Ringraziamo A. Sharoni da Bar-Ilan University per la fornitura dei film superconduttori. Questa ricerca è stata sostenuta dal Consiglio europeo della ricerca sovvenzione CER-2014-STG- 639792, integrazione Marie Curie Career Grant FP7-PEOPLE-2012-CIG-333.799, e Israele Science Foundation Grant ISF-1102/13.

1. L&#39;accesso a un sistema di scansione SQUID <ol><li> Utilizzare un sistema SQUID di scansione che comprende un sensore SQUID fabbricato su un chip 9, 10, stick slip fase di movimento grossolana, e uno scanner piezo-based per motion fine. Vedere la Figura 1. </li><li> Lucidare il chip SQUID in un angolo intorno al ciclo pickup. Il materiale del chip deve essere rimosso fino al prelievo del cappio. <ol><li> lucidare delicatamente il SQUID, utilizzando una carta di lucidatura 5-0,5 micron non magnetico. NOTA: Dopo la fase di lucidatura del ciclo pick-up può essere portato in prossimità, o contatto, con il campione. </li></ol></li></ol> 2. Deposizione di niobio (Nb) Thin Film con corrente continua (DC) di polverizzazione <ol><li> Ottenere un substrato. In questo lavoro, utilizzare un substrato di silicio di boro drogato con 500 nm di ossido di silicio. Altri substrati come SrTiO e MgO sono possibili. </li><li> Raggiungere una base di PRESSUre di 10 -7 Torr nella camera. Pre-sputter camera di evaporazione a temperatura ambiente con un obiettivo Nb 99,95%, in ambiente argon ad una pressione di 2,4 mTorr con una velocità di deposizione di 1,8 Å / s per 10 min. Si noti che il processo di deposizione può iniziare solo quando la pressione nella camera di base è inferiore a 10 -7 Torr. Se la pressione è più alta ripetere la fase di pre-sputtering. </li><li> Posizionare substrato nella camera. </li><li> Deposito Nb film sottile per sputtering a temperatura ambiente su un bersaglio Nb 99,95%, in ambiente argon ad una pressione di 2,4 mTorr con una velocità di deposizione di 1,8 Å / s. </li></ol> 3. Il campione-tip Allineamento <ol><li> In questa fase, allineare il sensore chip con il campione in modo che la punta del chip entra in contatto con il campione che si spostano i vortici. Per ottenere questo, utilizzare un angolo di allineamento di almeno 4 °. </li><li> Colla un cantilever flessibile su una piastra di condotta con uno strato dielettrico. Quindi, incollare il chi SQUIDp sul cantilever. La capacità tra il cantilever e una piastra statico determina il contatto con il campione e la portata della sollecitazione applicata. </li><li> campione del carico sul microscopio. Incollare il campione ad un campione designato montaggio utilizzando una pasta vernice o argento. Incollare il supporto per l&#39;elemento Z piezoelettrico (Figura 1a). </li><li> Collegare il sistema di movimento grossolano stick slip a un controller. </li><li> Impostare imaging ottico da due angolazioni - parte anteriore e il lato del chip. Utilizzare due telescopi posti su fasi di traduzione, diretto verso la parte anteriore del chip e uno dei suoi lati. </li><li> Utilizzando il stick slip fase di movimento grossolani Z, spostare il campione ad una distanza di 1 micron dal sensore, in modo che la riflessione del sensore è visibile sul campione. NOTA: Il contatto tra il campione e il sensore in questa fase possono danneggiare la SQUID. </li><li> Spostare il campione di 0,5 - 1 mm di distanza dal sensore utilizzando la fase Z stick slip movimento grossolana per evitare di danneggiare l&#39;SQUID. </li><li> Ruotare le viti di allineamento (Figura 1a) per ottenere angoli anteriori uguali (cioè, angoli ai lati della punta del chip fanno con la sua riflessione, come si vede in Figura 1c). </li><li> Spostare il campione ad