Presentations |
| "Nanomorphism of C60 on Metal Surfaces," Tonya Coffey and Jackie Krim, Appalachian Regional Microscopy Society October Meeting, Fall 2004. |
"The Pepsi Challenge," Dustin Stansbury and Jon Jones, Student Research and Creative Endeavors Day at ASU, Spring 2005. Abstract: Using data obtained from experimental procedures, the current study presents some insights concerning the effects of gaseous environments on the viscosity of fluids at surface interfaces and the consequent effects on the frictional forces at those interfaces. Based on the theory that nanobubbles formed at solid-fluid interfaces may be responsible for changes in viscosity that reduce or increase friction at those surface boundaries, we suggest that a similar, macroscopic effect can be observed in soft drinks where bubbles are formed by carbon dioxide gas escaping from solution. We further suggest that more bubbles formed at the surface of a liquid-solid interface will decrease the viscosity of the fluid at the surface boundary. Preliminary research consisted of taking frequency and resistance data using various soft drinks and was conducted with a research quality quartz crystal microbalance (RQCM). This preliminary research has supported our predictions by providing a liquid-solid interface with which a shearing force can be measured accurately. |
"Scanning Probe Microscopy at Appalachian State University," Dennis Gilfillan and Brandon McGuire, Student Research and Creative Endeavors Day at ASU, Spring 2006. Abstract: Our nanotechnology and nanotribology lab at Appalachian State University offers both Scanning Tunneling Microscopy and Atomic Force Microscopy. The process of Scanning Tunneling Microscopy (STM) involves moving a metal tip extremely close (but not touching) to a chosen, conductive sample. While scanning the sample, a bias voltage is applied between tip and sample, which results in a net tunneling current. Maintaining a constant tunneling current while raster-scanning the tip across the sample allows the separation between the two to be measured, resulting in a topographical image of the sample. Contact Atomic Force Microscopy (AFM) is the process of raster-scanning a chosen sample with a tip at the end of a very flexible cantilever. As the cantilever bends in response to changes in sample topography, the deflection of the cantilever is measured by a laser which bounces off the back of the cantilever onto a four quadrant photodiode. As the sample is scanned, a constant pressure is maintained by the tip on the sample by interpreting the voltages from the photodiode and appropriately moving the tip up and down in response to the changing photodiode voltage. The up and down motion of the tip is then used to construct a topography image, and the lateral deflection of the cantilever measures friction forces. While the STM can only be used with conducting samples, the AFM is useful for non-conducting surfaces as well. We use these techniques for nanotechnology research, and assist others in the use of Scanning Probe Microscopy for outside research. |
| "The Change of Viscosity due to the effect of bubbles on the solid/liquid interface with a QCM ," Jon Jones, National Conference on Undergraduate Research, Asheville, NC Spring 2006. Abstract: It has been suggested that gaseous nanobubbles formed at solid-fluid interfaces may be responsible for changes in viscosity that reduce or increase friction at those surface boundaries. We suggest that a similar, macroscopic effect can be observed in soft drinks when bubbles are formed on the interface by carbon dioxide gas escaping from the solution. Here, we present measurements of the changing viscosity at the interface of a gold electrode submerged in seltzer water. We measure the viscosity using a Quartz Crystal Microbalance (QCM) in an RQCM system (Research Quartz Crystal Microbalance). Our QCM's are piezoelectric resonators that oscillate at 5 MHz with high quality factors (~10^5 ). With the RQCM system, we monitor changes in the resonant frequency of our quartz oscillator, and from the frequency measurements we can determine the viscosity. We see that the measured viscosity of the seltzer water is decreased due to the presence of bubbles on the gold electrode. As the seltzer water goes flat with increasing time, the measured viscosity increases, approaching the viscosity of water as expected. We correlate the frequency/viscosity measurements with video acquired of the bubbles on the QCM surface, and relate the viscosity to the area of the crystal face covered in gaseous bubbles vs. liquid. |
"Nanotechnology/Nanotribology at Appalachian State University and the Physics of Bubbles," Tonya Coffey, Invited talk to Davidson Physics Department, Fall 2006. |
"The Physics of Bubbles," Tonya Coffey, Seminar for Computer Science Department at Appalachian State University, Fall 2006. |
"Alcohols as Vapor Phase Lubricants for Micromachines and the Physics of Bubbles," Tonya Coffey, Invited talk to Chemistry Department at the University of Georgia in Athens, Fall 2006. |
"QCM Studies of Alcohols as Vapor Phase Lubricants," Heather Nemetz and Jon Jones, SESAPS, Poster Presentation, Fall 2006, Williamsburg VA. The future of nanotechnology depends in part upon the development of successful lubrication for micromachines (MEMS). Atomic Force Microscopy (AFM) research at Pennsylvania State University* has suggested alcohols such as propanol, butanol, ethanol, and pentanol to be potential vapor phase lubricants for MEMS; propanol at its vapor pressure can greatly reduce the friction on silicon dioxide surfaces. Due to the relatively high vapor pressure of these alcohols, all surfaces of a MEMS, including buried interfaces not easily reached by solid coatings, should become coated in thin layers of the alcohol upon exposure. We are testing the ability of the alcohols to migrate to buried interfaces in the MEMS. The mass uptake of the alcohols will be measured using the quartz crystal microbalance (QCM) in a vacuum chamber. The resonant frequency of the QCM drops as alcohols adsorb on its face. The uptake of the alcohols is measured as the pressure increases using different geometries of the canned crystals, allowing us to simulate a buried interface. The aforementioned alcohols are first thermally distilled, then leaked into the chamber until vapor pressure of the alcohol is reached. We see significant mass uptake even in extreme geometries, where the entire QCM face is only accessible through a tiny hole in the can encasing the QCM, 0.0006" in diameter. *K. Strawhecker et al., Trib. Lett. 19, 17 (2005). |
"The Effect of Nanoscopic Bubbles at a Solid/Liquid Interface," Heather Nemetz, Jon Jones, and Tonya Coffey, Poster Presentation at Appalachian Regional Microscopy Society Annual Meeting, Boone, NC, Fall 2006. |
"QCM Studies of Alcohols at Vapor Phase Lubricants," Jon Jones and Heather Nemetz, Poster Presentation at Appalachian Regional Microscopy Society Annual Meeting, Fall 2006. "The effect of nanoscale bubbles on viscosity at the solid/liquid interface using QCM," Tonya Coffey and Jon Jones, IVC conference, Stockholm, Sweden, Summer 2007. "Diet Coke and Mentos: What is really behind this physical reaction?" Tonya Coffey, Young Investigator for 2007 at Appalachian Regional Microscopy Society Annual Meeting, Fall 2007. |