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Kang Liu, Yishu Zhou, Fang Yuan, Xiaobao Mo, Peihua Yang, Qian Chen, Jia Li, Tianpeng Ding, Jun Zhou
Herein we report a self-powered multimodal temperature and force sensor based on the reverse electrowetting effect and the thermogalvanic effect in a liquid droplet. The deformation of the droplet and the temperature difference across the droplet can induce an alternating pulse voltage and a direct voltage, respectively, which is easy to separate/analyze and can be utilized to sense the external force and temperature simultaneously. In addition, an integral display system that can derive information from external temperature/force concurrently is constructed...
November 16, 2016: Angewandte Chemie
Zhen Zhang, Collin Hitchcock, Robert F Karlicek
The electrowetting-on-dielectric (EWOD) lens is a good candidate for dynamic beam-shaping optics for advanced solid-state lighting systems. A geometric approximation model is described to predict the meniscus shape of a rectangular EWOD lens with arbitrary voltages and small Bond numbers. The model approximates the meniscus geometry as being a part of a compound toroidal surface. The model was compared with free-energy minimization simulations and experiments with the largest standard deviation between the geometric model and the simulation for a wide variety of bias voltages being less than 2%...
November 10, 2016: Applied Optics
Min-Yu Chiang, Yao-Wen Hsu, Hsin-Yi Hsieh, San-Yuan Chen, Shih-Kang Fan
Formation of multifunctional, heterogeneous, and encoded hydrogel building blocks, or microgels, by crosslinking and assembly of microgels are two essential steps in establishing hierarchical, complicated, and three-dimensional (3D) hydrogel architectures that recapitulate natural and biological structures or originate new materials by design. However, for the variety of the hydrogel materials crosslinked differently and for the varied scales of microgels and architectures, the formation and assembly processes are usually performed separately, which increases the manufacturing complexity of designed hydrogel materials...
October 2016: Science Advances
Rassoul Tabassian, Jung-Hwan Oh, Sooyeun Kim, Donggyu Kim, Seunghwa Ryu, Seung-Min Cho, Nikhil Koratkar, Il-Kwon Oh
The wettability of graphene on various substrates has been intensively investigated for practical applications including surgical and medical tools, textiles, water harvesting, self-cleaning, oil spill removal and microfluidic devices. However, most previous studies have been limited to investigating the intrinsic and passive wettability of graphene and graphene hybrid composites. Here, we report the electrowetting of graphene-coated metal meshes for use as electroactive flow control devices, utilizing two antagonistic functions, hydrophobic repellency versus liquid permeability...
October 31, 2016: Nature Communications
Deborah J Lomax, Pallav Kant, Aled T Williams, Hollie V Patten, Yuqin Zou, Anne Juel, Robert A W Dryfe
The control of wetting behaviour underpins a variety of important applications from lubrication to microdroplet manipulation. Electrowetting is a powerful method to achieve external wetting control, by exploiting the potential-dependence of the liquid contact angle with respect to a solid substrate. Addition of a dielectric film to the surface of the substrate, which insulates the electrode from the liquid thereby suppressing electrolysis, has led to technological advances such as variable focal-length liquid lenses, electronic paper and the actuation of droplets in lab-on-a-chip devices...
October 5, 2016: Soft Matter
Zuzana Brabcova, Glen McHale, Gary George Wells, Carl V Brown, Michael Ian Newton, Andrew M J Edwards
The wetting of solid surfaces can be modified by altering the surface free energy balance between the solid, liquid, and vapour phases. Liquid dielectrophoresis (L-DEP) can produce wetting on normally non-wetting surfaces, without modification of the surface topography or chemistry. L-DEP is a bulk force acting on the dipoles of a dielectric liquid and is not normally considered to be a localized effect acting at the interface between the liquid and a solid or other fluid. However, if this force is induced by a non-uniform electric field across a solid-liquid interface, it can be used to enhance and control the wetting of a dielectric liquid...
