Enhancement of mixing operation through new movement strategies in digital microfluidic biochips
01 Mar 2017-pp 611-614
TL;DR: In this paper, a new application area of DMFB using equilateral triangular electrodes instead of square electrodes has been proposed, considering the design issues and the fluidic constraints while performing all the modular operations.
Abstract: Microfluidic biochip is a lab-on-a-chip system that replaces conventional laboratory experiments. Digital Microfluidic Biochip (DMFB) handles liquids as discrete droplets, and offers highly reconfigurable and scalable technology. DMFB combines electronics with biology opening the new application areas of Microelectronics, Biochemistry, and Biomedical sciences. A new application area of DMFB using equilateral triangular electrodes instead of square electrodes has been proposed, considering the design issues and the fluidic constraints while performing all the modular operations. The improvement of sample-reagent mixing procedure is a key challenge issue in bioassay implementation as mixing is the most dominating operation in DMFB; hence, the Triangular DMFB (TEDMB) system leads over the existing DMFB system. In this paper, we have presented a study of TEDMB mixers and developed mixing library for TEDMB synthesis.
Citations
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TL;DR: In this article, the performance of droplet movement over a newly designed and fabricated triangular coplanar electrode system utilizing the principle of electrowetting on dielectric (EWOD) is extensively probed and compared with results available in the literature.
Abstract: The improvements in the dynamic performance of droplet movement over a newly designed and fabricated triangular coplanar electrode system utilizing the principle of electrowetting on dielectric (EWOD) is extensively probed and compared with results available in the literature. The process is further explored by developing a model, taking into account the pertinent driving and retarding forces, the role of the effective contact line length and an in-situ evaluation of the contact line friction coefficient. Furthermore, the efficiency of the fabricated digital microfluidic platform is quantified and compared in terms of driving force and velocities.
4 citations
04 Jul 2019
TL;DR: The structural and behavioural facets of the proposed hexagonal electrode digital microfluidic biochip (HDMFB) are discussed regarding its associated methodology in comparison with the existing square electrodes.
Abstract: Digital based microfluidic biochip appeals to the notion of microfluidic technology, with a wide variety of applications in electronics, biology, chemistry, environmental science, etc. Such a composite system replaces the conventional laboratory experiments by handling liquids as discrete with nanolitre or microliter volumes and providing reconfigurable and scalable devices following the electrowetting on dielectric (EWOD) principle. In this paper, we have focused on a new application area of digital microfluidic biochip technology with regular hexagonal electrode instead of conventional square electrodes. The structural and behavioural facets of the proposed hexagonal electrode digital microfluidic biochip (HDMFB) are discussed regarding its associated methodology in comparison with the existing square electrodes. Additionally, care is taken about the key challenges to influence the multiplexed bioassay operation, control pin assignment for safe droplet routing and mixing operation. An algorithm is proposed here to control the whole HDMFB array with minimum pin sharing. Finally, a scheduled bioassay is performed on the HDMFB and the result is compared with the existing one.
2 citations
TL;DR: In this article , a combination of digital microfluidics (DMF) and droplet microfluidics (DrMF) on a single substrate, where DMF enables droplet mixing and further acts as a controlled liquid supplier for a high-throughput nano-liter droplet generator.
Abstract: Microfluidic-based platforms have become a hallmark for chemical and biological assays, empowering micro- and nano-reaction vessels. The fusion of microfluidic technologies (digital microfluidics, continuous-flow microfluidics, and droplet microfluidics, just to name a few) presents great potential for overcoming the inherent limitations of each approach, while also elevating their respective strengths. This work exploits the combination of digital microfluidics (DMF) and droplet microfluidics (DrMF) on a single substrate, where DMF enables droplet mixing and further acts as a controlled liquid supplier for a high-throughput nano-liter droplet generator. Droplet generation is performed at a flow-focusing region, operating on dual pressure: negative pressure applied to the aqueous phase and positive pressure applied to the oil phase. We evaluate the droplets produced with our hybrid DMF–DrMF devices in terms of droplet volume, speed, and production frequency and further compare them with standalone DrMF devices. Both types of devices enable customizable droplet production (various volumes and circulation speeds), yet hybrid DMF–DrMF devices yield more controlled droplet production while achieving throughputs that are similar to standalone DrMF devices. These hybrid devices enable the production of up to four droplets per second, which reach a maximum circulation speed close to 1540 µm/s and volumes as low as 0.5 nL.
