Name: high-speed optical diagnostics of a supersonic ping-pong cannon
Uploaded: 2023-03-24T13:10:00
Description: Watch this Scientific Journal Video about High-Speed Optical Diagnostics of a Supersonic Ping-Pong Cannon at JoVE.com

Questo lavoro è supportato dalla NSF Division of Undergraduate Education (premio # 2021157) come parte del programma IUSE: EHR

1. Costruzione e montaggio del cannone da ping-pong (PPC)
<ol><li>Assemblare tutti i componenti del PPC secondo la Figura 1.</li>
	<li>Inserire due finestre acriliche ad alta trasparenza nei lati del cannone per consentire il rilevamento ottico attraverso l'interno del cannone.<ol><li>Praticare due fori da 1/2 attraverso i lati opposti del PVC vicino all'uscita del cannone.</li>
		<li>Preparare due finestre acriliche spesse da 1/8 usando un incisore laser. Scarica i tre fi...

<ol>
	<li>Peterson, R. W., Pulford, B. N., Stein, K. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+ping-pong+cannon:+A+closer+look.">The ping-pong cannon: A closer look.</a> The Physics Teacher. 43 (1), 22-25 (2005).</li><li>Olson, G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+role+of+shock+waves+in+expansion+tube+accelerators.">The role of shock waves in expansion tube accelerators.</a> American Journal of Physics. 74 (12), 1071-1076 (2006).</li><li>Cockman, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Improved+vacuum+bazooka.">Improved vacuum bazooka.</a> The Physics Teacher. 41 (4), 246-247 (2003).</li><li>Ayars, E., Buchholtz, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+the+vacuum+cannon.">Analysis of the vacuum cannon.</a> American Journal of Physics. 72 (7), 961-963 (2004).</li><li>Thuecks, D. J., Demas, H. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Modeling+the+effect+of+air-intake+aperture+size+in+the+ping-pong+ball+cannon.">Modeling the effect of air-intake aperture size in the ping-pong ball cannon.</a> American Journal of Physics. 87 (2), 136-140 (2019).</li><li>Liepmann, H. W., Roshko, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Elements of gas dynamics. , (1957).</li><li>Settles, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Schlieren and shadowgraph techniques. , (2001).</li><li>Geisert, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+single+mirror+schlieren+optical+system.">A single mirror schlieren optical system.</a> American Journal of Physics. 52 (5), 467 (1984).</li><li>French, R. M., Gorrepati, V., Alcorta, E., Jackson, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+mechanics+of+a+ping-pong+ball+gun.">The mechanics of a ping-pong ball gun.</a> Experimental Techniques. 32 (1), 24-30 (2008).</li><li>French, M., Zehrung, C., Stratton, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+supersonic+ping-pong+gun.">A supersonic ping-pong gun.</a> arXiv. , (2013).</li><li>French, F., Choudhuri, R., Stratton, J., Zehrung, C., Huston, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+modular+supersonic+ping-pong+gun.">A modular supersonic ping-pong gun.</a> arXiv. , (2018).</li><li>Fredrick, C. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Complementary+studies+on+supersonic+nozzle+flow:+heterodyne+interferometry,+high-speed+video+shadowgraphy,+and+numerical+simulation.">Complementary studies on supersonic nozzle flow: heterodyne interferometry, high-speed video shadowgraphy, and numerical simulation.</a> WIT Transactions on Modelling and Simulation. 59, 223-234 (2015).</li></ol>

Abbiamo presentato un metodo per la costruzione di un PPC e di un SSPPC insieme alla diagnostica ottica per la misura delle velocità delle palle e per la caratterizzazione della propagazione degli urti in prossimità dell'uscita del cannone. Il PPC standard è costruito con una sezione di 2 m di 1,5 in tubo in PVC schedule 80. Il tubo è dotato di flange a ciascuna estremità, raccordi a vuoto a connessione rapida e finestre acriliche vicino all'uscita per la diagnostica laser. Uno schema dettagliato del PPC è mostrato...