una distanza di 1 micron dal sensore. Controllare gli angoli e ripetere il punto 3.7 e 3.8, se necessario. </li><li> Ruotare le viti di allineamento per ottenere un angolo di 4 gradi tra il sensore e il campione (Figura 1d). Assicurarsi che la punta del chip è la parte che entra in contatto con il campione. </li></ol> 4. Misure <ol><li> Caricare la testa di scansione (Figura 1a) ad un sistema 4 K raffreddamento. NOTA: Testina di scansione deve essere collegato a un piatto freddo, e circondato da una lattina di vuoto. Collegare una bobina attorno alla latta di applicazione di campo magnetico esterno (bassi campi di vari Gauss sono sufficienti per questo studio). Coprire questa configurazione con uno scudo Mu-metal. </li><li> Raffreddare in presenza di magnecampo tic, applicando corrente attraverso la bobina che circonda il microscopio. Scegliere accuratamente l&#39;intensità di campo per ottenere la densità desiderata vortex. Utilizzare 1Φ 0 = 20,7 G / micron 2 per calcolare il campo cooldown. Ad esempio, per 10 vortici in 10 micron dalla superficie 10 um, applicano 2.07 G. </li><li> Per il passaggio ad un nuovo campione di calore densità vortice di sopra della temperatura di transizione superconduttore (per NB, di calore superiore a 10 K). Applicare il nuovo campo. </li><li> Raffreddare campione a 4,2 K. </li><li> Girare campo magnetico fuori. Accendere SQUID su. </li><li> Spostare il campione vicino al SQUID utilizzando il sistema di movimento grossolano stick slip. <ol><li> Applicare tensioni crescenti sul cubo Z-stick slip per spostare il campione più vicino al chip SQUID. </li><li> Applicare la tensione tra la mensola e la piastra per leggere la capacità utilizzando un ponte capacità (0,1-1 V tipicamente). </li><li> Sweep la tensione sull&#39;elemento Z piezoelettrico. Misurare la capacità tra la mensola e la piattaformae. Se si verifica una grande variazione della capacità, il campione è in contatto con il chip SQUID. </li><li> Se il campione non ha fatto il contatto con il chip, ripetere i punti 4.6.1-4.6.3 fino a quando si osserva il contatto. </li><li> Opzionale: Utilizzare motion corso per regolare la distanza tra la punta e il campione in modo che il contatto avviene a basse tensioni (0 - 10 V applicata al piezo Z). </li><li> Una volta che vi sia un contatto, ripetere i punti 4.6.2-4.6.3 in diverse posizioni per determinare gli angoli di inclinazione della superficie e per definire il piano del campione, rispetto al sensore. </li></ol></li><li> Sweep la tensione sugli elementi X e Y piezoelettrici per spostare il campione rispetto al sensore. Scansione ad un&#39;altezza costante sopra il campione, senza contatto tra la punta e il campione, per mappare la distribuzione vortice. Ottenere una altezza scansione costante variando la tensione sul piezo Z secondo le posizioni X e Y, e al piano definito in 4.6. </li><li> Scegli un vortice e scansione arouND di determinare con precisione la posizione del suo centro. Si noti che la posizione vortice è relativo al prelievo del cappio del SQUID, non al punto di contatto. </li><li> Girare SQUID off. </li><li> Applicare una tensione che è superiore alla tensione touchdown alla z piezo eo rubinetto vicino al centro del vortice o spazzare il vortice trascinando il sensore (a contatto con il campione) lentamente il campione ad una posizione desiderata. Il vortice si muoverà verso il rubinetto o in senso ampio. Valori tipici per aggiungere alla tensione piezo z applicata sono 2-5 V. </li><li> Accendere SQUID su. </li><li> Immagine nuovamente ad un&#39;altezza costante senza contatto per individuare la nuova posizione del vortice. </li></ol>

