Projection based stereolithography process for 3D biomanufacturing of biomaterials.
Stereolithography is highly versatile and precise process of solid free form additive manufacturing technique. Process requires biocompatible liquid photopolymer resin as a material which is one of the limitation of the process also. Curing liquid resin with a high intensity UV radiations at times causes over-curing which is highly undesirable.
In this project, behavior of different biomaterials have been observed under same condition and the results have been plotted and regression analysis for each has been done. The study of graphs and coefficient of determination of process with different ...view middle of the document...
4. Now control unit in setup directs the ultraviolet laser that scans and illuminates the top most layer of the photosensitive liquid and hardens it. The resin in the pattern is solidified to a defined depth, causing it to adhere to a support platform.
5. The supporting platform which supports the newly formed layer in liquid resin is lowered to the depth of one layer and a new layer of resin takes/recoats the position of previous layer. Depth of curing is slightly deeper than the height of the downwards motion of supporting platform.
6. This process is repeated layer by layer, hardening layer over layer until the part whole part is finished.
Once the last layer is cured the liquid resin is drained and the object is detached from the supporting platform. Now this pattern, once again the curing of object is done in UV light to improve the mechanical strength of the object. 
Melchels et al, Paper “A review on stereolithography and its applications in biomedical engineering” suggests that the setups are differentiated only in build orientation and in the method of illumination. 
According to build orientation of stereolithography apparatus: -
(a) Top Exposure setup
(b) Bottom Exposure setup
Fig. 1. Schematic of (a) Top Exposure and (b) Bottom Exposure. Picture credit: Yaghmaie et al. 2014.
In top exposure setup, the setup is supported by the platform which is dipped in the pool of the liquid resin. After top layer is polymerized and then the platform moves downwards to specified distance along with the attached top layer.
In bottom exposure, the photopolymer liquid resin is illuminated from the bottom of the setup and the top layer is attached to the supporting platform which moves up once the top layer is attached to it. As soon as it moves upwards the liquid resin takes its place and plain second layer of liquid resin is exposed to get projected. In this technique platform is not dipped inside the liquid resin vat.
Build orientation wise, as discussed you can observe that the bottom exposure approach is better than the top exposure because: -
* The vat depth is independent of the object height. Less liquid resin is required in vat.
* Recoating for the next layer is not required.
* Illuminated layer is not exposed to the atmosphere, so oxygen inhibition is limited.
* Saves waste of liquid resin in case multiple resin use. Resin can also be peppitted from the above.
Second differentiation can be done on the basis of method of illumination wise, in Mask Image Projection based Stereolithography (MIP-SL) apparatus,
(a) Scanning-based Stereolithography (b) Projection-based Stereolithography
Fig. 1. Schematic of (a) SSL and (b) PSL. Picture credit: (Yaghmaie et al.2014)
* In this technique, a digital mirror device (DMD), an array of several millions of small mirrors that can be independently turned to an on and off state and thus projects the two-dimensional pixel pattern image...