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Now showing items 1 - 16 of 1153

  • Calibration and Characteristics of an Electrowetting Laser Scanner

    Lim, Wei Yang   Zohrabi, Mo   Gopinath, Juliet T.   Bright, Victor M.  

    We present a calibration method to correct for fabrication variations and optical misalignment in a two-dimensional electrowetting scanner. These scanners are an attractive option due to being transmissive, nonmechanical, having a large scan angle (+/- 13.7 degrees), and low power consumption (mu W). Fabrication imperfections lead to non-uniform deposition of the dielectric or hydrophobic layerwhich results in actuation inconsistency of each electrode. To demonstrate our calibration method, we scan a 5 x 5 grid target using a four-electrode electrowetting prism and observe a pincushion type optical distortion in the imaging plane. Zemax optical simulations verify that the symmetric distortion is due to the projection of a radial scanning surface onto a flat imaging plane, while in experiment we observe asymmetrical distortion due to optical misalignment and fabrication imperfections. By adjusting the actuation voltages through an iterative Delaunay triangulation interpolation method, the distortion is corrected and saw an improvement in the mean error across 25 grid points from 43 mu m (0.117 degrees) to 10 mu m (0.027 degrees). Schematic of a four electrode electrowetting laser scanner used to generate a 25-point grid target.
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    The present invention relates to the unexpected discovery of novel methods of preparing nanodevices and/or microdevices with predetermined patterns. In one aspect, the methods of the invention allow for engineering structures and films with continuous thickness equal to or less than 50 nm.
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  • Nonlinear Mechanics of Interlocking Cantilevers

    Brown, Joseph J.   Mettler, Ryan C.   Supekar, Omkar D.   Bright, Victor M.  

    The use of large-deflection springs, tabs, and other compliant systems to provide integral attachment, joining, and retention is well established and may be found throughout nature and the designed world. Such systems present a challenge for mechanical analysis due to the interaction of contact mechanics with large-deflection analysis. Interlocking structures experience a variable reaction force that depends on the cantilever angle at the contact point. This paper develops the mathematical analysis of interlocking cantilevers and provides verification with finite element analysis and physical measurements. Motivated by new opportunities for nanoscale compliant systems based on ultrathin films and two-dimensional (2D) materials, we created a nondimensional analysis of retention tab systems. This analysis uses iterative and elliptic integral solutions to the moment-curvature elastica of a suspended cantilever and can be scaled to large-deflection cantilevers of any size for which continuum mechanics applies. We find that when a compliant structure is bent backward during loading, overlap increases with load, until a force maximum is reached. In a force-limited scenario, surpassing this maximum would result in snap-through motion. By using angled cantilever restraint systems, the magnitude of insertion force relative to retention force can vary by 50x or more. The mathematical theory developed in this paper provides a basis for fast analysis and design of compliant retention systems, and expands the application of elliptic integrals for nonlinear problems.
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  • Mechanical Interfacing Using Suspended Ultrathin Films From ALD

    Brown, Joseph J.   Bright, Victor M.  

    Interlocking microstructures formed from suspended ultrathin films create a mechanical bond between heterogeneous microfabricated dies. Films approximately 34 nm in thickness have been fabricated using atomic layer deposition in conjunction with standard surface micromachining. Bonding surfaces consist of polyimide pillars with a pitch of 19.8-29 mu m that support nanofilm cantilevers, with an areal density of 9.52 x 10(3) joints/mm(2) for square surface tiling and 4.14 x 10(3) joints/mm(2) for triangle tiling. Cantilevers 2.2 and 3.1 mu m in length provide length-to-thickness aspect ratios of 65: 1 and 91: 1, respectively. Bonding of complementary mating surfaces has been observed optically through transparent flexible substrates. [2015-0240]
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    The present invention relates to novel nano- and micro-electromechanical devices and novel methods of preparing them. In one aspect, the invention includes methods of preparing a nanodevice. In certain embodiments, the methods comprise coating a polymer layer with a first at least one thin solid material layer using atomic layer deposition (ALD), thus forming an ALD-generated layer. In other embodiments, the methods comprise patterning the first at least one thin solid material layer to form a nanodevice. In yet other embodiments, the methods comprise releasing the nanodevice from the polymer layer.
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  • Large extinction ratio optical electrowetting shutter

    Montoya, Ryan D.   Underwood, Kenneth   Terrab, Soraya   Watson, Alexander M.   Bright, Victor M.   Gopinath, Juliet T.  

