Molecular Self-Assembly Fabrication

Since multiple electrical and optical functionality must be combined in the fabrication of an OLED, many workers have turned to the techniques of molecular self-assembly in order to optimize the microstructure of the materials used. In turn, such approaches necessitate the incorporation of additional chemical functionality into the molecules. For example, the successive dipping of a substrate into solutions of polyanion and polycation leads to the deposition of poly-ionic bilayers [59, 60]. Since the precursor form of PPV is cationic, this is a very appealing way to tailor its properties. Anionic polymers that have been studied include sulfonatcd polystyrene [59] and sulfonatcd polyanilinc 159, 60]. Thermal conversion of the precursor PPV then results in an electroluminescent blended polymer film. 

Fabricating and repairing complex materials systems. Mechanical methods currently in use (e g., riveting of metals) cannot be applied reliably to the composite materials of the future. Chemical methods (e g., adhesion and molecular self-assembly) will come to the fore. 

Zhang, S. (2003). Fabrication of novel biomaterials through molecular self-assembly. Nat. Biotechnol. 21, 1171-1178. 

We study MESA for three reasons, (i) MESA bridges the gap between molecular self-assembly, which has been successful at the nanometer level, and conventional fabrication of machines and parts, which has been successful for scales greater than 100 pm [refs. 16-23], Few techniques exist to assemble or fabricate objects or arrays in the size region between several nanometers and hundreds of microns, and new techniques in this regime would be welcome, (ii) We wished to develop systems of self-assembly in which we could control the parameters affecting self-assembly more easily than we can with molecules, (iii) We wished to extend the ideas and methods of self-assembly in chemistry and biology to self-assembly on the mesoscale. 

Various nanoscale architecture can be designed, including solid spheres, hollow spheres, tubes, porous particles, solid particles, and branched structures (Table 2).To achieve such nanostructures, different fabrication methods are used depending on the types of material. The methods used for nanoscale assembly include molecular self-assembly, bioaggregation, nanomanipulation, photochemical patterning, molecular imprinting, layer-by-layer electrsostatic deposition, and vapor deposition. 

M. Ferreira, J.FI. Cheung, M.F. Rubner, Molecular Self-Assembly of Conjugated Polyions - A New Process for Fabricating Multilayer Thin Film Heterostructures , Thin Solid Films, 244, 806 (1994)... 

In this study, we report a very effective and widely applicable method for fabricating of nanostructures of an inert material for the biomolecular nanoarrays. The stable nanostructures of the PEG and PVA hydrogels were directly fabricated on gold substrates by UV-NIL (Fig. la). The site-selective nanoarray of various biomolecules such as protein and tethered lipid bilayer raft membrane (tLBRM) was constructed from a nanoimprinted inert materials by stepwise molecular self-assembly (Fig. lb and Ic). 

Scaffolds can be fabricated by using different types of methodologies such as fiber bonding, salt leaching, gas-induced foaming, phase separation, electrospinning, solid freeform fabrication, and molecular self assembly [15, 17]. Some of the fabrication techniques are discussed below. 

M. Ferreira, J. FF. Cheung, M. F. Rubner, Molecular self-assembly of conjugated polyions - a new process for fabricating multilayer thin-film heterostructures, Thin Solid Films 1994, 244, 806. 

Noncentrosymmetric order induced by electric field poling or by molecular self-assembly processes must be stable at the elevated temperatures encountered in device fabrication and operation. Conservatively, this means stability at temperatures on the order of 100 C in general, with precise requirements determined by the particular device application pursued and the device fabrication protocols followed. The requirement of stability at elevated temperatures frequently mandates additional lattice hardening to stabilize induced noncentrosymmetric order. 

---