Electrowetting-based actuation of liquid droplets for microfluidic applications

The design and performance of a miniaturized coplanar capacitive sensor is presented whose electrode arrays can also function as resistive microheaters for thermocapillary actuation of liquid films and droplets. Optimal compromise between large capacitive signal and high spatial resolution is obtained for electrode widths comparable to the liquid film thickness measured, in agreement with supporting numerical simulations which include mutual capacitance effects. An interdigitated, variable width design, allowing for wider central electrodes, increases the capacitive signal for liquid structures with non-uniform height profiles. The capacitive resolution and time response of the current design is approximately 0.03 pF and 10 ms, respectively, which makes possible a number of sensing functions for nanoliter droplets. These include detection of droplet position, size, composition or percentage water uptake for hygroscopic liquids. Its rapid response time allows measurements of the rate of mass loss in evaporating droplets.

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“…Combining these two results produces the expression for the field penetration depth given by eqn. (2).…”

Section: Discussionmentioning

confidence: 99%

Capacitive sensing of droplets for microfluidic devices based on thermocapillary actuation

et al. 2004

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“…In several lab-on-a-chip applications, droplet manipulation has been demonstrated using electrohydrodynamic (EHD) forces. [13][14][15] Systems based on electrowetting [16][17][18] and dielectrophoresis 19,20 have also been used to dispense, transport, merge, and divide droplets. These approaches are not limited to unidirectional serial flow processes, where segregated samples are periodically generated and transported in the same direction through microchannels; rather, they allow droplets to be transported arbitrarily on a microfabricated control grid.…”

Section: Microfluidic Implementationmentioning

confidence: 99%

Digital microfluidics using soft lithography

et al. 2006

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Although microfluidic chips have demonstrated basic functionality for single applications, performing varied and complex experiments on a single device is still technically challenging. While many groups have implemented control software to drive the pumps, valves, and electrodes used to manipulate fluids in microfluidic devices, a new level of programmability is needed for end users to orchestrate their own unique experiments on a given device. This paper presents an approach for programmable and scalable control of discrete fluid samples in a polydimethylsiloxane (PDMS) microfluidic system using multiphase flows. An immiscible fluid phase is utilized to separate aqueous samples from one another, and a novel ''microfluidic latch'' is used to precisely align a sample after it has been transported a long distance through the flow channels. To demonstrate the scalability of the approach, this paper introduces a ''generalpurpose'' microfluidic chip containing a rotary mixer and addressable storage cells. The system is general purpose in that all operations on the chip operate in terms of unit-sized aqueous samples; using the underlying mechanisms for sample transport and storage, additional sensors and actuators can be integrated in a scalable manner. A novel high-level software library allows users to specify experiments in terms of variables (i.e., fluids) and operations (i.e., mixes) without the need for detailed knowledge about the underlying device architecture. This research represents a first step to provide a programmable interface to the microfluidic realm, with the aim of enabling a new level of scalability and flexibility for lab-on-a-chip experiments.

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“…The standard configuration shown in Fig. 1a corresponds to that proposed by Pollack et al 3 An array of electrodes is first patterned on a glass substrate. The electrodes are placed underneath a dielectric layer which is covered by a thin hydrophobic coating.…”

Section: Introductionmentioning

confidence: 99%

Water-oil core-shell droplets for electrowetting-based digital microfluidic devices

et al. 2008

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Digital microfluidics based on electrowetting-on-dielectric (EWOD) has recently emerged as one of the most promising technologies to realize integrated and highly flexible lab-on-a-chip systems. In such EWOD-based digital microfluidic devices, the aqueous droplets have traditionally been manipulated either directly in air or in an immiscible fluid such as silicone oil. However, both transporting mediums have important limitations and neither offers the flexibility required to fulfil the needs of several applications. In this paper, we report on an alternative mode of operation for EWOD-based devices in which droplets enclosed in a thin layer of oil are manipulated in air. We demonstrate the possibility to perform on-chip the fundamental fluidic operations by using such water-oil core-shell droplets and compare systematically the results with the traditional approach where the aqueous droplets are manipulated directly in air or oil. We show that the core-shell configuration combines several advantages of both the air and oil mediums. In particular, this configuration not only reduces the operation voltage of EWOD-based devices but also leads to higher transport velocities when compared with the manipulation of droplets directly in air or oil.

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Electrowetting-based actuation of liquid droplets for microfluidic applications

Cited by 1,338 publications

References 10 publications

Capacitive sensing of droplets for microfluidic devices based on thermocapillary actuation

Capacitive sensing of droplets for microfluidic devices based on thermocapillary actuation

Digital microfluidics using soft lithography

Water-oil core-shell droplets for electrowetting-based digital microfluidic devices

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