One photon 3D polymerization via direct laser writing

A way to produce 3D scaffold is via laser stereolithography. We propose a method of direct laser writing for micro-stereolithography in which we use as light source a low power blue diode laser with a wavelength of 448nm. The material chosen for scaffold fabrication is a polyethylene glycol diacrylate (PEGDA) solution at concentration of 75% in ethanol. We chose a short PEGDA molecule with a molecular weight of 575 g/mol, in order to obtain a better control over the polymerization. We used Irgacure 819 as photoinitiator to initiate the photopolymerization. The absorption of the Irgacure 819 almost drops to zero at the excitation wavelength, so the efficiency of the photopolymerization is strongly reduced. Since the intensity of the light reduces by a factor 5 within a penetration depth, equal to the depth of focus of the optical system, we achieve a fine control of the vertical and lateral photopolymerization of the solution. The threshold for effective polymerization is not reached outside that region.