Proposal No. CTS-0421147 Principal Investigator: A.J. Smits, Princeton University
This grant is for the development of a nanoscale thermal anemometry probe (NSTAP) capable of measuring fluid flow on spatial and temporal scales two orders of magnitude smaller than can currently be studied with existing instrumentation is proposed. Through an understanding of the fundamental mechanical and electronic properties of metallic nanowires, this research will enable the production of a free standing nanowire suspended between two current carrying contacts. The nanowire, forming the sensing element of the NSTAP, will be capable of measuring microscale turbulence in high Reynolds number laboratory flows that is currently inaccessible due to lack of available measurement techniques. Furthermore, the increased surface area to volume ratio of the metallic nanowire in comparison to conventional probes will yield a device that not only has higher resolving power, but also is more sensitive and rapid in its response to changing flows. Although the operating principle of the NSTAP is identical to that of successful existing thermal anemometry practices, unconventional instrumentation is necessary to calibrate and acquire data from the probe due to the extremely small scale and high frequency response of the nanowire. The NSTAP will provide answers to some of the most basic and fundamental questions regarding turbulence. A secondary benefit that arises from the successful fabrication of the NSTAP is the ability to reach out across the typical boundaries of fluid mechanics to study mechanical and electronic properties metallic nanowires for on-chip interconnects. The development of free-standing metallic nanowires will enable the study of effects such as electromigration, recrystallization, and intrinsic stress evolution that occur due to current flow in the wire, independent of effects caused by the substrate. The success of this work will have broader implications for researchers in fluid mechanics, materials science and electrical engineering, and will fundamentally affect the use of nanowires for sensing applications. This project will greatly benefit from close collaborations among a diverse blend of student and faculty researchers in fluid mechanics and materials science enabling both types of specialists to learn about the other's field. The NSTAP development will be readily accessible for undergraduate participation through term projects and summer research experience in the use of standard nanofabrication techniques. The implementation of the NSTAP will educate students through the disparate practices of both nanofabrication and turbulence measurements. Finally, the results obtained will be broadly disseminated to attract researchers and industrial collaborations to further the implementation of the NSTAP in fundamental fluid mechanics research.
