The authors would like to thank Professor Yuzuru Takashima at the University of Arizona for discussions on optical imaging, Mr. Karl Urbanek for assistance with high power lasers, and Max Yuen for discussions of Brownian motion. The authors send further thanks to Professor Kenneth Crozier at Harvard University for helpful discussions on optical trapping experiments. Funding was provided in part by the United States National Science Foundation (award number 1028372).

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The authors have nothing to disclose.

El NOCB combina las poderosas fuerzas de captura y pequeño tamaño trampa de enfoques plasmónicas con la capacidad para el transporte de partículas, siempre disponibles sólo para las técnicas de centrado de vigas convencionales. Único en el NOCB, las propiedades de captura y transporte del sistema son el resultado de los patrones de la superficie y no de la conformación del haz de iluminación. Siempre que la iluminación es lo suficientemente brillante y su polarización o longitud de onda se puede modular, las ...

Capture, el interrogatorio y la manipulación de nanopartículas individuales son de creciente importancia en la nanotecnología. Las pinzas ópticas han convertido en una técnica de manipulación particularmente exitoso para experimentos en biología molecular 1-4 química 5-7 y nano-ensamblaje 7-10 donde han permitido experimentos innovadores tales como la medición de las propiedades mecánicas de las moléculas de ADN individuales 4 y la clasificación de células por sus propiedades ópticas 11,12. Descubrimientos sobre estas fronteras se abren el estudio de sistemas aún más pequeños, y dar paso a la ingeniería de nuevos productos y técnicas prácticamente beneficiosos. A su vez, esta tendencia impulsa la necesidad de nuevas técnicas para manipular partículas más pequeñas y rudimentarias. Además, hay un empuje para construir dispositivos &quot;lab-on-a-chip &#39;para llevar a cabo estas funciones de forma más barata y en un paquete más pequeño para traer pruebas químicas y biológicas dellaboratorio y en el campo para médicos y otros fines 13,14. Desafortunadamente, atrapamiento óptico convencional (COT) no puede satisfacer todas las demandas crecientes de la nanotecnología. COT opera sobre el mecanismo de utilizar una alta apertura numérica (NA) de lente de objetivo para llevar la luz láser a un foco apretado, creando un pico localizado en intensidad óptica y los altos gradientes en la energía del campo electromagnético. Estos gradientes de densidad de energía ejercen una fuerza neta sobre las partículas de dispersión de luz que en general los lleva hacia el centro del foco. Atrapando partículas más pequeñas requiere mayor potencia óptica o un enfoque más ajustado. Sin embargo, los rayos de luz enfocado obedecen el principio de difracción, lo que limita el tamaño mínimo del punto focal y coloca un límite superior en el gradiente de densidad de energía. Esto tiene dos consecuencias inmediatas: COT no pueden atrapar pequeños objetos de manera eficiente, y COT tiene problemas para discriminar entre partículas muy próximas entre sí, una resolución de capturalimitación conoce como el problema de los &quot;dedos gordos. Además, la aplicación de captura de partículas múltiples con COT requiere que los sistemas de la óptica de dirección del haz o moduladores espaciales de luz, componentes que aumentan drásticamente el costo y la complejidad de un sistema de captura óptica. Una forma de sortear las limitaciones fundamentales de los haces enfocados convencionales de luz, dijo para propagar en el campo lejano, es en lugar de explotar los gradientes de energía electromagnética óptico en el campo cercano. El campo cercano decae exponencialmente alejado de fuentes de campos electromagnéticos, lo que significa que no sólo es muy localizada a estas fuentes, pero también exhibe muy altos gradientes en su densidad de energía. Los cerca de campos de resonadores nano-metálicos, tales como aberturas bowtie, pilares nano, y grabados en forma de C, se ha demostrado que presentan concentraciones extraordinarias de energía electromagnética, reforzada por la acción plasmónica de oro y plata en casi infrlongitudes de onda ARED y ópticas. Estos resonadores se han utilizado para atrapar partículas