Schematic of photochemistry of photopolymerisation reaction. (a) The dye absorbs a photon from the incident light with wavelength $\lambda =533 \mathrm{nm}$. (b) Through a redox reaction the dye transfers its energy to the initiator, thereby activating it. (c) The photopolymerisation is initiated when the activated radical generator binds to a monomer. The generation of radicals is propagated along the chain to form a polymer chain [21]. (d) At $t_0$ the photopolymerisation reaction forms a dense mesh in the illuminated areas causing shrinkage. A monomer gradient forms. (e) After a certain exposure time, $t_0+\Delta t$, diffusion of monomers cause the illuminated areas to swell, as it is presented in [22]. An index matching liquid evens out the surface relief.