<ol>
	<li>Olson Reichhardt, C. J., Hastings, M. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Do+Vortices+Entangle?.">Do Vortices Entangle?.</a> Phys. Rev. Lett. 92, 157002 (2004).</li><li>Milo&#353;evi&#263;, M. V., Berdiyorov, G. R., Peeters, F. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fluxonic+cellular+automata.">Fluxonic cellular automata.</a> Appl. Phys. Lett. 91, 212501 (2007).</li><li>Kalisky, B., 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=Scanning+Probe+Manipulation+of+Magnetism+at+the+LaAlO3/SrTiO3+Heterointerface.">Scanning Probe Manipulation of Magnetism at the LaAlO3/SrTiO3 Heterointerface.</a> Nano Lett. 12, 4055-4059 (2012).</li><li>Silva, C. C. D. S., Van de Vondel, J., Morelle, M., Moshchalkov, V. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Controlled+multiple+reversals+of+a+ratchet+effect.">Controlled multiple reversals of a ratchet effect.</a> Nature. 440, 651-654 (2006).</li><li>Kalisky, B., 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=Dynamics+of+single+vortices+in+grain+boundaries:+I-V+characteristics+on+the+femtovolt+scale.">Dynamics of single vortices in grain boundaries: I-V characteristics on the femtovolt scale.</a> Appl. Phys. Lett. 94, 202504 (2009).</li><li>Embon, L., 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=Probing+dynamics+and+pinning+of+single+vortices+in+superconductors+at+nanometer+scales.">Probing dynamics and pinning of single vortices in superconductors at nanometer scales.</a> Sci. Rep. 5, 7598 (2015).</li><li>Auslaender, O. M., 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=Mechanics+of+individual+isolated+vortices+in+a+cuprate+superconductor.">Mechanics of individual isolated vortices in a cuprate superconductor.</a> Nature Phys. 5, 35-39 (2008).</li><li>Kalisky, B., 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=Behavior+of+vortices+near+twin+boundaries+in+underdoped+Ba(Fe1-xCox)2As2.">Behavior of vortices near twin boundaries in underdoped Ba(Fe1-xCox)2As2.</a> Phys. Rev. B. 83, 064511 (2011).</li><li>Huber, M. E., 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=Gradiometric+micro-SQUID+susceptometer+for+scanning+measurements+of+mesoscopic+samples.">Gradiometric micro-SQUID susceptometer for scanning measurements of mesoscopic samples.</a> Rev. Sci. Instrum. 79, 053704 (2008).</li><li>Koshnick, N. C., 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=A+terraced+scanning+super+conducting+quantum+interference+device+susceptometer+with+submicron+pickup+loops.">A terraced scanning super conducting quantum interference device susceptometer with submicron pickup loops.</a> Appl. Phys. Lett. 93, 243101 (2008).</li><li>Kremen, A., 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=Mechanical+Control+of+Individual+Superconducting+Vortices.">Mechanical Control of Individual Superconducting Vortices.</a> Nano Lett. 16, 1626-1630 (2016).</li></ol>

