Studies of bilayers and vesicle adsorption to solid substrates: development of a miniature streaming potential apparatus (SPA).

A new miniature streaming potential apparatus (SPA) was developed to determine the streaming potentials (Psi(str)) and zeta potentials (zeta) of substrates under different ionic conditions while simultaneously visualizing the state of the surfaces, such as the adsorption of surfactants or polymers, using fluorescence microscopy and/or fluorescence recovery after photobleaching (FRAP). Experimental results with different surfaces show that the new SPA provides streaming potential values (hence zeta potentials) that agree with results obtained using traditional electrokinetic analyzers. Using the new SPA, the formation of supported lipid bilayers (SLBs) on glass from fluorescently labeled, unilamellar (approximately 100 nm diameter), charge neutral dimyristoyl-sn-glycero-3-phosphocholine (DMPC) vesicles was studied in aqueous electrolyte solutions at different lipid concentrations.

Normal and shear forces generated during the ordering (directed assembly) of confined straight and curved nanowires.

The effects of shape on nanowire interactions and shear-induced ordering were studied. Both the normal and lateral forces were sensitive to the particles' curvature. (i) No adhesion was observed between the confining surfaces, and the force profiles were short-ranged and mostly reversible for straight wires but longer-ranged and irreversible for curved wires.