    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. (C) 2016 Optical Society of America
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  • Real-Time Detection of Reverse-Osmosis Membrane Scaling via Raman Spectroscopy

    Supekar, Omkar D.   Brown, Joseph J.   Greenberg, Alan R.   Gopinath, Juliet T.   Bright, Victor M.  

    Scaling remains a serious barrier to membrane-based desalination. While some real-time techniques have proven effective for scaling detection, none provides the crucial capability of chemical identification with high temporal and spatial resolution under realistic operating conditions. In this work, we describe a real-time technique for detection of early stage scaling via chemical quantification using Raman spectroscopy. Experiments utilized a custom bench-scale flow cell integrated with a commercial Raman microscope that accesses the membrane through a 10 mm optical window. Calcium sulfate was used as a model foulant at high concentration (1.8 g/L) to minimize the time required for membrane scaling. The experiments were conducted with a commercial brackish water reverse-osmosis thin film composite membrane operating at a feed pressure of 1.17 MPa (170 psi) and a feed flow velocity of 4.7-5.6 cm/s. Raman measurements were made in real time at a laser excitation wavelength of 785 nm. Real-time results were validated with post-mortem SEM and energy-dispersive X-ray analysis and indicated the capability to detect early-stage scaling characterized by a relatively modest reduction in the permeate flow rate.
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  • Hemispherical micro-resonators from atomic layer deposition

    Gray, Jason M.   Houlton, John P.   Gertsch, Jonas C.   Brown, Joseph J.   Rogers, Charles T.   George, Steven M.   Bright, Victor M.  

    Hemispherical shell micro-resonators may be used as gyroscopes to potentially enable precision inertial navigation and guidance at low cost and size. Such devices require a high degree of symmetry and large quality factors (Q). Fabricating the devices from atomic layer deposition (ALD) facilitates symmetry through ALD's high conformality and low surface roughness. To maximize Q, the shells' geometry is optimized using finite element method (FEM) studies to reduce thermoelastic dissipation and anchor loss. The shells are fabricated by etching hemispherical molds in Si (1 1 1) substrates with a 2:7:1 volumetric ratio of hydrofluoric:nitric:acetic acids, and conformally coating and patterning the molds with ALD Al2O3. The Al2O3 shells are then released from the surrounding Si substrate with an SF6 plasma. The resulting shells typically have radii around 50 mu m and thicknesses close to 50 nm. The shells are highly symmetric, with radial deviations between 0.22 and 0.49%, and robust enough to be driven on resonance at amplitudes 10 x their thickness, sufficient to visualize the resonance mode shapes in an SEM. Resonance frequencies are around 60 kHz, with Q values between 1000 and 2000. This Q is lower than the 10(6) predicted by FEM, implying that Q is being limited by unmodeled sources of energy loss, most likely from surface effects or material defects.
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  • Ultra-thin 3D Nano-Devices from Atomic Layer Deposition on Polyimide

    Eigenfeld, Nathan T.   Gray, Jason M.   Brown, Joseph J.   Skidmore, George D.   George, Steven M.   Bright, Victor M.  

    A new nanofabrication process for nano/micro-devices through the combination of inorganic nanomaterials from atomic layer deposition (ALD) on 3-dimensional organic polyimide substrates is developed. The first suspended ALD structures with multiple patterned suspended levels on the order of 10 nm are fabricated and results surrounding the mechanical stability of ultra-thin suspended structures are discussed.
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  • Enhanced Response Time of Electrowetting Lenses with Shaped Input Voltage Functions

    Supekar, Omkar D.   Zohrabi, Mo   Gopinath, Juliet T.   Bright, Victor M.  