Il PPC è una dimostrazione di fisica popolare utilizzata per mostrare l'immensa pressione dell'aria a cui le persone sono continuamente esposte 1,2,3,4,5. La dimostrazione prevede il posizionamento di una pallina da ping-pong in una sezione di tubo che ha un diametro interno approssimativamente uguale al diametro della palla. Il tubo viene sigillato su ciascuna estremità con nastro adesivo ed evacuato ad una pressione interna inferiore a 2 Torr. Il nastro su un'estremità del tubo viene perforato, il che consente all'aria di entrare nel cannone e fa sì che la palla subisca accelerazioni di picco di circa 5.000 g. La palla, che viene accelerata dalla sola pressione atmosferica, esce dal cannone ad una velocità di circa 300 m/s dopo aver percorso 2 m.
Sebbene il PPC sia comunemente utilizzato come una semplice dimostrazione della pressione atmosferica, è anche un apparato che esibisce una complessa fisica del flusso comprimibile, che ha portato a numerosi progetti studenteschi a tempo indeterminato. La dinamica della palla è influenzata da fattori secondari come l'attrito della parete, la perdita d'aria intorno alla palla e la formazione di onde d'urto da parte della palla in accelerazione. La sostanziale accelerazione della palla introduce un'onda di compressione di grande ampiezza che viaggia lungo il tubo davanti alla palla. Queste compressioni viaggiano più velocemente della velocità del suono locale, con conseguente irripidimento dell'onda di compressione e l'eventuale formazione di un'onda d'urto6. Il lavoro precedente ha studiato il rapido accumulo di pressione all'uscita del tubo a causa delle riflessioni dell'onda d'urto tra la sfera e l'uscita nastrata del tubo e il conseguente distacco del nastro prima dell'uscita della sfera2. Il video ad alta velocità che utilizza una tecnica di imaging schlieren a specchio singolo ha rivelato la risposta del nastro alle onde d'urto riflettenti e l'eventuale distacco del nastro all'uscita del PPC 7,8 (Video 1). Pertanto, il PPC serve sia come una semplice dimostrazione della pressione dell'aria che intriga il pubblico di tutte le età sia come un dispositivo che esibisce una complessa fisica dei fluidi, che può essere studiata in grande dettaglio in un ambiente di laboratorio.
Con il PPC standard, le velocità della pallina da ping-pong sono limitate dalla velocità del suono. Questa versione base del PPC è trattata nell'ambito di questo articolo, insieme a un cannone modificato utilizzato per spingere la palla a velocità supersoniche. In precedenti lavori di French et al., le velocità supersoniche delle palline da ping-pong sono state raggiunte utilizzando il flusso guidato dalla pressione attraverso un ugello convergente-divergente 9,10,11. L'SSPPC qui presentato utilizza un tubo pressurizzato (driver) per fornire un differenziale di pressione maggiore sulla pallina da ping-pong rispetto a quello fornito dalla sola pressione atmosferica. Un sottile diaframma in poliestere viene utilizzato per separare il tubo del driver dal tubo evacuato (guidato) contenente la sfera. Questo diaframma si rompe sotto una pressione di misura sufficiente (generalmente 5-70 psi, a seconda dello spessore del diaframma), accelerando così la pallina da ping-pong a velocità fino a Mach 1,4. La pallina da ping-pong supersonica produce un'onda d'urto stazionaria, come si può vedere utilizzando tecniche di imaging shadowgraph ad alta velocità 7,12 (Video 2).
Un laser HeNe a bassa potenza (classe II) viene utilizzato per effettuare studi diagnostici ottici sulle prestazioni del cannone. Il raggio laser HeNe è diviso in due percorsi, con un percorso che attraversa una serie di finestre acriliche vicino all'uscita del cannone e il secondo percorso che attraversa appena oltre l'uscita del cannone. Ogni percorso termina su un fotoricevitore e il segnale viene visualizzato su un oscilloscopio a doppio canale. La traccia dell'oscilloscopio registrata durante lo sparo del cannone rivela informazioni sia sulla velocità della pallina da ping-pong accelerata che sul flusso comprimibile e sulle onde d'urto che precedono l'uscita della palla dal cannone. La velocità della pallina da ping-pong da 40 mm di diametro in ogni posizione del raggio è direttamente correlata al tempo in cui la pallina blocca la trave. Una sensibile configurazione di rilevamento degli urti "a lama di coltello" si ottiene coprendo metà del rilevatore con un pezzo di nastro isolante nero e posizionando il bordo del nastro al centro del fascio2. Con questa configurazione, lievi deflessioni del raggio laser He-Ne, prodotte dall'indice comprimibile indotto dal flusso dei gradienti di rifrazione, sono chiaramente visibili come picchi di tensione sulla traccia dell'oscilloscopio. Le onde d'urto che viaggiano verso l'uscita del cannone e le onde d'urto riflesse deviano il raggio in direzioni opposte e sono, quindi, identificate da un picco di tensione positivo o negativo.
In questo articolo vengono fornite istruzioni per la costruzione e l'utilizzo di un PPC e SSPPC ottimizzato, nonché tecniche di diagnostica ottica (Figura 1, Figura 2 e Figura 3). Le tecniche diagnostiche ottiche e le misure sono state sviluppate attraverso i precedenti anni di studio 1,2.

