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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 14, 2018: Lab on a Chip
Cesar Palma, Robert David Deegan
In traditional electrowetting-on-dielectric devices droplet are moved about a substrate using electric fields produced by an array of discrete electrodes. Here we show that a drop can be driven across a substrate with a localized light beam by exploiting the photoelectrowetting effect, a light-activated variant of electrowetting-on-dielectric. Droplet transport actuated by photoelectrowetting 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...
February 19, 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...
January 31, 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, or RNA-Seq, impose tradeoffs between spatial resolution and multiplexing...
January 29, 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...
January 12, 2018: Journal of Colloid and Interface Science
Nie Jinhui, 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 micro-fluidic 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...
January 17, 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 Degen 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. Integration of biomaterials with three-dimensional (3-D) microdevice components offers exciting opportunities for communities developing miniature bioelectronics with enhanced performances 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-/nano- structures (widely known as the Cassie-Baxter state) represent a significant challenge to biomaterial integration...
January 4, 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...
December 27, 2017: 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 6, 2017: Physical Chemistry Chemical Physics: PCCP
Alper Tunga Celebi, Murat Barisik, Ali Beskok
Motivated by electrowetting-based flow control in nano-systems, water transport in graphene nano-channels is investigated as a function of the applied electric field. Molecular dynamics simulations are performed for deionized water confined in graphene nano-channels subjected to opposing surface charges, creating an electric field across the channel. Water molecules respond to the electric field by reorientation of their dipoles. Oxygen and hydrogen atoms in water face the anode and cathode, respectively, and hydrogen atoms get closer to the cathode compared to the oxygen atoms near the anode...
October 28, 2017: Journal of Chemical Physics
Ying-Jia Li, Brian P Cahill
An electrowetting-on-dielectric (EWOD) electrode was developed that facilitates the use of low alternating voltages (≤5 VAC). This allows online investigation of the frequency dependence of electrowetting by means of impedance spectroscopy. The EWOD electrode is based on a dielectric bilayer consisting of an anodic tantalum pentoxide (Ta2O5) thin film (d = 59.35 nm) with a high relative permittivity (εd = 26.3) and a self-assembled hydrophobic silane monolayer. The frequency dependence of electrowetting was studied using an aqueous μL-sized sessile droplet on the planar EWOD electrode in oil...
November 2, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Lei Li, Rong-Ying Yuan, Jin-Hui Wang, Qiong-Hua Wang
We report an electrically controlled optofluidic zoom system which can achieve a large continuous zoom change and high-resolution image. The zoom system consists of an optofluidic zoom objective and a switchable light path which are controlled by two liquid optical shutters. The proposed zoom system can achieve a large tunable focal length range from 36mm to 92mm. And in this tuning range, the zoom system can correct aberrations dynamically, thus the image resolution is high. Due to large zoom range, the proposed imaging system incorporates both camera configuration and telescope configuration into one system...
September 18, 2017: Optics Express
Alireza Ousati Ashtiani, Hongrui Jiang
We demonstrate an electrowetting-based liquid optical phase shifter. The phase shifter consists of two immiscible liquid layers with different refractive indices. Sandwiched between the two liquids is a rigid membrane that moves freely along the optical axis and supported by a compliant surround. When applied with a pressure, the thicknesses of both liquid layers change, which induces a difference in optical path, resulting in a phase shift. A miniaturized electrowetting-based actuator is used to produce hydraulic pressure...
April 2017: Journal of Microelectromechanical Systems
Andrej Berg, Christine Peter, Karen Johnston
The structure and dynamics of water at gold surfaces are important for a variety of applications, including lab on a chip and electrowetting. Classical molecular dynamics (MD) simulations are frequently used to investigate systems with water-gold interfaces, such as biomacromolecules in gold nanoparticle dispersions, but the accuracy of the simulations depends on the suitability of the force field. Density functional theory (DFT) calculations of a water molecule on gold were used as a benchmark to assess force field accuracy...
October 26, 2017: Journal of Chemical Theory and Computation
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