Electrochemically enabled polyelectrolyte multilayer devices: from fuel cells to sensors

With an ever-increasing need for thin, flexible and functional materials in electrochemical systems, the layer-by-layer (LbL) technique provides a simple and affordable route in creating new, active electrodes and electrolytes. The LbL technique, which is based upon the alternate adsorption of oppositely charged species from aqueous solution, possesses unprecedented control of materials selection (e.g. polyelectrolytes, clays, nanoparticles, proteins), materials properties (e.g. conductivity, glass-transition temperature) and architecture (e.g. blends, stratified-layers, pores). These advantages make LbL assemblies excellent candidates for use in proton-exchange membrane and direct methanol fuel-cells, batteries, electrochromic devices, solar cells, and sensors. This review addresses the design of LbL films for electrochemical systems and recent progress.