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Siti Noor Idora Syafinaz Zulkepli, Nor Hisham Hamid, Vineeta Shukla
In recent years, the number of interdisciplinary research works related to the development of miniaturized systems with integrated chemical and biological analyses is increasing. Digital microfluidic biochips (DMFBs) are one kind of miniaturized systems designed for conducting inexpensive, fast, convenient and reliable biochemical assay procedures focusing on basic scientific research and medical diagnostics. The role of a dielectric layer in the digital microfluidic biochips is prominent as it helps in actuating microliter droplets based on the electrowetting-on-dielectric (EWOD) technique...
May 8, 2018: Biosensors
Si Kuan Thio, Dongyue Jiang, Sung-Yong Park
Optofluidics is an emerging research field that combines the two disciplines of microfluidics and optics. By using microfluidic technologies for light control, optofluidic devices can offer several advantages over solid-type optical components, including optical-grade smoothness at the fluidic interface and a high degree of optical tunability without bulky and complex mechanical moving parts. These features have made optofluidic devices more versatile and reconfigurable to improve their optical performances...
May 4, 2018: Lab on a Chip
Udita Uday Ghosh, Sunando DasGupta
The balance of intermolecular and surface forces plays a critical role in the transport phenomena near the contact line region of an extended meniscus in several technologically important processes. Externally applied fields can alter the equilibrium and stability of the meniscus with concomitant effects on its shape, spreading characteristics and may even lead to oscillation. This article provides a detailed account of the present and past efforts in exploring the behavior of curved thin liquid films, subjected to mild thermal perturbations, heat input, electrical and magnetic fields for pure as well as colloidal suspensions - including the effects of particle charge and polarity...
April 17, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Afzal Khan, Kun Huang, Ming Hu, Xuegong Yu, Deren Yang
Superhydrophobic surfaces can be fabricated by using the self-assembled nano-architecture of 3C-SiC one-dimensional (1D) nanostructures as they are capable of forming a dense network of micro/nano air pockets without any help from external sources. Herein, metal catalyzed growth of 3C-SiC nanowires/nanorods on Si substrates via vapor-liquid-solid (VLS) mechanism using five different catalysts, i.e. chemically synthesized Au nanoparticles and direct current (DC) sputtered thin films of Au, Cu, Ni and Ti are reported...
April 15, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Michail E Kavousanakis, Nikolaos T Chamakos, Kosmas Ellinas, Angeliki Tserepi, Evangelos Gogolides, Athanasios G Papathanasiou
Collapse (Cassie to Wenzel) wetting transitions impede the electrostatically induced reversible modification of wettability on superhydrophobic surfaces, unless a strong external actuation (e.g. substrate heating) is applied. Here we show that collapse transitions can be prevented (the droplet remains suspended on the solid roughness protrusions) when the electrostatic force, responsible for the wetting modification, is smoothly distributed along the droplet surface. The above argument is initially established theoretically and then verified experimentally...
March 20, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Cynthia Wong, Michal E Pawlowski, Alessandra Forcucci, Catherine E Majors, Rebecca Richards-Kortum, Tomasz S Tkaczyk
Fluorescence microscopy can be a powerful tool for cell-based diagnostic assays; however, imaging can be time consuming and labor intensive to perform. Tunable systems give the ability to electronically focus at user selected depths inside an object volume and may simplify the opto-mechanical design of the imaging system. We present a prototype of a universal, tunable, miniature fluorescence microscope built from poly(methyl methacrylate) singlets that incorporates miniature, electrowetted lenses for electronic focusing...
March 1, 2018: Biomedical Optics Express
Guijun Chen, Xiaohua Liu, Sufen Li, Ming Dong, Dongyue Jiang
When a water droplet slides down a hydrophobic surface, a major energy it possesses is kinetic energy. However, people may ignore another important energy source: triboelectrification. To quantify and utilize triboelectrification energy, a phenomenon is presented in this study: one droplet slides down a tilted chip with a hydrophobic coating and patterned electrodes, triboelectrification happens and the induced charges are transferred to another horizontally placed chip with copper wires, on which another droplet is actuated by the transferred charges...
