Applications of multiphoton-excited photochemistry to microsecond capillary electrophoresis, photolithography, and the development of smart materials
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Laser-based techniques have become essential tools for probing biological molecules in systems that demand high spatial and temporal control. This dissertation presents the development of micro-analytical techniques based on multiphoton excitation (MPE) to promote highly localized, three-dimensional (3D) photochemistry of biologically relevant molecules on submicron dimensions. Strategies based on capillary electrophoresis (CE) have been developed for the rapid separation and spectroscopic analysis of short-lived photochemical reaction products. High-speed separation and analysis are achieved through a combination of very high electric fields and a laser-based optical system that uses MPE for both the generation and detection of hydroxyindole photoproducts on the time scale of microseconds. MPE was also used for the development of photolithographic techniques for the creation of microstructured protein-based materials with highly defined three-dimensional (3D) topographies. Specifically, a multiphoton lithographic (MPL) technique was developed that used a low-cost microchip laser for the rapid prototyping of 3D microarchitectures when combined with dynamic optical masking. Furthermore, MPL was used to create novel “smart” biomaterials that reproducibly respond with tunable actuation to changes in the local chemical and thermal environment. The utility of these materials for creating biocompatible cellular microenvironments was demonstrated and presents a novel approach for studying small populations of microorganisms. Finally, through the development of a multifocal approach that used multiple laser beams to promote the photocrosslinking of biological molecules, the speed and versatility of MPL was extended to allow both the parallel fabrication of 3D microstructures and the rapid creation of large-scale biomaterials with highly defined spatial features.