El apoyo financiero de la ERC a través del Advanced Investigator subvención HYMEM, por la DFG a través de la Iniciativa de nanosistemas Múnich (NIM) ya través de la Sonderforschungsbereich (SFB1032), proyecto A8 se agradece. Estamos agradecidos con el Dr. Alexander Ohlinger, Dr. Sol Carretero-Palacios y spas Nedev de apoyo y fructíferos debates.

1. Configuración Experimental <ol><li> Utilice un microscopio-encima de la derecha y un condensador de campo oscuro de aceite con una apertura numérica (NA) = 1,2 para la iluminación de campo oscuro. Utilice un objetivo de inmersión en agua con un aumento de 100X y un NA = 1,0 para las observaciones de partículas y atrapamiento. Utilice un objetivo de aire con un aumento de 10X y una NA = 0,2 para seguir el movimiento de la Nauplio. </li><li> Utilice una configuración de pinzas ópticas con una nm láser de onda continua 1064 acoplada al microscopio-encima de la derecha. Establecer la potencia del láser de la trampa óptica a 100 mW (medido con un medidor de potencia después de que el objetivo). </li><li> Utilice una cámara CMOS de alta velocidad o una réflex digital de lente única (DSLR) para detectar e imagen del movimiento de las partículas de oro en la trampa óptica y el movimiento de la Nauplio. </li><li> Utilice un filtro de muesca para impedir que el láser entra en la cámara. </li><li> Utilice un medidor de potencia para medir la potencia del láser después de que el objetivo. </li></ol> 2. Preparación de la muestra </p&gt; <ol><li> Pipetear una gota de agua (180 l) en un portaobjetos de vidrio de microscopio y la posición de la muestra en el microscopio de campo oscuro. </li><li> Pipetear una Nauplio de un pequeño tanque de agua a la gota de agua. </li><li> Utilice un objetivo de aire 10 veces para observar el movimiento de la Nauplio en la solución y grabar una secuencia de vídeo. </li><li> Utilice una nanopartícula de oro con un diámetro de 60 nm como un detector para observar el movimiento del fluido generada por el nauplio. Por lo tanto, añadir 5 l de una solución de partículas altamente diluido en la gota de agua, de manera que aproximadamente una partícula se puede ver en el campo de visión con un objetivo de inmersión en agua 100X. </li></ol> 3. Experimento de seguimiento de partículas <ol><li> Trampa una nanopartícula de oro con las pinzas ópticas. Por lo tanto, llevar el 1,064 nm láser atrapando cerca de una nanopartícula de oro que se difunde en solución moviendo la platina del microscopio. Las fuerzas ópticas atractivas tiran de la nanopartícula de oro hacia el punto focal de thhaz de láser de correo. La partícula atrapada no se difunde más y más bien mantiene su posición. Tome una secuencia de vídeo de la nanopartícula atrapado con la cámara réflex digital a una velocidad de 50 Hz durante 30 s. </li><li> Apague el láser de la pinza óptica y suelte la nanopartícula de oro de la trampa. </li><li> Utilice un programa de rastreo de partículas a Lectura de la posición de la partícula de oro atrapada ópticamente en cada fotograma de la secuencia de vídeo. Una transformación rápida de Fourier (FFT) de xy-posición de la partícula en el tiempo revela un espectro de frecuencia. NOTA: En este caso, se ha utilizado un código de programa informático &#39;IGOR PRO&#39; auto-escrito para analizar la posición del centro de partícula en el plano xy con el tiempo y para el análisis FFT. </li><li> Como alternativa a un código IGOR auto-escrita utilizar el programa de libre acceso &#39;Video SPOT Rastreador&#39; para el seguimiento