EWOD using nonaqueous liquids

Ahmadi, Maziar; Bermejo, Sandra; Castañer, Luís

doi:10.1016/j.mee.2015.04.085

Cited by 1 publication

(3 citation statements)

References 17 publications

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“…In all cases, a homogeneous nano-porous structure is seen. This is clearly different from other structures PTFE layers reported in the literature where the morphology of the layer is highly modified after different specific treatments [3,6,7,16,17]. Fig.…”

Section: Morphology Changescontrasting

confidence: 75%

“…These changes have been reported as the main cause of surface modification from a chemical point of view [7,19]. As a consequence, the explanation for the change in hydrophobic behaviour could be similar to another already known process [3,16]. The exposition to UV light promotes cleaning and produce radical formation over the surface.…”

Section: Chemical Modificationmentioning

confidence: 81%

“…A layer of hexamethyldisilazane (HMDS) is then deposited onto the alumina layer. Our previous work [16] has proved that the use of HMDS not only increases the adhesion over alumina but also gets better contact angle values over the hydrophobic layer. A mixture of 10:1 FC40 solvent and Teflon Dupont AF1600 was prepared and Table 3 Percentage Recovery for 6 different temperatures and 4 different UV exposition times.…”

Section: Sample Fabricationmentioning

confidence: 96%

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Surface modification of polytetrafluoroethylene thin films by non-coherent UV light and water treatment for electrowetting applications

López

Cedeño-Mata

Domínguez-Pumar

et al. 2020

Progress in Organic Coatings

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The electrowetting on dielectric or EWOD phenomenon is used in a wide range of applications, such as Liquid Lenses, Lab-on-Chip devices, or EWOD displays, among others. Its chemical resistance, electrical stability, ease of application, and low cost make polytetrafluoroethylene (PTFE) the preferred hydrophobic dielectric layer for such applications. However, the hydrophobic behaviour represents a challenge for spin coating other layers over its surface. As a consequence, several techniques are implemented to modify the surface of PTFE. These methods are complex, time-consuming, and produce morphology changes over the surface that are difficult and sometimes impossible to recover. In this work, we propose a new surface modification method that is based on a non-coherent UV light exposition method and a specific water treatment, that lead to a change from hydrophobic to hydrophilic, and a perfect recovery from hydrophilic to hydrophobic behaviour. Experiments: In this work, the fabrication of the hydrophobic layer treatment starts with the creation of a thin layer of alumina (Al O 2 3) over a glass substrate using an atomic layer deposition technique (ALD). A mixture of 10:1 FC40 solvent and Teflon Dupont AF1600 was coated over the alumina layer. The Teflon film was exposed to UV light produced by a low-pressure mercury (Hg) lamp for a period that ranges from 3−6 min. The results were analysed by scanning electron microscopy, x-ray spectroscopy, and static deionized water contact angle measurements. Findings: Contact angles dependent on UV light exposure time were observed. From the scanning electron microscopy analysis, it was confirmed that the UV treatment does not produce morphology changes over the surface. Nevertheless, the x-ray spectroscopy revealed that the UV exposed samples react when they are brought into contact with deionized water, improving the adhesion of the surface. The original hydrophobic behaviour of the surface is recovered (up to 98 %) after 3 h of thermal treatment. Furthermore, the thermal recovery analysis reveals a correlation between the recovery percentage and the applied temperature.

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