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Reconfigurable ion selective sensor array enabled by digital microfluidics

In this Research we present a proof of concept demonstration of a reconfigurable ion selective electrodes (ISE) array enabled by an electro wetting on dielectric (EWOD) digital microfluidics, for the first time. The on-chip preparation of an ISE array includes Electroplating, Chemical Oxidation and forming a thin layer of arbitrary ion selective membrane. The calibration curve of fabricated ISE shows complete agreement with conventional ones.


The proposed device with the capability of on-chip ISE fabrication has many advantages such as automation simplicity, minimal membrane consumption, longer lifetime and ease of integrability in lab-on-a-chip (LOC) platforms. This new method of fabrication allows to reconfigure the sensors array online without any interruption or the disassembling of the device while increasing the lifetime of the sensor.


Study of Compound droplet dynamics and separation techniques

Compound droplets composed of two or more immiscible liquids have a lot of potential applications in microscale biological and chemical technologies. Compound droplets have been used in on-chip liquid-liquid extraction[1], to improve Electrowetting on Dielectric operation[2] and also to accommodate reactant agents[3]. Typical EWOD applications usually involve the manipulation of single phase liquids in air medium. Because of multi-phases being involved, the dynamics of compound droplets in EWOD would be very different than that of single phase droplets where liquid-liquid interfacial tension add another dimension to this phenomena. A very few studies have been performed to understand the basic physics of compound droplets in pressure driven continuous microfluidics, although none in DMF platform.


Our study focuses to address some of the basic aspects of compound droplet behavior in EWOD platform including deformation during motion and separation kinetics of constituent components. The effects of viscous and capillary forces on deformation and the relation between different dimensionless numbers including capillary (Ca) and electrowetting (EW) number will be investigated experimentally. Another aim of the current study is to characterize the parameters involved to achieve complete separation of the components of the compound droplet which is a very crucial and challenging step in many applications[1].

References:

[1] Wijethunga, Pavithra AL, et al. "On-chip drop-to-drop liquid microextraction coupled with real-time concentration monitoring technique." Analytical chemistry 83.5 (2011): 1658-1664.

[2] Brassard, Daniel, et al. "Improving the operation of electrowetting-based digital microfluidic systems by using water-oil core-shell droplets." (2008).

[3] Barikbin, Zahra, et al. "Ionic liquid-based compound droplet microfluidics for ‘on-drop’separations and sensing." Lab on a Chip 10.18 (2010): 2458-2463.


Drop-to-Drop Liquid Microextraction (DTD-LLME)

Samples analyzed contain various components some of which are not desired as they increase the complexity of the analysis. Hence, these samples before they are used undergo a series of extraction steps to concentrate the required constituents and remove the non desired ones.

Electrowetting on dielectric serves as a very good tool to manipulate droplets in nano-liter scale and could be used for such extraction steps which can be further used for tests and analysis in the microfluidic system.


References:

Wijethunga, Pavithra AL, et al. "On-chip drop-to-drop liquid microextraction coupled with real-time concentration monitoring technique." Analytical chemistry 83.5 (2011): 1658-1664.


On chip cooling of hotspots using EWOD

Advancements in micro-nano fabrication has given birth to complex processors with billions of transistors. These transistors are responsible for the massive heat dissipation of a computer.

On many occasions, the heat dissipated by the processor is not uniform spatially and temporally. Hotspots are generated depending on the usage.


The digital/discrete nature of EWOD holds promise to cool those hotspots. We are investigating and optimizing the cooling of hotspots using EWOD.


References:

[1] Bindiganavale, Govindraj Shreyas. "Study of Hotspot Cooling for Integrated Circuits Using Electrowetting on Dielectric Digital Microfluidic System." Thesis. The University of Texas at Arlington, 2015. Print.


Other Research Area

  • Disease diagnostic technology
  • Chemical Synthesis Using EWOD
  • Particle Sepration Using Maragoni flow
  • Lab-on-a-chip applications