Self-focusing 3D lithography with varying refractive index polyethylene glycol diacrylate

This work presents self-focusing 3D lithography based on the refractive index changes of polyethylene glycol diacrylate (PEGDA) during photopolymerization. Since the polymerization of PEGDA leads to an increase in the refractive index, the UV light rays in the PEGDA undergo a refraction effect during exposure, thus being focused and forming 3D photopolymerized structures. We demonstrate the potential of self-focusing 3D lithography by fabricating PEGDA microneedles and trapezoid-shaped microwells. Their structures well match our theoretical estimation. Therefore, our theoretical approach can provide a short route to realizing on-demand, complicated 3D structures of refractive-index-variable materials with single UV exposure.