WPI Wetting Studies Group - Rafael Garcia P. I.
Student MQP Projects
Student research-based senior theses called MQPs (Major Qualifying Projects) constitute an important part of WPI's project oriented curriculum. Unlike master's theses, these projects are designed to be completed within an academic year and must be sensitive to individual student abilities and strengths.
The titles and abstracts of various undergraduate senior theses (MQPs) that I have advised are provided below. Note that at least two of the projects I have advised do not involve my own research, but were insprired by student initiative. If you have an idea for a project, please come on by and we can discuss.
There is always a need for students to participate in my research activities! Notably, I am presently also advising the BS/MS research of Ken Osborne, who for his Master's thesis is using the program written for his Senior thesis to study the temperature-dependence of the contact angle of water. Ergys Subashi, who graduated this year, as a Graduate Student is now extending his studies of liquid crystalline thick-thin transitions to studying the effect of quenched random disorder on this two-dimensional Ising-like transition.
Complete versions of the theses themselves are also available from my website: Student MQPs
"Rutherford Scattering and GeLi Detection," Joseph Mullin, Dericc Orso, Matthew SilvaSa, January, 2009
Gamma detection is an important part of understanding our physical world and how life is affected by it. While gamma detection is important, interpreting numerical results creates context under which to understand the data. By testing soil samples across all of campus, we found that WPI soil exposes students to slightly more than half the national yearly average of all background radiation. Furthermore, simple relations such as the Rutherford scattering theory, although already understood and in practice, can still be more simply understood through the use of mathematical models. Through the use of MATLAB, one can predict how the alpha particles will perform in the laboratory. Through MATLAB we created a two dimensional model of how alpha particles are scattered by a single atom or by a sheet of atoms of some thickness. Only through this understanding of the data can one truly learn valuable laboratory practice and applications of physics theory.
"Modeling RF Excitation of a CO2 Laser," Daniel LaTorella, January, 2009
In this project I used a Matlab model to predict the ion sheath thickness of a CO2 gas laser excited with an RF discharge. This sheath region is unique to the RF discharge, and inhibits laser performance. I predicted the sheath thickness to within 4% of experimentally measured values, which is a negligible error when making laser gain measurements.
"Thickness Coexistence in Thin Films of 4-n-octyl-4'-cyanobiphenyl (8CB) Liquid Crystalline Systems," Ergys Subashi, April, 2008
Certain thermotropic liquid crystal films exhibit a strange phenomenon in which two different thicknesses coexist side-by-side on a solid surface. For 5CB these two film thicknesses appear to correspond to two different phases: nematic and isotropic. As the temperature is increased, this coexistence persists for a temperature range which depends on the initial thickness of the film. We have found that a similar phenomenon is present in films that have a smectic A phase, such as 8CB. For these films we observe a coexistence region very similar to that of 5CB just below the nematic-to-isotropic transition temperature TNI. We find that for 8CB films 47-70 nm thick there is an additional coexistence region near the smectic A to nematic transition temperature TAN that is strikingly different from the one observed near TNI . For 8CB films thinner than 47 nm these two coexistence behaviors merge and no intermediate uniform phase between TAN and TNI is observed. In this MQP thesis, an extensive phase diagram for 8CB films on silicon is presented along with the quantitative analysis of each coexistence region. We conclude that within our experimental uncertainty thin-thick coexistence regions satisfy a lever rule similar to other thermodynamic systems.
"Determining the Contact Angle of a Droplet on a Substrate," Ken Osborne, March, 2008
The objective of this Major Qualifying Project was to determine the contact angle of a droplet on a substrate at the so-called three-phase contact line. This was done by writing a program that examined pictures in order to determine contact angle. The program accomplished its goals by approximating substrates as lines, and droplet as partial circles. The program utilized Matlab's image processing toolbox. The program was validated through outside media in order to test the validity of the quoted contact angles. Results generated by the program have been compared with three distinct types of pictures with known contact angles. In the validation process, results from the program was tested against a picture of a shaded obtuse triangle resting on a line with known angle 45.0+-0.5o ; the program found the contact angle to be 43.3+-2.6 o. The second angle examined was a computer generated shaded circle piece. This circle piece has a contact angle of 45.0+-0.5o; the program found the contact angle to be 45.1+-0.3o. The program was finally matched up against a print-out of one of the pictures analyzed. The contact angle was determined via protractor, and was measured to be 67.3+-0.5o; while the contact angle analysis program found the contact angle to be 68.1+-1.3o.
"Quantum Conductance," Christopher Bruner, April, 2008 (advised with Prof. Nancy Burnham)
Quantum conductance is the observed change, in discrete steps, of the electrical conductance in an electrical element. The purposes of the project are to build a circuit similar to Foley et al. to show quantum conductance, to build a display for the circuit to show future students quantum conductance, and to design a laboratory experiment for PH 2651 so that students can repeat the experiment for themselves. The histogram of the conductance steps showed that majority occurred in integral multiples of the quantum conductance, which is 7.75x105 siemens, but half and quarter multiple steps were also seen. Due to time constraints, the designing of the PH 2651 laboratory experiment was not done.
"DC Glow-discharge Plasma Gun," Justin R. Carmichael, 2008.
The ion source for the Spallation Neutron Source of Oak Ridge National Laboratory is required to produce a substantial amount of H- current. To help the ion source produce this current, a DC, glow-discharge plasma gun was designed using coupled fluid dynamic, heat transfer, mechanical stress and deformation, and ion/electron trajectory simulations. In this report, the initial design, simulations results, and experimental data will be discussed.
"Quartz Crystal Microbalance Measurements of Adsorption Potential Well-Depths," Ryan Foltz, April, 2006
Changes in the resonant frequency of a quartz crystal microbalance (QCM), can be used to measure film thicknesses on the order of 0.1 monolayer or less that are adsorbed on the microbalance's electrode surfaces. The well-depth of the adsorption potential for molecules on a flat surface is a key parameter for determining the wetting transition temperature for molecules on that surface. However, it is difficult quantity to predict with precision using theoretical models. A QCM was used to determine the well-depth of the adsorption potential for for nitrous oxide and other polar molecules on flat surfaces. We compare our data with available theoretical predictions.
"Wetting Behavior of Nitrous Oxide," Robert Scott Weiler, April, 2006
The Cahn wetting theory predicts that, if a liquid does not wet a solid substrate at low temperature, then it will eventually wet at some higher temperature Tw. This theory has never been verified for polar liquids on solid surfaces, nor near room temperature. Nitrous Oxide is polar with a criti- cal temperature of 36.4oC, making it suitable for studying the Cahn theory for polar liquids near room temperature.
"Quartz Microbalance Apparatus for the Study of Wetting Phenomena," Mordecai Waegell, December 12, 2005
Droplets and uniform films are two equilibrium states of liquid on a substrate, also referred to as partial wetting and complete wetting respectively. A Quartz Crystal Microbalance (QCM) is a device capable of measuring film thickness on a substrate. A QCM apparatus was constructed for observation of the wetting transition between these two states. A computer program was designed to run experiments using this apparatus.
"Observing a Wetting Transition of Water on Graphite," Shinya Segawa, April, 2004
Water does not wet on the graphite surface at room temperature, but a prediction states that there should be a transition to complete wetting at an elevated temperature. Our goal is to experimentally observe a wetting transition of water on graphite and determine the wetting temperature. The result is that we observed a partial wetting transition near 325K, but we did not observe a transition to complete wetting up to 500K. Further future work is still necessary.