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high-speed optical diagnostics of a supersonic ping-pong cannon

Il tradizionale cannone da ping-pong (PPC) è un apparato educativo che lancia una pallina da ping-pong lungo un tubo evacuato a velocità quasi soniche usando solo la pressione atmosferica. L'SSPPC, una versione aumentata del PPC, raggiunge velocità supersoniche accelerando la palla con una pressione superiore a quella atmosferica. Forniamo istruzioni per la costruzione e l'utilizzo di un PPC e SSPPC ottimizzato.
La diagnostica ottica è implementata allo scopo di indagare la dinamica dei cannoni. Un laser HeNe che viene inviato attraverso due finestre acriliche vicino all'uscita del tubo viene terminato su un sensore fotoricevitore. Un microprocessore misura il tempo in cui il raggio è ostruito dalla pallina da ping-pong per calcolare automaticamente la velocità della palla. I risultati vengono immediatamente presentati su un display LCD. 
Una configurazione ottica a lama di coltello fornisce un mezzo altamente sensibile per rilevare le onde d'urto tagliando una frazione del fascio HeNe sul sensore. Le onde d'urto causano deflessioni indotte dalla rifrazione del fascio, che si osservano come piccoli picchi di tensione nel segnale elettrico dal fotoricevitore. 
I metodi presentati sono altamente riproducibili e offrono l'opportunità di ulteriori indagini in un ambiente di laboratorio.

Qui, forniamo istruzioni per la costruzione e l'utilizzo di un PPC e di un SSPPC, insieme all'implementazione della diagnostica ottica per la caratterizzazione degli urti e le misurazioni della velocità. Vengono inoltre forniti risultati sperimentali rappresentativi. I sistemi completati del PPC e dell'SSPPC, insieme agli accessori necessari, sono illustrati nelle figure 1 e 2. L'SSPPC è una versione aumentata del PPC, in cui una sezione di guida e pressurizza...

Watch this Scientific Journal Video about High-Speed Optical Diagnostics of a Supersonic Ping-Pong Cannon at JoVE.com

High-Speed Optical Diagnostics of a Supersonic Ping-Pong Cannon

Descriviamo un metodo per la costruzione di un cannone da ping-pong supersonico (SSPPC) insieme a tecniche diagnostiche ottiche per la misurazione delle velocità della palla e la caratterizzazione della propagazione delle onde d'urto durante lo sparo del cannone.

Diagnostica ottica ad alta velocità di un cannone da ping-pong supersonico

The traditional ping-pong cannon (PPC) is an educational apparatus that launches a ping-pong ball down an evacuated pipe to nearly sonic speeds using ...

