Porous materials with well-defined pore shapes, sizes and distributions are highly desired in many emerging applications, particularly for biomedical materials and devices. However, conventional methods for processing porous materials only demonstrated limited capability in morphological control. One promising solution is the porogen templating process, where a structured porogen pattern is created first and subsequently used as a template or mold for generation of the desired porous material. Particularly, with solid freeform fabrication, porogen templates having complex internal structures can be additively fabricated, and they can then be used as molds for molding of porous materials and devices. This article attempts to offer a constructive overview on the state of the art of porogen patterning and inverse molding, with the goal of explaining the working mechanisms and providing unbiased accounts of the pros and cons of existing techniques and process variants. The article further intends to provide a fundamental understanding of the constituent elements and corresponding building blocks in porogen templating processes. An increased understanding of these elements will facilitate the development of more capable new processes.
Assessment of the state of the art of pressurized fluidized bed combustion systems