Failure Modes during Low-Voltage Electrowetting

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• 作者：Marcel Mibus ; Xiaoyu Hu ; Carl Knospe ; Michael L. Reed ; Giovanni Zangari
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2016
• 出版时间：June 22, 2016
• 年：2016
• 卷：8
• 期：24
• 页码：15767-15777
• 全文大小：644K
• 年卷期：0
• ISSN：1944-8252

文摘

Low-voltage electrowetting devices allow significant contact angle changes below a 50 V bias; however, operation under prolonged cycling and failure modes have not yet been sufficiently elucidated. In this work, the failure modes and performance degradation of Cytop (23–210 nm)/aluminum oxide (15–44 nm) bilayers have been investigated. Contact angle and leakage current were measured during stepped voltage measurements up to failure, showing three electrowetting response regimes: ideal Young–Lippmann behavior, contact angle saturation, and dielectric breakdown. The onset of ionic conduction in aluminum oxide and the resulting breakdown control when the layer would ultimately fail, but the thickness of the Cytop layer determined the achievable contact angle versus voltage characteristics. Cyclic electrowetting measurements studied the repeatability of contact angle change using an applied voltage above or below the voltage drop needed for polymer breakdown (V_T). Results show repeatable electrowetting below V_T and a rapidly diminishing contact angle response above V_T. The leakage current and injected charge cannot be used to comprehensively assess the stability of the system during operation. The contact potential difference measured with a Kelvin probe provides an alternative means of assessing the extent of the damage.