Name: trapping of micro particles in nanoplasmonic optical lattice
Uploaded: 2017-09-05T12:30:00.000+00:00
Duration: 7 min 20 s
Description: Watch this Scientific Journal Video about Trapping of Micro Particles in Nanoplasmonic Optical Lattice at JoVE.com

Y. T. Y. agradece a fondos del Ministerio de ciencia y tecnología bajo números de concesión más 105-2221-E-007-MY3 y de la Universidad Nacional Tsing Hua en grant números 105N518CE1 y 106N518CE1.

1. configuración óptica Nota: el principio de la óptica configuración se ilustra en la figura 1.
Kit de pinzas de <ol><li>conjunto a la óptica (véase la Tabla de materiales) y el módulo de fluorescencia (véase Tabla de materiales) según sus manuales. Fuente 470 nm azul luz emite luz de diodo (LED) se conectan al módulo fluorescente.</li>
	<li>Reemplazar la alta apertura numérica (NA) (NA = 1.25, aumento 100 x) objetivo de microscopio (WD) de la distancia del objetivo de inmersión de aceite por un trabajo largo (longitud focal 3.6mm, WD = 10,6 mm, NA = 0.5).</li>
	<li>Quitar la lente en la sección de expansión de la viga del kit montado para conseguir sueltos enfocar el rayo láser.</li>
	<li>Vuelta en la alimentación y la corriente para el laser de diodo de longitud de onda 980 nm y uso la cargada junto cámara de dispositivo (CCD) para asegurarse de que el rayo láser esté correctamente alineado. 
	Nota: Si el rayo láser está bien alineado, la cámara mostrará un punto gaussiano.</li>
</ol> 2. Nanofabricación <ol><li>marcador fabricación. 
	Nota: Los marcadores ayudarán a colocar la matriz de nanoplasmonic durante el proceso de la fabricación y posterior captura experimento. El proceso detallado se ilustra en la figura 1 complementaria.
	<ol><li>Película de óxido de estaño (ITO) de indio depósito 40 nm en un cubreobjetos de espesor 0,17 mm con farfulla. 
		Nota: La película de ITO ayuda descarga electrones durante el proceso de litografía subsecuente la viga e.</li>
		<li>Vuelta capa una capa de 8 μm de photoresist positivo con giro velocidad 4000 rpm y tiempo 30 s con un recubridor spin.</li>
		<li>Suave cuece al horno la muestra a 90 ° C por 5 min y alinee la muestra con el photomask para marcador y exponer la muestra a la luz de 80 UV s en el alineador máscara.</li>
		<li>Tomar la muestra en el revelador del photoresist para 130 s.</li>
		<li>Depositar una capa de 2 nm de cromo y una capa de nm 40 de oro en la muestra usando la evaporación térmica. 18</li> <li>tomar la muestra en acetona y colóquelo en un limpiador ultrasónico de funcionamiento 43 kHz y 150 W durante 5 min para lift off</li>
	</ol></li> <li>Fabricación de matriz Nanoplasmonic <ol><li>capa de vuelta una capa de la viga e resistir PMMA 120K con velocidad 5000 rpm durante 30 s en un recubridor spin. Cueza al horno la muestra a 160 ° C por 3 min sobre una placa caliente.</li>
		<li>Vuelta capa otra capa de resistir e-beam PMMA 960K con velocidad 5000 rpm durante 30 s en un recubridor spin. Cueza al horno la muestra a 160 ° C por 3 min sobre una placa caliente.</li>
		<li>Escritor de uso e-beam para exponer la viga e resistir con aceleración tensión de 30 kV y dosis 400 C/cm 2.</li>
		<li>Depositar una capa de nm 40 de oro en un evaporador térmico.</li>
		<li>Tomar la muestra en acetona y colóquelo en un limpiador ultrasónico durante 5 minutos para lift off</li>
	</ol></li></ol> 3. Sistema de enfriamiento y su calibración de la temperatura de la muestra Nota: la muestra diseño de la etapa de enfriamiento se muestra en la figura 2 complementaria.
<ol><li>Haciendo el circuito driver para muestra enfriamiento <ol><li>resistencias, transistores de ensambladura bipolar los transistores de efecto de campo poder óxido de metal en el circuito personalizado siguiendo el diagrama del circuito en suplementario Figura 3 . Todos estos componentes con soldador de la soldadura.</li>
		<li>Los cables de conexión entre el puerto de control del tablero del circuito y el tablero de control electrónico. Conecte los cables entre el puerto de salida de los circuitos y refrigeración termoeléctrica del elemento (TEC). Coloque el elemento de la TEC en el escenario de la muestra con el hundimiento del calor. 