de la partícula en el video. Utilice el software comercial &quot;Origen&quot; para llevar a cabo la transformación de Fourier de los datos de seguimiento: <ol&gt; <li> Arrastre el archivo de vídeo en el programa abierto &#39;Video SPOT Rastreador&#39;. </li><li> Pulse con el ratón sobre la partícula se ve en la primera imagen de la secuencia de vídeo y una región circular de que aparezca de interés. </li><li> Elija &quot;simétrico&quot; y &quot;optimizar&quot; en la ventana de comandos superior para optimizar el seguimiento de la partícula. </li><li> Clic del ratón &quot;tala&quot; en la ventana de comandos superior y seleccione una carpeta para guardar los datos. Los datos de seguimiento se guardarán como una hoja de cálculo de datos. </li><li> Clic del ratón &quot;juego de video&quot; en la ventana de comandos izquierda del programa de seguimiento y espere hasta que se analizan todos los fotogramas del vídeo. </li><li> Cierra el programa y abrir la hoja de cálculo de datos guardado con &#39;Origen&#39;. Establezca los valores de columna como &quot;y 1&quot; e &quot;y 2&quot;. </li><li> Establecer intervalos de tiempo para cada fotograma de vídeo como &quot;x&quot; en la hoja de cálculo de datos &#39;Origen&#39;. </li><li> Marque la x-Posición de la columna y realizar una FFT eligiendo &quot;Análisis de datos&quot; y &quot;FFT&quot; en la ventana de comandos de arriba. Repetir el paso de la columna de la posición y. </li><li> Trazar las amplitudes de la señal FFT calculada en x-e y-dirección frente a la frecuencia. </li></ol></li></ol> 4. Simulación <ol><li> Calcular los α polarizabilidad de la partícula de oro de 60 nm mediante el uso del programa de ordenador &#39;Mathematica&#39;. <ol><li> Utilizar la ecuación (1) para calcular la polarizabilidad de acuerdo con Kuwata et al 16.: <img alt="Ecuación 1" fo:content-width="3in" src="/files/ftp_upload/51502/51502eq1.jpg" width="300" /> (1) </li><li> Definir los tres parámetros siguientes en el código de programa: el complejo de función dieléctrica dependiente de la longitud de onda de la partícula de oro, el radio de nanopartículas, y el índice de refracción del medio circundante. </li></ol></li><li> Utilizar la descripción de los elecdistribución del campo tric de un haz gaussiano centrado según Agayan et al 17 para el cálculo de las fuerzas ópticas que actúan sobre una partícula de oro de 60 nm.: <img alt="Ecuación 2" fo:content-width="4in" src="/files/ftp_upload/51502/51502eq2.jpg" width="500" /> (2) <ol><li> . Usar ecuaciones (3) - (6) de Agayan et al 17 para calcular tanto, el gradiente y la dispersión de las fuerzas que actúan sobre la partícula: <img alt="Ecuación 3" fo:content-width="3.5in" src="/files/ftp_upload/51502/51502eq3.jpg" width="350" /> (3) <img alt="Ecuación 4" fo:content-width="3in" src="/files/ftp_upload/51502/51502eq4.jpg" width="300" /> (4) <img alt="Ecuación 5" fo:content-width="5in" src="/files/ftp_upload/51502/51502eq5.jpg" width="500" /> (5) <img alt="Ecuación 6" fo:content-width="3in" src="/files/ftp_upload/51502/51502eq6.jpg" width="300" /> (6) </li><li> En el código del programa, definir los parámetros para la potencia del láser, la apertura numérica de la OBJETIVO, y el complejo polarizabilidad de la nanopartícula. </li><li> Sumar la fuerza del gradiente y la fuerza de dispersión para calcular la fuerza óptica total que actúa sobre la partícula de oro en una trampa óptica. </li></ol></li><li> Ejecutar la simulación pulsando simultáneamente &quot;Control&quot; y &quot;Enter&quot;. </li></ol>

