Essay On 2. 3 Cross Linking By Two Photon Polymerization

2.3 Cross-linking by two photon polymerization (2PP) Rapid prototyping approaches [28, 29] (e.g., stereolithography, electrospinning, and 3D fiber deposition modeling) have garnered attention for fabricating materials for tissue engineering and other biomedical applications. However, those techniques have lower resolution and are not effectively used to mimic features of the architecture of the natural cells and/or tissues. Recently, 2PP has been employed to create the 3D materials because it can generate the structures with feature sizes in the range of sub-100 nm to hundreds of microns [30]. In addition, it is also a simple direct laser writing technique that the users can easily fabricate 3D structures from CAD files, which can include†¦show more content†¦Additional modules such as galvano-scanners [31] or spatial light modulators [32] can be added to provide faster scanning to improve process throughput. There are benefits and drawbacks to the use of two photon polymerization. One benefit of this technique stems from the localized absorption at the focal point; not only is the two photon absorption a non-diffraction limited phenomenon allowing features smaller than the wavelength of light used, polymerization can occur anywhere within the bulk of the polymer. A device to apply additional photopolymer to the surface, as in stereolithography, is not required; switching to subsequent layers involves the simple movement of the z-stage. In fact, 2PP breaks out of the â€Å"layer-by-layer† paradigm and could do away with layer-based fabrication altogether. For example, a 2PP apparatus containing a spatial light modulator demonstrates the fabrication of a tetrahedron using only the spatial light modulator to move the focus in all three dimensions; no mechanical movement of the sample was required [33]. On the other hand, 2PP is a slow process due to its resolution and is often eq uated to painting with a fine-tip pen. While stereolithography can project an entire 2D image per layer using well-established technologies, 2PP only takes place at the focal point so wide structures take long periods to time to make. 2.4 Cross-linking by gamma irradiation At present,