Direct polymer melt deposition

There are also a number of other molding techniques to pattern polymers on substrates. One technique is capillary force lithography (CFL), which is a technique in which a patterned PDMS mold is placed on a layer of polymer that is either noncross-linked or heated above its melting point. In CFL, surface tension directs the movement of the polymer melt into the void spaces of the PDMS mold. This process can be merged with different types of polymers to enable cell and protein deposition on substrates. 

Primary crystallization occurs when chain segments from a molten polymer that is below its equilibrium melting temperature deposit themselves on the growing face of a crystallite or a nucleus. Primary crystal growth takes place in the "a and b directions, relative to the unit cell, as shown schematically in Fig. 7.8. Inevitably, either the a or b direction of growth is thermodynamically favored and lamellae tend to grow faster in one direction than the other. The crystallite thickness, i.e., the c dimension of the crystallite, remains constant for a given crystallization temperature. Crystallite thickness is proportional to the crystallization temperature. 

Antimony trioxide occurs in several modifications of which the senarmontite form is the preferred one for polymer uses. This does occur as a natural mineral but the deposits are generally too impure for direct use and virtually all the material used in polymers is made synthetically. The principal synthetic method is to blow air through the molten metal or its sulphide. The metal oxide sublimes from the melt and is recovered by cooling and filtration. Particle size is an important factor governing performance and this is controlled by factors such as the temperature and the cooHng rate. 

Fused deposition modeling (FDM) is a technology where the melt extrasion method is used to deposit filaments of thermal plastics according to a specific pattern. Similar to 3DP, the layout for FDM consists of a printhead able to move along X and Y directions above a build platform. The polymer is extraded through the heated nozzle and laid down as filaments according to the CAD design. The build platform is then lowered and another layer can be built, until the scaffold is completed. ... 

Vadimsky [23] described a useful method for preparation of thin films from the melt or solution. The method involves the evaporation of carbon onto freshly cleaved mica or fractured NaCl crystal substrates. The thin polymer film is cast onto the carbon coated substrate or the substrate is dipped into a polymer solution. After solvent evaporation, the film is scored and removed from the glass by floating it onto a water surface. The specimen can also be deposited directly onto the substrate followed by carbon coating. Geil [24,25], in a variation of this method, deformed PE single crystals by deposition on a Mylar substrate and drawing it before carbon coating and TEM examination. 

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