Newsletter  2021.1  Index

Theme : "Mechanical Engineering Congress, 2020 Japan (MECJ-20)” Preface Masaaki MOTOZAWA, Hideo MORI Pending Issues in Large-Eddy Simulation of Turbulent Flows Takeo KAJISHIMA (Osaka University) Unsteady Flows in Turbomachines (What We Should Know and How We Can Apply to Designing) Ken-ichi FUNAZAKI (Iwate University) Modeling of a Two-Phase Flow Simulation with the Evaporation of the Gas Diffusion Layer in a Polymer Electrolyte Fuel Cell Ryuya NAGAYAMA, Satoshi SAKAIDA, Kotaro TANAKA, Mitsuru KONNO (Ibaraki University) Statistical Mechanical Analysis of Nanoparticle Behavior for Measurement of Flow Velocity Distribution in Nanochannels by Particle Tracking Velocimetry Minori TANAKA (Keio University), Itsuo HANASAKI (Tokyo University of Agriculture and Technology), Yutaka KAZOE (Keio University) Memorandum Record of the 2020 JSME Annual Meeting -as a committee member of the web conference- Yasumasa ITO (Nagoya University)

 

Statistical Mechanical Analysis of Nanoparticle Behavior for Measurement of Flow Velocity Distribution in Nanochannels by Particle Tracking Velocimetry

Minori TANAKA Keio University	Itsuo HANASAKI Tokyo University of Agriculture and Technology	Yutaka KAZOE Keio University

Abstract

Understanding fluid flows in nano-space (10-1000 nm) is important for development of nanofluidics. Commonly used method for measuring fluid flows is particle image velocimetry (PIV), which visualizes the flow by tracking the motion of tracer particles suspended in fluid. The conventional PIV developed for micro-spaces is micro PIV⁽¹⁾. Micro PIV measures the flow velocity at focal plane and scans across the channel by moving the focal plane to obtain the depth-wise flow profile. Since the spatial resolution of micro PIV is few micro-meters, which is determined by the depth of field of microscope, micro PIV cannot be applied to the measurement of fluid flows in nanochannels. Our research group therefore developed defocus nano particle image velocimetry⁽²⁾, which exploits out of focus particle image to detect the depth-wise position of particles with the spatial resolution of 10 nm. However, in nanospaces, displacement of the particles due to Brownian motion compared to the size of the space becomes relatively large, causing significant error in detecting the particle position. Thus, it is necessary to find out time resolution in which case the influence of Brownian motion is small enough to be neglected. In the present study, we carried out simulation based on Langevin equation to evaluate the influence of Brownian motion and found that the time resolution of 360 μs or less is required to reduce the influence of Brownian motion. Based on this finding, we experimentally measured velocity distribution of pressure driven flow in a nanochannel of 400 nm depth and succeeded in reducing the influence of Brownian motion. The result suggested unique characteristics of nanochannel flow, which will further be studied in future work.

Key words

Particle tracking velocimetry, Defocus, Brownian motion, Langevin simulation, Nanochannel, Nanofluidics

Figures

Fig.1  Principle of micro PIV(left) and defocus nano PIV(right)

References

(1)	Santiago, J.G., Wereley, S.T., Meinhart, C.D., Beebe, D.J, Adrian, R.J, “A particle image velocimetry system for microfluidics” Experiments in Fluids, 1998. 25(4): pp. 316-319.
(2)	Shibata, K., Kazoe, Y., Mawatari, K., and Kitamori, T., “Defocusing nano particle image velocimetry for nanochannel flows”, Proceedings of MicroTAS2017, 2017: pp. 261-262.