Polymer Microstructures through Two-Photon Crosslinking

Two-photon crosslinking of polymers (2PC) is proposed as a novel method for the fabrication of freestanding microstructures via two-photon lithography. During this process in the confocal volume, two-photon absorption leads to (formal) C,H-insertion reactions, and consequently to a strictly localized crosslinking of the polymer. To achieve this, the polymer is coated as a solvent-free (glassy) film onto an appropriate substrate, and the desired microstructure is written by 2PC into this glass. In all regions outside of the focal volume where no two-photon process occurs, the polymer remains uncrosslinked and can be washed away during a developing process. Using a self-assembled monolayer containing the same photoreactive group allows covalent attachment of the forming freestanding structures to the substrate, and thus guarantees an improved stability of these structures against shear-induced detachment. As the two photon process is carried out in the glassy state, in a simple way, multilayer structures can be used to write structures having a varying chemical composition perpendicular to the surface. As an example, the 2PC process is used to build a structure from both protein-repellent and protein-adsorbing polymers so that the resulting 3D structure exhibits spatially controlled protein adsorption.

Two-photon crosslinking of polymers is a new method for the fabrication of microstructures via two-photon lithography. Here, in the confocal volume two-photon absorption leads to a (formal) C,H-insertion reaction. Using a self-assembled monolayer containing the same photoreactive group allows the forming freestanding structures to covalently attach to the substrate.

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