October 3, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
Yogesh B Sawane, Satishchandra B Ogale, Arun G Banpurkar
We demonstrate a consistent electrowetting response on ferroelectric poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) insulator covered with a thin Teflon AF layer. This bilayer exhibits a factor of 3 enhancement in the contact angle modulation compared to that of conventional single-layered Teflon AF dielectric. On the basis of the proposed model the enhancement is attributed to the high value of effective dielectric constant (εeff ≈ 6) of the bilayer. Furthermore, the bilayer dielectric exhibits a hysteresis-free contact angle modulation over many AC voltage cycles...
September 14, 2016: ACS Applied Materials & Interfaces
Lei Li, Di Wang, Chao Liu, Qiong-Hua Wang
We report an ultrathin zoom telescopic objective that can achieve continuous zoom change and has reduced compact volume. The objective consists of an annular folded lens and three electrowetting liquid lenses. The annular folded lens undertakes the main part of the focal power of the lens system. Due to a multiple-fold design, the optical path is folded in a lens with the thickness of ~1.98mm. The electrowetting liquid lenses constitute a zoom part. Based on the proposed objective, an ultrathin zoom telescopic camera is demonstrated...
August 8, 2016: Optics Express
Sin-Hyung Lee, In-Ho Lee, Jiyoon Kim, Chang-Min Keum, Eui-Sang Yu, Sin-Doo Lee
We demonstrated a new architecture of an electrowetting-on-dielectric (EWOD) device to transport a liquid droplet by the spatial modulation of an electric field produced using an embedded undulating electrode. The undulating electrode was constructed on an array of dielectric microstructures with different periods in region by region to generate a gradually varying lateral electric field. The contact angle of a droplet of water on the EWOD surface was found to decrease monotonically from 120 degrees to about 50 degrees with increasing the strength of the electric field...
June 2016: Journal of Nanoscience and Nanotechnology
Guohui Zhang, Marc Walker, Patrick R Unwin
We demonstrate low-voltage electrowetting at the surface of freshly cleaved highly oriented pyrolytic graphite (HOPG). Using cyclic voltammetry (CV), electrowetting of a droplet of a sodium perchlorate solution is observed at moderately positive potentials on high-quality (low step edge coverage) HOPG, leading to significant changes in the contact angle and relative contact diameter that are comparable to the results of the widely studied electrowetting on dielectric (EWOD) system, but over a much lower voltage range...
August 2, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
F Invernizzi, S Dulio, M Patrini, G Guizzetti, P Mustarelli
Energy harvesting from human motion is a research field under rapid development. In this tutorial review we address the main physical and physico-chemical processes which can lead to energy generation, including electromagnetism, piezoelectricity, and electrostatic generation. Emphasis is put on the relationships among material properties and device efficiency. Some new and relatively less known approaches, such as triboelectric nanogeneration (TENG) and reverse electrowetting (REWOD), are reported in more detail...
July 11, 2016: Chemical Society Reviews
Elaheh Shekaramiz, Ganeshkumar Varadarajalu, Philip J Day, H Kumar Wickramasinghe
Single cell transfection techniques are essential to understand the heterogeneity between cells. We have developed an integrated electrowetting nanoinjector (INENI) to transfect single cells. The high transfection efficiency, controlled dosage delivery and ease of INENI fabrication promote the widespread application of the INENI in cell transfection assays.
2016: Scientific Reports
Daniel Kopp, Hans Zappe
We demonstrate a new means to fabricate three-dimensional liquid lenses which may be tuned in focal length and astigmatism. Using actuation by electrowetting-on-dielectrics, astigmatism in arbitrary directions may be tuned independently, with almost no cross talk between orthogonal orientations. The lens is based on electrodes structured on planar polyimide foils and subsequently rolled, enabling high-resolution patterning of complex electrodes along the azimuthal and radial directions of the lens. Based on a design established through fluidic and optical simulations, the astigmatism tuning is experimentally verified by a change of the corresponding Zernike coefficients measured using a Shack-Hartmann wavefront sensor...
June 15, 2016: Optics Letters
Amir Shahzad, A R Masud, Jang-Kun Song
Electrowetting (EW) enables facile manipulation of a liquid droplet on a hydrophobic surface. In this study, manipulation of an electrolyte droplet having a small floating object on it was investigated on a solid hydrophobic substrate under the EW process. Herein, the floating object exhibited a vertical motion under an applied electric field owing to the spreading and contraction of the droplet on its connecting substrates. The field-induced height variation of the floating object was significantly influenced by the thicknesses of the dielectric and hydrophobic materials...
