Web Release Date: December 15,
Method for Microfluidic Whole-Chip Temperature Measurement Using Thin-Film Poly(dimethylsiloxane)/Rhodamine B
Department of Mechanical and Mechatronics Engineering, University of Waterloo, 200 University Avenue West, Waterloo, Ontario, Canada, N2L 3G1
Received for review June 16, 2007. Accepted October 22, 2007.
Abstract:
A novel method is presented for on-chip temperature
measurements using a poly(dimethylsiloxane) (PDMS)
thin film dissolved with Rhodamine B dye. This thin film
is sandwiched between two glass substrates (one of which
is 150 
m thick) and bonded to a microchannel molded
in a PDMS substrate. Whole-chip (liquid and substrate)
temperature measurements can be obtained via fluorescent intensity visualization. For verification purposes, the
thin film was tested with a tapered microchannel subjected to Joule heating, with resulting axial temperature
gradients comparing well with numerical simulations.
Errors induced by the definite film thickness are discussed and accounted for during experimental and analytical analysis. Alternative validation using the traditional
in-channel Rhodamine B injection method was also attempted. The thin film has several advantages over
traditional methods. First, false intensity readings due to
adsorption and absorption of Rhodamine B into PDMS
channels are eliminated. Second, whole-chip temperature
measurements are possible. Third, separation of working
liquid from Rhodamine B dye prevents possible electrophoresis effects.
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