Analytical Sciences

Flow Velocity Detector in a Microchip Based on a Photothermally Induced Grating

Kenji KATAYAMA,* Yoshikuni KIKUTANI,** and Takehiko KITAMORI**^,***

*Department of Applied Chemistry, Faculty of Science and Technology, Chuo University, 1-13-27 Kasuga, Bunkyo, Tokyo 112-8551, Japan
**Micro Chemistry Group, Kanagawa Academy of Science and Technology, East 307 KSP Bldg., 3-2-1 Sakado, Takatsu, Kawasaki 213-0012, Japan
***Department of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656, Japan

A new photothermal technique was developed for measuring the flow velocity and making solute concentration measurements in a microchip by using the same optical and instrumental setup. Collinear pump and probe light were irradiated onto a microchip surface on which a grating pattern was fabricated. The pump light induced a temperature change with the grating pattern in a microchannel, and a refractive index change due to a subsequent temperature rise was monitored by a heterodyned diffraction signal of the probe light. The flow velocity and concentration were obtained by monitoring the motion and intensity change of the thermally induced grating, respectively. The dynamic range of the flow velocity measurement was 0.17 - 670 mm/s, which is sufficient for covering most chemical applications of a microchip. The detection limit of the concentration measurement was 2 × 10^-6 M for a rhodamine B solution.

J-STAGE: View this article in J-STAGE