Abstract
In electrowetting devices, hydrophobic insulating layer, namely dielectric layer, is capable of reversibly switching surface wettability through applied electric field. It is critically important but limited by material defects in dielectricity, reversibility, film forming, adhesiveness, price and so on. To solve this key problem, we introduced a novel fluorinated polyacrylate—poly(1H,1H,2H,2H-perfluoroctylmethacrylate (PFMA) to construct micron/submicron-scale dielectric layer via facile spray coating of nanoemulsion for replacing the most common Teflon AF series. All the results illustrated that, continuous and dense PFMA film with surface relief less than 20 nm was one-step fabricated at 110 °C, and exhibited much higher static water contact angle of 124°, contact angle variation of 42°, dielectric constant of about 2.6, and breakdown voltage of 210 V than Teflon AF 1600. Particularly, soft and highly compatible polyacrylate mainchain assigned five times much better adhesiveness than common adhesive tape, to PFMA layer. As a promising option, PFMA dielectric layer may further facilitate tremendous development of electrowetting performances and applications.
Highlights
Compared with early electrowetting-on-a-conductor, electrowetting-on-dielectric (EWOD) exhibits two outstanding advantages using the covering of hydrophobic insulator on electrode: (i) capability of lowering contact angle hysteresis to make surface microfluids move ; (ii) capability of applying much higher electric field for great contact angle variation [11]
We developed a novel fluorinated polyacrylate—PFMA dielectric layer for EWOD
All the results indicate that PFMA dielectric layer possesses relatively smooth surface, superexcellent light transmission, strong hydrophobility, and high dielectric constant of about 2.6
Summary
Compared with early electrowetting-on-a-conductor, electrowetting-on-dielectric (EWOD) exhibits two outstanding advantages using the covering of hydrophobic insulator on electrode: (i) capability of lowering contact angle hysteresis to make surface microfluids move ; (ii) capability of applying much higher electric field for great contact angle variation [11]. Hereinto this hydrophobic insulator is critical to the electrowetting effect of EWOD. Polymers 2017, 9, 217 surface fluorinated silicon nanosphere [21], and mesoporous silica [22] et al, These inorganic materials exhibit low driving voltage but their high polarity may induce weak hydrophobility and dielectric failure (including dielectric breakdown, ion permeation and charging effect). Difficult fabrication of thin film limits their application
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