Electrically Controlled Localized Charge Trapping at Amorphous Fluoropolymer–Electrolyte Interfaces. Issue 2 (11th December 2019)

• Record Type: Journal Article
• Authors: Wu, Hao; Dey, Ranabir; Siretanu, Igor; van den Ende, Dirk; Shui, Lingling; Zhou, Guofu; Mugele, Frieder
• Is Part Of: Small. Volume 16:Issue 2(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2019-12-11
• Subjects: charge trapping -- electrets -- electrowetting -- hydrophobic–water interfaces -- surface charges; Nanotechnology -- Periodicals; Nanoparticles -- Periodicals; Microtechnology -- Periodicals; 620.5
• DOI: 10.1002/smll.201905726
• Languages: English
• ISSNs: 1613-6810

Abstract

Abstract: Charge trapping is a long‐standing problem in electrowetting on dielectric, causing reliability reduction and restricting its practical applications. Although this phenomenon is investigated macroscopically, the microscopic investigations are still lacking. In this work, the trapped charges are proven to be localized at the three‐phase contact line (TPCL) region by using three detecting methods—local contact angle measurements, electrowetting (EW) probe, and Kelvin probe force microscopy. Moreover, it is demonstrated that this EW‐assisted charge injection (EWCI) process can be utilized as a simple and low‐cost method to deposit charges on fluoropolymer surfaces. Charge densities near the TPCL up to 0.46 mC m −2 and line widths of the deposited charge ranging from 20 to 300 µm are achieved by the proposed EWCI method. Particularly, negative charge densities do not degrade even after a "harsh" testing with a water droplet on top of the sample surfaces for 12 h, as well as after being treated by water vapor for 3 h. These findings provide an approach for applications which desire stable and controllable surface charges. Abstract : Charge trapping induced by electrowetting (EW) at high voltage is revealed to be localized in the vicinity of the three‐phase contact line. While a drawback for most conventional EW applications, it is demonstrated that this EW‐assisted charge injection can serve as a simple and low‐cost method to deposit stable charge patterns on fluoropolymer surfaces with microscale resolution.