Photoresist formulations 3d microprinting techniques

3D micro-printing process via two-photon polymerisation for producing degradable 3D polymeric nano- or microstructures having sub-micrometre resolution, said process comprising the steps of:

• (a) providing a photoresist formulation comprising:
• (i) Cyclic ketene acetal monomers of general formula (I):
• selected from the group consisting of:
• 2-methylene-1,3-dioxane, 4-methyl-2-methylene-1,3-dioxane, 4,4,5,5-tetramethyl-2-methylene-1,3-dioxane, 2,4-dimethylene-1,3-dioxane, 2-methylene-hexhydrobenzo[d][1,3]dioxole, 2-methylene-1,3-dioxane, 4,6-dimethyl-2-methylene-1,3-dioxane, 5,5-dimethyl-2-methylene-1,3-dioxane, 2-methylene-4-phenyl-1,3-dioxane, 2-methylene-5,5-diphenyl-1,3-dioxane, 2-methylene-1,3-dioxepane (MDO), 4,7-dimethyl-2-methylene-1,3-dioxepane, 3-methylene-1,5-dihydrobenzo[e][1,3]dioxepine, 4-methylene-3,5-dioxabicyclo[5.1.0]octane, 2-(difluoromethylene)-1,3-dioxepane, 5,6-dimethoxy-2-methylene-1,3-dioxepane, 2-methylene-1,3-dithiepane, 3,9-dimethylene-1,5,8,10-tetraoxaspiro[5.5]undecane, and a combination thereof;
• (ii) vinyl and/or (meth)acrylic monomers selected from the group consisting of:
• pentaerythritol tetraacrylate, pentaerythritol triacrylate, 1,4-butanediol diacrylate, 1,3-butanediol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, bisphenol A diacrylate, tricyclo[5.2.1.02,6]decanedimethanol diacrylate, trimethylolpropane triacrylate, ethyl acrylate, ethylene-methyl acrylate, methyl methacrylate, 2-chloroethyl vinyl ether, 2-hydroxyethyl acrylate, hydroxyethyl methacrylate, butyl acrylate, 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, chloroprene, styrene, and a combination thereof;
• (iii) at least one photoinitiator;
• (b) focusing a laser beam within said photoresist formulation by directing said laser beam until localised polymerisation of said photoresist into a 3D cross-linked polymeric nano- or microstructure is achieved;
• (c) removing the non-cross-linked portion of photoresist by washing with a solvent.