The researchers wanted to speed up the collection of viral particles -- in this case, of vesicular stomatitis virus, a common animal virus -- at the right place on a substrate, while also doing it in media at physiological ionic strength.
The UB researchers used their expertise in a technique called directed assembly, in which they design external electrical and fluid flow fields in order to "drive" nanoparticles to specific locations and in specific concentrations on a substrate.
"This paper shows that by using electrodes separated by just a few micrometers together with electrothermally induced fluid flow, we can accelerate the transport of viral particles from aqueous suspensions with physiological ionic strength to specific points on a surface, allowing them to reach local concentrations high enough to allow subsequent rapid detection," Alexandridis explained.
"We achieved this not by accident, but by design," he continued. "We hypothesized that the application of these external fields would cause the nanoparticles to act in a certain way. We designed electrodes to generate the required forces for the system of interest and then put our design to the test." In the research, the UB engineers used directed assembly to tailor dielectrophoretic forces, which act through a nonuniform electric field, overcoming an obstacle that occurs whenever nanoparticles are involved.
"When you work with microscopic objects dispersed in a liquid, gravity is very important," explained Alexandridis. "But at the nanoscale, gravity doesnt matter. So when you are trying to manipulate matter at the nanoscale, electrical fields and fluid fields may work best. By using directed assembly, we can tailor the forces acting on the nanoparticles. The ability to use several forces acting in tandem becomes important."