1. Thermal fluctuations of electromagnetic field: contribution to van der Waals and Casimir forces (Ning Gu and Arvind Narayanaswamy)
The aim of this project is to investigate the contribution of thermal fluctuations of the electromagnetic field to near-field forces, such as van der Waals and Casimir forces. The dyadic Green's function technique and the fluctuation-dissipation theorem will be used to determine forces between two microspheres, a configuration that is frequently used for measuring forces. Though measurements of this thermal contribution to near-field forces is difficult due to its small magnitude compared to the forces due to zero-point fluctuations. The experimental technique I have developed to measure near-field radiative energy transfer will be used to indirectly measure the force due to thermal fluctuations and compare with theoretical results obtained as part of this project. (This project will be partially funded by NSF award 0853723)
2. Thermal property measurements of micro/nanoscale structures using bi-material cantilevers (Carlo Canetta, Ning Gu, and Arvind Narayanaswamy)
We have developed a technique to quantify the thermal conductance of bi-material cantilevers. In this project, we will use the deflection of a bi-material cantilever to determine the thermal resistance of thin film materials, and eventually, micro/nanoscale liquid structures, soft materials such as polymers, and possibly single molecules. (This project will be partially funded by DARPA)
3. Non-linear dynamics of bi-material atomic force cantilevers (Carlo Canetta and Arvind Narayanaswamy)
Bi-material AFM cantilevers have been used as extremely sensitive temperature sensors, calorimeter, chemical, and biological sensors. The deflection of the cantilever in response to temperature changes can be detected using an optical lever or interferometric technique. However, we have noticed that the resonance frequency of a triangular bi-material AFM cantilever also shows an unexpected and significant shift in response to temperature. Interestingly, it is the second resonance frequency and not the fundamental frequency that shows this shift. This phenomenon could be the basis for a new type of temperature sensor using the bi-material cantilever. The goal of this project is to understand the physics underlying the shift in resonance frequency in response to temperature. Experimental measurements of the resonance frequency will be compared to finite element simulations using COMSOL. Based on these results, a simplified model describing these effects will be proposed.
4. Pattern formation due to particle accumulation at liquid-gas interfaces (Patrick Duggan, Mateo Chaskel, and Arvind Narayanaswamy)
A few years ago, the PI (Arvind) noticed an intriguing phenomenon that occurs in coffee cups (coffee with milk or creamer). When a cup of coffee is not disturbed for a sufficiently long period (approx. 1-3 hours), one notices beautiful star like patterns that form on the surface of the coffee. One simplistic explanation is that cream particles rise to the liquid-air interface and agglomerate at the interface due to attractive lateral capillary forces between particles. However, our observations have shown that the agglomeration is a complicated phenomenon. Hidden behind the seemingly static pattern is a rich array of motions of the particles - both on the interface as well as underneath. The goal of this project is to investigate this phenomenon and propose a theory that can explain the star-like patterns that form. Patrick Duggan and Mateo Chaskel are junior undergraduate students who are working on this project.
5. Pattern formation due to surface tension driven flows (Mateo Chaskel and Arvind Narayanaswamy)
When a drop of a liquid (fountain pen ink) is placed on the interface between another miscible liquid (water) of comparable viscosity and higher surface tension, a unique and rapid phenomenon takes place. The ink droplet spreads out on the surface rapidly to an outer limit. On reaching the outer limit, the pattern begins to retract inwards towards the center, forming a star like pattern in the process. It should be mentioned that the physics underlying the star-like patterns seen in this phenomenon have very little in common with that described in the previous project. Surprisingly, this phenomenon does not seem to be reported in literature yet. The purpose of this project is to develop a mathematical theory explaining the rapid expansion and subsequent formation of star-like patterns. We have also replicated this pattern formation with aqueous solution of sodium dodecyl sulfate (SDS) and observing the pattern formation process by fluorescent emission of rhodamine B dye.Contact Information :
Arvind Narayanaswamy
500 W120 Street
Rm. 228A, S.W. Mudd Building
New York, NY 10027
Ph: 212 854 0303
Fax: 212 854 3304
Email: arvind dot narayanaswamy at columbia dot edu
News :
Carlo Canetta passes his qualifier exams. Congratulations Carlo.
The Swamy group gets their first NSF grant! Big relief to everyone concerned.
Links :
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