The authors have nothing to disclose.

manipolazione di successo di vortici dipende da diversi passaggi critici. È importante allineare il sensore ad un angolo, in modo che la punta del chip sarà il primo a fare contatto con il campione. In secondo luogo, è importante notare che la forza esercitata sul campione è determinata dalle proprietà meccaniche del cantilever che il chip è montato. Nel regime elastica, la forza applicata è proporzionale alla deflessione, x, secondo la legge di Hooke: F = -kx Se k è la costan...

Vortici sono oggetti magnetici su scala nanometrica, costituite tipo 2 superconduttori in presenza di campo magnetico esterno. In un campione privo di difetti, vortici possono muoversi liberamente. Tuttavia, diversi difetti nel risultato materiale in regioni di superconduttività ridotta che sono energeticamente favorevole per vortici. Vortici tendono a decorare queste regioni, noti anche come i siti di pinning. In questo caso, la forza necessaria per spostare un vortice deve essere maggiore della forza pinning. Proprietà di vortici, come la densità vortice, forza di interazione e gamma, possono essere facilmente determinati dal campo esterno, la temperatura o la geometria del campione. La capacità di controllare queste proprietà loro un buon sistema modello per il comportamento materia condensata che può essere facilmente regolato, nonché idonei per applicazioni elettroniche 1, 2 rende. Il controllo della posizione dei singoli vortici è essenziale per la progettazione di tale loElementi gici. Controllo meccanico delle nanoparticelle magnetiche era stato raggiunto prima. Kalisky et al. recentemente utilizzato scansione superconduttori dispositivo interferenza quantistica (SQUID) per studiare l&#39;influenza di stress meccanico locale sulla patch ferromagnetici nelle interfacce di ossidi complessi 3. Sono stati in grado di cambiare l&#39;orientamento del patch di scansione a contatto, premendo la punta del SQUID nel campione, applicando una forza di fino a 1 μN nel processo. Abbiamo usato un metodo simile nel nostro protocollo per spostare vortici. In studi esistenti di manipolazione vortice, movimento è stata ottenuta applicando corrente al campione, creando così Lorentz forza 4, 5, 6. Mentre questo metodo è efficace, non è locale, e per controllare un singolo vortice, è necessaria fabbricazione aggiuntivo. Vortici possono anche essere manipulated applicando campo magnetico esterno, per esempio con un microscopio a forza magnetica (MFM) o con una bobina di campo SQUID 7, 8. Questo metodo è efficace e locale, ma la forza applicata da questi strumenti è piccola, e può superare la forza pinning solo ad alte temperature, vicino alla temperatura critica del superconduttore. Il nostro protocollo permette efficace, manipolazione locale a basse temperature (4 K) senza ulteriore realizzazione del campione. Abbiamo vortici di immagini usando la microscopia a scansione SQUID. Il sensore è fabbricato in un chip di silicio che è lucidato in un angolo, e incollato su un cantilever flessibile. Il cantilever viene utilizzato per il rilevamento capacitivo della superficie. Il chip è posto ad un angolo al campione, in modo che il punto di contatto è sulla punta del chip. Applichiamo forze fino a 2 μN spingendo il chip nel campione. Si passa il campione relativo al SQUID da elementi piezoelettrici. Ci muoviamoil vortice toccando la punta di silicio accanto ad un vortice, o da spazzare esso, toccando il vortice.

<table><tbody><tr><td>stick slip coarse motion system</td><td>attocube</td><td>ANPx-101</td><td>x,y motion</td></tr><tr><td>stick slip coarse motion system</td><td>attocube</td><td>ANPz-101</td><td>z motion</td></tr><tr><td>stick slip coarse motion system controller</td><td>Attocube</td><td>ANC 300</td><td></td></tr><tr><td>high voltage amplifier</td><td>Attocube</td><td>ANC 250</td><td></td></tr><tr><td>data acquisition card</td><td>National Instruments</td><td>NI&amp;nbsp;PCIe-6363</td><td></td></tr><tr><td>piezo elements</td><td>Piezo Systems Inc</td><td>T2C</td><td>non magnetic</td></tr><tr><td>low noise voltage preamplifier</td><td>Stanford Research Systems</td><td>SR 560</td><td></td></tr><tr><td>capacitance bridge</td><td>General Radio</td><td>1615A</td><td></td></tr><tr><td>telescope</td><td>NAVITAR</td><td>1-504516</td><td></td></tr><tr><td>camera</td><td>MOTICAM</td><td>MP2</td><td></td></tr><tr><td>dewar</td><td>Cryofab</td><td>N/A</td><td></td></tr><tr><td>insert</td><td>ICE oxford</td><td>N/A</td><td></td></tr><tr><td>Mu-metal shield</td><td>Amuneal</td><td>N/A</td><td></td></tr><tr><td>vacuum cap</td><td>ICE oxford</td><td>N/A</td><td></td></tr><tr><td>sputtering system</td><td>AJA international Inc</td><td>N/A</td><td></td></tr><tr><td>lapping film</td><td>3M</td><td>261X</td><td>non magnetic</td></tr><tr><td>Nb target</td><td>Kurt J. Lesker</td><td>EJTNBXX351A2</td><td></td></tr><tr><td>GE Varnish</td><td>CMR-Direct</td><td>02-33-001</td><td>for cryogenic heatsinking</td></tr><tr><td>Silver paste</td><td>Structure Probe Inc</td><td>05063-AB</td><td></td></tr></tbody></table>

