A new paper from the group is out today that has arisen out of our collaboration with Henry White at U. of Utah and his student Deric Holden. The basic idea is this:  Grant Hendrickson from our group previously observed, using a simple filtration set-up, that microgels could pass through pores that were nearly 10-times smaller than the equilibrium diameter of the spheres. Importantly, this could be done with low pressure differentials (<100 mmHg) that mimicked the pressures found in the kidney during renal filtration. Some time later, Henry and Deric helped us look at this a bit more closely using resistive pulse analysis of microgel translocation through a glass nanopore membrane. Now in the latest paper, published online in Soft Matter, we have examined the current transients that arise when the microgels are pushed through the nanopores at different pressure differentials and hence at different rates. These data indicate that the microgels can pass through either under volume conserving, or under solvent draining conditions, with solvent drainage being observed when the translocation velocity is lower than the estimated gel deswelling velocity. The hope is that experiments such as these will help in the design of soft materials that penetrate through biological pores and junctions more effectively, either to increase the efficacy of drug delivery, or to reduce retention in organs following clearance from the circulation.

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