3D Photofixation Lithography in Diels-Alder Networks.

3D structures are written and developed in a crosslinked polymer initially formed by a Diels-Alder reaction. Unlike conventional liquid resists, small features cannot sediment, as the reversible crosslinks function as a support, and the modulus of the material is in the MPa range at room temperature. The support structure, however, can be easily removed by heating the material, and depolymerizing the polymer into a mixture of low-viscosity monomers. Complex shapes are written into the polymer network using two-photon techniques to spatially control the photoinitiation and subsequent thiol-ene reaction to selectively convert the Diels-Alder adducts into irreversible crosslinks.