A simple U‐shaped device with a superhydrophobic coating used to sort droplets by surface tension

• Published in: Journal of the Chinese Chemical Society (Taipei) 2021-05, Vol.68 (5), p.770-775
• Main Authors: Feng, Rui, Li, Xin‐Ming, Wang, Lin, Li, Wan‐Yuan, Zhang, Yu‐Ping
• Format: Article
• Language: English
• Subjects: Beeswax; beverage; Chemical analysis; Contact angle; Droplets; Ethanol; Grooves; Hydrophobic surfaces; Hydrophobicity; liquid droplet; Microfluidics; Nanoparticles; Silicon dioxide; superhydrophobic material; Surface tension; Titanium dioxide
• ISSN: 0009-4536; 2192-6549
• DOI: 10.1002/jccs.202100028

Manipulation of droplets is an issue of great interest and challenge in microfluidics and chemical analysis domains. Herein, an ethanol suspension of beeswax and TiO2 (25 ± 5 nm), and SiO2 (7–40 nm) nanoparticles was sprayed on the surface of a self‐fabricated U‐shaped device. The resulted superhydrophobic coating enabled liquid droplets to roll back and forth in the groove of semicircular arc freely. According to the apparent difference of whole rolling distance, liquid droplets with less difference of surface tension were distinguished and sorted precisely. More importantly, the elegant analytical device was used to determine the surface tension for some typical food liquids and a relative error less than 5% was obtained, compared with the results measured by the contact angle goniometer. It could be used potentially as a simple, fast, and inexpensive diagnostic platform to sort liquid droplets and determine their surface tension values quantitatively. A simple device was fabricated with a groove with both width and depth of 2 mm along the middle of the semicircular arc. The liquid droplets with different surface tension were sorted according to their different rolling distance, after the arc surface was sprayed with a superhydrophobic material, along with the determination of their surface tension values.