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New methods to transport fluids in micro-sized devices

Published in:
Lincoln Laboratory Journal, Vol. 17, No. 2, December 2008, pp. 70-80.

Summary

Applications of microfluidics require a self-contained, active pumping system in which the package size is comparable to the volume of fluid being transported. Over the past decade, several systems have been developed to address this issue, but either these systems have high power requirements or the microfabrication is too complex to be cost efficient. A recent effort at Lincoln Laboratory using an emerging technology called electrowetting has led to the development of several novel micropump concepts for pumping liquids continuously, as well as for pumping discrete volumes.
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Summary

Applications of microfluidics require a self-contained, active pumping system in which the package size is comparable to the volume of fluid being transported. Over the past decade, several systems have been developed to address this issue, but either these systems have high power requirements or the microfabrication is too complex...

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Irreversible electrowetting on thin fluoropolymer films

Published in:
Langmuir, Vol. 23, No. 24, 20 November 2007, pp. 12429-12435.

Summary

A study was conducted to investigate electrowetting reversibility associated with repeated voltage actuations for an aqueous droplet situated on a silicon dioxide insulator coated with an amorphous fluoropolymer film ranging in thickness from 20 to 80 nm. The experimental results indicate that irreversible trapped charge may occur at the aqueous-solid interface, giving rise to contact angle relaxation. The accumulation of trapped charge was found to be related to the applied electric field intensity and the breakdown strength of the fluoropolymer. On the basis of the data, an empirical model was developed to estimate the amount of trapped charge in the fluoropolymer as well as the voltage threshold for the onset of irreversible electrowetting.
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Summary

A study was conducted to investigate electrowetting reversibility associated with repeated voltage actuations for an aqueous droplet situated on a silicon dioxide insulator coated with an amorphous fluoropolymer film ranging in thickness from 20 to 80 nm. The experimental results indicate that irreversible trapped charge may occur at the aqueous-solid...

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Low voltage electrowetting using thin fluoroploymer films

Published in:
J. Colloid and Interface Sci., Vol. 303, No. 2, 15 November 2006, pp. 517-524.

Summary

This paper investigates the nonideal electrowetting behavior of thin fluoroploymer films. Results are presented for a three phase system consisting of: (1) an aqueous water droplet containing sodium dodecyl sulfate (SDS), (2) phosphorous-doped silicon topped with SiO2 and an amorphous fluoroploymer (aFP) insulating top layer on which the droplet is situated, and (3) a dodecane oil that surrounds the droplet. The presented measurements indicate that the electrowetting equation is valid down to a 6 nm thick aFP film on a 11 nm thick SiO2. At this dielectric thickness, a remarkable contact angle change of over 100degreescan be achieved with an applied voltage less than 3 V across the system. The data also shows that for this water/surfactant/oil system, contact angle saturation is independent of the electric field, and is reached when the surface energy of the solid-water interface approaches zero.
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Summary

This paper investigates the nonideal electrowetting behavior of thin fluoroploymer films. Results are presented for a three phase system consisting of: (1) an aqueous water droplet containing sodium dodecyl sulfate (SDS), (2) phosphorous-doped silicon topped with SiO2 and an amorphous fluoroploymer (aFP) insulating top layer on which the droplet is...

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