Femtosecond Laser Nanomachining and Applications to Micro/Nanofluidics for Single Cell Analysis.

Abstract

Femtosecond laser machining has huge potential to impact micro/nanofluidics with its ability to arbitrarily abricate 3-dimensional geometries with feature sizes down to nanometer scales. Because cleanroom facilities, multilayer configurations, and glass bonding are not necessary to achieve 3-dimensional subsurface nanofeatures in glass, current planar lithography-etch-bond processes are easily combined with femtosecond laser machining; a hybrid machining based on these two methods constitutes a promising fabrication method for next generation microchip processes. The major challenge facing fs laser machining is that increasing the length of subsurface capillaries is very difficult; the normalized length (length/diameter) had previously been limited to 50. In this dissertation, a new phenomenon, acoustic nodeformation, is shown to be the major barrier to increasing capillary length, and a theoretical model for node formation is established. Based on the node equation, degassed water, which is introduced to the ablation site to assist machining, is found to substantially overcome node formation. Thus, a novel degassed-water-assisted fs laser machining process is developed, improving the normalized length of submicron-scale capillaries to longer than 1000. Nano-capillary electrophoresis (nCE) is demonstrated, initiating a submicronscale separation regime with millisecond-fast separations and 1 femtoliter injection volumes (1000 times smaller than a single cell volume). Also, the current-controlled dielectric breakdown is found to convert a thin glass wall to an electrode, which is the core part in the nCE device zero-flow sample loader. This phenomenon can be further exploited in many novel micro/nanofluidic modules such as electrokinetic pumps, nanosensors, and nanoactuators with freedom to directly embed these modules in glass chips. These new micro/nanofluidic devices and modules will contribute to many novel biotechnology investigations, including single cell proteomics, cell characterization, DNA analysis, electrophysiology, and biological assays.