March 27, 2018: Lab on a Chip
Cesar Palma, Robert D Deegan
In traditional electrowetting-on-dielectric (EWOD) devices, droplets are moved about a substrate using electric fields produced by an array of discrete electrodes. In this study, we show that a drop can be driven across a substrate with a localized light beam by exploiting the photoelectrowetting (PEW) effect, a light-activated variant of EWOD. Droplet transport actuated by PEW eliminates the need for electrode arrays and the complexities entailed in their fabrication and control, and offers a new approach for designing lab-on-a-chip applications...
March 13, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Ali Farzbod, Hyejin Moon
This paper presents the demonstration of on-chip fabrication of a potassium-selective sensor array enabled by electrowetting on dielectric digital microfluidics for the first time. This demonstration proves the concept that electrochemical sensors can be seamlessly integrated with sample preparation units in a digital microfluidic platform. More significantly, the successful on-chip fabrication of a sensor array indicates that sensors become reconfigurable and have longer lifetime in a digital microfluidic platform...
May 30, 2018: Biosensors & Bioelectronics
Eszter N Tóth, Akshar Lohith, Manas Mondal, Jia Guo, Akiyoshi Fukamizu, Nader Pourmand
In highly polarized cells such as neurons, compartmentalization of mRNA and of local protein synthesis enables remarkably fast, precise, and local responses to external stimuli. These responses are highly important for neuron growth cone guidance, synapse formation, and regeneration following injury. Because an altered spatial distribution of mRNA can result in mental retardation or neurodegenerative diseases, subcellular transcriptome analysis of neurons could be a useful tool for studying these conditions, but current techniques, such as in situ hybridization, bulk microarray, and RNA-Seq, impose tradeoffs between spatial resolution and multiplexing...
March 30, 2018: Journal of Biological Chemistry
Edward Bormashenko
Gradient, chemically modified, flat surfaces enable directed transport of droplets. Calculation of apparent contact angles inherent for gradient surfaces is challenging even for atomically flat ones. Wetting of gradient, flat solid surfaces is treated within the variational approach, under which the contact line is free to move along the substrate. Transversality conditions of the variational problem give rise to the generalized Young equation valid for gradient solid surfaces. The apparent (equilibrium) contact angle of a droplet, placed on a gradient surface depends on the radius of the contact line and the values of derivatives of interfacial tensions...
April 1, 2018: Journal of Colloid and Interface Science
Jinhui Nie, Zewei Ren, Jiajia Shao, Chaoran Deng, Liang Xu, Xiangyu Chen, Meicheng Li, Zhong Lin Wang
Electrowetting technique is an actuation method for manipulating position and velocity of fluids in the microchannels. By combining electrowetting technique and a freestanding mode triboelectric nanogenerator (TENG), we have designed a self-powered microfluidic transport system. In this system, a mini vehicle is fabricated by using four droplets to carry a pallet (6 mm × 8 mm), and it can transport some tiny object on the track electrodes under the drive of TENG. The motion of TENG can provide both driving power and control signal for the mini vehicle...
February 27, 2018: ACS Nano
Quoc Vo, Haibin Su, Tuan Tran
Droplet spreading on substrates by electrowetting exhibits either of the two transient behaviours: one characterised by contact line oscillation, and the other one by slow spreading dynamics. The transition between these behaviours remains elusive due to the current limited understanding of the spreading dynamics on the hydrodynamical and electrical properties of electrowetting systems. To understand this transition we propose a model capturing the transition's occurrence based on both the hydrodynamical and electrical parameters...
January 16, 2018: Scientific Reports
Sangwook Chu, Thomas E Winkler, Adam D Brown, James N Culver, Reza Ghodssi
In this work, we introduce an electrowetting-assisted 3-D biofabrication process allowing both complete and localized functionalization of bionanoreceptors onto densely arranged 3-D microstructures. The integration of biomaterials with 3-D microdevice components offers exciting opportunities for communities developing miniature bioelectronics with enhanced performance and advanced modes of operation. However, most biological materials are stable only in properly conditioned aqueous solutions, thus the water-repellent properties exhibited by densely arranged micro/nanostructures (widely known as the Cassie-Baxter state) represent a significant challenge to biomaterial integration...
