Sensitivity-optimized microfluidic H-sensor for rapid diffusion measurements


P. Domagalski1,2, M. Ottens2 and A. Bardow1,3

1Process and Energy Department, Delft University of Technology, Netherlands
2Department of Biotechnology, Delft University of Technology, Netherlands
3Chair of Technical Thermodynamics, RWTH Aachen University, Germany

Keywords: diffusion, microfluidics, optimal experimental design
property: diffusion cofficients
material: liquids

Since the revelation of diffusion principles 150 years ago, diffusivity measurements challenge both the analytical and engineering society. Available techniques for diffusion measurements are usually complex and/or time consuming. The resulting lack of measurement data reduces the design reliability of mass-transfer-involving processes.

In recent years, miniaturization and Lab-on-chip technology are promising to speed up diffusion measurements as the drastic decrease of characteristic distances minimizes the diffusion time. First micro-fluidic diffusion experiments have been developed where usually optically active/labeled spices in the low Fourier number regime (Fo << 1) are analyzed (e.g., [1,2]). While such setups offer the potential to become a standard diffusion measurement system, a rigorous optimization towards this goal has been lacking.

In this work, we therefore present an optimized H-cell-based microfluidic setup for diffusivity measurements in liquids. Model-based optimal experimental design methods have been employed to identify the best design and measurement conditions. In contrast to earlier designs, it is found that the measurement sensitivity increases drastically at an optimal finite Fourier number. The design predictions have been validated experimentally. This work further explores the practical advantages of the optimized setup such as rapid measurement, minimal sample amounts, low price, free choice of detection system and the ability of concentration-dependant diffusivity measurements.

 These findings show clearly that the H-cell setup designed and operated according to the identified principles is a valuable tool for diffusivity measurements. The developed setup could lead to an efficient method for high-throughput analysis of novel (bio)chemical systems with respect to mass transport characteristics.

References
  1. A.E. Kamholz, E.A. Schilling, P. Yager, Biophysical Journal 80, 4 (2001)

  2. T. Hotta, S. Nii, T. Yajima, F. Kawaizumi, Chemical Engineering & Technology 30, 2 (2007)

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