Forniamo istruzioni per costruire e utilizzare un cannone da ping pong supersonico insieme a tecniche diagnostiche ottiche per misurare la velocità della palla e rilevare le onde d'urto. La configurazione ottica del bordo del coltello è altamente sensibile alle piccole deflessioni trasversali di un raggio laser e fornisce un mezzo per rilevare le onde d'urto associate al cannone. Per iniziare, alimenta i ricevitori fotografici e il modulo laser collegandoli a un alimentatore a corrente limitata a 15 volt e a un alimentatore laser.Quindi, collegare i ricevitori di foto ai due canali dell'oscilloscopio utilizzando cavi BNC. Per la configurazione diagnostica ottica, posizionare il laser perpendicolarmente al cannone fabbricato con il primo raggio che attraversa le finestre acriliche all'interno del tubo e il secondo appena fuori dall'uscita del cannone. Posiziona del nastro isolante nero su metà del sensore del ricevitore fotografico, creando una configurazione di rilevamento degli urti a lama di coltello.Per evitare il clipping, regolare la posizione del fascio sul bordo del coltello in modo che la tensione di base sia circa il 50% del massimo. Quindi, regola le impostazioni sull'oscilloscopio per raccogliere 20 milioni di punti dati. Utilizzare la manopola scala orizzontale per impostare la velocità di acquisizione dati su 500 megahertz.Ruotare la manopola del grilletto per scattare a una tensione leggermente inferiore alla linea di base impostata acquisita dal ricevitore foto. Prima di sparare il PPC, indossare protezioni per orecchie e occhi. Inserire una pallina da ping pong nell'uscita del cannone e soffiare leggermente nell'estremità del cannone fino a quando non colpisce il raccordo a vuoto vicino all'ingresso del tubo.Sigillare la flangia di uscita del cannone e il cappuccio acrilico usando due pezzi di nastro quadrato. Assicurarsi che il raggio laser sia centrato sul bordo del coltello, che il grilletto sia posizionato correttamente e che il contenitore di cattura sia sicuro. Accendere la pompa per vuoto per evacuare il tubo a una pressione assoluta ridotta inferiore a due Torr.Una volta raggiunto un vuoto sufficiente, utilizzare una punta a testa larga per perforare il nastro all'ingresso. Dopo la cottura, spegnere la pompa per vuoto e rimuovere il nastro residuo dalla flangia di uscita e dal cappuccio acrilico. Per sparare il PPC supersonico, chiudere la valvola che collega il tubo del driver al compressore d'aria e riempire il serbatoio del compressore d'aria.Soffia la palla, come dimostrato in precedenza. Dopo aver sigillato la flangia di uscita supersonica in PPC, inserire un sottile diaframma in poliestere pretagliato tra due guarnizioni in gomma e posizionarle tra il driver del cannone e le sezioni guidate. Collegare le due sezioni utilizzando quattro morsetti a camme.Una volta ridotta la pressione nel tubo, rilasciare la pressione dal compressore d'aria nel tubo del driver, consentendo alla pressione di aumentare fino a quando il diaframma non si rompe e l'aria compressa all'interno del tubo del driver riempie il tubo guidato evacuato. Dopo l'accensione supersonica del PPC, spegnere il compressore d'aria e la pompa per vuoto. Rimuovere il diaframma e il nastro in poliestere rotti dal cannone.L'onda d'urto propagatrice, riflessa durante tutto il processo di sparo del cannone, era rappresentata da una variazione di tensione rispetto al tempo. Un picco positivo o negativo dimostra la direzione dell'onda d'urto nel segnale e la velocità è stata calcolata attraverso la larghezza dell'impulso quadrato, prodotta dalla palla che taglia il raggio. Un microprocessore è stato utilizzato per elaborare il segnale proveniente dal raggio trasversale all'interno del tubo per calcolare e visualizzare automaticamente la velocità della palla vicino all'uscita del cannone.Le tracce dell'oscilloscopio hanno dimostrato l'accensione a doppio canale del PPC supersonico. La traccia superiore rappresenta il raggio che attraversa l'interno del cannone, vicino all'uscita. Mentre la traccia inferiore corrisponde al raggio che attraversa il percorso della pallina da ping pong dopo essere uscito dal cannone.Un segnale di cutoff indicava che la palla passava e ostruiva ogni trave. Il grafico del differenziale di pressione rispetto al numero di Mach ha rivelato che i diaframmi spessi 0,001 e 0,002 pollici si rompono a un differenziale di pressione sufficiente per accelerare la pallina da ping pong a velocità supersonica. La velocità della palla era costantemente maggiore di Mach 1,3 con un diaframma spesso 0,002 pollici.Il cannone da ping pong supersonico presentato e la diagnostica ottica aumenteranno il valore del cannone, sia come dispositivo dimostrativo che come apparato per esperimenti di laboratorio successivi.

