Geometry-driven mass transport dynamics within permeable 3D-microstructures fabricated via two-photon polymerization

Abstract

The geometric scalability offered by two-photon stereolithography (2PS) has contributed to its rapidly becoming widespread in multiple well-established or emerging applications. Taking advantage of this flexible parameterization, we have developed an original fluorescence imaging method that enables mapping the real-time diffusion of quenching species moving throughout permeable three-dimensional (3D) microstructures with modular geometries (cones, pyramids, squares, etc.) fabricated by 2PS. In this strategy, we first methodically characterize the 2P polymerization performances of a Y-shaped triphenylamine photoinitiator series whose initiation efficiency perfectly echoes that measured upon one-photon excitation. In particular, we show that the photoinitiation mechanism implies a covalent integration of the triphenylamine-based fluorophores into the photopolymer leading to the microfabrication of blue emissive 3D-objects which can be spatially ‘switched-off’ during the inner diffusion of copper(II) cations used as oxidative quenchers. The modulation of microstructure geometry not only regulates the global symmetry of diffusion profiles but also accounts for a topological control of the quenching propagation dynamics at the local scale.