    Adaptive optical lenses based on the electrowetting principle are being rapidly implemented in many applications, such as microscopy, remote sensing, displays, and optical communication. To characterize the response of these electrowetting lenses, the dependence upon direct current (DC) driving voltage functions was investigated in a low-viscosity liquid system. Cylindrical lenses with inner diameters of 2.45 and 3.95 mm were used to characterize the dynamic behavior of the liquids under DC voltage electrowetting actuation. With the increase of the rise time of the input exponential driving voltage, the originally underdamped system response can be damped, enabling a smooth response from the lens. We experimentally determined the optimal rise times for the fastest response from the lenses. We have also performed numerical simulations of the lens actuation with input exponential driving voltage to understand the variation in the dynamics of the liquid liquid interface with various input rise times. We further enhanced the response time of the devices by shaping the input voltage function with multiple exponential rise times. For the 3.95 mm inner diameter lens, we achieved a response time improvement of 29% when compared to the fastest response obtained using single-exponential driving voltage. The technique shows great promise for applications that require fast response times.
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  • SF4 as the Fluorination Reactant for Al2O3 and VO2 Thermal Atomic Layer Etching

    Gertsch, Jonas C.   Cano, Austin M.   Bright, Victor M.   George, Steven M.  

    Thermal atomic layer etching (ALE) is an important technique for the precise isotropic etching of nanostructures. Thermal ALE of many materials can be achieved using a two-step fluorination and ligand-exchange reaction mechanism. Most previous thermal ALE processes have used HF as the fluorination reactant. Alternative fluorination reactants may be needed because HF is a weak nucleophilic fluorination reactant. Stronger fluorination agents may be required for the fluorination of some materials. To demonstrate the usefulness of SF4 as an alternative to HF, thermal Al2O3 ALE was compared using SF4 or HF together with Sn(acac)(2) as the metal precursor for ligand exchange. SF4 and HF were observed to behave similarly as fluorination reactants during Al2O3 ALE. The mass gains during the initial SF4 and HF exposures on Al2O3 atomic layer deposition (ALD) films at 200 degrees C were comparable at 35 and 38 ng/cm(2), respectively, using quartz crystal microbalance measurements. In addition, the etch rates were similar at 0.20 and 0.28 angstrom/cycle for Al2O3 ALE using SF4 and HF, respectively, at 200 degrees C. Thermal VO2 ALE was also performed for the first time using SF4 or HF and Sn(acac)(2) as the reactants. There was evidence that SF4 is a stronger fluorination reactant than HF for VO2 fluorination. The mass gains during the initial SF4 and HF exposures on VO2 ALD films were 38 and 20 ng/cm(2), respectively, at 200 degrees C. Thermal VO2 ALE also had a higher etch rate when fluorinating with SF4 compared with HF. Etch rates of 0.30 and 0.11 angstrom/cycle were measured for VO2 ALE using SF4 and HF, respectively, together with Sn(acac)(2) at 200 degrees C. Fourier transform infrared experiments were also used to monitor fluorination of the Al2O3 and VO2 ALD films by SF4 or HF. FTIR difference spectroscopy was used to observe the increase of Al-F and V-F stretching vibrations and the loss of the Al-O and V-O/V=3DO stretching vibrations for Al2O3 and VO2, respectively, versus SF4 or HF exposure at 200 degrees C. Additional absorbance features after fluorination of the Al2O3 ALD films by SF4 were consistent with SFx surface species. SF4 is a useful fluorination agent for thermal ALE processes and can be used as an alternative to HF. In addition, SF4 may be necessary when fluorination requires a stronger fluorination reactant than HF.
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  • SF4 as the Fluorination Reactant for Al2O3 and VO2 Thermal Atomic Layer Etching

    Gertsch, Jonas C   Cano, Austin M.   Bright, Victor M.   George, Steven M.  

