Electrowetting of complex fluids : perspectives for rheometry on chip
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 temper...
| Veröffentlicht in: | Langmuir : the ACS journal of surfaces and colloids. - 1992. - 25(2009), 2 vom: 20. Jan., Seite 1245-52 |
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| 1. Verfasser: | |
| Weitere Verfasser: | , , |
| Format: | Online-Aufsatz |
| Sprache: | English |
| Veröffentlicht: |
2009
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| Zugriff auf das übergeordnete Werk: | Langmuir : the ACS journal of surfaces and colloids |
| Schlagworte: | Journal Article Research Support, Non-U.S. Gov't Oils Solutions Water 059QF0KO0R Gelatin 9000-70-8 |
| Zusammenfassung: | 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 degrees 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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| Beschreibung: | Date Completed 27.02.2009 Date Revised 21.11.2013 published: Print Citation Status MEDLINE |
| ISSN: | 1520-5827 |
| DOI: | 10.1021/la803080k |