"The science of colloidal EDP is well known but the particles are substantially larger than the solvent molecules. Many nanoparticles, however, are about the same size as the solvent molecules, which makes the process considerably more complicated and difficult to control," Dickerson explains.
To get the method to work, in fact, Dickerson and his colleagues had to invent of new form of EDP, which they call sacrificial layer electrophoretic deposition. They added a spun-cast layer of polymer to the electrodes that serves as a pattern that organizes the nanoparticles as they are deposited. Then, after the deposition process is completed, they dissolve (sacrifice) the polymer layer to free the nanoparticle film.
According to the researchers, films made in this fashion stick together because the electrical field slams the nanoparticles into the film with sufficient force to pack the particles together tightly enough to allow naturally attractive inter-particle forces to bind the particles together.
So far the Dickerson group has used the technique to make films out of two different types of nanoparticles iron oxide and cadmium selenide and they believe the technique can be used with a wide variety of other nanoparticles.
"The technique is liberating because you can make these films from the materials you want and use them where you want," Dickerson says.
|Contact: David F. Salisbury|