LAYER BY LAYER (LbL) SELF-ASSEMBLY STRATEGY AND ITS APPLICATIONS

This report reviews the technique of layer-by-layer (LbL) self-assembly, in particular cases involving electrostatic interactions between thin film monolayers. LbL selfassembly is used in a variety of different applications, two of which discussed in the report are LbL MEMS and LbL protein multilayers. In the fabrication of LbL MEMS, multilayers of polymer-clay-magnetite nanocrystal are deposited via photolithographic steps on a wafer. The final product is a free-standing cantilever that responds to a magnetic field. The LbL technique, applied to MEMS, allows the precise tailoring of surface interactions, and hence is useful for the fabrication of surface-based devices. In the application of trapping active proteins, polyamidoamine dendrimers and heme proteins are integrated in a multilayer thin film structure that allows the retention of intact biological activity. The pH of the system can significantly affect the interaction strength, and although oppositely charged species are favourable for electrostatic interactions, it is not a requirement for multilayer formation. Finally, electroactivity is explored in relations to bilayer number. It is concluded that electroactivity decreases as the bilayer number increases, and it is important to control film thickness for effective electron exchange in devices.