scanning squid study of vortex manipulation by local contact

Local, deterministic manipulation of individual vortices in type 2 superconductors is challenging. The ability to control the position of individual vortices is necessary in order to study how vortices interact with each other, with the lattice, and with other magnetic objects. Here, we present a protocol for vortex manipulation in thin superconducting films by local contact, without applying current or magnetic field. Vortices are imaged using a scanning superconducting quantum interference device (SQUID), and vertical stress is applied to the sample by pushing the tip of a silicon chip into the sample, using a piezoelectric element. Vortices are moved by tapping the sample or sweeping it with the silicon tip. Our method allows for effective manipulation of individual vortices, without damaging the film or affecting its topography. We demonstrate how vortices were relocated to distances of up to 0.8 mm. The vortices remained stable at their new location up to five days. With this method, we can control vortices and move them to form complex configurations. This technique for vortex manipulation could also be implemented in applications such as vortex based logic devices.

Il nostro protocollo è stato testato con successo su migliaia di singoli, vortici ben separati in due campioni di Nb, e nove campioni di NbN. Noi generiamo nuovi vortici sullo stesso campione riscaldando il campione sopra Tc, e raffreddamento di nuovo a 4,2 K in presenza di un campo magnetico. Abbiamo scelto il campo magnetico esterno per ottenere la densità desiderata vortex. Mostriamo qui i dati da questi esperimenti. Questi risultati sono stati descritti in dettaglio da Kremen e...

Watch this Scientific Journal Video about Scanning SQUID Study of Vortex Manipulation by Local Contact at JoVE.com

Scanning SQUID Study of Vortex Manipulation by Local Contact

We present a protocol for manipulation of individual vortices in thin superconducting films, using local mechanical contact. The method does not include applying current, magnetic field or additional fabrication steps.

La scansione SQUID Studio di Vortex manipolazione da locale Contatto

Local, deterministic manipulation of individual vortices in type 2 superconductors is challenging. The ability to control the position of individual ...

scanning-squid-study-of-vortex-manipulation-by-local-contact

Research

JoVE Journal

Engineering

6.8K Views.  Bar-Ilan University. We present a protocol for manipulation of individual vortices in thin superconducting films, using local mechanical contact. The method does not include applying current, magnetic field or additional fabrication steps. 

Video: Scanning SQUID Study of Vortex Manipulation by Local Contact

Quantitatively Measuring In situ Flows using a Self-Contained Underwater Velocimetry Apparatus (SCUVA)

The ability to directly measure velocity fields in a fluid environment is necessary to provide empirical data for studies in fields as diverse as oceanography, ecology, biology, and fluid mechanics. Field measurements introduce practical challenges such as environmental conditions, animal availability, and the need for field-compatible measurement techniques. To avoid these challenges, scientists typically use controlled laboratory environments to study animal-fluid interactions. However, it is reasonable to question whether one can extrapolate natural behavior (i.e., that which occurs in the field) from laboratory measurements. Therefore, in situ quantitative flow measurements are needed to accurately describe animal swimming in their natural environment.
We designed a self-contained, portable device that operates independent of any connection to the surface, and can provide quantitative measurements of the flow field surrounding an animal. This apparatus, a self-contained underwater velocimetry apparatus (SCUVA), can be operated by a single scuba diver in depths up to 40 m. Due to the added complexity inherent of field conditions, additional considerations and preparation are required when compared to laboratory measurements. These considerations include, but are not limited to, operator motion, predicting position of swimming targets, available natural suspended particulate, and orientation of SCUVA relative to the flow of interest. The following protocol is intended to address these common field challenges and to maximize measurement success.

Quantitatively Measuring In situ Flows using a Self-Contained Underwater Velocimetry Apparatus SCUVA

This protocol provides instructions on how to use a self-contained underwater velocimetry apparatus (SCUVA), which is designed for quantification of in situ animal-generated flows. In addition, this protocol addresses challenges posed by field conditions, and includes operator motion, predicting position of animals, and orientation of SCUVA.

Misura quantitativamente In situ Flussi utilizzando un autorespiratore subacqueo Velocimetry (SCUVA)

The ability to directly measure velocity fields in a fluid environment is necessary to provide empirical data for studies in fields as diverse as ...