extremadamente pequeñas con alta eficiencia y resolución de 15-22 de. Si bien esta técnica ha demostrado ser eficaz para atrapar las partículas pequeñas, también ha demostrado ser limitado en su capacidad de transportar partículas sobre el rango apreciable, lo cual es necesario si los sistemas de campo cercano son para interconectar con sistemas de campo lejano o microfluídica. Recientemente, nuestro grupo ha propuesto una solución a este problema. Cuando resonadores se colocan muy juntos, una partícula puede migrar, en principio, de una trampa óptica de campo cercano a la siguiente sin ser liberado de la superficie. La dirección de transporte se puede determinar si las trampas adyacentes se pueden activar y desactivar por separado. Una disposición lineal de tres o más resonadores direccionables, en el que cada resonador es sensible a una polarización o longitud de onda de luz diferente de la de sus vecinos, funciona como una cinta transportadora óptico, el transporte de nanopartiCiclos de más de una distancia de varias micras en un chip. El llamado &#39;nano-óptica Cinta transportadora&#39; (NOCB) es único entre los esquemas de captura resonador plasmónicas, ya que no sólo puede contener partículas en el lugar, pero también puede moverlos a alta velocidad a lo largo de pistas estampadas, recoger o dispersar partículas, mezclar y hacer cola, e incluso ordenarlos por propiedades tales como su movilidad 23. Todas estas funciones se controlan mediante la modulación de la polarización o longitud de onda de la iluminación, sin necesidad de óptica de dirección del haz. Como una trampa óptica de campo cercano, la NOCB atrapando resolución es mayor que la de trampas ópticas enfocada de haz convencionales, por lo que puede diferenciar entre partículas en las proximidades; porque utiliza una nanoestructura de metal para concentrar la luz en un atrapando así, es de bajo consumo, y no requiere de componentes ópticos caros, como un alto objetivo NA. Además, muchos NOCBs pueden funcionar en paralelo, a alta den embalajesidad, en el mismo sustrato, y 1 W de potencia puede pasar por encima de las aberturas 23 1200. Hemos demostrado recientemente la primera NOCB polarización impulsada, sin problemas propulsar una nanopartícula de ida y vuelta a lo largo de una pista 24 4.5 micras. En este artículo se presentan los pasos necesarios para diseñar y fabricar el dispositivo, ópticamente activarlo y reproducimos el experimento transporte. Esperamos que lo que esta técnica más ampliamente disponibles ayudará a cerrar la brecha de tamaño entre la óptica de microfluidos, campo lejano y dispositivos a nanoescala y experimentos.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>HSQ e-beam resist</td>
			<td>Dow Corning</td>
			<td>XR-1541-006</td>
			<td></td>
		</tr>
		<tr>
			<td>PMMA</td>
			<td>MicroChem</td>
			<td>950A2 M230002</td>
			<td></td>
		</tr>
		<tr>
			<td>Fast curing optical adhesive</td>
			<td>Norland Optical Adhesive</td>
			<td>NOA 81</td>
			<td></td>
		</tr>
		<tr>
			<td>Fluorescent carboxyl microspheres</td>
			<td>Bangs Laboratories</td>
			<td>FC02F, FC03F</td>
			<td></td>
		</tr>
		<tr>
			<td>Fluorescent carboxylate-modified microspheres</td>
			<td>Molecular Probes</td>
			<td>F-8888</td>
			<td></td>
		</tr>
		<tr>
			<td>Quartz slide</td>
			<td>SPI Supplies</td>
			<td>1020-AB</td>
			<td></td>
		</tr>
		<tr>
			<td>Inverted fluorescent microscope</td>
			<td>Nikon</td>
			<td>ECLIPSE TE2000-U</td>
			<td></td>
		</tr>
		<tr>
			<td>Nd:YAG laser</td>
			<td>Lightwave Electronics</td>
			<td>221-HD-V04</td>
			<td></td>
		</tr>
		<tr>
			<td>sCMOS camera</td>
			<td>PCO</td>
			<td>EDGE55</td>
			<td></td>
		</tr>
		<tr>
			<td>CCD camera</td>
			<td>Watec</td>
			<td>WAT-120N</td>
			<td></td>
		</tr>
		<tr>
			<td>Zero-order half-wave plate</td>
			<td>Thorlabs</td>
			<td>WPH05M-1064</td>
			<td></td>
		</tr>
		<tr>
			<td>Triton X-100</td>
			<td>Sigma-Aldrich</td>
			<td>T8787</td>
			<td></td>
		</tr>
		<tr>
			<td>Distilled water</td>
			<td>Invitrogen</td>
			<td>10977-023</td>
			<td></td>
		</tr>
		<tr>
			<td>Si Wafer</td>
			<td>Silicon Quest International</td>
			<td>708069</td>
			<td></td>
		</tr>
		<tr>
			<td>Optical lenses</td>
			<td>Thorlabs</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

