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Direct UV laser writing on chromium coated lithium niobate (LiNbO3) crystals is found to produce spontaneous domain inversion associated with the exposed UV laser tracks. Experimental evidence suggests that this effect is attributed to local out-diffusion of oxygen, reducing the LiNbO3 crystal surface due to the presence of chromium. The thin chromium film becomes hot and reactive after absorbing the UV laser radiation thus acting as an oxygen getter. This very efficient process enables the inversion of domains at lower intensities as compared to other direct laser based poling methods practically eliminating the deleterious surface damage induced by the direct absorption of the UV laser radiation by the crystal. Furthermore, the versatility of this domain fabrication method, is demonstrated by the production of inverted domain structures on Z-, Y- and 128°YX-cut substrates. © 2014 Optical Society of America.

Patterning customized arrays of microscale Galinstan or EGaIn liquid metals enables the creation of a variety of microfabricated systems. Current techniques for creating microsized 3D structures of liquid metals are limited by the large dimension or low aspect ratio of such structures, and time-consuming processes. Here, a novel technique for creating 3D microstructures of Galinstan using dielectrophoresis is introduced. The presented technique enables the rapid creation of Galinstan microstructures with various dimensions and aspect ratios. Two series of proof-of-concept experiments are conducted to demonstrate the capabilities of this technique. First, the 3D Galinstan microstructures are utilized as 3D microelectrodes to enhance the trapping of tungsten trioxide (WO3) nanoparticles flowing through a microfluidic channel. Second, the patterned Galinstan microstructures are utilized as microfins to improve the dissipation of heat within a microfluidic channel that is located onto a hot spot. The presented technique can be readily used for creating customized arrays of 3D Galinstan microstructures for a wide range of applications. [ABSTRACT FROM AUTHOR]

We present a technique for domain engineering the surface of lithium niobate crystals with features as small as 100 nm. A film of chromium (Cr) is deposited on the lithium niobate surface and patterned using electron beam lithography and lift-off and then irradiated with a wide diameter beam of intense visible laser light. The regions patterned with chromium are domain inverted while the uncoated regions are not affected by the irradiation. With the ability to realize nanoscale surface domains, this technique could offer an avenue for fabrication of nano-photonic and phononic devices. [ABSTRACT FROM AUTHOR]

In this work, a selective solar absorber made of nanostructured titanium gratings deposited on an ultrathin MgF 2 spacer and a tungsten ground film is proposed and experimentally demonstrated. Normal absorptance of the fabricated solar absorber is characterized to be higher than 0.9 in the UV, visible and, near infrared (IR) regime, while the mid-IR emittance is around 0.2. The high broadband absorption in the solar spectrum is realized by the excitation of surface plasmon and magnetic polariton resonances, while the low mid-IR emittance is due to the highly reflective nature of the metallic components. Further directional and polarized reflectance measurements show wide-angle and polarization-insensitive high absorption within solar spectrum. Temperature-dependent spectroscopic characterization indicates that the optical properties barely change at elevated temperatures up to 350 °C. The solar-to-heat conversion efficiency with the fabricated metamaterial solar absorber is predicted to be 78% at 100 °C without optical concentration or 80% at 400 °C with 25 suns. The performance could be further improved with better fabrication processes and geometric optimization during metamaterial design. The strong spectral selectivity, favorable diffuse-like behavior, and good thermal stability make the metamaterial selective absorber promising for significantly enhancing solar thermal energy harvesting in various systems at mid to high temperatures. [ABSTRACT FROM AUTHOR]

Chaotic advection plays an important role in microplatforms for a variety of applications. Currently used mechanisms for inducing chaotic advection in small scale, however, are limited by their complicated fabrication processes and relatively high power consumption. Here, a soft actuator is reported which utilizes a droplet of Galinstan liquid metal to induce harmonic Marangoni flow at the surface of liquid metal when activated by a sinusoidal signal. This liquid metal actuator has no rigid parts and employs continuous electrowetting effect to induce chaotic advection with exceptionally low power consumption. The theory behind the operation of this actuator is developed and validated via a series of experiments. The presented actuator can be readily integrated into other microfluidic components for a wide range of applications. [ABSTRACT FROM AUTHOR]

Semiconducting properties of nanoparticle coating on liquid metal marbles can present opportunities for an additional dimension of control on these soft objects with functional surfaces in aqueous environments. We show the unique differences in the electrochemical actuation mechanisms of liquid metal marbles with n- and p-type semiconducting nanomaterial coating. A systematic study on such liquid metal marbles shows voltage dependent nanoparticle cluster formation and morphological changes of the liquid metal core during electrochemical actuations and these observations are unique to p-type nanomaterial coated liquid metal marbles. [ABSTRACT FROM AUTHOR]

We report the realization of high-resolution bulk domains achieved using a shallow, structured, domain inverted surface template obtained by UV laser-induced poling inhibition in MgO-doped lithium niobate. The quality of the obtained bulk domains is compared to those of the template and their application for second harmonic generation is demonstrated. The present method enables do- main structures with a period length as small as 3 µm to be achieved. Furthermore, we propose a potential physical mechanism that leads to the transformation of the surface template into bulk domains. [ABSTRACT FROM AUTHOR]

A new platform described as the liquid metal/metal oxide (LM/MO) framework is introduced. The constituent spherical structures of these frameworks are made of micro- to nanosized liquid metal spheres and nanosized metal oxides, combining the advantages of both materials. It is shown that the diameters of the spheres and the stoichiometry of the structures can be actively controlled. Additionally, the liquid suspension of these spheres demonstrates tuneable plasmon resonances. These spherical structures are assembled to form LM/MO frameworks which are capable of demonstrating high sensitivity towards low concentrations of heavy metal ions, and enhanced solar light driven photocalalytic activities. These demonstrations imply that the LM/MO frameworks are a suitable candidate for the development of future high performance electronic and optical devices. [ABSTRACT FROM AUTHOR]

