Elastomeric mold

Spin casting can use plastic molds, such as silicone, to produce close tolerance, highly cost effective, limited production in a variety of materials. The process uses easily adjustable centrifugal force to inject liquid thermoset plastics into a circular disc-shaped elastomeric mold under pressure, completely and rapidly filling the mold cavities. 

Recently it has been shown that hydrogel layers of variable thickness can be prepared on solid substrates by photolithographic technique [47], The technique called PRINT (particle replication in non-wetting templates) [48,49] utilizes elastomeric molds from a low surface energy perfluoropolyether network. The molds prevent the formation of an interconnecting film between molded objects and allow production of monodisperse microgel particles of different sizes, shapes, compositions, and surface functionalities. 

A common application for elastomeric molds is for micro- or nanocontact printing, where a self-assembled monolayer (SAM) is placed on both planar and curved surfaces via contact with the reliefs on the mold (Figure 6.66). SAMs will be an important architecture for the next generation of nanostructured materials. 

In drybag pressing, the elastomeric mold is fixed into the pressure vessel. The mold is filled with powder and sealed with a cover plate. Then pressure is applied between the mold and the vessel wall. After pressure release, the cover is removed and the part removed. Then the procedure starts again. Pressure vessels with both top and bottom plate are also in use, and allow more rapid removal of the compact. 

Isostatic pressing is a technique in which the law of Pascal is applied. In other terms, if a powder is put into an elastomeric mold and sealed and put into a pressure vessel filled with a liquid, the pressure in the vessel will be transmitted to all surfaces in all directions, directly proportionate to the... 

Figure 3.1 Illustration of the soft molding method, (a) An elastomeric mold is placed on a polymer film that is spin coated onto a substrate, and then slightly pressed down to form the pattern on the spin-coated polymer film, (b) After releasing the pressure, the whole structure is left undisturbed fora period of time...

All techniques making use of elastomeric molds are suited to the patterning of nonplanar and/or flexible substrates, due to the flexibUity of the used mold, to the low imprinting temperature of several processes, and to the fact the precursor is spin coated (or deposited) on the mold, not on the substrate. However, if the substrate has a large radius of curvature, the mold thickness cannot be too high in order to decrease the drawbacks of elastic deformation of the stamp resulting from conformal contact to a nonplanar surface [23]. The main drawback relates to a change in the pitch across the patterned area as the radius of curvature of the substrate increases. 

The injection molding process is the latest and most important process for the manufacture of elastomeric molded parts. It was initially used for years in the plastics industry before it was used in the rubber industry. 

An inexpensive elastomer mold is characterized by low life-cycle costs, which means long periods of time between necessary mold cleaning, long service life, and robust process windows at relatively low purchase prices. The selection of the correct process, the optimal rheological and thermal design, the use of suitable steel and the precise manufacture of the relevant (function-determining) dimension, as well as the suitable coating lead to the optimal result in the elastomeric mold manufacture. 

Replica molding can produce multiple molds, replicas, and patterned surfaces from a single master in a simple and reliable way. The key step of RM is to use an elastomeric mold to replicate the relief of a 3D surface. This technique allows for highly complex structures in the master to be replicated... 

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