Active surface tension driven micropump using droplet/meniscus pressure gradient

    Authors

    R. Shabani;H. J. Cho

    Comments

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    Abbreviated Journal Title

    Sens. Actuator B-Chem.

    Keywords

    Micropump; Microvalve; Electrowetting on dielectric; Droplet; Surface; tension; Contact angle; DRUG-DELIVERY; LINE ENERGY; EVAPORATION; ACTUATION; SEPARATION; DROPLETS; DEVICES; SYSTEM; CHIP; Chemistry, Analytical; Electrochemistry; Instruments & Instrumentation

    Abstract

    An active micropump with a simple layout and no moving parts is designed and fabricated which has on demand flow on/off capability. The micropump is based on droplet/meniscus pressure gradient generated by electrowetting on dielectric (EWOD). By altering the contact angle between liquid and solid using an electric field a pressure gradient was induced and a small droplet was pumped into the channel via a uniform flow rate. A surface tension based propellant method was introduced as a low power consumption actuation method in microfluidic devices. The liquid contact angle on the EWOD substrate was measured vs. electric potential and was used to obtain the capacitance of the substrate by fitting Young-Lippmann's equation. The capacitance of the EWOD substrate was also calculated to be 10 +/- 0.6 mu F/m(2) by measuring the dielectric layer thickness which showed excellent agreement with the former method. EWOD setup parameters such as capacitance, saturation contact angle, hysteresis contact angle and onset voltage were discussed. A coupled theoretical-experimental model was developed to predict how much voltage is needed to start the micropump for different droplet sizes. The modeling results revealed that for droplets with a radius smaller than 0.4 mm the droplet will start going into the channel even when no voltage is applied. For any larger droplet, a certain voltage is needed to start the pump. It was also shown that decreasing the size of the input droplet and increasing the voltage will result in an increase in the pump flow. A model for describing the shrinkage of the micropump input droplet was developed, based on direct observations, which was in agreement with the forced wetting described in literature. This model was compared to the other models used to describe passively pumped droplets and evaporating microdrops. (C) 2012 Elsevier B.V. All rights reserved.

    Journal Title

    Sensors and Actuators B-Chemical

    Volume

    180

    Publication Date

    1-1-2013

    Document Type

    Article

    Language

    English

    First Page

    114

    Last Page

    121

    WOS Identifier

    WOS:000317152700017

    ISSN

    0925-4005

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