Small-scale pumps will be the heartbeat of many future micro/ nanoscale platforms. However, the integration of small-scale pumps is presently hampered by limited flow rate with respect to the input power, and their rather complicated fabrication processes. These issues arise as many conventional pumping effects require intricate moving elements. Here, we demonstrate a system that we call the liquid metal enabled pump, for driving a range of liquids without mechanical moving parts, upon the application of modest electric field. This pump incorporates a droplet of liquid metal, which induces liquid flow at high flow rates, yet with exceptionally low power consumption by electrowetting/deelectrowetting at the metal surface. We present theory explaining this pumping mechanism and show that the operation is fundamentally different from other existing pumps. The presented liquid metal enabled pump is both efficient and simple, and thus has the potential to fundamentally advance the field of microfluidics. [ABSTRACT FROM AUTHOR]

This paper reports on an investigation of mass transport of blood cells at micro-scale stenosis where local strain-rate micro-gradients trigger platelet aggregation. Using a microfluidic flow focusing platform we investigate the blood flow streams that principally contribute to platelet aggregation under shear micro-gradient conditions. We demonstrate that relatively thin surface streams located at the channel wall are the primary contributor of platelets to the developing aggregate under shear gradient conditions. Furthermore we delineate a role for red blood cell hydrodynamic lift forces in driving enhanced advection of platelets to the stenosis wall and surface of developing aggregates. We show that this novel microfluidic platform can be effectively used to study the role of mass transport phenomena driving platelet recruitment and aggregate formation and believe that this approach will lead to a greater understanding of the mechanisms underlying shear-gradient dependent discoid platelet aggregation in the context of cardiovascular diseases such as acute coronary syndromes and ischemic stroke. [ABSTRACT FROM AUTHOR]

Liquid metal marbles that are droplets of liquid metal encapsulated by micro- or nanoparticles are introduced. Droplets of galinstan liquid metal are coated with insulators (including Teflon and silica) and semiconductors (including WO3, TiO2, MoO3, In2O3 and carbon nanotubes) by rolling over a powder bed and also by submerging in colloidal suspensions. It is shown that these marbles can be split and merged, can be suspended on water, and are even stable when moving under the force of gravity and impacting a flat solid surface. Furthermore, the marble coating can operate as an active electronic junction and the nanomaterial coated liquid metal marble can act as a highly sensitive electrochemical based heavy metal ion sensor. This new element thus represents a significant platform for the advancement of research into soft electronics. [ABSTRACT FROM AUTHOR]

We investigate the physical origins of etching observed during Ti diffusion. The relationship between observed etch depth and water vapor content in the annealing environment is quantified. The dynamics of the etching process are also identified. It is discovered that water vapor content is essential for etching and that there is a characteristic delay before etching is observed. From these observations we can conclude that the process is electrochemical in nature with ionic defects diffusing into the Ti strip from the lithium niobate and these defects catalyzing the dissociation of water into reactive ions. [ABSTRACT FROM AUTHOR]

We present evidence of etching LiNbO3 when annealing two wafers in contact with an intermediate Ti strip. Etched features are characterized qualitatively using atomic force microscopy. The impact of the Ti strip thickness on the depth and roughness of the etched surface is quantified. Etched trenches of similar depths to the original Ti film are achieved with very smooth etched surface. [ABSTRACT FROM AUTHOR]

We demonstrate photochemically induced actuation of liquid metal marbles, which are liquid metal droplets encased in micro/nanoparticles. The WO3 nanoparticles coated marbles are placed in H2O2 solution, and their surfaces are illuminated with UV light. The semiconducting WO3 coating behaves as a photocatalyst to trigger a photochemical reaction, generating oxygen bubbles that propel the marble. The actuation of the marbles is investigated under different H2O2 concentrations, light intensities, and marble dimensions. Equations describing the fundamentals of such actuations are presented. [ABSTRACT FROM AUTHOR]

On page 144, Kourosh Kalantar‐zadeh, Arnan Mitchell, and co‐workers introduce liquid metal marbles by encapsulating droplets of liquid metal in micro/nanoparticles that are insulating or semiconducting. The physical properties of the liquid metal marbles are investigated. The ability to form active electronic junctions using liquid metal marbles and its use as a highly sensitive, electrochemical‐based, heavy metal ion sensor is demonstrated. [ABSTRACT FROM AUTHOR]

Solvothermally synthesized Ga2O3 nanoparticles are incorporated into liquid metal/metal oxide (LM/MO) frameworks in order to form enhanced photocatalytic systems. The LM/MO frameworks, both with and without incorporated Ga2O3 nanoparticles, show photocatalytic activity due to a plasmonic effect where performance is related to the loading of Ga2O3 nanoparticles. Optimum photocatalytic efficiency is obtained with 1 wt % incorporation of Ga2O3 nanoparticles. This can be attributed to the sub-bandgap states of LM/MO frameworks, contributing to pseudo-ohmic contacts which reduce the free carrier injection barrier to Ga2O3.

We report the observation, first to our knowledge, of optical waveguiding found beneath trenches etched in congruent lithium niobate using the recently reported etching during the indiffusion of Ti process. Observations of multi-mode and single-mode guiding at visible wavelengths and preliminary measurements of waveguide insertion losses are presented.