1 citations
01 Jan 2021
TL;DR: In this paper, the structural and behavioral aspects of the architectures as mentioned earlier and throwing sight to the enhancement of two primary modular operations such as droplet routing and mixing are addressed.
Abstract: “Digital microfluidic biochip (DMFB)” emanates as one of the most promising technologies in the discipline of “Lab-on-a-Chip (LoC)” environment, which encompasses several application areas like biology, electronics, chemistry, etc., by replacing the conventional laboratory equipment. The geometry of digital microfluidic biochips is realized on a 2D grid with regular three-, four- and six-sided polygons. In this paper, we address the structural and behavioural aspects of the architectures as mentioned earlier and throwing sight to the enhancement of two primary modular operations such as droplet routing and mixing. Furthermore, a complete and tangible comparative study is performed efficiently based on these three design methodologies.
References
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TL;DR: In this paper, the authors compare the various approaches used to derive the basic electrowetting equation, which has been shown to be very reliable as long as the applied voltage is not too high.
Abstract: Electrowetting has become one of the most widely used tools for manipulating tiny amounts of liquids on surfaces. Applications range from 'lab-on-a-chip' devices to adjustable lenses and new kinds of electronic displays. In the present article, we review the recent progress in this rapidly growing field including both fundamental and applied aspects. We compare the various approaches used to derive the basic electrowetting equation, which has been shown to be very reliable as long as the applied voltage is not too high. We discuss in detail the origin of the electrostatic forces that induce both contact angle reduction and the motion of entire droplets. We examine the limitations of the electrowetting equation and present a variety of recent extensions to the theory that account for distortions of the liquid surface due to local electric fields, for the finite penetration depth of electric fields into the liquid, as well as for finite conductivity effects in the presence of AC voltage. The most prominent failure of the electrowetting equation, namely the saturation of the contact angle at high voltage, is discussed in a separate section. Recent work in this direction indicates that a variety of distinct physical effects?rather than a unique one?are responsible for the saturation phenomenon, depending on experimental details. In the presence of suitable electrode patterns or topographic structures on the substrate surface, variations of the contact angle can give rise not only to continuous changes of the droplet shape, but also to discontinuous morphological transitions between distinct liquid morphologies. The dynamics of electrowetting are discussed briefly. Finally, we give an overview of recent work aimed at commercial applications, in particular in the fields of adjustable lenses, display technology, fibre optics, and biotechnology-related microfluidic devices.
1,962 citations
"Enhancement of mixing operation thr..." refers methods in this paper
...All the fluidic operations, like dispensing, routing, and mixing [4] of the sample and reagent droplet or sample preparation through dilution take place on an electrode array and the droplets of nanoliter or microliter volume can be managed independently with direct electrical control using EWOD[5] principle....
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TL;DR: To understand the opportunities and limitations of EWD microfluidics, this paper looks at the development of lab-on-chip applications in a hierarchical approach.
Abstract: The suitability of electrowetting-on-dielectric (EWD) microfluidics for true lab-on-a-chip applications is discussed. The wide diversity in biomedical applications can be parsed into manageable components and assembled into architecture that requires the advantages of being programmable, reconfigurable, and reusable. This capability opens the possibility of handling all of the protocols that a given laboratory application or a class of applications would require. And, it provides a path toward realizing the true lab-on-a-chip. However, this capability can only be realized with a complete set of elemental fluidic components that support all of the required fluidic operations. Architectural choices are described along with the realization of various biomedical fluidic functions implemented in on-chip electrowetting operations. The current status of this EWD toolkit is discussed. However, the question remains: which applications can be performed on a digital microfluidic platform? And, are there other advantages offered by electrowetting technology, such as the programming of different fluidic functions on a common platform (reconfigurability)? To understand the opportunities and limitations of EWD microfluidics, this paper looks at the development of lab-on-chip applications in a hierarchical approach. Diverse applications in biotechnology, for example, will serve as the basis for the requirements for electrowetting devices. These applications drive a set of biomedical fluidic functions required to perform an application, such as cell lysing, molecular separation, or analysis. In turn, each fluidic function encompasses a set of elemental operations, such as transport, mixing, or dispensing. These elemental operations are performed on an elemental set of components, such as electrode arrays, separation columns, or reservoirs. Examples of the incorporation of these principles in complex biomedical applications are described.