January 30, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Omkar D Supekar, Baris N Ozbay, Mo Zohrabi, Philip D Nystrom, Gregory L Futia, Diego Restrepo, Emily A Gibson, Juliet T Gopinath, Victor M Bright
Laser scanners are an integral part of high resolution biomedical imaging systems such as confocal or 2-photon excitation (2PE) microscopes. In this work, we demonstrate the utility of electrowetting on dielectric (EWOD) prisms as a lateral laser-scanning element integrated in a conventional 2PE microscope. To the best of our knowledge, this is the first such demonstration for EWOD prisms. EWOD devices provide a transmissive, low power consuming, and compact alternative to conventional adaptive optics, and hence this technology has tremendous potential...
December 1, 2017: Biomedical Optics Express
Maria Serena Maglione, Stefano Casalini, Stamatis Georgakopoulos, Marianna Barbalinardo, Vitaliy Parkula, Núria Crivillers, Concepció Rovira, Pierpaolo Greco, Marta Mas-Torrent
A switchable electrode, which relies on an indium-tin oxide conductive substrate coated with a self-assembled monolayer terminated with an anthraquinone group (AQ), is reported as an electrowetting system. AQ electrochemical features confer the capability of yielding a significant modulation of surface wettability as high as 26° when its redox state is switched. Hence, an array of planar electrodes for droplets actuation is fabricated and integrated in a microfluidic device to perform mixing and dispensing on sub-nanoliter scale...
March 2018: Small
Mo Zohrabi, Robert H Cormack, Connor Mccullough, Omkar D Supekar, Emily A Gibson, Victor M Bright, Juliet T Gopinath
We present numerical simulations of multielectrode electrowetting devices used in a novel optical design to correct wavefront aberration. Our optical system consists of two multielectrode devices, preceded by a single fixed lens. The multielectrode elements function as adaptive optical devices that can be used to correct aberrations inherent in many imaging setups, biological samples, and the atmosphere. We are able to accurately simulate the liquid-liquid interface shape using computational fluid dynamics...
December 11, 2017: Optics Express
Jia Wang, Philip H Chao, Sebastian Hanet, R Michael van Dam
Despite the increasing importance of positron emission tomography (PET) imaging in research and clinical management of disease, access to myriad new radioactive tracers is severely limited due to their short half-lives (which requires daily production) and the high cost and complexity of tracer production. The application of droplet microfluidics based on electrowetting-on-dielectric (EWOD) to the field of radiochemistry can significantly reduce the amount of radiation shielding necessary for safety and the amount of precursor and other reagents needed for the synthesis...
December 5, 2017: Lab on a Chip
Marcel Mibus, Giovanni Zangari
The electrowetting-on-dielectric behavior of Cytop/Tantalum oxide (TaOx) bilayers is studied by measuring their response vs applied voltage and under prolonged periodic cycling, below and above the threshold voltage VT corresponding to the breakdown field for the oxide. TaOx exhibits symmetric solid state I-V characteristics, with electronic conduction dominated by Schottky, Poole-Frenkel emission; conduction is attributed to oxygen vacancies (6 × 1016 cm-3 ), resulting in large currents at low bias. Electrolyte/Metal Oxide/Metal I-V characteristics show oxide degradation at (<5 V) cathodic bias; anodic bias in contrast results in stable characteristics until reaching the anodization voltage, where the oxide thickens, leading eventually to breakdown and oxygen production at the electrode...
December 6, 2017: ACS Applied Materials & Interfaces
G Bonfante, T Roux-Marchand, M-C Audry-Deschamps, L Renaud, P Kleimann, A Brioude, M Maillard
We explored polarization mechanisms at the interface between a dielectric material (an electrolyte) and an insulating liquid, during electrowetting actuation. Native surface charge density due to hydrophobic coating has been measured as an offset voltage for which the contact angle is at its minimum. Surface charge densities as low as 0.023 mC m-2 have been measured using this method, demonstrating that electrowetting can be used as a probe to measure native surface charge density. This effect strongly differs depending on the kind of polarization and is at the origin of major discrepancies between alternative and direct polarization during electrowetting actuation...
November 15, 2017: Physical Chemistry Chemical Physics: PCCP
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