Electrowetting of complex fluids: perspectives for rheometry on chip

Research output: Contribution to journalArticleAcademicpeer-review

18 Citations (Scopus)

Abstract

We explore the possibilities of electrowetting (EW) as a tool to assess the elastic properties of aqueous jellifying materials present in the form of a small droplet on a hydrophobic substrate. We monitored the EW response of aqueous solutions of gelatin (2−10 wt %) in ambient oil for various temperatures (8−40 °C) below and above the gel point. Whereas the drops remained approximately spherical cap-shaped under all conditions, the voltage-induced reduction of the contact angle became progressively less pronounced upon entering the gel state at lower temperatures. We modeled the decrease in contact angle by minimizing the total energy of the drops consisting of interfacial energies, electrostatic energy, and the elastic energy due to the deformation of the drop, which was taken into account in a modified Hertz model. This allowed fitting the data and extracting the elastic modulus G, which were found to agree well with macroscopic storage moduli G′ obtained with oscillatory shear rheometry. These results show that EW can be used as a tool for characterizing soft materials with the elastic moduli ranging (at least) from 10 to 1000 Pa. Our observations also create interesting perspectives for performing in situ rheological measurement inside microfluidic chips.
Original languageUndefined
Pages (from-to)1245-1252
Number of pages8
JournalLangmuir
Volume25
Issue number2
DOIs
Publication statusPublished - 2009

Keywords

  • IR-73454
  • METIS-256309

Cite this

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title = "Electrowetting of complex fluids: perspectives for rheometry on chip",
abstract = "We explore the possibilities of electrowetting (EW) as a tool to assess the elastic properties of aqueous jellifying materials present in the form of a small droplet on a hydrophobic substrate. We monitored the EW response of aqueous solutions of gelatin (2−10 wt {\%}) in ambient oil for various temperatures (8−40 °C) below and above the gel point. Whereas the drops remained approximately spherical cap-shaped under all conditions, the voltage-induced reduction of the contact angle became progressively less pronounced upon entering the gel state at lower temperatures. We modeled the decrease in contact angle by minimizing the total energy of the drops consisting of interfacial energies, electrostatic energy, and the elastic energy due to the deformation of the drop, which was taken into account in a modified Hertz model. This allowed fitting the data and extracting the elastic modulus G, which were found to agree well with macroscopic storage moduli G′ obtained with oscillatory shear rheometry. These results show that EW can be used as a tool for characterizing soft materials with the elastic moduli ranging (at least) from 10 to 1000 Pa. Our observations also create interesting perspectives for performing in situ rheological measurement inside microfluidic chips.",
keywords = "IR-73454, METIS-256309",
author = "A.G. Banpurkar and Duits, {Michael H.G.} and {van den Ende}, {Henricus T.M.} and Mugele, {Friedrich Gunther}",
year = "2009",
doi = "10.1021/la803080k",
language = "Undefined",
volume = "25",
pages = "1245--1252",
journal = "Langmuir",
issn = "0743-7463",
publisher = "American Chemical Society",
number = "2",

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Electrowetting of complex fluids: perspectives for rheometry on chip. / Banpurkar, A.G.; Duits, Michael H.G.; van den Ende, Henricus T.M.; Mugele, Friedrich Gunther.

In: Langmuir, Vol. 25, No. 2, 2009, p. 1245-1252.

Research output: Contribution to journalArticleAcademicpeer-review

TY - JOUR

T1 - Electrowetting of complex fluids: perspectives for rheometry on chip

AU - Banpurkar, A.G.

AU - Duits, Michael H.G.

AU - van den Ende, Henricus T.M.

AU - Mugele, Friedrich Gunther

PY - 2009

Y1 - 2009

N2 - We explore the possibilities of electrowetting (EW) as a tool to assess the elastic properties of aqueous jellifying materials present in the form of a small droplet on a hydrophobic substrate. We monitored the EW response of aqueous solutions of gelatin (2−10 wt %) in ambient oil for various temperatures (8−40 °C) below and above the gel point. Whereas the drops remained approximately spherical cap-shaped under all conditions, the voltage-induced reduction of the contact angle became progressively less pronounced upon entering the gel state at lower temperatures. We modeled the decrease in contact angle by minimizing the total energy of the drops consisting of interfacial energies, electrostatic energy, and the elastic energy due to the deformation of the drop, which was taken into account in a modified Hertz model. This allowed fitting the data and extracting the elastic modulus G, which were found to agree well with macroscopic storage moduli G′ obtained with oscillatory shear rheometry. These results show that EW can be used as a tool for characterizing soft materials with the elastic moduli ranging (at least) from 10 to 1000 Pa. Our observations also create interesting perspectives for performing in situ rheological measurement inside microfluidic chips.

AB - We explore the possibilities of electrowetting (EW) as a tool to assess the elastic properties of aqueous jellifying materials present in the form of a small droplet on a hydrophobic substrate. We monitored the EW response of aqueous solutions of gelatin (2−10 wt %) in ambient oil for various temperatures (8−40 °C) below and above the gel point. Whereas the drops remained approximately spherical cap-shaped under all conditions, the voltage-induced reduction of the contact angle became progressively less pronounced upon entering the gel state at lower temperatures. We modeled the decrease in contact angle by minimizing the total energy of the drops consisting of interfacial energies, electrostatic energy, and the elastic energy due to the deformation of the drop, which was taken into account in a modified Hertz model. This allowed fitting the data and extracting the elastic modulus G, which were found to agree well with macroscopic storage moduli G′ obtained with oscillatory shear rheometry. These results show that EW can be used as a tool for characterizing soft materials with the elastic moduli ranging (at least) from 10 to 1000 Pa. Our observations also create interesting perspectives for performing in situ rheological measurement inside microfluidic chips.

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KW - METIS-256309

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JO - Langmuir

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SN - 0743-7463

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