Ricerca

Bioingegneria

Quantitative and Qualitative Examination of Particle-particle Interactions Using Colloidal Probe Nanoscopy

Colloidal Probe Nanoscopy (CPN), the study of the nano-scale interactive forces between a specifically prepared colloidal probe and any chosen substrate using the Atomic Force Microscope (AFM), can provide key insights into physical interactions present within colloidal systems. Colloidal systems are widely existent in several applications including, pharmaceuticals, foods, paints, paper, soil and minerals, detergents, printing and much more.1-3 Furthermore, colloids can exist in many states such as emulsions, foams and suspensions. Using colloidal probe nanoscopy one can obtain key information on the adhesive properties, binding energies and even gain insight into the physical stability and coagulation kinetics of the colloids present within. Additionally, colloidal probe nanoscopy can be used with biological cells to aid in drug discovery and formulation development. In this paper we describe a method for conducting colloidal probe nanoscopy, discuss key factors that are important to consider during the measurement, and show that both quantitative and qualitative data that can be obtained from such measurements.

Colloidal probe nanoscopy can be used within a variety of fields to gain insight into the physical stability and coagulation kinetics of colloidal systems and aid in drug discovery and formulation sciences using biological systems. The method described within provides a quantitative and qualitative means to study such systems.

Esame quantitativa e qualitativa delle interazioni particella-particella colloidale Uso Probe Nanoscopia

Colloidal Probe Nanoscopy (CPN), the study of the nano-scale interactive forces between a specifically prepared colloidal probe and any chosen substrate ...

Chimica

Methods for Measuring the Orientation and Rotation Rate of 3D-printed Particles in Turbulence

Experimental methods are presented for measuring the rotational and translational motion of anisotropic particles in turbulent fluid flows. 3D printing technology is used to fabricate particles with slender arms connected at a common center. Shapes explored are crosses (two perpendicular rods), jacks (three perpendicular rods), triads (three rods in triangular planar symmetry), and tetrads (four arms in tetrahedral symmetry). Methods for producing on the order of 10,000 fluorescently dyed particles are described. Time-resolved measurements of their orientation and solid-body rotation rate are obtained from four synchronized videos of their motion in a turbulent flow between oscillating grids with R&#955; = 91. In this relatively low-Reynolds number flow, the advected particles are small enough that they approximate ellipsoidal tracer particles. We present results of time-resolved 3D trajectories of position and orientation of the particles as well as measurements of their rotation rates.

We use 3D printing to fabricate anisotropic particles in the shapes of jacks, crosses, tetrads, and triads, whose alignments and rotations in turbulent fluid flow can be measured from multiple simultaneous video images.

Metodi per misurare l&#39;orientamento e rotazione Tasso di particelle in turbolenza 3D-stampati

Experimental methods are presented for measuring the rotational and translational motion of anisotropic particles in turbulent fluid flows. 3D printing ...

Ingegneria

Hand Controlled Manipulation of Single Molecules via a Scanning Probe Microscope with a 3D Virtual Reality Interface

Considering organic molecules as the functional building blocks of future nanoscale technology, the question of how to arrange and assemble such building blocks in a bottom-up approach is still open. The scanning probe microscope (SPM) could be a tool of choice; however, SPM-based manipulation was until recently limited to two dimensions (2D). Binding the SPM tip to a molecule at a well-defined position opens an opportunity of controlled manipulation in 3D space. Unfortunately, 3D manipulation is largely incompatible with the typical 2D-paradigm of viewing and generating SPM data on a computer. For intuitive and efficient manipulation we therefore couple a low-temperature non-contact atomic force/scanning tunneling microscope (LT NC-AFM/STM) to a motion capture system and fully immersive virtual reality goggles. This setup permits &#34;hand controlled manipulation&#34; (HCM), in which the SPM tip is moved according to the motion of the experimenter&#39;s hand, while the tip trajectories as well as the response of the SPM junction are visualized in 3D. HCM paves the way to the development of complex manipulation protocols, potentially leading to a better fundamental understanding of nanoscale interactions acting between molecules on surfaces. Here we describe the setup and the steps needed to achieve successful hand-controlled molecular manipulation within the virtual reality environment.

