Il sostegno finanziario da parte del CER attraverso l&#39;Advanced Investigator Grant HYMEM, dalla DFG attraverso il Nanosystems Iniziativa Monaco di Baviera (NIM) e attraverso il Sonderforschungsbereich (SFB1032), progetto A8 Si ringrazia. Siamo grati al Dr. Alexander Ohlinger, Dr. Sol Carretero-Palacios e wellness Nedev per il supporto e discussioni fruttuose.

1. Setup sperimentale <ol><li> Utilizzare un microscopio in alto a destra e un campo condensatore olio scuro con una apertura numerica (NA) = 1.2 per l&#39;illuminazione a campo scuro. Utilizzare un obiettivo di immersione in acqua con ingrandimento 100X e NA = 1.0 per le osservazioni di particelle e trapping. Utilizzare un obiettivo aria con ingrandimento 10X e una NA = 0,2 per seguire il moto del Nauplius. </li><li> Utilizzare una configurazione pinzette ottiche con un nm laser ad onda continua 1.064 accoppiato nel microscopio in alto a destra. Impostare la potenza del laser della trappola ottica a 100 mW (misurata con un misuratore di potenza dopo l&#39;obiettivo). </li><li> Utilizzare una telecamera ad alta velocità CMOS o una reflex digitale a obiettivo singolo (DSLR) per rilevare e l&#39;immagine del movimento delle particelle d&#39;oro nella trappola ottica e il movimento del Nauplius. </li><li> Utilizzare un filtro notch per evitare il laser di entrare nella camera. </li><li> Utilizzare un misuratore di potenza per misurare la potenza del laser dopo l&#39;obiettivo. </li></ol> 2. Preparazione del campione </p&gt; <ol><li> Pipettare una goccia d&#39;acqua (180 mL) su un vetrino da microscopio e posizionare il campione sul microscopio a campo scuro. </li><li> Pipettare un Nauplius da un piccolo serbatoio di acqua alla goccia d&#39;acqua. </li><li> Utilizzare un obiettivo 10X aria per osservare il movimento del Nauplius nella soluzione e registrare un flusso video. </li><li> Utilizzare una nanoparticella di oro con un diametro di 60 nm come un rivelatore di osservare il moto del fluido generato dal Nauplius. Pertanto, aggiungere 5 ml di una soluzione di particella molto diluita nella goccia d&#39;acqua, in modo che circa una particella può essere visto nel campo visivo con un obiettivo 100X immersione in acqua. </li></ol> 3. Particle inseguimento Experiment <ol><li> Trappola una nanoparticella d&#39;oro con la pinzetta ottica. Pertanto, portare il 1.064 nm laser cattura vicino a una nanoparticella d&#39;oro che si sta diffondendo in soluzione spostando il palco microscopio. Le forze ottici attraenti tirare nanoparticelle d&#39;oro verso il punto focale del secoloraggio laser e. La particella intrappolata non si sta diffondendo più e invece mantiene la sua posizione. Prendete un flusso video della nanoparticella intrappolato con la fotocamera DSLR ad un frame rate di 50 Hz per 30 sec. </li><li> Spegnere il laser della pinzetta ottica e rilasciare il nanoparticelle d&#39;oro dalla trappola. </li><li> Utilizzare un programma di monitoraggio di particelle di leggere prima la posizione della particella oro otticamente intrappolati in ogni fotogramma del flusso video. Una trasformazione di Fourier veloce (FFT) di xy-posizione della particella nel tempo rivela uno spettro di frequenza. NOTA: Qui, un &#39;IGOR PRO&#39; codice informatico angolo scritta è stato utilizzato per analizzare la posizione centrale particella nel piano xy nel tempo e per l&#39;analisi FFT. </li><li> Come alternativa ad un codice IGOR auto-scritta usare il programma liberamente disponibile &#39;Video Spot Tracker&#39; per l&#39;inseguimento della particella nel video. Utilizzare il software commerciale &#39;Origin&#39; per eseguire la trasformazione di Fourier dei dati di monitoraggio: <ol&gt; <li> Trascinare il file video per il programma aperto &#39;Video Spot Tracker&#39;. </li><li> Clic del mouse sulla particella visto nella prima immagine del flusso video e una regione circolare appare di interesse. </li><li> Scegliere &quot;simmetrico&quot; e &quot;ottimizzare&quot; nella finestra del prompt dei comandi superiore per ottimizzare il monitoraggio della particella. </li><li> Clic del mouse &quot;logging&quot; nella finestra del prompt dei comandi in alto e scegli una cartella per salvare i dati. I dati di monitoraggio saranno salvati come un foglio di calcolo di dati. </li><li> Clic del mouse &quot;il video gioco&quot; sul prompt dei comandi finestra di sinistra del programma di monitoraggio e attendere che vengono analizzati tutti i fotogrammi del video. </li><li> Chiudere il programma e aprire il foglio dati salvati con &#39;Origin&#39;. Impostare i valori di colonna come &quot;y 1&quot; e &quot;y 2&quot;. </li><li> Impostare intervalli di tempo per ogni fotogramma video come &quot;x&quot; nel foglio dati &#39;Origin&#39;. </li><li> Mark x-Posizione della colonna ed eseguire una FFT scegliendo &quot;Analisi dei dati&quot; e &quot;FFT&quot; nella finestra del prompt dei comandi in alto. Ripetere il passaggio per la colonna posizione y. </li><li> Tracciare le ampiezze del segnale FFT calcolata in x-e y-direzione rispetto alla frequenza. </li></ol></li></ol> 4. Simulazione Numerica <ol><li> Calcolare i α polarizzabilità della particella oro 60 nm utilizzando il programma informatico &#39;Mathematica&#39;. <ol><li> Utilizzare l&#39;equazione (1) per calcolare la polarizzabilità secondo Kuwata et al 16.: <img alt="Equazione 1" fo:content-width="3in" src="/files/ftp_upload/51502/51502eq1.jpg" width="300" /> (1) </li><li> Definire i seguenti tre parametri nel codice programma: il complesso funzione dielettrica dipendente dalla lunghezza d&#39;onda della particella d&#39;oro, il raggio nanoparticelle, e l&#39;indice di rifrazione del mezzo circostante. </li></ol></li><li> Utilizzare la descrizione delle eletdistribuzione di campo trica di un fascio gaussiano focalizzato secondo Agayan et al 17 per calcolare le forze ottici agiscono su una particella d&#39;oro 60 nm.: <img alt="Equazione 2" fo:content-width="4in" src="/files/ftp_upload/51502/51502eq2.jpg" width="500" /> (2) <ol><li> . Utilizzare le equazioni (3) - (6) da Agayan et al 17 per calcolare sia, il gradiente e spargendo forze che agiscono sulla particella: <img alt="Equazione 3" fo:content-width="3.5in" src="/files/ftp_upload/51502/51502eq3.jpg" width="350" /> (3) <img alt="Equazione 4" fo:content-width="3in" src="/files/ftp_upload/51502/51502eq4.jpg" width="300" /> (4) <img alt="Equazione 5" fo:content-width="5in" src="/files/ftp_upload/51502/51502eq5.jpg" width="500" /> (5) <img alt="Equazione 6" fo:content-width="3in" src="/files/ftp_upload/51502/51502eq6.jpg" width="300" /> (6) </li><li> Nel codice di programma, definire i parametri per la potenza del laser, l&#39;apertura numerica della oggettivo, e il complesso polarizzabilità della nanoparticella. </li><li> Riassumere la forza di gradiente e la forza di scattering per calcolare la forza ottica totale agente sulla particella oro in una trappola ottica. </li></ol></li><li> Simula premendo contemporaneamente &quot;Control&quot; e &quot;Enter&quot;. </li></ol>

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Gli autori dichiarano di non avere interessi finanziari in competizione.

Microscopia a campo scuro è uno strumento potente per la visualizzazione nanoparticelle di oro con dimensioni inferiori al limite di diffrazione ottica, poiché la sezione trasversale dispersione delle nanoparticelle metalliche supera la loro sezione trasversale geometrica (cfr. Figura 2A) 18. In una configurazione pinzetta, questo approccio permette anche di distinguere se solo un singolo o multiplo nanoparticelle di oro sono intrappolati dal fascio laser perché plasmonica accoppiamento tr...

Valutazione della qualità delle acque sulla base di indicatori chimici e biologici è di fondamentale importanza per ottenere informazioni sulle condizioni di stato e ambientali di un ecosistema acquatico 1-3. Metodi classici per l&#39;analisi chimica dell&#39;acqua sono basati sulle proprietà organolettiche e la determinazione dei parametri fisico-chimici. Indicatori biologici, d&#39;altra parte, sono specie animali la cui presenza e vitalità fornire indicazioni sulle condizioni ambientali e l&#39;effetto di inquinanti per un ecosistema che si verificano trovi Esempi tipici di bioindicatori sono Copepods, un gruppo di piccoli crostacei acqua, che può essere trovato in quasi ogni habitat di acqua 4,5. Osservando l&#39;attività e la vitalità di queste specie da un campione di acqua può quindi essere utilizzato per ottenere informazioni sulle condizioni complessive di un ecosistema 5. Le larve di copepodi, che sono chiamati naupli, utilizzare colpi ritmici della loro antenne (ogni larva ha tre paia di appendages al loro regione della testa) per nuotare in acqua 6. La frequenza e l&#39;intensità di questi colpi è quindi un indicatore diretto di età, fitness, e le condizioni ambientali dell&#39;animale 7-10. Eventuali indagini su tali campioni sono di solito fatto con un microscopio osservando e contando i colpi antenna del naupli direttamente. A causa delle loro dimensioni (~ 100-500 micron) 11, questo spesso richiede di fare misurazioni sia uno per uno o per fissare un unico Nauplius ad un substrato. Qui, dimostriamo un nuovo approccio per osservare l&#39;attività di Copepodo larve in campioni di acqua utilizzando un nanoparticelle d&#39;oro otticamente intrappolati come un rilevatore ultrasensibile. Pinzette ottiche sono tipicamente utilizzati da molti gruppi come strumento sperimentale multa di applicare o misurare le forze tra le molecole fino alla gamma piconewton 12-14. Più recentemente, la gamma di applicazioni per pinzette ottiche è stata ampliata per osservare vibrazioni acustiche e risolverefluttuazioni nt in mezzi liquidi monitorando il movimento di nano e microparticelle che sono confinati in una trappola ottica 15. Particelle che vengono immersi in un liquido sono sottoposti a moto browniano. All&#39;interno di una trappola ottica, tuttavia, questo movimento è parzialmente attenuato da un laser indotto, forza forte pendenza. Pertanto, la rigidità della trappola ottica e la localizzazione della particella nel fuoco del fascio laser possono essere regolati tramite la potenza del laser. Allo stesso tempo, è possibile rivelare caratteristiche circa il potenziale di cattura e di analizzare le interazioni di molecole con la particella monitorando il moto delle particelle dipendente dal tempo nella trappola. Questo approccio rende possibile la presa la frequenza, l&#39;intensità e la direzione del movimento fluidico generato da un oggetto in movimento nel suo ambiente liquido. Si dimostra come questa idea generale può essere applicato per ottenere uno spettro di frequenza del moto di un individuo Nauplius senza il requisitointerferire direttamente con il campione. Questo approccio sperimentale introduce un nuovo concetto generale per l&#39;osservazione del comportamento mobili di esemplari acquatici in un modo molto sensibile. Per le osservazioni sulle specie bioindicatori, questo potrebbe espandere l&#39;attuale metodologia per l&#39;analisi delle acque e potrebbe essere applicata per ottenere informazioni sulla salute e l&#39;integrità degli ecosistemi acquatici.

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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

Mostriamo come pinzette ottiche possono fornire uno strumento sensibile per analizzare le vibrazioni fluidici generate dal movimento dei piccoli organismi acquatici. Una singola nanoparticella di oro tenuto da una pinzetta ottica viene utilizzato come sensore per quantificare il movimento ritmico di una larva Nauplius (Artemia salina) in un campione di acqua. Ciò si ottiene sorvegliando lo spostamento dipendente dal tempo della nanoparticella intrappolato in conseguenza dell&#39;attività Nauplius. Una analisi di Fourier della posizione della nanoparticella poi produce uno spettro di frequenza che è caratteristica per il movimento delle specie osservate. Questo esperimento dimostra la capacità di questo metodo per misurare e caratterizzare l&#39;attività di piccole larve acquatiche senza l&#39;obbligo di osservare direttamente e di ottenere informazioni sulla posizione delle larve rispetto alla particella intrappolata. Nel complesso, questo approccio potrebbe dare una panoramica sulla vitalità di alcune specie si trovano in una e acquaticaCoSystem e potrebbe ampliare la gamma di metodi convenzionali per l&#39;analisi di campioni d&#39;acqua.

Una illustrazione schematica della configurazione sperimentale è mostrato nella Figura 1A. Una configurazione di campo scuro è necessario rilevare otticamente lo spostamento di una particella d&#39;oro 60 nm in una trappola ottica 15. La lunghezza d&#39;onda di 1.064 nm per il laser trapping viene scelta per garantire un confinamento stabile del rivelatore di particelle d&#39;oro 12,14. Un divisore di fascio nel microscopio viene utilizzata per focalizzare il fascio cattura attra...

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

Usiamo tracciamento ottico di nanoparticelle plasmoniche per sondare e caratterizzare i movimenti frequenza degli organismi acquatici.

Analizzando il movimento del Nauplius &#39;<em&gt; Artemia salina</em&gt; &#39;Di monitoraggio ottico di nanoparticelle plasmoniche

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

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Research

JoVE Journal

Engineering

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

10.4K Views.  Ludwig-Maximilians-Universität.  Usiamo tracciamento ottico di nanoparticelle plasmoniche per sondare e caratterizzare i movimenti frequenza degli organismi acquatici. 

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.

Metamateriali Realizzazione tramite il metodo di disegno fibra

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

Ricerca

Ingegneria

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.

Trapping ottica di nanoparticelle

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.

Valutare plasmoniche Trasporti in Current-carrying Argento Nanowires

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.

Patterning via ottici saturabili Transitions - fabbricazione e la caratterizzazione

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.

Esperimenti su ultrasuoni lubrificazione Utilizzando un tribometro piezoelettrico-assistita e Profilometro ottico

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.

Multifunzionale ibrida Fe<sub&gt; 2</sub&gt; O<sub&gt; 3</sub&gt; -Au Nanoparticelle per un efficiente riscaldamento plasmoniche

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.

Proprietà elettroattivo Polymer Nanoparticelle Esporre fototermiche

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.

L&#39;utilizzo di nanoparticelle sacrificali per eliminare gli effetti del colpo-rumore in fori di contatto fabbricato da E-litografia a fascio

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.

Plasmonico cattura e rilascio di nanoparticelle in un ambiente di monitoraggio

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.

Citometria del flusso microfluidico di imaging mediante rilevazione asimmetrica Microscopia ottica di stretching (ATOM)

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