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SCIENTISTS IN ACTION

Construction and Testing of Coin Cells of Lithium Ion Batteries

Rechargeable lithium ion batteries have wide applications in electronics, where customers always demand more capacity and longer lifetime. Lithium ion batteries have also been considered to be used in electric and hybrid vehicles1 or even electrical grid stabilization systems2. All these applications simulate a dramatic increase in the research and development of battery materials3-7, including new materials3,8, doping9, nanostructuring10-13, coatings or surface modifications14-17 and novel binders18. Consequently, an increasing number of physicists, chemists and materials scientists have recently ventured into this area. Coin cells are widely used in research laboratories to test new battery materials; even for the research and development that target large-scale and high-power applications, small coin cells are often used to test the capacities and rate capabilities of new materials in the initial stage. 
 In 2010, we started a National Science Foundation (NSF) sponsored research project to investigate the surface adsorption and disordering in battery materials (grant no. DMR-1006515). In the initial stage of this project, we have struggled to learn the techniques of assembling and testing coin cells, which cannot be achieved without numerous help of other researchers in other universities (through frequent calls, email exchanges and two site visits). Thus, we feel that it is beneficial to document, by both text and video, a protocol of assembling and testing a coin cell, which will help other new researchers in this field. This effort represents the "Broader Impact" activities of our NSF project, and it will also help to educate and inspire students.
In this video article, we document a protocol to assemble a CR2032 coin cell with a LiCoO2 working electrode, a Li counter electrode, and (the mostly commonly used) polyvinylidene fluoride (PVDF) binder. To ensure new learners to readily repeat the protocol, we keep the protocol as specific and explicit as we can. However, it is important to note that in specific research and development work, many parameters adopted here can be varied. First, one can make coin cells of different sizes and test the working electrode against a counter electrode other than Li. Second, the amounts of C black and binder added into the working electrodes are often varied to suit the particular purpose of research; for example, large amounts of C black or even inert powder were added to the working electrode to test the "intrinsic" performance of cathode materials14. Third, better binders (other than PVDF) have also developed and used18. Finally, other types of electrolytes (instead of LiPF6) can also be used; in fact, certain high-voltage electrode materials will require the uses of special electrolytes7.

A protocol to construct and test coin cells of lithium ion batteries is described. The specific procedures of making a working electrode, preparing a counter electrode, assembling a cell inside a glovebox and testing the cell are presented.

Costruzione e collaudo di Pile Batterie agli ioni di litio

Rechargeable lithium ion batteries have wide applications in electronics, where customers always demand more capacity and longer lifetime.  Lithium ion ...

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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 ...

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 ...

High-resolution, High-speed, Three-dimensional Video Imaging with Digital Fringe Projection Techniques

Digital fringe projection (DFP) techniques provide dense 3D measurements of dynamically changing surfaces.&#160;Like the human eyes and brain, DFP uses triangulation between matching points in two views of the same scene at different angles to compute depth.&#160;However, unlike a stereo-based method, DFP uses a digital video projector to replace one of the cameras1. The projector rapidly projects a known sinusoidal pattern onto the subject, and the surface of the subject distorts these patterns in the camera&#8217;s field of view. Three distorted patterns (fringe images) from the camera can be used to compute the depth using triangulation.
Unlike other 3D measurement methods, DFP techniques lead to systems that tend to be faster, lower in equipment cost, more flexible, and easier to develop.&#160;DFP systems can also achieve the same measurement resolution as the camera.&#160;For this reason, DFP and other digital structured light techniques have recently been the focus of intense research (as summarized in1-5). Taking advantage of DFP, the graphics processing unit, and optimized algorithms, we have developed a system capable of 30&#160;Hz 3D video data acquisition, reconstruction, and display for over 300,000 measurement points per frame6,7.&#160;Binary defocusing DFP methods can achieve even greater speeds8.
Diverse applications can benefit from DFP techniques. Our collaborators have used our systems for facial function analysis9, facial animation10, cardiac mechanics studies11, and fluid surface measurements, but many other potential applications exist.&#160;This video will teach the fundamentals of DFP techniques and illustrate the design and operation of a binary defocusing DFP system.

This video describes the fundamentals of digital fringe projection techniques, which provide dense 3D measurements of dynamically changing surfaces.&#160;It also demonstrates the design and operation of a high-speed binary defocusing system based on these techniques.

Digital fringe projection (DFP) techniques provide dense 3D measurements of dynamically changing surfaces.&#160;Like the human eyes and brain, DFP uses ...

Construction of a High Resolution Microscope with Conventional and Holographic Optical Trapping Capabilities

High resolution microscope systems with optical traps allow for precise manipulation of various refractive objects, such as dielectric beads 1 or cellular organelles 2,3, as well as for high spatial and temporal resolution readout of their position relative to the center of the trap. The system described herein has one such "traditional" trap operating at 980 nm. It additionally provides a second optical trapping system that uses a commercially available holographic package to simultaneously create and manipulate complex trapping patterns in the field of view of the microscope 4,5 at a wavelength of 1,064 nm. The combination of the two systems allows for the manipulation of multiple refractive objects at the same time while simultaneously conducting high speed and high resolution measurements of motion and force production at nanometer and piconewton scale.

The system described herein employs a traditional optical trap as well as an independent holographic optical trapping line, capable of creating and manipulating multiple traps. This allows for the creation of complex geometric arrangements of refractive particles while also permitting simultaneous high-speed, high-resolution measurements of the activity of biological enzymes.

Costruzione di un microscopio ad alta risoluzione con convenzionali e Holographic Capabilities intrappolamento ottico

High resolution microscope systems with optical traps allow for precise manipulation of various refractive objects, such as dielectric beads 1 or cellular ...

High-speed Particle Image Velocimetry Near Surfaces

Multi-dimensional and transient flows play a key role in many areas of science, engineering, and health sciences but are often not well understood. The complex nature of these flows may be studied using particle image velocimetry (PIV), a laser-based imaging technique for optically accessible flows. Though many forms of PIV exist that extend the technique beyond the original planar two-component velocity measurement capabilities, the basic PIV system consists of a light source (laser), a camera, tracer particles, and analysis algorithms. The imaging and recording parameters, the light source, and the algorithms are adjusted to optimize the recording for the flow of interest and obtain valid velocity data. 
Common PIV investigations measure two-component velocities in a plane at a few frames per second. However, recent developments in instrumentation have facilitated high-frame rate (&gt; 1 kHz) measurements capable of resolving transient flows with high temporal resolution. Therefore, high-frame rate measurements have enabled investigations on the evolution of the structure and dynamics of highly transient flows. These investigations play a critical role in understanding the fundamental physics of complex flows.
A detailed description for performing high-resolution, high-speed planar PIV to study a transient flow near the surface of a flat plate is presented here. Details for adjusting the parameter constraints such as image and recording properties, the laser sheet properties, and processing algorithms to adapt PIV for any flow of interest are included.

A procedure for studying transient flows near boundaries using high-resolution, high-speed particle image velocimetry (PIV) is described here. PIV is a non-intrusive measurement technique applicable to any optically accessible flow by optimizing several parameter constraints such as the image and recording properties, the laser sheet properties, and analysis algorithms.

Alta velocità Particle Image Velocimetry prossimità di superfici

Multi-dimensional and transient flows play a key role in many areas of science, engineering, and health sciences but are often not well understood. The ...

