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Noninvasive picoliter volume thermometry based on backscatter interferometry
Author(s) -
Swinney Kelly,
Bornhop Darryl J.
Publication year - 2001
Publication title -
electrophoresis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.666
H-Index - 158
eISSN - 1522-2683
pISSN - 0173-0835
DOI - 10.1002/1522-2683(200106)22:10<2032::aid-elps2032>3.0.co;2-1
Subject(s) - interferometry , optics , laser , refractive index , materials science , backscatter (email) , volume (thermodynamics) , detector , chip , radius , optoelectronics , analytical chemistry (journal) , chemistry , physics , telecommunications , electrical engineering , computer security , chromatography , quantum mechanics , computer science , wireless , engineering
Using the on‐chip refractive index (RI) detector based on backscatter interferometry, sensitive, small volume, noninvasive thermometry can be performed. The current optical configuration for the on‐chip interferometric backscatter detector (OCIBD) is quite simple and consists of an unfocused laser, an unaltered chip with a hemispherical channel and a photodetector. Alignment is straightforward with the only requirement being that the beam fully fills the channel. The interaction of an unfocused laser beam with the uncoated etched channel with a curvature within the silica plate (chip) produces fringes whose positional changes scale with respect to the refractive index (RI), n, of the fluid in the channel. Due to the inherently high value of d n /d T for most fluids and the high sensitivity of OCIBD to RI changes, the measurement of small temperature variations in sub‐nanoliter volumes is possible. Performing OCIBD with a 75 νm diameter laser beam on a silica chip that contains an etched channel with a 40 νm radius facilitates noninvasive thermometry on a N ‐(2‐hydroxyethyl)piperazine‐ (2‐ethanesulfonic acid) (HEPES) solution in a 188×10 –12 L probe volume with a temperature resolution of 9.9×10 –4 °C, at the 99% confidence level.