I reduced the reaction volume in microfabricated suspended-membrane titration calorimeters to nanoliter droplets and improved the sensitivities to below a nanowatt with time constants of around 100ms. The device performance was characterized using exothermic acid-base neutralizations and a detailed numerical model. The finite element based numerical model allowed us to determine the sensitivities within 1% and the temporal dynamics of the temperature rise in neutralization reactions as a function of droplet size. The model was used to determine the optimum calorimeter design (membrane size and thickness, junction area, and thermopile thickness) and sensitivities for sample volumes of 1 nl for silicon nitride and polymer membranes. I obtained a maximum sensitivity of 153 pW/√Hz for a 1 µm SiN membrane and 79 pW/√Hz for a 1 µm polymer membrane. The time constant of the calorimeter system was determined experimentally by using a pulsed laser to increase the temperature of nanoliter sample volumes. For a 2.5 nanoliter sample volume, I experimentally determined a noise equivalent power of 500 pW/√Hz and a 1/e time constant of 110ms for a modified commercially available infrared sensor with a thin-film thermopile. Furthermore, I demonstrated detection of 1.4 nJ reaction energies from injection of 25 pl of 1 mM HCl into a 2.5 nl droplet of 1 mM NaOH.
| Identifer | oai:union.ndltd.org:VANDERBILT/oai:VANDERBILTETD:etd-11182011-114857 |
| Date | 07 December 2011 |
| Creators | Lubbers, Brad |
| Contributors | Franz Baudenbacher, Joel Tellinghuisen |
| Publisher | VANDERBILT |
| Source Sets | Vanderbilt University Theses |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.library.vanderbilt.edu/available/etd-11182011-114857/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to Vanderbilt University or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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