N. P. Malcolm, Department of Mechanical Engineering, University of Texas at Austin; A. Heltzel, PC Krause and Associates, Inc; A. Shi, J. R. Howell, Department of Mechanical Engineering, University of Texas at Austin A Finite Difference Time Domain (FDTD) simulation is employed to calculate electromagnetic field and charge density distributions at the junction between a gold nanoparticle (NP) tip of a scanning ZnO nanowire and gold NP bio-markers. This three-dimensional simulation calculates the magnetic and electric field components in a large matrix of Yee cells by solving Maxwell’s curl equations. An absorbing boundary condition is included to eliminate reflection back into the simulation chamber. In the specific simulations considered here, a laser pulse of single wavelength is incident on the backside of a transparent silicon dioxide micro-cantilever, and coupled into a ZnO nanowire grown from an opening on a metal coating of the front side of the cantilever. The simulation results reveal local field enhancement between the gold NP tip of the nanowire and only one of three 20 nm gold NPs with a 28 nm empty spacing between two adjacent NPs. The charge density distributions in the gold tip and the gold NP are calculated and correlated with the local field enhancement, which makes the gold tip of the scanning nanowire waveguide attractive for use in imaging gold NP bio-labels on cell membranes. Proceedings of 9th International Conference on Heat Transfer, 2009, San Francisco...
Read MoreLaser Nanosphere Lithography
Alex Heltzel, PC Krause and Associates, Inc. Book Chapter in Nanomanufacturing American Scientific Publishers, 2009. A. Heltzel, PC Krause and Associates, Inc. Book Chapter in...
Read MoreThermal-Hydraulic Performance of Microstructured Heat Exchangers
A. Heltzel, PC Krause and Associates, Inc. Three-dimensional conjugate heat transfer models are built to predict the steady-state performance of microscale pin-fin and cross-flow heat exchangers with hydraulic diameters on the order of 100 μm. Modeling, meshing, and segmentation techniques are presented to allow for macroscale simulation of the microstructured devices. The effect of variation in geometric and flow parameters is investigated. Hydraulic and thermal predictions are compared to published experimental and extended beyond the limited range of test data to provide performance within a wide parametric range. A discussion of the dominating and relevant thermal transport mechanisms in both fluids and solid clarifies the routes to optimizing heat transfer in these small scale heat exchangers. Journal of Aerospace, in press...
Read MoreAlex Heltzel
[gravatar email=”heltzel@pcka.com” class=”alignleft” size=”96″ default=”https://pcka.com/wp-content/uploads/2010/08/gravatar.jpg”]A. Heltzel received BSME and MSME from the University of Dayton in 2002 and 2003 respectively, and a PhD from the University of Texas at Austin in 2006. He is currently a Senior Engineer for PCKA. Dr. Heltzel is the principal investigator on NASA and Air Force projects involving emerging technologies in aerospace thermal management. He also conducts research in the field of micro/nanoscale energy transport. Prior to joining PCKA, he performed computational research at the Air Force Research Laboratory in support of low temperature jet fuel stability. He has acted as a consultant to technology startup companies, and authored a book chapter on laser materials processing. Dr. Heltzel has published several papers in the area of near-field optics and plasmonics, and was awarded the 2006 American Institute of Aeronautics and Astronautics (AIAA) Best Paper in Thermophysics for work on surface plasmon-based nanolithography. Selected Publications Heltzel, “Laser Nanosphere Lithography,” Book Chapter in Nanomanufacturing, American Scientific Publishers, 2009. Heltzel, “Thermal-Hydraulic Performance of Microstructured Heat Exchanger,” Journal of Aerospace, in press (2009). N. P. Malcolm, A. Heltzel, A. Shi, J. R. Howell, “ Simulation of Charge Density and Field Distribution of a Gold Nanoparticle Tip-Terminated Scanning Nanowire Waveguide for Molecular Imaging,” Proceedings of 9th International Conference on Heat Transfer, July, 2009, San Francisco, CA. N. P. Malcolm, A. Heltzel, K. V. Sokolov, L. Shi, J. R. Howell, “Simulation of a Plasmonic Tip-Terminated Scanning Nanowire Waveguide for Molecular Imaging,” Applied Physics Letters, 93, 193101, November 2008. Heltzel, L. Qu, L. Dai, “Optoelectronic Property Modeling of Carbon Nanotubes Grafted with Gold Nanoparticles,” Nanotechnology, 19, 245702, May 2008. N. P. Malcolm, A. Heltzel, L. Shi, J. R. Howell, “Simulation of Electromagnetic Field Distribution at a Nanowire Probe for Near Field Scanning Optical Microscopy,” ASME Micro/Nanoscale Heat Transfer International Conference, Tainan, Taiwan, 2008. Heltzel, “Thermal Performance Modeling of Micro Pin-Fin Heat Sinks for Aircraft Thermal Management,” AIAA Aerospace Sciences Conference, Reno, Nevada, January 2008. Heltzel, S. Theppakuttai, J. R. Howell, S. C. Chen, “Surface Plasmon-Based Nanolithography Assisted by Gold Nanospheres,” Nanotechnology, vol. 19, 025305, January 2008. PhysicsWorld Featured Paper. Heltzel, A. Battula, J. R. Howell, S. C. Chen, “Nanostructuring Borosilicate Glass with Near-Field Enhanced Energy Using a Femtosecond Laser Pulse,” Journal of Heat Transfer, vol. 129, no. 1, January 2007, pp 53-59. 10. Heltzel, S. Theppakuttai, S. C. Chen, J. R. Howell, “Excitation of Surface Plasmons with Gold Microspheres,” AIAA/ASME Joint Thermophysics and Heat Transfer Conference, September 2006, San Francisco, CA. 2006 AIAA Best Paper. 11. Heltzel, S. Theppakuttai, J. R. Howell, S. C. Chen, “Analytical and Experimental Investigation of Laser-Microsphere Interaction for Nanoscale Surface Modification”, Journal of Heat Transfer, vol. 127, no. 11, November 2005, pp...
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