1,094 citations
"Enhancement of mixing operation thr..." refers methods in this paper
...All the fluidic operations, like dispensing, routing, and mixing [4] of the sample and reagent droplet or sample preparation through dilution take place on an electrode array and the droplets of nanoliter or microliter volume can be managed independently with direct electrical control using EWOD[5] principle....
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TL;DR: This paper studies the effects of varying droplet aspect ratios on linear-array droplet mixers, and proposes mixing strategies applicable for both high and low aspect ratio systems, and presents a split-and-merge mixer that takes advantage of the ability to perform droplet splitting at these ratios.
Abstract: The mixing of analytes and reagents for a biological or chemical lab-on-a-chip is an important, yet difficult, microfluidic operation. As volumes approach the sub-nanoliter regime, the mixing of liquids is hindered by laminar flow conditions. An electrowetting-based linear-array droplet mixer has previously been reported. However, fixed geometric parameters and the presence of flow reversibility have prevented even faster droplet mixing times. In this paper, we study the effects of varying droplet aspect ratios (height ∶ diameter) on linear-array droplet mixers, and propose mixing strategies applicable for both high and low aspect ratio systems. An optimal aspect ratio for four electrode linear-array mixing was found to be 0.4, with a mixing time of 4.6 seconds. Mixing times were further reduced at this ratio to less than three seconds using a two-dimensional array mixer, which eliminates the effects of flow reversibility. For lower aspect ratio (≤0.2) systems, we present a split-and-merge mixer that takes advantage of the ability to perform droplet splitting at these ratios, resulting in a mixing time of less than two seconds.
491 citations
"Enhancement of mixing operation thr..." refers background in this paper
...Depending on the phase changes between two consecutive movements of a droplet three types of movements are familiar in general, namely, forward movement (Mf) for phase change of 0o, orthogonal movement (Mo) due to phase change of 90o, and backward movement (Mb) while the phase change is of 180o [8, 9]....
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...In the existing works, one problem addressed by the experiment is flow reversibility, due to harmonic motion of droplet among a set of electrodes, flow developed by any forward motion is countered by a backward motion [8, 9]....
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Book•
01 Nov 2009
TL;DR: In this article, the authors introduce the fundamental concepts of DC nonlinear electrokinetics due to field-induced double layer polarization and double layer effects, including dielectrophoresis and electrorotation.
Abstract: 1. Introduction and fundamental concepts 2. Classical equilibrium theory due to surface changes 3. Electroosmotic transport 4. Electrophoretic transport and separation 5. Field-induced dielectric polarization 6. DC nonlinear electrokinetics due to field-induced double layer polarization 8. Dielectrophoresis and electrorotation - double layer effects 9. Electrohydrodynamic atomization, electrospinning and discharge driven vortices.
186 citations
"Enhancement of mixing operation thr..." refers background in this paper
...As the active mixing is proportional to the rate of diffusion [10, 11] we can formally state the followings: Mb < Mo < Mf in terms of contribution towards the completion of mixing....
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TL;DR: This work proposes a system design methodology that attempts to apply classical high-level synthesis techniques to the design of digital microfluidic biochips and develops an optimal scheduling strategy based on integer linear programming and two heuristic techniques that scale well for large problem instances.
Abstract: Microfluidic biochips offer a promising platform for massively parallel DNA analysis, automated drug discovery, and real-time biomolecular recognition. Current techniques for full-custom design of droplet-based “digital” biochips do not scale well for concurrent assays and for next-generation system-on-chip (SOC) designs that are expected to include microfluidic components. We propose a system design methodology that attempts to apply classical high-level synthesis techniques to the design of digital microfluidic biochips. We focus here on the problem of scheduling bioassay functions under resource constraints. We first develop an optimal scheduling strategy based on integer linear programming. However, because the scheduling problem is NP-complete, we also develop two heuristic techniques that scale well for large problem instances. A clinical diagnostic procedure, namely multiplexed in-vitro diagnostics on human physiological fluids, is first used to illustrate and evaluate the proposed method. Next, the synthesis approach is applied to a protein assay, which serves as a more complex bioassay application. The proposed synthesis approach is expected to reduce human effort and design cycle time, and it will facilitate the integration of microfluidic components with microelectronic components in next-generation SOCs.
172 citations