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Los autores declaran que no tienen intereses financieros en competencia.

Microscopía de campo oscuro es una poderosa herramienta para la visualización de las nanopartículas de oro con dimensiones por debajo del límite de difracción óptica, puesto que la sección transversal de dispersión de las nanopartículas de metal excede su sección transversal geométrica (cp. Figura 2A) 18. En una configuración de pinza, este enfoque permite incluso distinguir si sólo un único o múltiples nanopartículas de oro son atrapados por el haz de láser porque acoplamien...

Evaluación de la calidad del agua sobre la base de indicadores químicos y biológicos es fundamental para obtener una perspectiva de las condiciones estatales y ambientales de un ecosistema acuático 1-3. Los métodos clásicos para el análisis químico de agua se basan en las propiedades organolépticas o la determinación de los parámetros fisicoquímicos. Los indicadores biológicos, por otro lado, son las especies animales cuya presencia y viabilidad dar una idea de las condiciones ambientales y el efecto de los contaminantes de un ecosistema que se producen pulg ejemplos típicos de bioindicadores son copépodos, un grupo de pequeños crustáceos de agua, que puede pueden encontrar en casi cualquier hábitat de agua 4,5. La observación de la actividad y la viabilidad de estas especies a partir de una muestra de agua de este modo se puede utilizar para obtener información sobre las condiciones generales de un ecosistema 5. Las larvas de copépodos, que son llamadas nauplios, utilice golpes rítmicos de sus antenas (cada larva tiene tres pares de appendabios en su región de la cabeza) para nadar en el agua 6. La frecuencia y la intensidad de estos golpes es por lo tanto un indicador directo de la edad, condición física y las condiciones ambientales del animal 7-10. Cualquier investigación sobre estos especímenes se hacen generalmente con un microscopio observando y contando los golpes de antena del Nauplii directamente. Debido a su tamaño (~ 100-500 m) 11, esto a menudo requiere hacer mediciones, ya sea uno a uno o de fijar una sola Nauplio a un sustrato. Aquí, nos demuestran un nuevo enfoque para observar la actividad de las larvas de copépodos en muestras de agua mediante el uso de una nanopartícula de oro atrapada ópticamente como detector ultrasensible. Las pinzas ópticas suelen ser utilizados por muchos grupos como una herramienta experimental bien aplicar o medir fuerzas entre las moléculas hasta el rango picoNewton 12-14. Más recientemente, la gama de aplicaciones para las pinzas ópticas se ha ampliado para observar las vibraciones acústicas y resolverfluctuaciones nt en medios líquidos mediante el control del movimiento de las nano-y micropartículas que están confinados en una trampa óptica 15. Las partículas que están inmersas en un líquido se someten a movimiento browniano. Dentro de una trampa óptica, sin embargo, este movimiento está parcialmente amortiguado por una, inducida por láser, fuerza del gradiente fuerte. Por lo tanto, la rigidez de la trampa óptica y la localización de la partícula dentro del foco del haz de láser pueden ajustarse por la potencia del láser. Al mismo tiempo, es posible revelar características sobre el potencial de atrapamiento y para analizar las interacciones de moléculas con la partícula mediante el control de la movimiento de las partículas en función del tiempo en la trampa. Este enfoque hace posible recoger la frecuencia, la intensidad y la dirección del movimiento de fluido que es generada por un objeto en movimiento en su entorno líquido. Se demuestra cómo esta idea general se puede aplicar para obtener un espectro de frecuencia de movimiento de un nauplio individuo sin el requisitopara interferir directamente con la muestra. Este enfoque experimental introduce un nuevo concepto general para la observación del comportamiento de la movilidad de los especímenes acuáticos de una manera muy sensible. Para las observaciones sobre las especies bioindicadores, esto podría ampliar la actual metodología para el análisis de agua y podría ser aplicado para obtener información sobre la salud y la integridad de los ecosistemas acuáticos.

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	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:244px;">Microscope Zeiss Axio Scope.A1</td>
			<td style="width:127px;">Carl Zeiss</td>
			<td style="width:201px;">490035-0012-000</td>
			<td style="width:303px;">dark field illumination</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:244px;">Water objective Achroplan</td>
			<td style="width:127px;">Carl Zeiss</td>
			<td style="width:201px;">440087</td>
			<td>100x magnification, NA=1.0</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:244px;">Air objective Epiplan</td>
			<td style="width:127px;">Carl Zeiss</td>
			<td style="width:201px;">442934</td>
			<td>10x magnification, NA=0.2</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:244px;">Dark field oil condenser</td>
			<td style="width:127px;">Carl Zeiss</td>
			<td style="width:201px;">445323</td>
			<td>NA=1.2</td>
		</tr>
		<tr height="23">
			<td height="23" style="height:23px;width:244px;">Cobolt Rumba CW 1064 nm DPSSL</td>
			<td style="width:127px;">Cobolt&#160;</td>
			<td style="width:201px;">1064-05-01-2000-500</td>
			<td>1064nm, CW, &#955;=1064nm, 2 Watt, TEM00</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:244px;">Beam expander</td>
			<td style="width:127px;">Edmund Optics</td>
			<td style="width:201px;"></td>
			<td>Part no. 1064 2-8X 64414</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:244px;">High Speed Camera Dimax HD</td>
			<td style="width:127px;">PCO. Germany</td>
			<td style="width:201px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:244px;">Color Camera Canon EOS 500 D&#160;</td>
			<td style="width:127px;">Canon</td>
			<td></td>
			<td>FAQ-ID: 8201395700</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:244px;">Notch filter StopLine 532/1064</td>
			<td style="width:127px;">Semrock</td>
			<td style="width:201px;">A11149-711265</td>
			<td>Part no. NF01-532U</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:244px;">Water&#160;</td>
			<td style="width:127px;"></td>
			<td style="width:201px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:244px;">Nauplius Artemia Salina</td>
			<td style="width:127px;"></td>
			<td style="width:201px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:244px;">Gold colloid</td>
			<td style="width:127px;">BBInternational</td>
			<td style="width:201px;">Batch 13741&#160;</td>
			<td>Diameter 60nm</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">MQMie Version 3.2&#160;</td>
			<td style="width:127px;">r. Michael Quinten</td>
			<td style="width:201px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Mathematica 8.0</td>
			<td style="width:127px;">Wolfram</td>
			<td style="width:201px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Comsol Multiphysics 4.0&#160;</td>
			<td style="width:127px;">COMSOL, Inc.</td>
			<td style="width:201px;"></td>
			<td></td>
		</tr>
	</tbody>
</table>

analyzing the movement of the nauplius 'artemia salina' by optical tracking of plasmonic nanoparticles