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  • The Development of Polymer-Based Flat Heat Pipes

    Oshman, Christopher   Shi, Bo   Li, Chen   Yang, Ronggui   Lee, Y. C.   Peterson, G. P.   Bright, Victor M.  

    In this paper, polymer-based flat heat pipes (PFHPs) with a thickness on the order of 1 mm have been successfully developed and tested. Liquid-crystal polymer (LCP) films with copper-filled thermal vias are employed as the case material. A copper micropillar/woven mesh hybrid wicking structure was designed and fabricated to promote evaporation/condensation heat transfer and the liquid supply to the evaporator of the PFHP. Water was selected as the working fluid because of its superior thermophysical properties. An experimental study was conducted to examine the PFHP performance. The test data demonstrated that the PFHP can operate with a heat flux of 11.94 W/cm(2) and results in effective thermal conductivity ranging from 650 to 830 W/m . K, with the value varying with the input heat flux and the tilt angle. With the employment of flexible LCP as casing material, the PFHP could potentially be directly integrated into a printed circuit board or flexible circuits for thermal management of heat-generating components. [2010-0280]
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  • Multi-layer atom chips for atom tunneling experiments near the chip surface

    Chuang, Ho-Chiao   Salim, Evan A.   Vuletic, Vladan   Anderson, Dana Z.   Bright, Victor M.  

    This paper describes the design and fabrication of an atom chip to be used in ultra-high-vacuum cells for cold-atom tunneling experiments. A fabrication process was developed to pattern micrometer- and nanometer-scale copper wires onto a single chip. The wires, with fabricated widths down to 200 nm, can sustain current densities of more than 7.5 x 10(7) A/cm(2). Partially suspended wires, developed in order to reduce the Casimir-Polder force between atoms and surface, were also fabricated and tested. Extensive measurements for variable wire width show that the sustainable currents are sufficiently large to allow chip-based atom tunneling experiments. Such chips may allow the realization of an atom transistor. (c) 2010 Elsevier B.V. All rights reserved.
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  • Interchangeable Stage and Probe Mechanisms for Microscale Universal Mechanical Tester

    Brown, Joseph J.   Dikin, Dmitriy A.   Ruoff, Rodney S.   Bright, Victor M.  

    A microfabricated mechanical test platform has been designed, fabricated, and operated. This system consists of a reusable chip capable of large-displacement actuation, which interfaces to a test coupon chip compatible with synthesis conditions for many nanomaterials. Because only normal forces are used for mechanical interfacing, the two chips are not permanently connected, allowing exchange of the test coupon chips. The actuated test platform chip contains a thermal actuator driving a compliant displacement amplification transmission, and a bulk-micromachined well in which the test coupon chips may be placed and removed. The displacement amplification structure provides 40 mu m of output displacement, extending a probe over the well and into contact with the test coupon. The test coupon contains compliant structures that are actuated by the probe from the test platform. [2011-0279]
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  • Optimization of spin-valve parameters for magnetic bead trapping and manipulation

    Altman, Wendy R.   Moreland, John   Russek, Stephen E.   Bright, Victor M.  

    Magneto-optic Kerr effect (MOKE) and magnetoresistance (MR) measurements were used to measure the switching characteristics of spin-valve (SV) arrays currently being developed to trap and release superparamagnetic beads within a fluid medium. The effect of SV size on switching observed by MOKE showed that a 1 mu mx8 mu m SV element was found to have optimal switching characteristics. MR measurements on a single 1 mu mx8 mu m SV switched with either an external applied magnetic field or a local magnetic field generated by an integrated write wire (current density ranging from 10(6) to 10(7) A/cm(2)) confirmed the MOKE findings. The 1 mu mx8 mu m SV low field switching was observed to be +8 and -2 mT with two stable states at zero field; the high field switching was observed to be -18 mT. The low switching fields and the large magnetic moment of the SV trap along with our observation of minimal magnetostatic effects for dense arrays are necessary design characteristics for high-force, switchable-magnet, microfluidic bead trap applications (C) 2010 Elsevier B.V. All rights reserved.
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