		&#8203; Nota: el TEC tiene un agujero en el centro para permitir que el rayo láser al pasar por.</li>
		<li>Conecte los cables de la placa de circuito a 5 V fuente de alimentación. Utilizar la cámara infrarroja de la visión de futuro para controlar la temperatura para comprobar si la refrigeración termoeléctrica es correctamente enfriando.</li>
	</ol></li> <li>Calibración de la temperatura medida en el futuro cámara y resistencia temperatura detector (RTD) termómetro infrarrojo.
	<ol><li>Coloque el termómetro RTD en un cubreobjetos en blanco y aplique una pequeña cantidad de pasta térmica sobre la misma para asegurar el buen contacto térmico entre el RTD termómetro y cubreobjetos de.</li>
		<li>Cambiar el ajuste de potencia de salida del circuito de control electrónico del elemento TEC cambiando el ciclo de trabajo de programación de modulación de anchura de pulso y esperar 3 minutos para asegurarse de que se alcance la temperatura de estado estacionario. Leer la temperatura con el termómetro RTD.</li>
		<li>Vuelta en la cámara infrarroja mirando hacia adelante y el monitor de la temperatura. Repetir este proceso en varios ajustes de potencia de salida para obtener la curva de calibración de temperatura. En suplementario figura 4 se muestra una curva de calibración de temperatura representante. 
		Nota: Es fundamental hacer calibración entre termómetro RTD y la cámara infrarroja mira hacia delante porque la lectura de la temperatura de la cámara infrarroja de la visión de futuro debe ser exacta para asegurar la temperatura correcta.</li>
	</ol></li></ol> 4. Captura de micropartículas <ol><li>diluir micro partículas de poliestireno de 2 de diámetro μm en agua desionizada en un microcentrifugetube con proporción de volumen apropiado. 
	Nota: La concentración de micropartículas se puede ajustar según el objetivo del experimento. Mientras que menor concentración permite un intervalo de tiempo de la muestra entre los eventos de captura de partículas individuales, mayor concentración acortará el tiempo para la captura de partículas múltiples. Para la captura de una partícula, una concentración típica es ~0.05% (w/v).</li>
	<li>Coloca la muestra con la matriz de nanoplasmonic en el escenario y girar en un 470 nm LED como la fuente de luz de fluorescencia y ajustar manualmente la potencia de 5 mW para la proyección de imagen de campo brillante.</li>
	<li>Utilice el marcador para ubicar la matriz nanoplasmonic, alinee la muestra y la cámara para asegurarse de que la matriz está en el centro de la región de interés en la pantalla del ordenador.</li>
	<li>Dispensar 10 μl de las diluida micro partículas de diámetro de 2 μm en la muestra con una micro pipeta.</li>
	<li>Encender la corriente para el diodo de láser de longitud de onda 980 nm para excitar la resonancia plasmónica de la matriz con una potencia en el rango de ~ 1 mW a 10 mW.</li>
	<li>Activar manualmente la fuente de alimentación para el tablero de control electrónico para enfriar la muestra a un estado estacionario de temperatura ~ 4 ° C.</li>
	<li>En el software de visualización, haga clic en el &#34; grabar video &#34; secuencia para abrir el cuadro de diálogo de grabación. Haga clic en el &#34; registro &#34; botón para iniciar el grabación 1.5 del movimiento de las partículas micro a una velocidad de 10 fotogramas/s sobre la muestra bajo la influencia de rayo láser mediante la cámara CCD de vídeo. Haga clic en el &#34; dejar de &#34; el botón para detener la grabación. Ver Video 1.</li>
</ol>

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Los autores no tienen nada que revelar.

El procedimiento aquí descrito permite al lector a reproducir confiablemente captura sobre una base diaria. Una pauta empírica general para el diseño de un enrejado óptico utilizable es utilizar un tamaño comparable para nanoarray plasmónica, distancia interdisc y atrapado de tamaño de partícula. Comparado con un nanoestructuras plasmónica solo, aislado, el diseño de enrejado óptico junto con la alta energía óptica proporcionada por el enfriamiento de la muestra a ~ 4 ° C utilizado aquí grandemente aumenta...

La captura óptica de partículas a escala micro fue desarrollada originalmente por Arthur Askin en la década de 1970. Desde su invención, la técnica se ha desarrollado como una herramienta versátil para el micro y nanomanipulación1,2. Convencionales óptico captura basándose en el campo lejano enfoque principio intrínsecamente limitada por la difracción en su confinamiento espacial, en donde la fuerza de captura disminuye dramáticamente (siguiente un ~unaley3 para una partícula de radio un) 3. para superar esos límites de difracción, los investigadores han desarrollado técnicas de captura óptica de campo cercano del campo evanescente óptico utilizando nanoestructuras plasmónica de metálico y, además, la captura de nanoescala objetos a las moléculas de proteína solo ha sido demostrada4,5,6,7,8,9,10,11. Por otra parte, la red óptica plasmónica nace de matrices de nanoestructuras plasmónica periódica para transporte de largo alcance de micro - y nanopartículas y múltiples partículas apilamiento11,12. Un obstáculo importante para interrumpir la captura en un enrejado óptico es convección fototérmica y se han hecho esfuerzos para aclarar sus efectos por varios grupos14,15,16,17. Usando la función de Green, Baffou et al. calcular un perfil de temperatura modelando cada nanoestructuras plasmónica como un calentador de punto y luego validado experimentalmente su modelo14. Grupo de Toussant también ha medido la convección inducida por plasmones con partícula velocimetry15. Grupo del autor ha caracterizado transporte cerca campo y convencionales y demuestra una estrategia de ingeniería para suprimir la convección de fototérmica16,17.
Aquí presentamos el diseño de una configuración óptica y un procedimiento detallado específicamente para experimentos de captura con red óptica plasmónica. El potencial óptico fue creado mediante la iluminación de una matriz de nanodiscs de oro con un haz gaussiano enfocado libremente. Un plan para suprimir la convección fototérmica de enfriar la muestra a una temperatura baja (~ 4 ° C) para la captura óptima es también describir aquí17. En aproximación de Boussinesq, da una estimación de orden de la magnitud de la velocidad de convección natural u por u ~L2 gβΔT / v, donde L es la escala de longitud de la fuente de calor y Δ T es el aumento de la temperatura en relación con la referencia debido a la calefacción.  g y β son la aceleración de la gravedad y el coeficiente de expansión térmica, respectivamente. En las temperaturas cerca de 4 ° C, la densidad del medio agua exhibe dependencia anómala de la temperatura y esto se traduce en un coeficiente de expansión térmica cercano a cero y, por tanto, una convección fototérmica vanishingly pequeñas.

<table><tbody><tr><td>Thermoelectric cooling element</td><td>Thorlabs</td><td>TEC 1.4-6</td><td>TEC element for sample cooling</td></tr><tr><td>RTD thermometer</td><td>Omega Engineering</td><td>RTD Thermometer 969C</td><td></td></tr><tr><td>Forward looking infrared camera</td><td>FLIR&amp;nbsp;</td><td>FLIR One</td><td>IR camera for temperature monitoring</td></tr><tr><td>light emitting diode light source</td><td>Touchbright</td><td></td><td>Light source for illumination for fluorescent imaging</td></tr><tr><td>Long working distance objective</td><td>Olympus</td><td>LMPLFLN</td><td>For illuminating the sample and imaging</td></tr><tr><td>Optical trap kit</td><td>Thorlabs</td><td>OTKB/M</td><td></td></tr><tr><td>Cover slip</td><td></td><td></td><td>thickness 0.17 mm</td></tr><tr><td>Scanning electron microscope</td><td>Hitachi</td><td>SEM-Hitachi S3400N</td><td></td></tr><tr><td>Electron beam blanker</td><td>DEBEN</td><td>PCD beam blanker</td><td>the blanker is added to the scanning electron microscope&amp;nbsp;</td></tr><tr><td>Thermal evaporator</td><td>SYSKEY Technology</td><td></td><td></td></tr><tr><td>Mask aligner</td><td>Karl Suss</td><td>MJB 3</td><td>For marker fabrication</td></tr><tr><td>Electron beam resist</td><td>Sigma Alrich</td><td>PMMA 120K</td><td>For e-beam lithography</td></tr><tr><td>Electron beam resist</td><td>Sigma Alrich</td><td>PMMA 960K</td><td>For e-beam lithography</td></tr><tr><td>Fluoresent labeled polystyrene microspheres</td><td>Polyscience</td><td></td><td>2 um diameter</td></tr><tr><td>Bipolar transistor</td><td>Mouser</td><td>2N3904</td><td>quantity 2 for TEC driver circuit</td></tr><tr><td>Bipolar transistor</td><td>Mouser</td><td>2N3906</td><td>quantity 2 for TEC driver circuit</td></tr><tr><td>MOSFET power transistor</td><td>Mouser</td><td>IRF5305</td><td>quantity 2 for TEC driver circuit</td></tr><tr><td>MOSFET power transistor</td><td>Mouser</td><td>IRF131ON</td><td>quantity 2 for TEC driver circuit</td></tr><tr><td>10 kOhm resistor</td><td>Mouser</td><td></td><td>quantity 6 for TEC driver circuit</td></tr><tr><td>910 Ohm resistor</td><td>Mouser</td><td></td><td>quantity 2 for TEC driver circuit</td></tr><tr><td>Photoresist</td><td>Microchemicals</td><td>AZ4620</td><td>For marker fabrication</td></tr><tr><td>Acetone</td><td>Sigma Alrich</td><td></td><td>For marker fabrication</td></tr><tr><td>Fluorescence Module for the OTKB/M, Metric Threads</td><td>Thorlabs</td><td>OTKB-FL/M</td><td></td></tr><tr><td>Fluorescent filter set</td><td>Thorlabs</td><td>MDF-FITC</td><td>For Fluorescein Isothiocyanate (FITC)</td></tr><tr><td>Ultrasonic cleaner</td><td>Delta</td><td>DC150H</td><td>For the lift off step</td></tr></tbody></table>

trapping of micro particles in nanoplasmonic optical lattice

La plasmónica pinzas ópticas ha sido desarrollado para superar los límites de la difracción de las pinzas ópticas convencionales de campo lejano. Plasmónica enrejado óptico consiste en una matriz de nanoestructuras, que exhiben una variedad de captura y transporte de comportamientos. Nos informe los procedimientos experimentales para atrapar micro-partículas en un enrejado óptico simple nanoplasmonic cuadrados. También describimos la configuración óptica y la nanofabricación de una matriz de nanoplasmonic. El potencial óptico se crea mediante la iluminación de una matriz de nanodiscs de oro con un haz gaussiano de longitud de onda de 980 nm y emocionante resonancia de plasmón. El movimiento de las partículas es supervisado por la proyección de imagen de la fluorescencia. También se describe un plan para suprimir la convección fototérmica para aumentar la potencia óptica utilizable para la captura óptima. Supresión de la convección se logra enfriamiento de la muestra a baja temperatura y utilizando el coeficiente de expansión térmica cercano a cero de un medio de agua. Transporte de partículas individuales y múltiples trampas de partículas se divulgan aquí.

Trayectorias de partículas individuales fueron grabadas por una cámara CCD en nuestro experimento y entonces, las imágenes fueron procesadas con un programa personalizado para extraer de la trayectoria de cada partícula16. Resultados representativos se muestran en la figura 3 y 1 Video para micro esferas con un diámetro de 2 μm. se observaron múltiples trampas de partículas dentro de la red óptica. Sucesivas i...

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Trapping of Micro Particles in Nanoplasmonic Optical Lattice

Se describe un procedimiento para atrapar ópticamente micro-partículas en enrejado óptico nanoplasmonic.

Captura de partículas Micro en enrejado óptico Nanoplasmonic

The plasmonic optical tweezer has been developed to overcome the diffraction limits of the conventional far field optical tweezer. Plasmonic optical ...

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6.5K vistas.  National Tsing Hua University. Se describe un procedimiento para atrapar ópticamente micro-partículas en enrejado óptico nanoplasmonic.

Video: Trapping of Micro Particles in Nanoplasmonic Optical Lattice

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 ...

Investigación

Ingeniería

Three-dimensional Optical-resolution Photoacoustic Microscopy

Optical microscopy, providing valuable insights at the cellular and organelle levels, has been widely recognized as an enabling biomedical technology. As the mainstays of in vivo three-dimensional (3-D) optical microscopy, single-/multi-photon fluorescence microscopy and optical coherence tomography (OCT) have demonstrated their extraordinary sensitivities to fluorescence and optical scattering contrasts, respectively. However, the optical absorption contrast of biological tissues, which encodes essential physiological/pathological information, has not yet been assessable. 
The emergence of biomedical photoacoustics has led to a new branch of optical microscopy optical-resolution photoacoustic microscopy (OR-PAM)1, where the optical irradiation is focused to the diffraction limit to achieve cellular1 or even subcellular2 level lateral resolution. As a valuable complement to existing optical microscopy technologies, OR-PAM brings in at least two novelties. First and most importantly, OR-PAM detects optical absorption contrasts with extraordinary sensitivity (i.e., 100%). Combining OR-PAM with fluorescence microscopy3 or with optical-scattering-based OCT4 (or with both) provides comprehensive optical properties of biological tissues. Second, OR-PAM encodes optical absorption into acoustic waves, in contrast to the pure optical processes in fluorescence microscopy and OCT, and provides background-free detection. The acoustic detection in OR-PAM mitigates the impacts of optical scattering on signal degradation and naturally eliminates possible interferences (i.e., crosstalks) between excitation and detection, which is a common problem in fluorescence microscopy due to the overlap between the excitation and fluorescence spectra. 
Unique for optical absorption imaging, OR-PAM has demonstrated broad biomedical applications since its invention, including, but not limited to, neurology5, 6, ophthalmology7, 8, vascular biology9, and dermatology10. In this video, we teach the system configuration and alignment of OR-PAM as well as the experimental procedures for in vivo functional microvascular imaging.

Optical-resolution photoacoustic microscopy (OR-PAM) is an emerging technology capable of imaging optical absorption contrasts in vivo with cellular resolution and sensitivity. Here, we provide a visualized instruction on the experimental protocols of OR-PAM, including system configuration, system alignment, typical in vivo experimental procedures, and functional imaging schemes.

Tridimensional óptico resolución microscopía fotoacústica

Optical microscopy, providing valuable insights at the cellular and organelle levels, has been widely recognized as an enabling biomedical technology. As ...

Bioingeniería

Utilization of Plasmonic and Photonic Crystal Nanostructures for Enhanced Micro- and Nanoparticle Manipulation

A method to manipulate the position and orientation of submicron particles nondestructively would be an incredibly useful tool for basic biological research. Perhaps the most widely used physical force to achieve noninvasive manipulation of small particles has been dielectrophoresis(DEP).1 However, DEP on its own lacks the versatility and precision that are desired when manipulating cells since it is traditionally done with stationary electrodes. Optical tweezers, which utilize a three dimensional electromagnetic field gradient to exert forces on small particles, achieve this desired versatility and precision.2 However, a major drawback of this approach is the high radiation intensity required to achieve the necessary force to trap a particle which can damage biological samples.3 A solution that allows trapping and sorting with lower optical intensities are optoelectronic tweezers (OET) but OET's have limitations with fine manipulation of small particles; being DEP-based technology also puts constraint on the property of the solution.4,5
This video article will describe two methods that decrease the intensity of the radiation needed for optical manipulation of living cells and also describe a method for orientation control. The first method is plasmonic tweezers which use a random gold nanoparticle (AuNP) array as a substrate for the sample as shown in Figure 1. The AuNP array converts the incident photons into localized surface plasmons (LSP) which consist of resonant dipole moments that radiate and generate a patterned radiation field with a large gradient in the cell solution. Initial work on surface plasmon enhanced trapping by Righini et al and our own modeling have shown the fields generated by the plasmonic substrate reduce the initial intensity required by enhancing the gradient field that traps the particle.6,7,8 The plasmonic approach allows for fine orientation control of ellipsoidal particles and cells with low optical intensities because of more efficient optical energy conversion into mechanical energy and a dipole-dependent radiation field. These fields are shown in figure 2 and the low trapping intensities are detailed in figures 4 and 5. The main problems with plasmonic tweezers are that the LSP's generate a considerable amount of heat and the trapping is only two dimensional. This heat generates convective flows and thermophoresis which can be powerful enough to expel submicron particles from the trap.9,10 The second approach that we will describe is utilizing periodic dielectric nanostructures to scatter incident light very efficiently into diffraction modes, as shown in figure 6.11 Ideally, one would make this structure out of a dielectric material to avoid the same heating problems experienced with the plasmonic tweezers but in our approach an aluminum-coated diffraction grating is used as a one-dimensional periodic dielectric nanostructure. Although it is not a semiconductor, it did not experience significant heating and effectively trapped small particles with low trapping intensities, as shown in figure 7. Alignment of particles with the grating substrate conceptually validates the proposition that a 2-D photonic crystal could allow precise rotation of non-spherical micron sized particles.10 The efficiencies of these optical traps are increased due to the enhanced fields produced by the nanostructures described in this paper.