Se demuestra cómo pinzas ópticas pueden proporcionar una herramienta sensible para analizar las vibraciones de fluidos generados por el movimiento de pequeños organismos acuáticos. Una sola nanopartícula de oro en poder de un pinzas ópticas se utiliza como un sensor para cuantificar el movimiento rítmico de una larva nauplio (Artemia salina) en una muestra de agua. Esto se consigue mediante el control de desplazamiento dependiente del tiempo de la nanopartícula atrapados como consecuencia de la actividad Nauplio. Un análisis de Fourier de la posición de la nanopartícula a continuación, se obtiene un espectro de frecuencias que es característica para el movimiento de las especies observadas. Este experimento demuestra la capacidad de este método para medir y caracterizar la actividad de pequeña larvas acuáticas sin el requisito para observar directamente y para obtener información acerca de la posición de las larvas con respecto a la partícula atrapada. En general, este enfoque podría dar una idea de la vitalidad de ciertas especies que se encuentran en un acuático ecosystem y podría ampliar la gama de métodos convencionales para el análisis de muestras de agua.

Una ilustración esquemática de la configuración experimental se muestra en la Figura 1A. Una configuración de campo oscuro es necesario detectar ópticamente el desplazamiento de una partícula de oro de 60 nm en una trampa óptica 15. La longitud de onda de 1064 nm para el láser de captura se elige para garantizar un confinamiento estable del detector de 12,14 partícula de oro. Un divisor de haz en el microscopio se utiliza para enfocar el haz de captura a través de la obje...

Watch this Scientific Journal Video about Analyzing the Movement of the Nauplius 'Artemia salina' by Optical Tracking of Plasmonic Nanoparticles at JoVE.com

Analyzing the Movement of the Nauplius &#039;Artemia salina&#039; by Optical Tracking of Plasmonic Nanoparticles

Utilizamos el seguimiento óptico de nanopartículas plasmónica para investigar y caracterizar los movimientos de frecuencia de los organismos acuáticos.

Analizando el movimiento de la Nauplio &#39;<em&gt; Artemia salina</em&gt; &#39;Por Optical Tracking de plasmónicas nanopartículas

We demonstrate how optical tweezers may provide a sensitive tool to analyze the fluidic vibrations generated by the movement of small aquatic organisms. A ...

analyzing-movement-nauplius-artemia-salina-optical-tracking-plasmonic

Research

JoVE Journal

Engineering

Analyzing the Movement of the Nauplius 'Artemia salina' by Optical Tracking of Plasmonic Nanoparticles

10.4K vistas.  Ludwig-Maximilians-Universität.  Utilizamos el seguimiento óptico de nanopartículas plasmónica para investigar y caracterizar los movimientos de frecuencia de los organismos acuáticos. 

Video: Analyzing the Movement of the Nauplius 'Artemia salina' by Optical Tracking of Plasmonic Nanoparticles

Fabricating Metamaterials Using the Fiber Drawing Method

Metamaterials are man-made composite materials, fabricated by assembling components much smaller than the wavelength at which they operate 1. They owe their electromagnetic properties to the structure of their constituents, instead of the atoms that compose them. For example, sub-wavelength metal wires can be arranged to possess an effective electric permittivity that is either positive or negative at a given frequency, in contrast to the metals themselves 2. This unprecedented control over the behaviour of light can potentially lead to a number of novel devices, such as invisibility cloaks 3, negative refractive index materials 4, and lenses that resolve objects below the diffraction limit 5. However, metamaterials operating at optical, mid-infrared and terahertz frequencies are conventionally made using nano- and micro-fabrication techniques that are expensive and produce samples that are at most a few centimetres in size 6-7. Here we present a fabrication method to produce hundreds of meters of metal wire metamaterials in fiber form, which exhibit a terahertz plasmonic response 8. We combine the stack-and-draw technique used to produce microstructured polymer optical fiber 9 with the Taylor-wire process 10, using indium wires inside polymethylmethacrylate (PMMA) tubes. PMMA is chosen because it is an easy to handle, drawable dielectric with suitable optical properties in the terahertz region; indium because it has a melting temperature of 156.6 &deg;C which is appropriate for codrawing with PMMA. We include an indium wire of 1 mm diameter and 99.99% purity in a PMMA tube with 1 mm inner diameter (ID) and 12 mm outside diameter (OD) which is sealed at one end. The tube is evacuated and drawn down to an outer diameter of 1.2 mm. The resulting fiber is then cut into smaller pieces, and stacked into a larger PMMA tube. This stack is sealed at one end and fed into a furnace while being rapidly drawn, reducing the diameter of the structure by a factor of 10, and increasing the length by a factor of 100. Such fibers possess features on the micro- and nano- scale, are inherently flexible, mass-producible, and can be woven to exhibit electromagnetic properties that are not found in nature. They represent a promising platform for a number of novel devices from terahertz to optical frequencies, such as invisible fibers, woven negative refractive index cloths, and super-resolving lenses.

