Presented here is a novel method for mixing in a microfluidic channel via an array of rotating magnetic microbeads. The microbeads rotate around circular permalloy (NiFe) features magnetized by a rotating external magnetic field. This system demonstrates rapid mixing in short channel lengths. The effectiveness of this system is quantified by analyzing the degree of mixing of two streams, one with fluorescence and one without. Our experiments and numerical simulations reveal that beads orbiting at a high velocity as compared to flow down the channel cause the fluid to form circular coronae that stretch across the microchannel leading to fluid mixing. Under these conditions, rotating magnetic microbeads were able to fully mix the streams in a 270 μm mixing region.
This paper presents work on the development of a microfluidic device using super-paramagnetic beads for sampling and mixing. The beads are manipulated via an external rotating permanent magnet in a microfluidic channel. Efficient mixing is achieved in a short distance with this method. Modeling shows the variables which influence the mixing are flow rate, bead rotation speed and the bead number density. Displacement of the bead relative the rotating magnetic field sets an upper limit on the bead rotation speed due to viscous drag. Future work will examine optimization of this system for capture of pathogens from a complex mixture.
Large-scale morphogenetic movements during early embryo development are driven by complex changes in biochemical and biophysical factors. Current models for amniote primitive streak morphogenesis and gastrulation take into account numerous genetic pathways but largely ignore the role of mechanical forces. Here, we used atomic force microscopy (AFM) to obtain for the first time precise biomechanical properties of the early avian embryo. Our data reveal that the primitive streak is significantly stiffer than neighboring regions of the epiblast, and that it is stiffer than the pre-primitive streak epiblast. To test our hypothesis that these changes in mechanical properties are due to a localized increase of actomyosin contractility, we inhibited actomyosin contractility via the Rho kinase (ROCK) pathway using the small-molecule inhibitor Y-27632. Our results using several different assays show the following: (1) primitive streak formation was blocked; (2) the time-dependent increase in primitive streak stiffness was abolished; and (3) convergence of epiblast cells to the midline was inhibited. Taken together, our data suggest that actomyosin contractility is necessary for primitive streak morphogenesis, and specifically, ROCK plays a critical role. To better understand the underlying mechanisms of this fundamental process, future models should account for the findings presented in this study.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.