Various Magnetic Protocols Homogeneity of reagents within a microfluidic chip has proven to be beneficial for the efficient capturing of elements and the reproducibility of testing. Fluid/reagent homogeneity, or mixture quality, is thus crucial. Two key elements are required to achieve enhanced mixing in microfluidic devices utilizing MPS: magnetic beads and a time-dependent magnetic field that controls these magnetic beads (for details, see the Supporting Information Text S1 Materials and Methods). Time-dependent magnetic fields, such as we apply here, can be generated by rotating or translating permanent magnets but achieving a relatively uniform field and relatively high rotation rates (as we need here) will be difficult in practice and requires a rather bulky setup.15 Electromagnets are preferred for PoC as the magnetic field is easily controlled both in terms of spatial field distribution and time dependency, they can be made small, and no moving parts are incorporated, which would require follow-up maintenance. A custom-built electromagnetic setup is used to generate the magnetic field; see Figure ?Figure22a.16 Poles P1CP4 can generate a magnetic field in the vertical plane and poles P5CP8 in the horizontal plane; by combining them, 3D manipulation of the magnetic beads (Figure ?Figure22c(2C3)) is possible..