Metamaterials at terahertz frequencies offer unique opportunities, but are challenging to fabricate in bulk. We adapt the fabrication procedure for microstructured polymer optical fibers to inexpensively fabricate metamaterials potentially on an industrial scale. We produce polymethylmethacrylate fibers containing ~10 &mu;m diameter indium wires separated by ~100 &mu;m, which exhibit a terahertz plasmonic response.

Los metamateriales Fabricacion mediante el método de dibujo de fibra

Metamaterials are man-made composite materials, fabricated by assembling components much smaller than the wavelength at which they operate 1. They owe ...

Investigación

Ingeniería

Optical Trapping of Nanoparticles

Optical trapping is a technique for immobilizing and manipulating small objects in a gentle way using light, and it has been widely applied in trapping and manipulating small biological particles. Ashkin and co-workers first demonstrated optical tweezers using a single focused beam1. The single beam trap can be described accurately using the perturbative gradient force formulation in the case of small Rayleigh regime particles1. In the perturbative regime, the optical power required for trapping a particle scales as the inverse fourth power of the particle size. High optical powers can damage dielectric particles and cause heating. For instance, trapped latex spheres of 109 nm in diameter were destroyed by a 15 mW beam in 25 sec1, which has serious implications for biological matter2,3.
A self-induced back-action (SIBA) optical trapping was proposed to trap 50 nm polystyrene spheres in the non-perturbative regime4. In a non-perturbative regime, even a small particle with little permittivity contrast to the background can influence significantly the ambient electromagnetic field and induce a large optical force. As a particle enters an illuminated aperture, light transmission increases dramatically because of dielectric loading. If the particle attempts to leave the aperture, decreased transmission causes a change in momentum outwards from the hole and, by Newton's Third Law, results in a force on the particle inwards into the hole, trapping the particle. The light transmission can be monitored; hence, the trap can become a sensor. The SIBA trapping technique can be further improved by using a double-nanohole structure.
The double-nanohole structure has been shown to give a strong local field enhancement5,6. Between the two sharp tips of the double-nanohole, a small particle can cause a large change in optical transmission, thereby inducing a large optical force. As a result, smaller nanoparticles can be trapped, such as 12 nm silicate spheres7 and 3.4 nm hydrodynamic radius bovine serum albumin proteins8. In this work, the experimental configuration used for nanoparticle trapping is outlined. First, we detail the assembly of the trapping setup which is based on a Thorlabs Optical Tweezer Kit. Next, we explain the nanofabrication procedure of the double-nanohole in a metal film, the fabrication of the microfluidic chamber and the sample preparation. Finally, we detail the data acquisition procedure and provide typical results for trapping 20 nm polystyrene nanospheres.

The following setup approach details low power optical trapping of dielectric nanoparticles using a double-nanohole in metal film.

Trampas ópticas de las nanopartículas

Optical trapping is a technique for immobilizing and manipulating small objects in a gentle way using light, and it has been widely applied in trapping ...

Evaluating Plasmonic Transport in Current-carrying Silver Nanowires

Plasmonics is an emerging technology capable of simultaneously transporting a plasmonic signal and an electronic signal on the same information support1,2,3. In this context, metal nanowires are especially desirable for realizing dense routing networks4. A prerequisite to operate such shared nanowire-based platform relies on our ability to electrically contact individual metal nanowires and efficiently excite surface plasmon polaritons5 in this information support. In this article, we describe a protocol to bring electrical terminals to chemically-synthesized silver nanowires6 randomly distributed on a glass substrate7. The positions of the nanowire ends with respect to predefined landmarks are precisely located using standard optical transmission microscopy before encapsulation in an electron-sensitive resist. Trenches representing the electrode layout are subsequently designed by electron-beam lithography. Metal electrodes are then fabricated by thermally evaporating a Cr/Au layer followed by a chemical lift-off. The contacted silver nanowires are finally transferred to a leakage radiation microscope for surface plasmon excitation and characterization8,9. Surface plasmons are launched in the nanowires by focusing a near infrared laser beam on a diffraction-limited spot overlapping one nanowire extremity5,9. For sufficiently large nanowires, the surface plasmon mode leaks into the glass substrate9,10. This leakage radiation is readily detected, imaged, and analyzed in the different conjugate planes in leakage radiation microscopy9,11. The electrical terminals do not affect the plasmon propagation. However, a current-induced morphological deterioration of the nanowire drastically degrades the flow of surface plasmons. The combination of surface plasmon leakage radiation microscopy with a simultaneous analysis of the nanowire electrical transport characteristics reveals the intrinsic limitations of such plasmonic circuitry.

