Thermocapillary Flow in Glass Tubes Coated with Photoresponsive Layers
| Autor: | A. M. Velazquez-Benitez, J. Rodrigo Vélez-Cordero, Juan Hernández-Cordero |
|---|---|
| Rok vydání: | 2014 |
| Předmět: |
Materials science
Optical fiber Capillary action business.industry Surfaces and Interfaces engineering.material Condensed Matter Physics law.invention Contact angle Hysteresis Optics Coating law Heat generation Electrochemistry engineering General Materials Science Capillary surface Composite material business Layer (electronics) Spectroscopy |
| Zdroj: | Langmuir. 30:5326-5336 |
| ISSN: | 1520-5827 0743-7463 |
| Popis: | Thermocapillary flow has proven to be a good alternative to induce and control the motion of drops and bubbles in microchannels. Temperature gradients are usually established by implanting metallic heaters adjacent to the channel or by including a layer of photosensitive material capable of absorbing radiative energy. In this work we show that single drops can be pumped through capillaries coated with a photoresponsive composite (PDMS + carbon nanopowder) and irradiated with a light source via an optical fiber. Maximum droplet speeds achieved with this approach were found to be ~300 μm/s, and maximum displacements, around 120% of the droplet length. The heat generation capacity of the coatings was proven having either a complete coating over the capillary surface or a periodic array of pearls of the photoresponsive material along the capillary produced by the so-called Rayleigh-Plateau instability. The effect of the photoresponsive layer thickness and contact angle hysteresis of the solid-liquid interface were found to be important parameters in the photoinduced thermocapillary effect. Furthermore, a linear relationship between the optical intensity I(o) and droplet velocity v was found for a wide range of the former, allowing us to analyze the results and estimate response times for heat transfer using heat conduction theory. |
| Databáze: | OpenAIRE |
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