Chemical sensors based on arrays of polymer-coated surface acoustic wave (SAW) devices are required for defense applications that provide a combination of sensitivity, selectivity, portability and response time. The primary challenge in the development of these polymer-based microsensors is the need to reproducibly deposit high quality, defect-free polymer coatings onto microelectrodes. Coating methods such as air brushing and solvent casting have proven unreliable and I have investigated the possibility of depositing polymer films on microelectrodes using electrostatic processing methods. In this work AC electrospraying was used to deposit nanoscale polymer films onto the surface of microelectrodes. The alternating polarity of the electric field eliminates surface charge accumulation and the polymers were deposited uniformly across both electrically insulating and conducting surface regions. In a different work, DC electrospraying was used to deposit patterned organic coatings onto the surface of microelectrodes. The surface of the microelectrode array consisted of an alternating pattern of insulating, grounded-metallic and ungrounded metallic regions, each with a width of 15µm. The charged particles were deposited only onto the grounded-metallic surface regions where there is an electrical path for charge dissipation. No polymer deposition was observed on the insulating or ungrounded-metallic regions due to the effects of surface charge accumulation. Also, I, DC electrodeposited organic molecules within the pores of ceramic film. Due to electrospraying, this film has a strong built-in electric field that induces Stark effect in the organic molecules, providing a unique new technology for bio and chemical sensing. Electrospinning has been used to produce polymer nanofibers with diameters ranging from a few microns to less than 100 nanometers. Due to mechanical oscillations of the electrically charged fibers during electrospinning, they are usually collected in the form of a non-woven mat without any significant fiber orientation. I have developed a new method for making highly aligned arrays of polymer nanofibers by using an AC coupled DC field to drive the electrospinning process. This new "biased AC electrospinning" method can be used to deposit aligned arrays of polymer nanofibers onto virtually any substrate. Potential applications of well-ordered nanofiber materials include tissue engineering, filtration, drug delivery and microelectronics.
| Identifer | oai:union.ndltd.org:vcu.edu/oai:scholarscompass.vcu.edu:etd_retro-1119 |
| Date | 01 January 2007 |
| Creators | Sarkar, Soumayajit |
| Publisher | VCU Scholars Compass |
| Source Sets | Virginia Commonwealth University |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Retrospective ETD Collection |
| Rights | © The Author |
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