Fast sol-gel technology: from fabrication to applications

A novel method to prepare crack-free sol-gel materials without shrinkage is reviewed. The method allows fabrication of a viscous sol-gel resin in a few minutes followed by either thermal-curing or UV-curing requiring several hours or several minutes, respectively. The method is distinguished by the short time required to achieve a solid monolith. The fast sol-gel method uses a combination of organically modified alkoxides with traditional alkoxides as precursors, to produce a final product which is an organic-inorganic hybrid with properties that vary from silicone rubbers to silica glass. Optical and physical properties, such as refractive index and thermal expansion, can be engineered by controlling the ratio between the precursors. This class of materials is a promising candidate for preparation of optical elements such as waveguides and submicron structured replicas and can also be used as an optical bonding material. This paper reviews the fast sol-gel technology, as well as methods to characterize the process and its final products. Various applications of fast sol-gel materials are presented.