fabrication and operation of a nano-optical conveyor belt

La técnica de usar rayos láser enfocados para atrapar y ejercer fuerzas sobre las partículas pequeñas ha permitido a muchos descubrimientos fundamentales en las ciencias biológicas y físicas a nanoescala en los últimos decenios. Los avances realizados en este campo invita a un mayor estudio de los sistemas aún más pequeños y en mayor escala, con herramientas que puedan ser distribuidos con mayor facilidad y hacen más accesible. Desafortunadamente, las leyes fundamentales de difracción limitan el tamaño mínimo del punto focal de un rayo láser, lo que hace que las partículas más pequeñas que un medio de longitud de onda de diámetro duro para atrapar y generalmente evita que un operador de discriminar entre las partículas que son más juntos de una media -wavelength. Esto impide la manipulación óptica de muchos nanopartículas estrechamente espaciados y limita la resolución de sistemas óptico-mecánicos. Además, la manipulación utilizando haces enfocados requiere la óptica de formación de haz o de dirección, que pueden ser muy voluminosos y caros. Dirigirseestas limitaciones en la escalabilidad del sistema de captura óptica convencional nuestro laboratorio ha ideado una técnica alternativa que utiliza la óptica de campo cercano para mover partículas a través de un chip. En lugar de centrarse rayos láser en el campo lejano, el cercano campo óptico de resonadores plasmónicas produce la mejora intensidad óptica local, necesario para superar las restricciones de la difracción y manipular partículas a mayor resolución. Resonadores estrechamente espaciadas producen trampas ópticas fuertes que pueden ser abordados para mediar en el hand-off de partículas de uno a otro de una manera cinta transportadora similar. Aquí se describe cómo diseñar y producir una cinta transportadora usando una superficie de oro con dibujos de resonadores en forma de C plasmónicas y cómo operar con luz láser polarizada para lograr la manipulación nanopartícula super-resolución y el transporte. El chip cinta transportadora nano-óptica puede producirse usando técnicas de litografía y fácilmente empaquetado y distribuido.

Figura 7 es una imagen del dispositivo final. En el centro de la superficie de oro de 1 cm x 1 cm es la matriz de CSE y patrones transportadoras, que pueden ser apenas visto desde una vista en ángulo. La Figura 6 es una imagen de microscopía electrónica de barrido de un patrón de ejemplo CSE en el dispositivo final. El movimiento de las partículas de un perla de poliestireno 390 nm viajar a través de una cinta transportadora nano-óptica 5 micras de lo...

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Fabrication and Operation of a Nano-Optical Conveyor Belt

The scalability and resolution of conventional optical manipulation techniques are limited by diffraction. We circumvent the diffraction limit and describe a method of optically transporting nanoparticles across a chip using a gold surface patterned with a path of closely spaced C-shaped plasmonic resonators.

Fabricación y operación de una banda transportadora nano-óptica

The technique of using focused laser beams to trap and exert forces on small particles has enabled many pivotal discoveries in the nanoscale biological ...

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11.5K vistas.  Stanford University. The scalability and resolution of conventional optical manipulation techniques are limited by diffraction. We circumvent the diffraction limit and describe a method of optically transporting nanoparticles across a chip using a gold surface patterned with a path of closely spaced C-shaped plasmonic resonators.

