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Proceedings Paper

Silica nanoparticle inline size measurement using refractive index gradient in a microfluidic cell
Author(s): Yi Qiao; Dave Hofeldt; Brian Graebel; John Ramthun; Michael Dolezal
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Paper Abstract

In this article, we report a technique that can measure the size of silica nanoparticles in a microfluidic Y-Cell. In this technique, silica nanoparticle dispersion and a buffer solution are pumped through a micro-fabricated microfluidic Y-Cell, in which these two solutions form laminar flows and nanoparticles diffuse into the buffer due to the concentration gradient. The diffusion of nanoparticles into buffer causes a refractive index gradient across the boundary between nanoparticle dispersion and buffer. The refractive index gradients at different positions of the boundary can be measured by optical method and this information is used to calculate the nanoparticle diffusion coefficient, which is then used to calculate the nanoparticle size. We have demonstrated this technique with 5nm and 20nm silica nanoparticles. This technique is relatively fast and easy to implement, and proves to be an ideal candidate for inline process monitoring applications where fast and qualitative measurement is desired.

Paper Details

Date Published: 9 September 2008
PDF: 7 pages
Proc. SPIE 7042, Instrumentation, Metrology, and Standards for Nanomanufacturing II, 70420J (9 September 2008); doi: 10.1117/12.798766
Show Author Affiliations
Yi Qiao, 3M Co. (United States)
Dave Hofeldt, 3M Co. (United States)
Brian Graebel, 3M Co. (United States)
John Ramthun, 3M Co. (United States)
Michael Dolezal, 3M Co. (United States)

Published in SPIE Proceedings Vol. 7042:
Instrumentation, Metrology, and Standards for Nanomanufacturing II
Michael T. Postek; John A. Allgair, Editor(s)

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