Micro and Nano-fluidic devices represent an emerging new area of medical therapeutics and diagnostics. Micro and Nano-scale systems have unique properties that lead to increasing the control, accuracy, efficiency, and speed, while reducing waste and operator error of various medical tests and drug delivery techniques. In order to fully realize the potential of this exciting field the flow behavior of relevant systems must be studied and understood so that new devices can be properly designed. Studying fluid flow behavior at such small scales requires the use of microscopy, and novel fabrication techniques are essential if there is any hope of realizing the potential of nano-scale devices.;Confocal microscopy is a well developed technique in the area of medical imaging due to its thin focus planes, increased resolution, and 3D imaging capabilities. However, until recently it has not been a viable technique for imaging dynamic systems where fast image capturing is required. This is due to the point scanning nature of the traditional confocal system in which single pixel intensities are measured with a scanning photon multiplying tube. New high-speed confocal systems have been developed utilizing arrays of pinholes on spinning disks that enable the use of a camera for faster full frame detection. A high-speed spinning disk confocal microscope system has been developed at Ohio State to use for studying dynamic processes and flow behavior within micro and nano-scale devices.;The high-speed confocal system was used to generate 3D particle tracking velocity profiles for fluid flow in a micro-channel, demonstrating the ability to track not just the flow at the center of the channel but at the top and bottom as well. This is a valuable tool for studying micro-devices in which 3D flow characteristics will be present. Gas-liquid bubble formation was studied in micro-channels and compared with simulations. It was determined that the dimensionless Capillary number, along with gas to liquid flow rate ratio and mixer geometry, could be used to accurately predict bubble size and frequency within a micro-channel mixer.;The flow of biological polymers in a micro-contraction was studied to gain insight into the fundamental molecular behavior of long chain polymer systems, as well as study the flow behavior of long chain DNA solutions that may be present in useful micro-fluidic devices where contraction geometries will be common. Unusual viscoelastic flow phenomena was observed, and a new jerky shear banding flow regime was identified at extremely high elastic numbers. Additionally, molecular staining of the biological polymers allowed the behavior of the long chain molecules to be observed during interesting flows. Next, this individual-chain visualization technique was used to produce the first molecular imaging of wall slip in entangled solutions. Chain disentanglement was observed under slip conditions for both channel flow and during rheometric shearing experiments.;Lastly, the transport of medically important DNA solutions across a nano-channel device was characterized to demonstrate its potential as a novel gene-delivery technique. Micro-channel arrays containing embedded nano-channels were fabricated using a novel DNA combing and imprinting nano-fabrication technique developed at Ohio State. The electrokinetic transport of antisense oligonucleotides, plasmid green fluorescent protein, and linear green fluorescent protein molecules was studied. The ability to control the amount of molecules that cross the nano-channel by varying electric field pulses was demonstrated to establish the potential for a novel nano-electroporation device.
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