May 2016: Physical Review. E
A Cavalli, B Bera, D van den Ende, F Mugele
The competitive wetting of oil and aqueous electrolytes on solid surfaces depends strongly on the surface charge of the solid-water and the water-oil interface. This charge density is generally not known a priori but changes as ions adsorb or desorb from or to the interfaces, depending on the composition of the fluid and the thickness of thin films of the aqueous phase that frequently arise on hydrophilic surfaces, such as minerals. We analyze the wettability of such systems by coupling standard Derjaguin-Landau-Verwey-Overbeek theory to a linearized charge regulation model...
April 2016: Physical Review. E
Nima Tamaddoni, Graham Taylor, Trevor Hepburn, S Michael Kilbey, Stephen A Sarles
Biomimetic membranes assembled from block copolymers attract considerable interest because they exhibit greater stability and longetivity compared to lipid bilayers, and some enable the reconstitution of functional transmembrane biomolecules. Yet to-date, block copolymer membranes have not been achieved using the droplet interface bilayer (DIB) method, which uniquely allows assembling single- and multi-membrane networks between water droplets in oil. Herein, we investigate the formation of poly(ethylene oxide)-b-poly(dimethyl siloxane)-b-poly(ethylene oxide) triblock copolymer-stabilized interfaces (CSIs) between polymer-coated aqueous droplets in solutions comprising combinations of decane, hexadecane and AR20 silicone oil...
June 21, 2016: Soft Matter
R Prakash, K Pabbaraju, S Wong, R Tellier, K V I S Kaler
Nucleic acid based diagnostic techniques are routinely used for the detection of infectious agents. Most of these assays rely on nucleic acid extraction platforms for the extraction and purification of nucleic acids and a separate real-time PCR platform for quantitative nucleic acid amplification tests (NATs). Several microfluidic lab on chip (LOC) technologies have been developed, where mechanical and chemical methods are used for the extraction and purification of nucleic acids. Microfluidic technologies have also been effectively utilized for chip based real-time PCR assays...
June 2016: Biomedical Microdevices
Daniel Kopp, Lukas Lehmann, Hans Zappe
We demonstrate an electrowetting-actuated optofluidic system based on a rotatable liquid prism implemented as a two-dimensional laser scanner. The system is fabricated through a novel technology using a patterned flexible polymeric foil on which a high density of electrodes is structured and which is subsequently inserted into a cylindrical housing. The resulting radial electrode array is used for electrowetting actuation of two fluids filled into the cylinder, which allows a controllable tilt and orientation of the planar liquid interface and thus represents a tunable rotating prism...
March 20, 2016: Applied Optics
Ryan D Montoya, Kenneth Underwood, Soraya Terrab, Alexander M Watson, Victor M Bright, Juliet T Gopinath
A large extinction ratio optical shutter has been demonstrated using electrowetting liquids. The device is based on switching between a liquid-liquid interface curvature that produces total internal reflection and one that does not. The interface radius of curvature can be tuned continuously from 9 mm at 0 V to -45 mm at 26 V. Extinction ratios from 55.8 to 66.5 dB were measured. The device shows promise for ultracold chip-scale atomic clocks.
May 2, 2016: Optics Express
Dongyue Jiang, Sung-Yong Park
Technical advances in electrowetting-on-dielectric (EWOD) over the past few years have extended our attraction to three-dimensional (3D) devices capable of providing more flexibility and functionality with larger volumetric capacity than conventional 2D planar ones. However, typical 3D EWOD devices require complex and expensive fabrication processes for patterning and wiring of pixelated electrodes that also restrict the minimum droplet size to be manipulated. Here, we present a flexible single-sided continuous optoelectrowetting (SCOEW) device which is not only fabricated by a spin-coating method without the need for patterning and wiring processes, but also enables light-driven 3D droplet manipulations...
May 21, 2016: Lab on a Chip
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