Laser fabrication of polymer micro-fluidic devices and systems
Abstract
Micro-fluidic devices and systems have many applications in clinical diagnostics, drug delivery, and micro-electronics cooling. So far, these micro-fluidic devices and systems are primarily fabricated using the well-established photo-lithography processes. In this work, laser-based techniques for fabricating polymer micro-fluidic devices and systems are studied. Polymer has many advantages as a micro-fluidic base material due to its low cost and various material properties suitable for micro-fluidic applications. In this work, basic characteristics of laser ablation for polymers are investigated. An ultraviolet laser is used for producing micro-structures on polymers. The ablation characteristics such as ablation depth, wall angle, and topography of the ablated surfaces are investigated. Two different laser fabrication techniques, direct laser writing and mask patterning, are proposed for machining various micro-structures. In order to assemble polymer micro-structures, special bonding processes such as silicon-on-glass bonding and laser bonding are developed and analyzed. The silicon-on-glass bonding provides a very strong and thin bonding layer. Laser bonding can be used to bond a transparent polymer with an opaque polymer and by controlling a laser power, precise local bonding can be achieved. A number of polymer devices such as micro-valves and diffuser micro-pumps are fabricated using the laser techniques. The polymer micro-check valve shows a great potential in its applications. A polymer diffuser micro-pump shows a flow rate up to 50 mm3/min at a frequency of 180 Hz. Finally, a micro-stamping process for rapid replication and mass production of micro-devices and systems is developed. New glass-ceramic stamps are developed for this process and the characteristics of these stamps are investigated. The fabricated glass stamps are then used in a hot-stamping process to replicate micro-structures. Many micro-structures such as micro-channels, micro-capillaries, and micro-diffusers are produced with this process. Overall, it has been found that the laser-based techniques are powerful and flexible, and are able to produce many structures that are difficult to make using photo-lithography.
Degree
Ph.D.
Advisors
Xu, Purdue University.
Subject Area
Mechanical engineering
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