http://smartech.gatech.edu/handle/1853/26721 Showcase for the research accomplishments of Ph.D. graduates. Search the Channel search http://smartech.gatech.edu/simple-search http://smartech.gatech.edu/handle/1853/31219 Title: Cell and Particle Behavior in Microfluidic Mixers: Applications in Cell Signaling Dynamics <br/> <br/>Authors: Hirsch, Alison <br/> <br/>Abstract: Fluid mixing is common in large-scale chemical processes. Recently, many biological or chemical processes are carried out in microfluidic systems, where mixing of solutes is predominantly a diffusion process due to the laminar nature of the flow at the micro scale. Different mixing strategies have been employed to effectively decrease the characteristic length for diffusion. However, particle mixing behavior in fluid is still not well understood. To assess the critical factors behind fluid-particle behavior at Reynolds numbers where inertial and viscous forces both play a role, we experimentally studied three dimensional particle distributions as a function of flow velocity, fluid and particle properties, and mixer geometries, using a fast microscopy technique we developed. Computational Fluid Dynamics was also used to understand the particle flow characteristics as influenced by relevant forces. With this knowledge, efficient unit operations in multiphase systems (e.g. mixing and separation) can be designed, especially in microfluidic technologies for many biological and medical applications that handle cells and beads. In particular, for our study in the signaling dynamics in T cell activation for adoptive-transfer cancer immune therapy. The microchip in this case provides a platform for obtaining well-controlled data points in parallel, superior to bench-top assay performances. <br/> <br/>Description: 2009 Ziegler Award Winner, presented as a keynote address at the 2009 School of Chemical and Biomolecular Engineering Fourth Year Colloquium, Wednesday October 14, 2009 at Georgia Institute of Technology. http://smartech.gatech.edu/handle/1853/31218 Title: Three-dimensional in Situ Temperature Measurement in Microsystems Using Brownian Motion of Nanoparticles <br/> <br/>Authors: Chung, Kwanghun <br/> <br/>Abstract: Recent developments in microsystems for chemical and biological analysis offer significant advantages over conventional methods, such as precise manipulation of samples and control of microenvironment. For many applications, the ability to control and measure temperature inside microfluidic devices is critical since temperature often affects biological or chemical processes. To address this need, we developed an in situ method for three-dimensionally resolved temperature measurement in microsystems. The temperature of the surrounding fluid is correlated from Brownian diffusion of suspended nanoparticles. We use video-microscopy in combination with image analysis software to selectively track nanoparticles in the focal plane. This method is superior with regards to reproducibility and reduced systematic errors since measuring Brownian diffusivity does not rely on fluorescence intensity or lifetime of fluorophores. The efficacy of the method is demonstrated by measuring spatial temperature profiles in various microfluidic devices that generate temperature gradients and by comparing these results with numerical simulations. We show that the method is accurate and can be used to extract spatial temperature variations in three dimensions. Compared to conventional methods that require expensive multiphoton optical sectioning setups, this technique is simple and inexpensive. In addition, we demonstrate the capability of this method as an in situ tool for simultaneously observing live cells under the microscope and monitoring the local temperature of the cell medium without biochemical interference, which is crucial for quantitative studies of cells in microfluidic devices. <br/> <br/>Description: 2009 Ziegler Award Winner, presented as a keynote address at the 2009 School of Chemical and Biomolecular Engineering Fourth Year Colloquium, Wednesday October 14, 2009 at Georgia Institute of Technology. http://smartech.gatech.edu/handle/1853/26725 Title: Fourth Year Colloquium, October 22, 2008 [Program] <br/> <br/>Abstract: Complete colloquium program, including abstacts and location information for the 2008 School of Chemical and Biomolecular Engineering Fourth Year Colloquium. http://smartech.gatech.edu/handle/1853/26724 Title: Dissolving Microneedles for Transdermal Drug Delivery <br/> <br/>Authors: Lee, Jeong Woo <br/> <br/>Abstract: Microfabrication technology has been adapted to produce micron- scale needles as a safer and painless alternative to hypodermic needle injection, especially for protein biotherapeutics and vaccines. This study presents a novel design that encapsulates sensitive biomolecules within microneedles that dissolve within the skin for bolus or sustained delivery and leave behind no biohazardous sharp medical waste. A novel fabrication process was developed based on casting a viscous aqueous solution during centrifugation to fill a micro-fabricated mold with biocompatible carboxymethylcellulose or amylopectin formulations. This process encapsulated sulforhodamine B, bovine serum albumin, and lysozyme as model drugs; lysozyme was shown to retain full enzymatic activity after encapsulation and to remain 96% active after storage for two months at room temperature. Microneedles were also shown to be strong enough to insert into human cadaver skin and then to dissolve within minutes. Bolus delivery was achieved by encapsulating model drug just within microneedle shafts. For the first time, sustained delivery over hours to days was achieved by encapsulating drug within the microneedle backing, which served as a controlled release drug reservoir that delivered drug by a combination of swelling the backing with interstitial fluid drawn out of the skin and drug diffusion into the skin via channels formed by dissolved microneedles. We conclude that dissolving microneedles can be designed to encapsulate sensitive biomolecules, insert into skin, and enable bolus or sustained release drug delivery. <br/> <br/>Description: 2008 Ziegler Award Winner, presented as a keynote address at the 2008 School of Chemical and Biomolecular Engineering Fourth Year Colloquium, Wednesday October 22, 2008.