title: Lateral actuation of an organic droplet on conjugated polymer electrodes via imbalanced interfacial tensions.
abstract: This paper presents a new mechanism for the controlled lateral actuation of organic droplets on dodecylbenzenesulfonate-doped polypyrrole (PPy(DBS)) electrodes at low voltages (∼0.9 V) in an aqueous environment. The droplet actuation is based on the tunable surface wetting properties of the polymer electrodes induced by electrochemical redox reactions. The contact angle of a dichloromethane (DCM) droplet on the PPy(DBS) surface switches between ∼119° upon oxidation (0.6 V) and ∼150° upon reduction (-0.9 V) in 0.1 M NaNO3 solution. The droplet placed across the reduced and oxidized PPy(DBS) electrodes experiences imbalanced interfacial tensions, which prompt the actuation of the droplet from the reduced electrode to the oxidized electrode. The lateral actuation of DCM droplets on two PPy(DBS) electrodes is demonstrated, and the actuation process is studied. The driving force due to the imbalanced interfacial tensions is estimated to be approximately 10(-7) N for a 6 μL droplet.
authors.affiliation: Department of Mechanical Engineering, Stevens Institute of Technology, New Jersey, 07030, USA. Eui-Hyeok.Yang@stevens.edu.
authors.forename: Wei
authors.initials: W
authors.lastname: Xu
authors.affiliation: Department of Mechanical Engineering, Stevens Institute of Technology, New Jersey, 07030, USA. Eui-Hyeok.Yang@stevens.edu.
authors.forename: Jian
authors.initials: J
authors.lastname: Xu
authors.affiliation: Department of Mechanical Engineering, Stevens Institute of Technology, New Jersey, 07030, USA. Eui-Hyeok.Yang@stevens.edu.
authors.forename: Xin
authors.initials: X
authors.lastname: Li
authors.affiliation: Department of Mechanical Engineering, Stevens Institute of Technology, New Jersey, 07030, USA. Eui-Hyeok.Yang@stevens.edu.
authors.forename: Ye
authors.initials: Y
authors.lastname: Tian
authors.affiliation: Department of Mechanical Engineering, Stevens Institute of Technology, New Jersey, 07030, USA. Eui-Hyeok.Yang@stevens.edu.
authors.forename: Chang-Hwan
authors.initials: CH
authors.lastname: Choi
authors.affiliation: Department of Mechanical Engineering, Stevens Institute of Technology, New Jersey, 07030, USA. Eui-Hyeok.Yang@stevens.edu.
authors.forename: Eui-Hyeok
authors.initials: EH
authors.lastname: Yang