A numerical investigation on AC electrowetting of a droplet

Hong, Jin; Ko, Sung Hee; Kang, Kwan Hyoung; Kang, In Seok

doi:10.1007/s10404-007-0246-4

Cited by 69 publications

(77 citation statements)

References 29 publications

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“…This implies that an electrically conducting droplet will behave like a dielectric droplet at sufficiently high AC frequencies [16]. The complex capacitance can be defined using the complex permittivity as:…”

Section: Ground Electrodementioning

confidence: 99%

“…Kumar et al [12] proposed a simplified RC circuit model to explain the contact angle variation of aqueous salt solutions. Hong et al [16] carried out detailed numerical modeling to predict the contact angle variation of a droplet with frequency of the AC voltage. Their numerical simulations showed that the electric field inside a droplet is very strongly dependent on the AC frequency; at a sufficiently high AC frequency, an electrically conducting droplet behaves like an insulating droplet due to the penetration of the electric field inside the droplet.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Electrical actuation of electrically conducting and insulating droplets using ac and dc voltages

Kumari¹,

Bahadur²,

Garimella³

2008

J. Micromech. Microeng.

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Electrical actuation of liquid droplets at the microscale offers promising applications in the fields of microfluidics and lab-on-chip devices. Much prior research has targeted the electrical actuation of electrically conducting liquid droplets using DC voltages (classical electrowetting). Electrical actuation of conducting droplets using AC voltages and the actuation of insulating droplets (using DC or AC voltages) has remained relatively unexplored. This paper utilizes an energy-minimization-based analytical framework to study the electrical actuation of a liquid droplet (electrically conducting or insulating) under AC actuation. It is shown that the electromechanical regimes of classical electrowetting, electrowetting under AC actuation, and insulating droplet actuation can be extracted from the generic electromechanical actuation framework, depending on the electrical properties of the droplet, the underlying dielectric layer and the frequency of the actuation voltage. The paper also presents experiments which quantify the influence of the AC frequency and the electrical properties of the droplet on its velocity under electrical actuation. Velocities of droplets moving between two parallel plates under AC actuation are experimentally measured; these velocities are then related to the actuation force on the droplet which is predicted by the electromechanical model developed in this work. It is seen that the droplet velocities are strongly dependent on the frequency of the AC actuation voltage; the cut-off AC frequency, above which the droplet fails to actuate, is experimentally determined and related to the electrical conductivity of the liquid. This paper then analyzes and directly compares the various electromechanical regimes for actuation of droplets in microfluidic applications.

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Section: Ground Electrodementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Electrical actuation of electrically conducting and insulating droplets using ac and dc voltages

Kumari¹,

Bahadur²,

Garimella³

2008

J. Micromech. Microeng.

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“…However, the present work uses a DC bias, and therefore, the liquid ribbon behaves as a perfect conductor and no electric field is present [25].…”

Section: Device Descriptionmentioning

confidence: 99%

Evaporative heat transfer from an electrowetted liquid ribbon on a heated substrate

Migliaccio

Garimella

2013

International Journal of Heat and Mass Transfer

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Evaporation of narrow water ribbons (of 5 and 7 μL volume) formed on a heated surface is investigated. Chemical and structural patterning of a silicon substrate is employed to fabricate a hydrophilic stripe that bisects hydrophobic pillar arrays of varied geometric roughness.Electrical heating of a 100 nm titanium layer on the back side of the device provides a constant heat flux. In the absence of electrical actuation, water introduced onto the substrate takes a bulging ribbon shape that is constrained to the immediate vicinity of the hydrophilic stripe.Electrowetting of the water ribbon spreads it into the hydrophobic pillar arrays on either side, leading to significant increases in maximum wetted width (up to 200%) and wettability (up to 80% reduction in contact angle). Infrared thermography is employed to characterize the cooling effect due to the spreading of the ribbon, while a goniometer monitors the ribbon shape. The heat transfer in each case is estimated through an energy balance analysis, and the results are compared with other electrowetting-based cooling techniques.

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“…A model for the display pixels hence requires accounting for the electric field distribution, as demonstrated in our earlier work (Manukyan et al 2011) and explained in the modelling paper by Oh et al (2012). Hong et al (2008), Drygiannakis et al (2009), andPooyan andPassandideh-Fard (2012) have simulated EWOD including the electric field strength in the dielectric layer and provide a thorough explanation of the numerical technique. Drygiannakis et al (2009) intention is to investigate contact angle saturation due to dielectric breakdown with this model.…”

Section: Introductionmentioning

confidence: 99%