Professor Shin-Hyun Kim says that as oxygen was considered an inhibitor during photopolymerization, photoresist techniques under UV light creates radicals which initialize a chemical reaction. So Kim and his team introduced the presence of varying levels of oxygen to prevents those reactions, and by exploiting the presence of oxygen, allowed "diffusion" to occur in parallel with the direction of the UV light. When it's sped up, the diffusion process develops horizontally and outward from the area affected by the UV light, and that meant they could build tiny, three-dimensional structures where none could be fabricated before. According to the research, the injection of external oxygen allowed them to manipulate diffusion strength--and the direction of the build process--to control the shape and size of the polymers within. You can read the whole story here: http://3dprint.com/56765/3d-printed-micropatterns/


Below is a look at the micropatterns able to be created: