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

Dette arbeidet støttes av NSF Divisjon for grunnutdanning (pris # 2021157) som en del av IUSE: EPJ-programmet

1. Bygging og montering av pingpongkanonen (PPC)
<ol><li>Monter alle komponentene i PPC i henhold til figur 1.</li>
	<li>Sett inn to akrylvinduer med høy klarhet i sidene av kanonen for å tillate optisk sondering over kanonens indre.<ol><li>Bor to 1/2 i hull gjennom motsatte sider av PVC nær kanonens utgang.</li>
		<li>Forbered to 1/8 i tykke akrylvinduer ved hjelp av en lasergraveringsmaskin. Last ned de tre supplerende svg-filene. MERK: Det er tre filer merket "JoV...

<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>

Vi har presentert en metode for konstruksjon av en PPC og en SSPPC sammen med optisk diagnostikk for måling av kulehastigheter og for karakterisering av støtutbredelse nær utgangen av kanonen. Standard PPC er konstruert med en 2 m seksjon på 1,5 i plan 80 PVC-rør. Røret er utstyrt med flenser i hver ende, hurtigkoblingsvakuumbeslag og akrylvinduer nær utgangen for laserdiagnostikk. Et detaljert skjema over PPC er vist i figur 1. Før avfyring settes en pingpongkule inn i kanonen, og e...

PPC er en populær fysikkdemonstrasjon som brukes til å vise det enorme lufttrykket som folk kontinuerlig blir utsatt for 1,2,3,4,5. Demonstrasjonen innebærer plassering av en pingpongball i en del av røret som har en indre diameter som er omtrent lik diameteren på ballen. Røret er forseglet i hver ende med tape og evakuert til et indre trykk på mindre enn 2 Torr. Båndet på den ene enden av røret er punktert, noe som gjør at luft kan komme inn i kanonen og får ballen til å oppleve toppakselerasjoner på ca. 5000 g. Ballen, som akselereres av atmosfærisk trykk alene, går ut av kanonen med en hastighet på ca. 300 m/s etter å ha reist 2 m.
Selv om PPC vanligvis drives som en enkel demonstrasjon av atmosfærisk trykk, er det også et apparat som viser kompleks komprimerbar strømningsfysikk, noe som har resultert i mange åpne studentprosjekter. Dynamikken til ballen påvirkes av sekundære faktorer som veggfriksjon, lekkasje av luft rundt ballen og dannelsen av sjokkbølger av den akselererende ballen. Den betydelige akselerasjonen av ballen introduserer en kompresjonsbølge med stor amplitude som beveger seg nedover røret foran ballen. Disse kompresjonene beveger seg raskere enn den lokale lydhastigheten, noe som resulterer i en brattere kompresjonsbølge og til slutt dannelse av en sjokkbølge6. Tidligere arbeid har studert den raske oppbyggingen av trykk ved utgangen av røret på grunn av refleksjonene av sjokkbølgen mellom ballen og den tapede utgangen av røret og den resulterende løsningen av båndet før utgangen av ballen2. Høyhastighets video ved hjelp av en enkeltspeil schlieren imaging teknikk har avslørt responsen av båndet til reflekterende sjokkbølger og eventuell løsrivelse av båndet ved utgangen av PPC 7,8 (Video 1). Dermed fungerer PPC både som en enkel demonstrasjon av lufttrykk som intrigerer publikum i alle aldre og som en enhet som viser kompleks væskefysikk, som kan studeres i detalj i en laboratorieinnstilling.
Med standard PPC er ping-pong-ballhastighetene begrenset av lydens hastighet. Denne grunnleggende versjonen av PPC er dekket i omfanget av dette papiret, sammen med en modifisert kanon som brukes til å øke ballen til supersoniske hastigheter. I tidligere arbeid av French et al. har supersoniske pingpong-ballhastigheter blitt oppnådd ved å utnytte trykkdrevet strømning gjennom en konvergerende divergerende dyse 9,10,11. SSPPC presentert her benytter et trykksatt (driver) rør for å gi en større trykkforskjell på pingpongballen enn det som er gitt av atmosfærisk trykk alene. En tynn polyestermembran brukes til å skille førerrøret fra det evakuerte (drevne) røret som inneholder kulen. Denne membranen sprekker under tilstrekkelig gagetrykk (vanligvis 5-70 psi, avhengig av membrantykkelsen), og akselererer dermed pingpongballen til hastigheter opp til Mach 1.4. Den supersoniske pingpongkulen produserer en stående sjokkbølge, som kan sees ved hjelp av høyhastighets skyggegrafavbildningsteknikker 7,12 (Video 2).
En laveffekt (klasse II) HeNe-laser brukes til å utføre optiske diagnostiske studier på kanonens ytelse. HeNe-laserstrålen er delt inn i to baner, med en bane som krysser gjennom et sett med akrylvinduer nær utgangen av kanonen og den andre banen krysser like forbi utgangen av kanonen. Hver bane avsluttes på en fotomottaker, og signalet vises på et tokanals oscilloskop. Oscilloskopsporet registrert under kanonens avfyring avslører informasjon om både hastigheten til den akselererte pingpongballen og de komprimerbare strømnings- og sjokkbølgene som går foran utgangen av ballen fra kanonen. Hastigheten til 40 mm diameter ping-pong ball på hvert strålested er direkte relatert til tiden ballen blokkerer strålen. Et følsomt "knivkant" støtdeteksjonsoppsett oppnås ved å dekke halvparten av detektoren med et stykke svart elektrisk tape og plassere kanten av båndet i midten av strålen2. Med dette oppsettet er små avbøyninger av He-Ne-laserstrålen, produsert av den komprimerbare strømningsinduserte indeksen for brytningsgradienter, tydelig synlige som spenningstopper på oscilloskopsporet. Sjokkbølgene som beveger seg mot kanonutgangen og de reflekterte sjokkbølgene avbøyer strålen i motsatte retninger og identifiseres derfor av enten en positiv eller negativ spenningspike.
Her gir vi instruksjoner for konstruksjon og bruk av en optimalisert PPC og SSPPC, samt optiske diagnostiske teknikker (figur 1, figur 2 og figur 3). De optiske diagnostiske teknikkene og målingene er utviklet gjennom tidligere år av studie 1,2.

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

Den tradisjonelle pingpongkanonen (PPC) er et pedagogisk apparat som skyter en pingpongball ned i et evakuert rør til nesten soniske hastigheter ved hjelp av atmosfærisk trykk alene. SSPPC, en forsterket versjon av PPC, oppnår supersoniske hastigheter ved å akselerere ballen med større enn atmosfærisk trykk. Vi gir instruksjoner for konstruksjon og bruk av en optimalisert PPC og SSPPC.
Optisk diagnostikk er implementert for å undersøke kanondynamikken. En HeNe-laser som sendes gjennom to akrylvinduer nær utgangen av røret, avsluttes på en fotomottakersensor. En mikroprosessor måler tiden strålen hindres av pingpongballen for automatisk å beregne ballens hastighet. Resultatene presenteres umiddelbart på en LCD-skjerm. 
Et optisk knivseggoppsett gir en svært følsom måte å oppdage sjokkbølger på ved å kutte av en brøkdel av HeNe-strålen ved sensoren. Sjokkbølger forårsaker brytningsinduserte avbøyninger av strålen, som observeres som små spenningstopper i det elektriske signalet fra fotomottakeren. 
Metodene som presenteres er svært reproduserbare og gir mulighet for videre undersøkelser i laboratorieinnstilling.

Her gir vi instruksjoner for konstruksjon og bruk av en PPC og en SSPPC, sammen med implementeringen av den optiske diagnostikken for sjokkkarakterisering og hastighetsmålinger. Representative eksperimentelle resultater er også gitt. De ferdige systemene til PPC og SSPPC, sammen med nødvendig tilbehør, er vist i figur 1 og figur 2. SSPPC er en forsterket versjon av PPC, hvor en drivende, trykksatt del av røret er koblet til det drevne røret til PPC. Det op...

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

Vi beskriver en metode for konstruksjon av en supersonisk pingpongkanon (SSPPC) sammen med optiske diagnostiske teknikker for måling av kulehastigheter og karakterisering av forplantende sjokkbølger under avfyring av kanonen.

Høyhastighets optisk diagnostikk av en supersonisk pingpongkanon

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 ...

Vi gir instruksjoner for å konstruere og betjene en supersonisk ping pong kanon sammen med optiske diagnostiske teknikker for å måle ballhastigheter og oppdage sjokkbølger. Det optiske knivkantoppsettet er svært følsomt for små traversavbøyninger av en laserstråle og gir et middel for å oppdage sjokkbølger forbundet med kanonen. For å begynne, koble fotomottakerne og lasermodulen ved å koble dem til en 15 volts nåværende begrenset strømforsyning og laserstrømforsyning.Fest deretter fotomottakerne til oscilloskopets to kanaler ved hjelp av BNC-kabler. For optisk diagnostisk oppsett, plasser laseren vinkelrett på den fabrikkerte kanonen med den første strålen som krysser gjennom akrylvinduene inne i røret, og den andre like utenfor kanonutgangen. Plasser svart elektrisk tape over halvparten av fotomottakersensoren, og skap et oppsett for støtdeteksjon med knivkant.For å unngå klipping, juster stråleposisjonen på knivkanten slik at grunnspenningen er omtrent 50% av maksimumet. Deretter justerer du innstillingene på oscilloskopet for å samle 20 millioner datapunkter. Bruk den vannrette skalaknappen til å angi datainnsamlingshastigheten til 500 megahertz.Vri utløserknappen for å utløse ved en spenning litt under den innstilte grunnlinjen som er oppnådd fra fotomottakeren. Før du skyter PPC, bruk øre- og øyevern. Sett en bordtenniskule inn i utgangen av kanonen og blås lett inn i enden av kanonen til den treffer vakuumbeslaget nær rørinngangen.Forsegl kanonens utgangsflens og akrylhette med to stykker firkantet tape. Forsikre deg om at laserstrålen er sentrert på knivkanten, at avtrekkeren er riktig plassert og at fangstbeholderen er sikker. Slå på vakuumpumpen for å evakuere røret til et redusert absolutt trykk på mindre enn to Torr.Når et tilstrekkelig vakuum er nådd, bruk en bredhodespiss til å punktere båndet ved inngangen. Etter avfyring, slå av vakuumpumpen og fjern eventuell gjenværende tape fra utgangsflensen og akrylhetten. For å skyte den supersoniske PPC, lukk ventilen som forbinder førerrøret til luftkompressoren og fyll luftkompressortanken.Blås ballen, som tidligere demonstrert. Etter å ha forseglet den supersoniske PPC-utgangsflensen, sett inn en tynn forhåndskuttet polyestermembran mellom to gummipakninger og plasser dem mellom kanonens driver og drevne seksjoner. Koble de to seksjonene ved hjelp av fire kamklemmer.Når trykket er redusert i røret, slipper du trykket fra luftkompressoren inn i driverrøret, slik at trykket kan øke til membranen sprekker og trykkluften i førerrøret fyller det evakuerte drevne røret. Etter supersonisk PPC-avfyring, slå av luftkompressoren og vakuumpumpen. Fjern den sprukne polyestermembranen og tapen fra kanonen.Den forplantende sjokkbølgen, reflektert gjennom kanonavfyringsprosessen, ble representert ved en spenningsendring med hensyn til tid. En positiv eller negativ pigg demonstrerer retningen til sjokkbølgen i signalet, og hastigheten ble beregnet gjennom kvadratpulsbredden, produsert av ballen som kuttet av strålen. En mikroprosessor ble brukt til å behandle signalet fra strålen som krysser rørets indre for automatisk å beregne og vise kulehastigheten nær kanonutgangen.Oscilloskopsporene demonstrerte tokanalsavfyringen av den supersoniske PPC. Det øvre sporet representerer bjelken som krysser kanonens indre, nær utgangen. Mens det nedre sporet tilsvarer strålen som krysser bordtennisballbanen etter å ha gått ut av kanonen.Et avskjæringssignal indikerte at ballen passerte og hindret hver stråle. Plottet av trykkdifferanse versus Mach-tall avslørte at 0,001 og 0,002 tommers tykke membraner brister ved tilstrekkelig trykkforskjell for å akselerere ping pong-ballen til supersonisk hastighet. Ballhastigheten var konsekvent større enn Mach 1.3 med en 0.002 tommers tykk membran.Den presenterte supersoniske ping pong-kanonen og den optiske diagnostikken vil øke verdien av kanonen, både som demonstrasjonsanordning og som apparat for påfølgende laboratorieforsøk.

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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.

Bygging og testing av Knappcelle av litium ion-batterier

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

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.

Fabrikkere Metamaterials Bruke Fiber Tegning Method

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.

Optisk fangst av Nanopartikler

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.

Bygging av en høyoppløselig mikroskop med konvensjonelle og Holografisk Optiske overlapping Capabilities

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.

High-speed Particle Bilde velocimetry nærheten Overflater

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.

Visualisering av High Speed ​​Flytende Jet Impaction på en 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 ...

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.

Fabrikasjon og drift av en Nano-Optical transportbånd

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.

Skrive Bragg Gitter i 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 ...

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.

Kompakt Lens-mindre Digital Holografisk mikroskop for MEMS inspeksjon og karakterisering

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