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Issue 42, 2016
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Ultra-low voltage electrowetting using graphite surfaces

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The control of wetting behaviour underpins a variety of important applications from lubrication to microdroplet manipulation. Electrowetting is a powerful method to achieve external wetting control, by exploiting the potential-dependence of the liquid contact angle with respect to a solid substrate. Addition of a dielectric film to the surface of the substrate, which insulates the electrode from the liquid thereby suppressing electrolysis, has led to technological advances such as variable focal-length liquid lenses, electronic paper and the actuation of droplets in lab-on-a-chip devices. The presence of the dielectric, however, necessitates the use of large bias voltages (frequently in the 10–100 V range). Here we describe a simple, dielectric-free approach to electrowetting using the basal plane of graphite as the conducting substrate: unprecedented changes in contact angle for ultra-low voltages are seen below the electrolysis threshold (50° with 1 V for a droplet in air, and 100° with 1.5 V for a droplet immersed in hexadecane), which are shown to be reproducible, stable over 100 s of cycles and free of hysteresis. Our results dispel conventional wisdom that reversible, hysteresis-free electrowetting can only be achieved on solid substrates with the use of a dielectric. This work paves the way for the development of a new generation of efficient electrowetting devices using advanced materials such as graphene and monolayer MoS2.

Graphical abstract: Ultra-low voltage electrowetting using graphite surfaces

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Publication details

The article was received on 08 Jul 2016, accepted on 21 Sep 2016 and first published on 22 Sep 2016

Article type: Paper
DOI: 10.1039/C6SM01565D
Citation: Soft Matter, 2016,12, 8798-8804
  • Open access: Creative Commons BY license
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    Ultra-low voltage electrowetting using graphite surfaces

    D. J. Lomax, P. Kant, A. T. Williams, H. V. Patten, Y. Zou, A. Juel and R. A. W. Dryfe, Soft Matter, 2016, 12, 8798
    DOI: 10.1039/C6SM01565D

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