Sharp observation by doctoral student Mengmeng Cui in Thomas Russell’s polymer science and engineering laboratory at the University of Massachusetts Amherst recently led her to discover how to kinetically trap and control one liquid within another, locking and separating them in a stable system over long periods, with the ability to tailor and manipulate the shapes and flow characteristics of each.
Russell, her advisor, points out that the advance holds promise for a wide range of different applications including in drug delivery, biosensing, fluidics, photovoltaics, encapsulation and bicontinuous media for energy applications and separations media.
He says, “It’s very, very neat. We’ve tricked the system into remaining absolutely fixed, trapped in a certain state for as long as we like. Now we can take a material and encapsulate it in a droplet in an unusual shape for a very long time. Any system where I can have co-continuous materials and I can do things independently in both oil and water is interesting and potentially valuable.”
Cui, with Russell and his colleague, synthetic chemist Todd Emrick, report their findings in the current issue of Science.
Russell’s lab has long been interested in jamming phenomena and kinetically trapped materials, he says. When Cui noticed something unusual in routine experiments, rather than ignore it and start again she decided to investigate further. “This discovery is really a tribute to Cui’s observational skills,” Russell notes, “that she recognized this could be of importance.”
Specifically, the polymer scientists applied an electric field to a system with two liquids to overcome the weak force that stabilizes nanoparticle assemblies at interfaces. Under the influence of the external field, a spherical drop changes shape to an ellipsoid with increased surface area, so it has many more nanoparticles attached to its surface.
Read more at: Phys.org