Direct three-dimensional microfabrication of hydrogels via two-photon lithography in aqueous solution

Hydrogels capable of releasing growth factors from very precise 3D structures to be placed on neural electrodes were microfabricated by two-photon lithography in aqueous solution. Hydrophobic chromophores with a large two-photon absorption cross section were solubilized using a nonionic surfactant and the resulting complex were applied with an oil soluble photoradical initiator to fabricate hydrogel microstructures. The results show that hydrogel microstructures are formed when the initiator 2,2-dimethoxy-2-phenyl acetophenone (Irgacure 651) and the 2-photon sensitive chromophore are present in the polymerizable mixture. The presence of water in the prepolymer solution helps in controlling important properties of the resulting structure such as modulus and the pore size which can be fine-tuned for its intended application.