Form and function in multilayer assembly: New applications at the nanoscale

New frontiers in materials and polymer science include the development of assembly processes that are flexible, allow the access and implementation of nanoscale structure and order, can provide access to a broad range of materials systems, and yet can be implemented at relatively low cost. The ability to fine tune the composition of nanostructured thin films on the nanometer length scale, when combined with inexpensive patterning and templating routes, provides a powerful tool for nano- and microscale assembly of devices and novel new material systems. The layer-by-layer electrostatic assembly technique is a rich, versatile, and significantly inexpensive approach to the formation of thin films via alternating adsorption of positively and negatively charged species from aqueous solutions; this method has also been extended to include the alternation of polymers with hydrogen-bond donor and acceptor groups. Polymer organic and organic/inorganic thin films formed using this technique may contain a number of different functional groups, including electro-optic, electroluminescent, conducting, and dielectric layers, and functional organic and inorganic nanoparticles. Newly developed materials systems based on alternating layer methods will be addressed, as well as a number of frontier areas and future areas for the use of these systems, ranging from nanomechanical composites to electrochemical devices and templated deposition of functional microspheres. Both new functionalities incorporated within these materials and new means of patterning and templating these structures in two and three dimensions will be addressed in this review.