Video: Fabrication and Operation of a Nano-Optical Conveyor Belt

Fabrication, Densification, and Replica Molding of 3D Carbon Nanotube Microstructures

The introduction of new materials and processes to microfabrication has, in large part, enabled many important advances in microsystems, lab-on-a-chip devices, and their applications. In particular, capabilities for cost-effective fabrication of polymer microstructures were transformed by the advent of soft lithography and other micromolding techniques 1, 2, and this led a revolution in applications of microfabrication to biomedical engineering and biology. Nevertheless, it remains challenging to fabricate microstructures with well-defined nanoscale surface textures, and to fabricate arbitrary 3D shapes at the micro-scale. Robustness of master molds and maintenance of shape integrity is especially important to achieve high fidelity replication of complex structures and preserving their nanoscale surface texture. The combination of hierarchical textures, and heterogeneous shapes, is a profound challenge to existing microfabrication methods that largely rely upon top-down etching using fixed mask templates. On the other hand, the bottom-up synthesis of nanostructures such as nanotubes and nanowires can offer new capabilities to microfabrication, in particular by taking advantage of the collective self-organization of nanostructures, and local control of their growth behavior with respect to microfabricated patterns. 
Our goal is to introduce vertically aligned carbon nanotubes (CNTs), which we refer to as CNT "forests", as a new microfabrication material. We present details of a suite of related methods recently developed by our group: fabrication of CNT forest microstructures by thermal CVD from lithographically patterned catalyst thin films; self-directed elastocapillary densification of CNT microstructures; and replica molding of polymer microstructures using CNT composite master molds. In particular, our work shows that self-directed capillary densification ("capillary forming"), which is performed by condensation of a solvent onto the substrate with CNT microstructures, significantly increases the packing density of CNTs. This process enables directed transformation of vertical CNT microstructures into straight, inclined, and twisted shapes, which have robust mechanical properties exceeding those of typical microfabrication polymers. This in turn enables formation of nanocomposite CNT master molds by capillary-driven infiltration of polymers. The replica structures exhibit the anisotropic nanoscale texture of the aligned CNTs, and can have walls with sub-micron thickness and aspect ratios exceeding 50:1. Integration of CNT microstructures in fabrication offers further opportunity to exploit the electrical and thermal properties of CNTs, and diverse capabilities for chemical and biochemical functionalization 3.

We present methods for fabrication of patterned microstructures of vertically aligned carbon nanotubes (CNTs), and their use as master molds for production of polymer microstructures with organized nanoscale surface texture. The CNT forests are densified by condensation of solvent onto the substrate, which significantly increases their packing density and enables self-directed formation of 3D shapes.

Fabricación, densificación, y la réplica de Moldeo por inyección de microestructuras 3D nanotubos de carbono

The introduction of new materials and processes to microfabrication has, in large part, enabled many important advances in microsystems, lab-on-a-chip ...

Investigación

Ingeniería

Synthesis and Operation of Fluorescent-core Microcavities for Refractometric Sensing

This paper discusses fluorescent core microcavity-based sensors that can operate in a microfluidic analysis setup. These structures are based on the formation of a fluorescent quantum-dot (QD) coating on the channel surface of a conventional microcapillary. Silicon QDs are especially attractive for this application, owing in part to their negligible toxicity compared to the II-VI and II-VI compound QDs, which are legislatively controlled substances in many countries. While the ensemble emission spectrum is broad and featureless, an Si-QD film on the channel wall of a capillary features a set of sharp, narrow peaks in the fluorescence spectrum, corresponding to the electromagnetic resonances for light trapped within the film. The peak wavelength of these resonances is sensitive to the external medium, thus permitting the device to function as a refractometric sensor in which the QDs never come into physical contact with the analyte. The experimental methods associated with the fabrication of the fluorescent-core microcapillaries are discussed in detail, as well as the analysis methods. Finally, a comparison is made between these structures and the more widely investigated liquid-core optical ring resonators, in terms of microfluidic sensing capabilities.

Fluorescent-core microcavity sensors employ a high-index quantum-dot coating in the channel of silica microcapillaries. Changes in the refractive index of fluids pumped into the capillary channel cause shifts in the microcavity fluorescence spectrum that can be used to analyze the channel medium.

