Abstract
Hydrofluoric acid (HF) etching of a silicon surface is demonstrated as an efficient means to create an interfacial chemical reaction flow, thus leading to self-propelled water-droplet motion. Before and after HF etching, the silicon surface exhibits a significant free energy change, represented by the increase of water contact angle from 0 to 60°. This favors self-propelled HF droplet motion with high-speed and long-distance, and in particular enables uphill motion. Even for a HF droplet 10 microliters in volume, vertical climbing along silicon strips is permitted. By investigating the temperature-dependent motion velocity, it confirms that the velocity is in positive proportion to the HF reaction rate.
Original language | English |
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Pages (from-to) | 5988-5991 |
Number of pages | 4 |
Journal | Soft Matter |
Volume | 8 |
Issue number | 22 |
DOIs | |
Publication status | Published - 14 Jun 2012 |
Externally published | Yes |