Silver nanowires can simultaneously transport electrons and optical information in the form of surface plasmons. A procedure is described here to realize such a shared circuitry and the limitations at propagating both information carriers are evaluated.

Plasmonics is an emerging technology capable of simultaneously transporting a plasmonic signal and an electronic signal on the same information ...

Patterning via Optical Saturable Transitions - Fabrication and Characterization

This protocol describes the fabrication and characterization of nanostructures using a novel nanolithographic technique called Patterning via Optical Saturable Transitions (POST). In this technique the chemical properties of organic photochromic molecules that undergo single-photon reactions are exploited, enabling rapid top-down nanopatterning over large areas at low light intensities, thereby, allowing for the circumvention of the far-field diffraction barrier.4 Simple, cost-effective, high throughput and resolution alternatives to nanopatterning are being explored, such as, two-photon polymerization5,6, beam pen lithography (BPL)7, scanning electron beam lithography (SEBL), and focused ion beam (FIB) patterning. However, multi-photon approaches require high light intensities, which limit their potential for high throughput and offer low image contrast. Although, electron and ion beam lithographic processes offer increased resolution, the serial nature of the process is limited to slow writing speeds, which also prevents patterning of features over large areas. Beam-pen lithography is an approach towards parallel near-field optical lithography. However, the gap between the source of the beam and the surface of the photoresist needs to be controlled extremely precisely for good pattern uniformity and this is very challenging to accomplish for large arrays of beams. Patterning via Optical Saturable Transitions (POST) is an alternative optical nanopatterning technique for patterning sub-wavelength features1-3. Since this technique uses single photons instead of electrons, it is extremely fast and does not require high light intensities1-3, opening the door to massive parallelization.

We report that the diffraction limit of conventional optical lithography can be overcome by exploiting the transitions of organic photochromic derivatives induced by their photoisomerization at low light intensities.1-3 This paper outlines our fabrication technique and two locking mechanisms, namely: dissolution of one photoisomer and electrochemical oxidation.

Patrones través ópticos saturable Transiciones - Fabricación y Caracterización

This protocol describes the fabrication and characterization of nanostructures using a novel nanolithographic technique called Patterning via Optical ...

Experiments on Ultrasonic Lubrication Using a Piezoelectrically-assisted Tribometer and Optical Profilometer

Friction and wear are detrimental to engineered systems. Ultrasonic lubrication is achieved when the interface between two sliding surfaces is vibrated at a frequency above the acoustic range (20 kHz). As a solid-state technology, ultrasonic lubrication can be used where conventional lubricants are unfeasible or undesirable. Further, ultrasonic lubrication allows for electrical modulation of the effective friction coefficient between two sliding surfaces. This property enables adaptive systems that modify their frictional state and associated dynamic response as the operating conditions change. Surface wear can also be reduced through ultrasonic lubrication. We developed a protocol to investigate the dependence of friction force reduction and wear reduction on the linear sliding velocity between ultrasonically lubricated surfaces. A pin-on-disc tribometer was built which differs from commercial units in that a piezoelectric stack is used to vibrate the pin at 22 kHz normal to the rotating disc surface. Friction and wear metrics including effective friction force, volume loss, and surface roughness are measured without and with ultrasonic vibrations at a constant pressure of 1 to 4 MPa and three different sliding velocities: 20.3, 40.6, and 87 mm/sec. An optical profilometer is utilized to characterize the wear surfaces. The effective friction force is reduced by 62% at 20.3 mm/sec. Consistently with existing theories for ultrasonic lubrication, the percent reduction in friction force diminishes with increasing speed, down to 29% friction force reduction at 87 mm/sec. Wear reduction remains essentially constant (49%) at the three speeds considered.

We present a protocol for using a piezoelectrically-assisted tribometer and optical profilometer to investigate the dependence of ultrasonic wear and friction reduction on linear velocity, contact pressure, and surface properties.

Los experimentos en ultrasónico Lubricación El uso de un Tribómetro asistida piezoeléctrico y Perfilómetro óptico

Friction and wear are detrimental to engineered systems. Ultrasonic lubrication is achieved when the interface between two sliding surfaces is vibrated at ...

