Here, we present a novel approach for the transient permeabilization of cells. We combined laminar shear flow in a microchannel with chaotic advection employing surface acoustic waves. First, as a fundamental result on the one hand, and as a kind of reference measurement for the more complex acoustofluidic approach on the other hand, we studied the permeabilization of cells in pure shear flow in a microchannel with Y-geometry. As a proof of principle, we used fluorescent dyes as model drugs and investigated their internalization into HeLa cells. We found that drug uptake scaled non-linearly with flow rate and thus shear stress. For calcein, we obtained a maximal enhancement factor of about 12 at an optimum flow rate of Q = 500 µL/h in the geometry used here compared to static incubation. This result is discussed in the light of structural phase transitions of lipid membranes accompanied by non-linear effects, as the plasma membrane is the main barrier to overcome. Second, we demonstrated the enhanced permeabilization of acoustically trapped cells in surface acoustic wave induced vortices in a microchannel, with an enhancement factor of about 18 compared to quasi-static incubation. Moreover, we optimized the trapping conditions regarding flow rate, the power level of the surface acoustic wave, and trapping time. Finally, we showed that our method is not limited to small molecules but can also be applied to compounds with higher molecular weight.
Giant anomalous Hall effect (AHE) and magneto-optical activity can emerge in magnets with topologically nontrivial degeneracies. However, identifying the specific band-structure features such as Weyl points, nodal lines, or planes which generate the anomalous response is a challenging issue. Since the low-energy interband transitions can govern the static AHE, we addressed this question in the prototypical magnetic Weyl semimetal Co 3 Sn 2 S 2 also hosting nodal lines by broadband polarized reflectivity and magneto-optical Kerr effect spectroscopy with a focus on the far-infrared range. In the linear dichroism spectrum we observe a strong resonance at 40 meV, which also appears in the optical Hall conductivity and primarily determines the static AHE, and thus confirms its intrinsic origin. Our material-specific theory reproduces the experimental data remarkably well and shows that strongly tilted nodal-line segments around the Fermi energy generate the resonance. While the Weyl points only give vanishing contributions, these segments of the nodal lines gapped by the spin-orbit coupling dominate the low-energy optical response and generate the giant AHE.
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.