Reliable and low-voltage electrowetting on thin parylene films

The stability of an electrowetting system is dependent upon the choice of liquids, the dielectric material and the operating voltage. Substantial progress is reported herein on use of 300 nm thick poly(α, α, α′, α′-tetrafluoro-para-xylylene) (Parylene HT) films for almost 100° of reliable electrowetting modulation at only 15 V. Not only does Parylene HT exhibit improved resistance to dielectric failure as compared to poly(2-chloro-para-xylylene) (Parylene C), but Parylene HT is shown to sustain continuous DC electrowetting to < 70° for > 6 h. Furthermore, Parylene HT has a surface energy such that when electrowetting in an alkane oil ambient, a Young's angle of about 170° can be achieved without the traditional fluoropolymer top-coat. Also presented is a discussion of electric field enhancement when electrowetting in an oil bath. It is shown that Parylene HT is a promising candidate for low-voltage and large-area electrowetting devices such as displays and lab-on-chip.