Síntesis y funcionamiento de los núcleos fluorescentes microcavidades de Percepción refractométrico

This paper discusses  fluorescent core microcavity-based sensors that can operate in a microfluidic  analysis setup. These structures are based on the ...

Fabrication, Operation and Flow Visualization in Surface-acoustic-wave-driven Acoustic-counterflow Microfluidics

Surface acoustic waves (SAWs) can be used to drive liquids in portable microfluidic chips via the acoustic counterflow phenomenon. In this video we present the fabrication protocol for a multilayered SAW acoustic counterflow device. The device is fabricated starting from a lithium niobate (LN) substrate onto which two interdigital transducers (IDTs) and appropriate markers are patterned. A polydimethylsiloxane (PDMS) channel cast on an SU8 master mold is finally bonded on the patterned substrate. Following the fabrication procedure, we show the techniques that allow the characterization and operation of the acoustic counterflow device in order to pump fluids through the PDMS channel grid. We finally present the procedure to visualize liquid flow in the channels. The protocol is used to show on-chip fluid pumping under different flow regimes such as laminar flow and more complicated dynamics characterized by vortices and particle accumulation domains.

In this video we first describe fabrication and operation procedures of a surface acoustic wave (SAW) acoustic counterflow device. We then demonstrate an experimental setup that allows for both qualitative flow visualization and quantitative analysis of complex flows within the SAW pumping device.

Fabricación, operación y visualización del flujo en la superficie-acústico de ondas impulsadas Microfluídica Acústica contraflujo

Surface acoustic waves (SAWs) can be used to drive liquids in portable microfluidic chips via the acoustic counterflow phenomenon. In this video we ...

Fabrication and Testing of Microfluidic Optomechanical Oscillators

Cavity optomechanics experiments that parametrically couple the phonon modes and photon modes have been investigated in various optical systems including microresonators. However, because of the increased acoustic radiative losses during direct liquid immersion of optomechanical devices, almost all published optomechanical experiments have been performed in solid phase. This paper discusses a recently introduced hollow microfluidic optomechanical resonator. Detailed methodology is provided to fabricate these ultra-high-Q microfluidic resonators, perform optomechanical testing, and measure radiation pressure-driven breathing mode and SBS-driven whispering gallery mode parametric vibrations. By confining liquids inside the capillary resonator, high mechanical- and optical- quality factors are simultaneously maintained.

Parametric optomechanical excitations have recently been experimentally demonstrated in microfluidic optomechanical resonators by means of optical radiation pressure and stimulated Brillouin scattering. This paper describes the fabrication of these microfluidic resonators along with methodologies for generating and verifying optomechanical oscillations.

Fabricación y Pruebas de microfluidos optomecánicos Osciladores

Cavity optomechanics experiments that parametrically couple the phonon modes and photon modes have been investigated in various optical systems including ...

Fabrication Process of Silicone-based Dielectric Elastomer Actuators

This contribution demonstrates the fabrication process of dielectric elastomer transducers (DETs). DETs are stretchable capacitors consisting of an elastomeric dielectric membrane sandwiched between two compliant electrodes. The large actuation strains of these transducers when used as actuators (over 300% area strain) and their soft and compliant nature has been exploited for a wide range of applications, including electrically tunable optics, haptic feedback devices, wave-energy harvesting, deformable cell-culture devices, compliant grippers, and propulsion of a bio-inspired fish-like airship. In most cases, DETs are made with a commercial proprietary acrylic elastomer and with hand-applied electrodes of carbon powder or carbon grease. This combination leads to non-reproducible and slow actuators exhibiting viscoelastic creep and a short lifetime. We present here a complete process flow for the reproducible fabrication of DETs based on thin elastomeric silicone films, including casting of thin silicone membranes, membrane release and prestretching, patterning of robust compliant electrodes, assembly and testing. The membranes are cast on flexible polyethylene terephthalate (PET) substrates coated with a water-soluble sacrificial layer for ease of release. The electrodes consist of carbon black particles dispersed into a silicone matrix and patterned using a stamping technique, which leads to precisely-defined compliant electrodes that present a high adhesion to the dielectric membrane on which they are applied.