Multifunctional Hybrid Fe2O3-Au Nanoparticles for Efficient Plasmonic Heating

One of the most widely used methods for manufacturing colloidal gold nanospherical particles involves the reduction of chloroauric acid (HAuCl4) to neutral gold Au(0) by reducing agents, such as sodium citrate or sodium borohydride. The extension of this method to decorate iron oxide or similar nanoparticles with gold nanoparticles to create multifunctional hybrid Fe2O3-Au nanoparticles is straightforward. This approach yields fairly good control over Au nanoparticle dimensions and loading onto Fe2O3. Additionally, the Au metal size, shape, and loading can easily be tuned by changing experimental parameters (e.g., reactant concentrations, reducing agents, surfactants, etc.). An advantage of this procedure is that the reaction can be done in air or water, and, in principle, is amenable to scaling up. The use of such optically tunable Fe2O3-Au nanoparticles for hyperthermia studies is an attractive option as it capitalizes on plasmonic heating of gold nanoparticles tuned to absorb light strongly in the VIS-NIR region. In addition to its plasmonic effects, nanoscale Au provides a unique surface for interesting chemistries and catalysis. The Fe2O3 material provides additional functionality due to its magnetic property. For example, an external magnetic field could be used to collect and recycle the hybrid Fe2O3-Au nanoparticles after a catalytic experiment, or alternatively, the magnetic Fe2O3 can be used for hyperthermia studies through magnetic heat induction. The photothermal experiment described in this report measures bulk temperature change and nanoparticle solution mass loss as functions of time using infrared thermocouples and a balance, respectively. The ease of sample preparation and the use of readily available equipment are distinct advantages of this technique. A caveat is that these photothermal measurements assess the bulk solution temperature and not the surface of the nanoparticle where the heat is transduced and the temperature is likely to be higher.

Multifunctional Hybrid Fe2O3-Au Nanoparticles for Efficient Plasmonic Heating

We describe the synthesis and properties of multifunctional Fe2O3-Au nanoparticles produced by a wet chemical approach and investigate their photothermal properties using laser irradiation. The composite Fe2O3-Au nanoparticles retain the properties of both materials, creating a multifunctional structure with excellent magnetic and plasmonic properties.

Multifuncional híbrido Fe<sub&gt; 2</sub&gt; O<sub&gt; 3</sub&gt; -Au Nanopartículas para la calefacción eficiente plasmónicas

One of the most widely used methods for manufacturing colloidal gold nanospherical particles involves the reduction of chloroauric acid (HAuCl4) to ...

Electroactive Polymer Nanoparticles Exhibiting Photothermal Properties

A method for the synthesis of electroactive polymers is demonstrated, starting with the synthesis of extended conjugation monomers using a three-step process that finishes with Negishi coupling. Negishi coupling is a cross-coupling process in which a chemical precursor is first lithiated, followed by transmetallation with ZnCl2. The resultant organozinc compound can be coupled to a dibrominated aromatic precursor to give the conjugated monomer. Polymer films can be prepared via electropolymerization of the monomer and characterized using cyclic voltammetry and ultraviolet-visible-near infrared (UV-Vis-NIR) spectroscopy. Nanoparticles (NPs) are prepared via emulsion polymerization of the monomer using a two-surfactant system to yield an aqueous dispersion of the polymer NPs. The NPs are characterized using dynamic light scattering, electron microscopy, and UV-Vis-NIR-spectroscopy. Cytocompatibility of NPs is investigated using the cell viability assay. Finally, the NP suspensions are irradiated with a NIR laser to determine their effectiveness as potential materials for photothermal therapy (PTT).

A protocol is presented for the synthesis and preparation of nanoparticles consisting of electroactive polymers.

Propiedades Electroactivos Polymer Nanopartículas Exponer fototérmica

A method for the synthesis of electroactive polymers is demonstrated, starting with the synthesis of extended conjugation monomers using a three-step ...

Use of Sacrificial Nanoparticles to Remove the Effects of Shot-noise in Contact Holes Fabricated by E-beam Lithography

Nano-patterns fabricated with extreme ultraviolet (EUV) or electron-beam (E-beam) lithography exhibit unexpected variations in size. This variation has been attributed to statistical fluctuations in the number of photons/electrons arriving at a given nano-region arising from shot-noise (SN). The SN varies inversely to the square root of a number of photons/electrons. For a fixed dosage, the SN is larger in EUV and E-beam lithographies than for traditional (193 nm) optical lithography. Bottom-up and top-down patterning approaches are combined to minimize the effects of shot noise in nano-hole patterning. Specifically, an amino-silane surfactant self-assembles on a silicon wafer that is subsequently spin-coated with a 100 nm film of a PMMA-based E-beam photoresist. Exposure to the E-beam and the subsequent development uncover the underlying surfactant film at the bottoms of the holes. Dipping the wafer in a suspension of negatively charged, citrate-capped, 20 nm gold nanoparticles (GNP) deposits one particle per hole. The exposed positively charged surfactant film in the hole electrostatically funnels the negatively charged nanoparticle to the center of an exposed hole, which permanently fixes the positional registry. Next, by heating near the glass transition temperature of the photoresist polymer, the photoresist film reflows and engulfs the nanoparticles. This process erases the holes affected by SN but leaves the deposited GNPs locked in place by strong electrostatic binding. Treatment with oxygen plasma exposes the GNPs by etching a thin layer of the photoresist. Wet-etching the exposed GNPs with a solution of I2/KI yields uniform holes located at the center of indentations patterned by E-beam lithography. The experiments presented show that the approach reduces the variation in the size of the holes caused by SN from 35% to below 10%. The method extends the patterning limits of transistor contact holes to below 20 nm.

