title: In Situ Control of Underwater-Pinning of Organic Droplets on a Surfactant-Doped Conjugated Polymer Surface.
abstract: Controlling the pinning of organic droplets on solid surfaces is of fundamental and practical interest in the field of material science and engineering, which has numerous applications such as surface cleaning, water treatment, and microfluidics. Here, a rapid in situ control of pinning and actuation of organic droplets is demonstrated on dodecylbenzenesulfonate-doped polypyrrole (PPy(DBS)) surfaces in an aqueous environment via an electrochemical redox process. A dramatic change of the pinning results from the transport of DBS(-) molecules between the PPy(DBS) surface and the aqueous environment, as well as from a simultaneous alternation of the surface oleophobicity to organic liquids during the redox process. This in situ control of the droplet pinning enables a stop-and-go droplet actuation, applicable to both polar and apolar organic droplets, at low voltages (∼0.9 V) with an extremely low roll-off angle (∼0.4°).
authors.affiliation: Department of Mechanical Engineering, Stevens Institute of Technology , Hoboken, New Jersey 07030, United States.
authors.forename: Wei
authors.initials: W
authors.lastname: Xu
authors.affiliation: Department of Mechanical Engineering, Stevens Institute of Technology , Hoboken, New Jersey 07030, United States.
authors.forename: Jian
authors.initials: J
authors.lastname: Xu
authors.affiliation: Department of Mechanical Engineering, Stevens Institute of Technology , Hoboken, New Jersey 07030, United States.
authors.forename: Chang-Hwan
authors.initials: CH
authors.lastname: Choi
authors.affiliation: Department of Mechanical Engineering, Stevens Institute of Technology , Hoboken, New Jersey 07030, United States.
authors.forename: Eui-Hyeok
authors.initials: EH
authors.lastname: Yang
keywords: actuation; droplets; pinning; polypyrrole; surfactants