This manuscript shows the fabrication process for the manufacture of dielectric elastomer soft actuators based on silicone membranes. The three key stages of production are presented in detail: blade casting of thin silicone membranes; pad printing of compliant electrodes; and the assembly of all the components.

Proceso de fabricación de elastómeros dieléctricos actuadores basados ​​en silicona

This contribution demonstrates the fabrication process of dielectric elastomer transducers (DETs). DETs are stretchable capacitors consisting of an ...

Fabrication and Operation of Acoustofluidic Devices Supporting Bulk Acoustic Standing Waves for Sheathless Focusing of Particles

Acoustophoresis refers to the displacement of suspended objects in response to directional forces from sound energy. Given that the suspended objects must be smaller than the incident wavelength of sound and the width of the fluidic channels are typically tens to hundreds of micrometers across, acoustofluidic devices typically use ultrasonic waves generated from a piezoelectric transducer pulsating at high frequencies (in the megahertz range). At characteristic frequencies that depend on the geometry of the device, it is possible to induce the formation of standing waves that can focus particles along desired fluidic streamlines within a bulk flow. Here, we describe a method for the fabrication of acoustophoretic devices from common materials and clean room equipment. We show representative results for the focusing of particles with positive or negative acoustic contrast factors, which move towards the pressure nodes or antinodes of the standing waves, respectively. These devices offer enormous practical utility for precisely positioning large numbers of microscopic entities (e.g., cells) in stationary or flowing fluids for applications ranging from cytometry to assembly.

Acoustofluidic devices use ultrasonic waves within microfluidic channels to manipulate, concentrate and isolate suspended micro and nanoscopic entities. This protocol describes the fabrication and operation of such a device supporting bulk acoustic standing waves to focus particles in a central streamline without the aid of sheath fluids.

Fabricación y funcionamiento de los dispositivos de apoyo a granel Acoustofluidic ondas acústicas pie para Sheathless Centrándose de partículas

Acoustophoresis refers to the displacement of suspended objects in response to directional forces from sound energy. Given that the suspended objects must ...

Fabrication and Characterization of Superconducting Resonators

Superconducting microwave resonators are of interest for a wide range of applications, including for their use as microwave kinetic inductance detectors (MKIDs) for the detection of faint astrophysical signatures, as well as for quantum computing applications and materials characterization. In this paper, procedures are presented for the fabrication and characterization of thin-film superconducting microwave resonators. The fabrication methodology allows for the realization of superconducting transmission-line resonators with features on both sides of an atomically smooth single-crystal silicon dielectric. This work describes the procedure for the installation of resonator devices into a cryogenic microwave testbed and for cool-down below the superconducting transition temperature. The set-up of the cryogenic microwave testbed allows one to do careful measurements of the complex microwave transmission of these resonator devices, enabling the extraction of the properties of the superconducting lines and dielectric substrate (e.g., internal quality factors, loss and kinetic inductance fractions), which are important for device design and performance.

Superconducting microwave resonators are of interest for detection of light, quantum computing applications and materials characterization. This work presents a detailed procedure for fabrication and characterization of superconducting microwave resonator scattering parameters.

Fabricación y caracterización de resonadores superconductores

Superconducting microwave resonators are of interest for a wide range of applications, including for their use as microwave kinetic inductance detectors ...

Solvent Bonding for Fabrication of PMMA and COP Microfluidic Devices

Thermoplastic microfluidic devices offer many advantages over those made from silicone elastomers, but bonding procedures must be developed for each thermoplastic of interest. Solvent bonding is a simple and versatile method that can be used to fabricate devices from a variety of plastics. An appropriate solvent is added between two device layers to be bonded, and heat and pressure are applied to the device to facilitate the bonding. By using an appropriate combination of solvent, plastic, heat, and pressure, the device can be sealed with a high quality bond, characterized as having high bond coverage, bond strength, optical clarity, durability over time, and low deformation or damage to microfeature geometry. We describe the procedure for bonding devices made from two popular thermoplastics, poly(methyl-methacrylate) (PMMA), and cyclo-olefin polymer (COP), as well as a variety of methods to characterize the quality of the resulting bonds, and strategies to troubleshoot low quality bonds. These methods can be used to develop new solvent bonding protocols for other plastic-solvent systems.

