Affiliations: Advanced Software Technology & Mechatronics
Research Institute, Creation Core Kyoto Mikuruma 310, 448-5 Kajiicho,
Kamigyo-ku, Kyoto 602-0841, Japan. E-mail: kanda@astem.or.jp | Graduate School of Engineering, Tokyo Metropolitan
University, 1-1 Minamiohsawa, Hachiohji-shi, Tokyo 192-0397, Japan
Abstract: The presence of bio-substances in the near-wall region in micro
bio-chemical analysis chips is an important topic but one which is difficult to
investigate directly. In this paper we developed an accurate 3D-TIRFM
technique, which was used to investigate the three-dimensional positions of
nano-particles. The depth was calibrated using a piezo stage. As an example of
an application of this technique, the concentration profile of nano-particles
near a wall surface was investigated. The results showed that the concentration
profile was non-uniform and lower than that in the bulk. In addition the ionic
strength of the solvent strongly influenced the concentration profile. It was
concluded that the non-uniform concentration profile is due to the influence of
the electric double layer around the particles and the surface. This
demonstrates the importance of selecting suitable electric characteristics,
since a non-uniform and low concentration profile near the wall will affect the
reaction efficiency and the sensitivity in micro bio-chemical analysis.
Keywords: Evanescent light, Microchannel flow, Concentration profile, Near wall, 3D-TIRFM
