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Temperature effect on microchannel oil-in-water emulsification

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Abstract

Microchannel (MC) emulsification is a promising technique to produce monodisperse emulsions by spontaneous interfacial-tension-driven droplet generation. The purpose of this study was to systematically characterize the effect of temperature on droplet generation by MC emulsification, which is a major uncharted area. The temperature of an MC emulsification module was controlled between 10 and 70°C. Refined soybean oil was used as the dispersed phase and a Milli-Q water solution containing sodium dodecyl sulfate (1 wt%) as the continuous phase. Monodisperse oil-in-water (O/W) emulsions with a coefficient of variation below 4% were produced, and at all the operating temperatures, their average droplet diameter ranged from 32 to 38 μm. We also investigated the effect of flow velocity of the dispersed phase on droplet generation characteristics. The maximum droplet generation rate (frequency) from a channel at 70°C exceeded that at 10°C by 8.1 times, due to the remarkable decrease in viscosity of the two phases. Analysis using dimensionless numbers indicated that the flow of the dispersed phase during droplet generation could be explained using an adapted capillary number that includes the effect of the contact angle of the dispersed phase to the chip surface.

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Abbreviations

A disk :

Initial disk area of a dispersed phase (m2)

A drop :

Droplet surface area (m2)

A MC :

Channel cross-sectional area (m2)

Ca d :

Capillary number of a dispersed phase (-)

\( Ca_{\text{d}}^{\theta } \) :

Adapted capillary number of a dispersed phase (-)

CV:

Coefficient of variation (-)

d drop :

Droplet diameter (m)

\( \bar{d} \) :

Dimensionless droplet diameter (-)

d n,drop :

Number-weighted mean droplet diameter (m)

d MC :

Channel hydraulic diameter (m)

f MC :

Frequency per channel (s−1)

f MC,max :

Maximum frequency per channel (s−1)

g :

Acceleration due to gravity (m/s2)

Δh d :

Height of a dispersed phase chamber (m)

h terrace :

Terrace height (m)

ΔP d :

Pressure applied to a dispersed phase (Pa)

ΔP d,bt :

Breakthrough pressure of a dispersed phase (Pa)

T C :

Celsius temperature (ºC)

t det :

Detachment time (s)

t gen :

Droplet generation time (s)

U d,MC :

Flow velocity of a dispersed phase inside a channel (m)

γ:

Dynamic interfacial tension (N/m)

γ0 :

Interfacial tension between the two phases in the absence of surfactant (N/m)

κ:

Relative rate of surfactant creation (s)

τd :

Diffusion of surfactant molecules (s)

γeq :

Equilibrium interfacial tension (N/m)

ηc :

Viscosity of a continuous phase (Pa s)

ηd :

Viscosity of a dispersed phase (Pa s)

θd :

Contact angle of a dispersed phase (°)

ξ:

Viscosity ratio of a dispersed phase to a continuous phase (-)

ρd :

Density of a dispersed phase (kg/m3)

σ:

Standard deviation (m)

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Acknowledgment

This work was supported by the Food Nanotechnology Project of the Ministry of Agriculture, Forestry, and Fisheries of Japan.

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Authors and Affiliations

  1. Food Engineering Division, National Food Research Institute, 2-1-12 Kannondai, Tsukuba, Ibaraki, 305-8642, Japan

    Katerina Butron Fujiu, Isao Kobayashi, Kunihiko Uemura & Mitsutoshi Nakajima

  2. Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki, 305-8572, Japan

    Katerina Butron Fujiu & Mitsutoshi Nakajima

Authors
  1. Katerina Butron Fujiu
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  2. Isao Kobayashi
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  3. Kunihiko Uemura
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  4. Mitsutoshi Nakajima
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Correspondence to Isao Kobayashi or Mitsutoshi Nakajima.

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Butron Fujiu, K., Kobayashi, I., Uemura, K. et al. Temperature effect on microchannel oil-in-water emulsification. Microfluid Nanofluid 10, 773–783 (2011). https://doi.org/10.1007/s10404-010-0708-y

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  • DOI: https://doi.org/10.1007/s10404-010-0708-y

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