Plasmonic tweezers and photonic crystal nanostructures are shown to produce useful enhancements in the efficiency and orientation control of optically trapping micro- and nano-particles.

Utilización de nanoestructuras fotónicas de cristal plasmónicos y para la manipulación mejorada de Micro y nanopartículas

A method to manipulate the position and orientation of submicron particles nondestructively would be an incredibly useful tool for basic biological ...

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

We demonstrate how optical tweezers may provide a sensitive tool to analyze the fluidic vibrations generated by the movement of small aquatic organisms. A single gold nanoparticle held by an optical tweezer is used as a sensor to quantify the rhythmic motion of a Nauplius larva (Artemia salina) in a water sample. This is achieved by monitoring the time dependent displacement of the trapped nanoparticle as a consequence of the Nauplius activity. A Fourier analysis of the nanoparticle&#39;s position then yields a frequency spectrum that is characteristic to the motion of the observed species. This experiment demonstrates the capability of this method to measure and characterize the activity of small aquatic larvae without the requirement to observe them directly and to gain information about the position of the larvae with respect to the trapped particle. Overall, this approach could give an insight on the vitality of certain species found in an aquatic ecosystem and could expand the range of conventional methods for analyzing water samples.

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

We use optical tracking of plasmonic nanoparticles to probe and characterize the frequency movements of aquatic organisms.

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 ...

Fabrication and Operation of a Nano-Optical Conveyor Belt

The technique of using focused laser beams to trap and exert forces on small particles has enabled many pivotal discoveries in the nanoscale biological and physical sciences over the past few decades. The progress made in this field invites further study of even smaller systems and at a larger scale, with tools that could be distributed more easily and made more widely available. Unfortunately, the fundamental laws of diffraction limit the minimum size of the focal spot of a laser beam, which makes particles smaller than a half-wavelength in diameter hard to trap and generally prevents an operator from discriminating between particles which are closer together than one half-wavelength. This precludes the optical manipulation of many closely-spaced nanoparticles and&#160;limits the&#160;resolution of optical-mechanical systems. Furthermore, manipulation using focused beams requires beam-forming or steering optics, which can be very bulky and expensive. To address these limitations in the system scalability of conventional optical trapping our lab has devised an alternative technique which utilizes near-field optics to move particles across a chip. Instead of focusing laser beams in the far-field, the optical near field of plasmonic resonators produces the necessary local optical intensity enhancement to overcome the restrictions of diffraction and manipulate particles at higher resolution. Closely-spaced resonators produce strong optical traps which can be addressed to mediate the hand-off of particles from one to the next in a conveyor-belt-like fashion. Here, we describe how to design and produce a conveyor belt using a gold surface patterned with plasmonic C-shaped resonators and how to operate it with polarized laser light to achieve super-resolution nanoparticle manipulation and transport. The nano-optical conveyor belt chip can be produced using lithography techniques and easily packaged and distributed.

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 ...

Optical Trap Loading of Dielectric Microparticles In Air

We demonstrate a method to trap a selected dielectric microparticle in air using radiation pressure from a single-beam gradient optical trap. Randomly scattered dielectric microparticles adhered to a glass substrate are momentarily detached using ultrasonic vibrations generated by a piezoelectric transducer (PZT). Then, the optical beam focused on a selected particle lifts it up to the optical trap while the vibrationally excited microparticles fall back to the substrate. A particle may be trapped at the nominal focus of the trapping beam or at a position above the focus (referred to here as the levitation position) where gravity provides the restoring force. After the measurement, the trapped particle can be placed at a desired position on the substrate in a controlled manner. 
In this protocol, an experimental procedure for selective optical trap loading in air is outlined. First, the experimental setup is briefly introduced. Second, the design and fabrication of a PZT holder and a sample enclosure are illustrated in detail. The optical trap loading of a selected microparticle is then demonstrated with step-by-step instructions including sample preparation, launching into the trap, and use of electrostatic force to excite particle motion in the trap and measure charge. Finally, we present recorded particle trajectories of Brownian and ballistic motions of a trapped microparticle in air. These trajectories can be used to measure stiffness or to verify optical alignment through time domain and frequency domain analysis. Selective trap loading enables optical tweezers to track a particle and its changes over repeated trap loadings in a reversible manner, thereby enabling studies of particle-surface interaction.