Solvent bonding is a simple and versatile method for fabricating thermoplastic microfluidic devices with high quality bonds. We describe a protocol to achieve strong, optically clear bonds in PMMA and COP microfluidic devices that preserve microfeature details, by a judicious combination of pressure, temperature, an appropriate solvent, and device geometry.

Unión con disolvente para la fabricación de PMMA y CP dispositivos de microfluidos

Thermoplastic microfluidic devices offer many advantages over those made from silicone elastomers, but bonding procedures must be developed for each ...

Construction and Operation of a Light-driven Gold Nanorod Rotary Motor System

The possibility to generate and measure rotation and torque at the nanoscale is of fundamental interest to the study and application of biological and artificial nanomotors and may provide new routes towards single cell analysis, studies of non-equilibrium thermodynamics, and mechanical actuation of nanoscale systems. A facile way to drive rotation is to use focused circularly polarized laser light in optical tweezers. Using this approach, metallic nanoparticles can be operated as highly efficient scattering-driven rotary motors spinning at unprecedented rotation frequencies in water.
In this protocol, we outline the construction and operation of circularly-polarized optical tweezers for nanoparticle rotation and describe the instrumentation needed for recording the Brownian dynamics and Rayleigh scattering of the trapped particle. The rotational motion and the scattering spectra provides independent information on the properties of the nanoparticle and its immediate environment. The experimental platform has proven useful as a nanoscopic gauge of viscosity and local temperature, for tracking morphological changes of nanorods and molecular coatings, and as a transducer and probe of photothermal and thermodynamic processes.

Plasmonic gold nanorods can be trapped in liquids and rotated at kHz frequencies using circularly-polarized optical tweezers. Introducing tools for Brownian dynamics analysis and light scatteringspectroscopy leads to a powerful system for research and application in numerous fields of science.

Construcción y operación de un sistema del Motor rotatorio de Nanorod oro impulsado por la luz

The possibility to generate and measure rotation and torque at the nanoscale is of fundamental interest to the study and application of biological and ...

Fabrication of Refractive-index-matched Devices for Biomedical Microfluidics

The use of microfluidic devices has emerged as a defining tool for biomedical applications. When combined with modern microscopy techniques, these devices can be implemented as part of a robust platform capable of making simultaneous complementary measurements. The primary challenge created by the combination of these two techniques is the mismatch in refractive index between the materials traditionally used to make microfluidic devices and the aqueous solutions typically used in biomedicine. This mismatch can create optical artifacts near the channel or device edges. One solution is to reduce the refractive index of the material used to fabricate the device by using a fluorinated polymer such as MY133-V2000 whose refractive index is similar to that of water (n = 1.33). Here, the construction of a microfluidic device made out of MY133-V2000 using soft lithography techniques is demonstrated, using O2 plasma in conjunction with an acrylic holder to increase the adhesion between the MY133-V2000 fabricated device and the polydimethylsiloxane (PDMS) substrate. The device is then tested by incubating it filled with cell culture media for 24 h to demonstrate the ability of the device to maintain cell culture conditions during the course of a typical imaging experiment. Finally, quantitative phase microscopy (QPM) is used to measure the distribution of mass within the live adherent cells in the microchannel. This way, the increased precision, enabled by fabricating the device from a low index of refraction polymer such as MY133-V2000 in lieu of traditional soft lithography materials such as PDMS, is demonstrated. Overall, this approach for fabricating microfluidic devices can be readily integrated into existing soft lithography workflows in order to reduce optical artifacts and increase measurement precision.

This protocol describes the fabrication of microfluidic devices from MY133-V2000 to eliminate artifacts that often arise in microchannels due to the mismatching refractive indices between microchannel structures and an aqueous solution. This protocol uses an acrylic holder to compress the encapsulated device, improving adhesion both chemically and mechanically.

Fabricación de dispositivos emparejados de índice refractivo para microfluidos biomédica

The use of microfluidic devices has emerged as a defining tool for biomedical applications. When combined with modern microscopy techniques, these devices ...