Thin Films Made Easy

Transparent thin films of conducting polymer nanofibers can be deposited onto various materials by means of a solution-based procedure that is simpler, less expensive, and quicker than common deposition methods, according to researchers at the University of California, Los Angeles, who developed the technique (Proc. Natl. Acad. Sci. USA, DOI: 10.1073/pnas.1008595107). Spin-coating, electrodeposition, and other methods are used to form polymer thin films for devices such as organic solar cells and light-emitting diodes. But various shortcomings limit broader application of these methods. For example, spin-coating can lead to inefficient material usage, and electrically driven methods exclude the possibility of depositing films on nonconducting surfaces. Julio M. D'Arcy, Richard B. Kaner, Yang Yang, and coworkers may have found a way around those problems. The researchers report that emulsifying a mixture of two immiscible liquids and nanofibers of polyaniline, polythiophene, and other conducting polymers leads to a surface tension gradient at the interface between the liquids. That condition triggers viscous flow, which causes the polymer to coat the nearby surfaces within seconds of standing after being agitated.