A protocol for launching and stably trapping selected dielectric microparticles in air is presented.

Cargando óptica Trampa de micropartículas en dieléctrica del aire

We demonstrate a method to trap a selected dielectric microparticle in air using radiation pressure from a single-beam gradient optical trap. Randomly ...

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 ...

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 ...

Monitoring Conformational Dynamics of Single Unmodified Proteins using Plasmonic Nanotweezers

Current single-molecule techniques to characterize proteins typically require labels, tethers, or the use of non-native solution conditions. Such changes can alter protein biophysics and reduce the usefulness of the data acquired. Plasmonic nanotweezers is a technique that uses localized surface plasmon resonance (LSPR) on gold nanostructures to enhance the electric field within a confined hotspot region. This field enhancement allows for the use of low laser powers to trap single nanoparticles far smaller than conventional optical tweezers, down to only a few nanometers in diameter, such as single proteins. Trapping of single protein molecules within the hotspot region induces a shift in the local refractive index (nprotein &#62; nwater), altering light scattering as a product of the molecule&#39;s polarisability, which is affected by its volume, shape anisotropy, and refractive index. An avalanche photodiode (APD) collects the subsequent changes in light scattering. These alterations can then be analyzed to determine changes in the trapped molecule, including its size, global conformation, and dynamics of conformational change over time. The incorporation of microfluidics within the system allows for controlled environmental changes and real-time monitoring of their subsequent effects on the molecule. In this protocol, we demonstrate the steps to trap single protein molecules, alter their environmental solution conditions, and monitor their corresponding conformational changes using a plasmonic nanotweezers system.

Plasmonic nanotweezers use localized surface plasmon resonance in gold nanostructures to trap single nanoparticles, including proteins, within a nanometer-scale optical field. Changes in the scattered signal reveal protein presence and conformational dynamics, enabling monitoring without fluorophore modifications or surface tethering.

Monitorización de la dinámica conformacional de proteínas individuales no modificadas mediante nanopinzas plasmónicas

Current single-molecule techniques to characterize proteins typically require labels, tethers, or the use of non-native solution conditions. Such changes ...

Optical Trapping of Plasmonic Nanoparticles for In Situ Surface-Enhanced Raman Spectroscopy Characterizations

Surface-enhanced Raman spectroscopy (SERS) enables the ultrasensitive detection of analyte molecules in various applications due to the enhanced electric field of metallic nanostructures. Salt-induced silver nanoparticle aggregation is the most popular method for generating SERS-active substrates; however, it is limited by poor reproducibility, stability, and biocompatibility. The present protocol integrates optical manipulation and SERS detection to develop an efficient analytical platform to address this. A 1064 nm trapping laser and a 532 nm Raman probe laser are combined in a microscope to assemble silver nanoparticles, which generate plasmonic hotspots for in situ SERS measurements in aqueous environments. Without aggregating agents, this dynamic plasmonic silver nanoparticle assembly enables an approximately 50-fold enhancement of the analyte molecule signal. Moreover, it provides spatial and temporal control to form the SERS-active assembly in as low as 0.05 nM analyte-coated silver nanoparticle solution, which minimizes the potential perturbation for in vivo analysis. Hence, this optical trapping-integrated SERS platform holds great potential for efficient, reproducible, and stable molecular analyses in liquids, especially in aqueous physiological environments.

Optical Trapping of Plasmonic Nanoparticles for In Situ Surface-Enhanced Raman Spectroscopy Characterizations

The present protocol describes a convenient approach to integrating optical trapping and surface-enhanced Raman spectroscopy (SERS) to manipulate plasmonic nanoparticles for sensitive molecular detection. Without aggregating agents, the trapping laser assembles plasmonic nanoparticles to enhance the SERS signals of target analytes for in situ spectroscopic measurements.

Captura óptica de nanopartículas plasmónicas para caracterizaciones de espectroscopía Raman mejorada en superficie in situ

Surface-enhanced Raman spectroscopy (SERS) enables the ultrasensitive detection of analyte molecules in various applications due to the enhanced electric ...