Droplet microfluidics on a planar surface

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dc.contributor Aalto-yliopisto fi
dc.contributor Aalto University en
dc.contributor.author Torkkeli, Altti
dc.date.accessioned 2012-02-10T09:27:57Z
dc.date.available 2012-02-10T09:27:57Z
dc.date.issued 2003-10-03
dc.identifier.isbn 951-38-6237-2
dc.identifier.issn 1455-0849
dc.identifier.uri https://aaltodoc.aalto.fi/handle/123456789/2202
dc.description.abstract This work reports on the modelling of, and experiments on, a method in which liquid is transported as droplets on a planar hydrophobic surface with no moving parts, merely through electrostatic forces generated by the underlying electrodes. Two-directional transportation along a straight electrode path and across a junction, fusion of two droplets and methods for importing, exporting and filtering of water droplets were demonstrated, and can be used as basic functions of a lab-on-a-chip type microfluidic system. In this work, the electrostatic droplet actuation is for the first time demonstrated on super-hydrophobic surfaces. Such surfaces are composed of air-filled pores and exhibit a very low droplet sliding resistance due to reduced contact angle hysteresis and a high water contact angle (usually > 150°). This work shows that superhydrophobic surfaces can be used to reduce the minimum voltage and to increase the maximum speed under certain conditions, but there are some harmful side-effects. First of all, the electrostatic pressure can push water into the surface pores, which hinders actuation. The phenomenon can also be treated as a vertical electrowetting effect. Another drawback is that the use of superhydrophobic surfaces makes actuation more critical to the properties of the liquid. For example, actuation of biological buffer solutions was not successful. For these reasons, it is concluded that it is more beneficial to use a smooth surface with low hysteresis than a superhydrophobic surface in droplet actuation. Electrostatic droplet actuation is a potential method for manipulating liquid on a microscopic scale, but there is still work to do. This work contains a detailed examination of the droplet actuation mechanism, and trapping of charges in the solid-liquid interface is found to be the most severe problem that needs to be solved. en
dc.format.extent 194, [19]
dc.format.mimetype application/pdf
dc.language.iso en en
dc.publisher VTT Technical Research Centre of Finland en
dc.publisher VTT fi
dc.relation.ispartofseries VTT publications en
dc.relation.ispartofseries 504 en
dc.subject.other Electrical engineering en
dc.subject.other Physics en
dc.title Droplet microfluidics on a planar surface en
dc.type G4 Monografiaväitöskirja fi
dc.description.version reviewed en
dc.contributor.department Department of Electrical and Communications Engineering en
dc.contributor.department Sähkö- ja tietoliikennetekniikan osasto fi
dc.subject.keyword microfluidics en
dc.subject.keyword lab-on-a-chip en
dc.subject.keyword electrostatic droplet actuation en
dc.subject.keyword electrowetting en
dc.subject.keyword superhydrophobic surface en
dc.subject.keyword MEMS en
dc.identifier.urn urn:nbn:fi:tkk-001721
dc.type.dcmitype text en
dc.type.ontasot Väitöskirja (monografia) fi
dc.type.ontasot Doctoral dissertation (monograph) en

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