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J. Stampfl:
"Materials for lithography-based additive manufacturing technologies";
Talk: Erich-Schmid-Kolloquium, Erich Schmid Institut, ÖAW, Leoben; 12-07-2010.

Lithography based Additive Manufacturing Technologies (AMT) like stereolithography and two photon lithog-raphy allow the fabrication of complex cellular structures with defined pore sizes and geometries, suitable for applications as scaffolds in biomedical applications. Achievable wall thicknesses range down to several hundred nanometers. In addition to fabricating scaffolds ex-vivo using conventional AMT, two photon lithography facilitates in-vivo-writing of scaffolds.
Using inkjet-based AMT it is possible to fabricate multi-material structures. Available materials which can be used with such inkjet-printers include soft elastomer-like materials and hard, highly crosslinked polymers. By combining these materials in a laminated multi-material structure the toughness of the resulting composite can be increased by a factor of 3 compared to the toughness of the individual components.
A further benefit of using photopolymers is the fact that the mechanical properties (elastic modulus, strength) can be easily tuned by varying the crosslink density and by adding filler materials. By adding water, hydrogels can be obtained. By filling the resin formulation with inorganic fillers (ceramic particles) composite materials can be obtained. Nevertheless, problems arise when conventionally used resins based on (meth)acrylate chemistry are used. Due to unreacted acrylate groups such resins might exhibit cytotoxicity toward osteoblast-like cells, and a high local concentration of poly(acrylic acid), formed by in vivo degradation, may impair cell function. Therefore, vinyl ester, vinyl carbonate and vinyl carbamate based monomers, forming harmless poly(vinyl alcohol) upon in-vivo degradation, have been developed. They exhibit high photoreactivity and good mechanical properties. In vitro biocompatibility assays revealed that the concentrations leading to cytotoxic cell damage are about two orders of magnitude higher compared to similar acrylate systems.