Uniformly sized nanoparticles can remove fluctuations in contact hole dimensions patterned in poly(methyl methacrylate) (PMMA) photoresist films by electron beam (E-beam) lithography. The process involves electrostatic funneling to center and deposit nanoparticles in contact holes, followed by photoresist reflow and plasma- and wet-etching steps.

El uso de nanopartículas de sacrificio para eliminar los efectos del ruido de disparo en orificios de contacto fabricadas por haz de electrones de litografía

Nano-patterns fabricated with extreme ultraviolet (EUV) or electron-beam (E-beam) lithography exhibit unexpected variations in size. This variation has ...

Plasmonic Trapping and Release of Nanoparticles in a Monitoring Environment

Plasmonic tweezers use surface plasmon polaritons to confine polarizable nanoscale objects. Among the various designs of plasmonic tweezers, only a few can observe immobilized particles. Moreover, a limited number of studies have experimentally measured the exertable forces on the particles. The designs can be classified as the protruding nanodisk type or the suppressed nanohole type. For the latter, microscopic observation is extremely challenging. In this paper, a new plasmonic tweezer system is introduced to monitor particles, both in directions parallel and orthogonal to the symmetric axis of a plasmonic nanohole structure. This feature enables us to observe the movement of each particle near the rim of the nanohole. Furthermore, we can quantitatively estimate the maximal trapping forces using a new fluidic channel.

A microchip fabrication process that incorporates plasmonic tweezers is presented here. The microchip enables the imaging of a trapped particle to measure maximal trapping forces.

Plasmónica la captura y liberación de nanopartículas en un entorno de monitorización

Plasmonic tweezers use surface plasmon polaritons to confine polarizable nanoscale objects. Among the various designs of plasmonic tweezers, only a few ...

Microfluidic Imaging Flow Cytometry by Asymmetric-detection Time-stretch Optical Microscopy (ATOM)

Scaling the number of measurable parameters, which allows for multidimensional data analysis and thus higher-confidence statistical results, has been the main trend in the advanced development of flow cytometry. Notably, adding high-resolution imaging capabilities allows for the complex morphological analysis of cellular/sub-cellular structures. This is not possible with standard flow cytometers. However, it is valuable for advancing our knowledge of cellular functions and can benefit life science research, clinical diagnostics, and environmental monitoring. Incorporating imaging capabilities into flow cytometry compromises the assay throughput, primarily due to the limitations on speed and sensitivity in the camera technologies. To overcome this speed or throughput challenge facing imaging flow cytometry while preserving the image quality, asymmetric-detection time-stretch optical microscopy (ATOM) has been demonstrated to enable high-contrast, single-cell imaging with sub-cellular resolution, at an imaging throughput as high as 100,000 cells/s. Based on the imaging concept of conventional time-stretch imaging, which relies on all-optical image encoding and retrieval through the use of ultrafast broadband laser pulses, ATOM further advances imaging performance by enhancing the image contrast of unlabeled/unstained cells. This is achieved by accessing the phase-gradient information of the cells, which is spectrally encoded into single-shot broadband pulses. Hence, ATOM is particularly advantageous in high-throughput measurements of single-cell morphology and texture &#8211; information indicative of cell types, states, and even functions. Ultimately, this could become a powerful imaging flow cytometry platform for the biophysical phenotyping of cells, complementing the current state-of-the-art biochemical-marker-based cellular assay. This work describes a protocol to establish the key modules of an ATOM system (from optical frontend to data processing and visualization backend), as well as the workflow of imaging flow cytometry based on ATOM, using human cells and micro-algae as the examples.

Microfluidic Imaging Flow Cytometry by Asymmetric-detection Time-stretch Optical Microscopy ATOM

This protocol describes the implementation of an asymmetric-detection time-stretch optical microscopy system for single-cell imaging in ultrafast microfluidic flow and its applications in imaging flow cytometry.

Microfluidic Imaging Cytometría de flujo por Asimétrica de detección de tiempo de estiramiento Microscopía óptica (ATOM)

Scaling the number of measurable parameters, which allows for multidimensional data analysis and thus higher-confidence statistical results, has been the ...