Visualization of High Speed Liquid Jet Impaction on a Moving Surface

Two apparatuses for examining liquid jet impingement on a high-speed moving surface are described: an air cannon device (for examining surface speeds between 0 and 25 m/sec) and a spinning disk device (for examining surface speeds between 15 and 100 m/sec). The air cannon linear traverse is a pneumatic energy-powered system that is designed to accelerate a metal rail surface mounted on top of a wooden projectile. A pressurized cylinder fitted with a solenoid valve rapidly releases pressurized air into the barrel, forcing the projectile down the cannon barrel. The projectile travels beneath a spray nozzle, which impinges a liquid jet onto its metal upper surface, and the projectile then hits a stopping mechanism. A camera records the jet impingement, and a pressure transducer records the spray nozzle backpressure. The spinning disk set-up consists of a steel disk that reaches speeds of 500 to 3,000 rpm via a variable frequency drive (VFD) motor. A spray system similar to that of the air cannon generates a liquid jet that impinges onto the spinning disc, and cameras placed at several optical access points record the jet impingement. Video recordings of jet impingement processes are recorded and examined to determine whether the outcome of impingement is splash, splatter, or deposition. The apparatuses are the first that involve the high speed impingement of low-Reynolds-number liquid jets on high speed moving surfaces. In addition to its rail industry applications, the described technique may be used for technical and industrial purposes such as steelmaking and may be relevant to high-speed 3D printing.

Two experimental devices for examining liquid jet impingement on a high-speed moving surface are described: an air cannon device and a spinning disk device. The apparatuses are used to determine optimal approaches to the application of liquid friction modifier (LFM) onto rail tracks for top-of-rail friction control.

Visualizzazione di Liquid High Speed ​​Jet Occlusione su una superficie mobile

Two apparatuses for examining liquid jet impingement on a high-speed moving surface are described: an air cannon device (for examining surface speeds ...

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.

Fabbricazione e funzionamento di un nano-ottica Nastro trasportatore

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

Writing Bragg Gratings in Multicore Fibers

Fiber Bragg gratings in multicore fibers can be used as compact and robust filters in astronomical and other research and commercial applications. Strong suppression at a single wavelength requires that all cores have matching transmission profiles. These gratings cannot be inscribed using the same method as for single-core fibers because the curved surface of the cladding acts as a lens, focusing the incoming UV laser beam and causing variations in exposure between cores. Therefore we use an additional optical element to ensure that the beam shape does not change while passing through the cross-section of the multicore fiber. This consists of a glass capillary tube which has been polished flat on one side, which is then placed over the section of the fiber to be inscribed. The laser beam enters the fiber through the flat surface of the capillary tube and hence maintains its original dimensions. This paper demonstrates the improvements in core-to-core uniformity for a 7-core fiber using this method. The technique can be generalized to larger multicore fibers.

We describe a technique for inscribing identical fiber Bragg gratings into each core of a multicore fiber. This is achieved by introducing an additional surface into the optical path to mitigate lensing by the curved surface of the fiber cladding.

Scrivendo di Bragg in fibra Multicore

Fiber Bragg gratings in multicore fibers can be used as compact and robust filters in astronomical and other research and commercial applications. Strong ...

Compact Lens-less Digital Holographic Microscope for MEMS Inspection and Characterization

A micro-electro-mechanical-system (MEMS) is a widely used component in many industries, including energy, biotechnology, medical, communications, and automotive. However, effective inspection and characterization metrology systems are needed to ensure the functional reliability of MEMS. This study presents a system based on digital holography as a tool for MEMS metrology. Digital holography has gained increasing attention in the past 20 years. With the fast development and decreasing cost of sensor arrays, resolution of such systems has increased broadening potential applications. Thus, it has attracted attention from both research and industry sides as a potential reliable tool for industrial metrology. Indeed, by recording the interference pattern between an object beam (which contains sample height information) and a reference beam on a CCD camera, one can retrieve the quantitative phase information of an object. However, most of digital holographic systems are bulky and thus not easy to implement on industry production lines. The novelty of the system presented is that it is lens-less and thus very compact. In this study, it is shown that the Compact Digital Holographic Microscope (CDHM) can be used to evaluate several characteristics typically consider as criteria in MEMS inspections. The surface profiles of MEMS in both static and dynamic conditions are presented. Comparison with AFM is investigated to validate the accuracy of the CDHM.

We present a compact reflection digital holographic system (CDHM) for inspection and characterization of MEMS devices. A lens-less design using a diverging input wave providing natural geometrical magnification is demonstrated. Both static and dynamic studies are presented.

Lens-meno compatta digitale olografico microscopio per MEMS di ispezione e caratterizzazione

A micro-electro-mechanical-system (MEMS) is a widely used component in many industries, including energy, biotechnology, medical, communications, and ...