We demonstrate the precise manipulation of individual organic molecules on a metal surface with the tip of a scanning probe microscope driven in 3D by the experimenter's hand using a motion capture system and fully immersive virtual reality goggles.

A mano controllata manipolazione di singole molecole attraverso un microscopio a scansione di sonda con una realtà virtuale 3D

Considering organic molecules as the functional building blocks of future nanoscale technology, the question of how to arrange and assemble such building ...

Investigating the Three-dimensional Flow Separation Induced by a Model Vocal Fold Polyp

The fluid-structure energy exchange process for normal speech has been studied extensively, but it is not well understood for pathological conditions. Polyps and nodules, which are geometric abnormalities that form on the medial surface of the vocal folds, can disrupt vocal fold dynamics and thus can have devastating consequences on a patient&#39;s ability to communicate. Our laboratory has reported particle image velocimetry (PIV) measurements, within an investigation of a model polyp located on the medial surface of an in&#160;vitro driven vocal fold model, which show that such a geometric abnormality considerably disrupts the glottal jet behavior. This flow field adjustment is a likely reason for the severe degradation of the vocal quality in patients with polyps. A more complete understanding of the formation and propagation of vortical structures from a geometric protuberance, such as a vocal fold polyp, and the resulting influence on the aerodynamic loadings that drive the vocal fold dynamics, is necessary for advancing the treatment of this pathological condition. The present investigation concerns the three-dimensional flow separation induced by a wall-mounted prolate hemispheroid with a 2:1 aspect ratio in cross flow, i.e. a model vocal fold polyp, using an oil-film visualization technique. Unsteady, three-dimensional flow separation and its impact of the wall pressure loading are examined using skin friction line visualization and wall pressure measurements.

Vocal fold polyps can disrupt vocal fold dynamics and thus can have devastating consequences on a patient&#39;s ability to communicate. Three-dimensional flow separation induced by a wall-mounted model polyp and its impact on the wall pressure loading are examined using particle image velocimetry, skin friction line visualization, and wall pressure measurements.

Investigare la separazione tridimensionale del flusso indotta da un modello di polipo piega vocale

The fluid-structure energy exchange process for normal speech has been studied extensively, but it is not well understood for pathological conditions. ...

Visualization of Flow Field Around a Vibrating Pipeline Within an Equilibrium Scour Hole

An experimental method is presented in this paper to facilitate visualization of the detailed flow fields and determination of the near-boundary shear and normal stresses within an equilibrium scour hole induced by a vibrating pipeline. This method involves the implementation of a pipeline vibration system in a straight flume, a time-resolved particle image velocimetry (PIV) system for pipeline displacement tracking and flow fields measurements. The displacement time-series of the vibrating pipeline are obtained by using the cross-correlation algorithms. The steps for processing raw particle laden images obtained by using the time-resolved PIV are described. The detailed instantaneous flow fields around the vibrating pipeline at different vibrating phases are calculated by using a multiple-time-interval cross-correlation algorithm to avoid displacement bias error in the flow regions with a large velocity gradient. By applying the wavelet transform technique, the captured images that have the same vibrating phase are accurately cataloged before the phase-averaged velocity fields are obtained. The key advantages of the flow measurement technique described in this paper are that it has a very high temporal and spatial resolution and can be simultaneously used to obtain the pipeline dynamics, flow fields, and near-boundary flow stresses. By using this technique, more in-depth studies of the 2-dimensional flow field in a complex environment, such as that around a vibrating pipeline, can be conducted to better understand the associated sophisticated scour mechanism.

The goal of the protocol is to enable visualization of the detailed flow fields and determination of the near-boundary shear and normal stresses within an equilibrium scour hole induced by a vibrating pipeline.

Visualizzazione del campo di flusso intorno a una pipeline vibrante all'interno di un foro di equilibrio

An experimental method is presented in this paper to facilitate visualization of the detailed flow fields and determination of the near-boundary shear and ...

Ambiente

Fabrication of Magnetic Nanostructures on Silicon Nitride Membranes for Magnetic Vortex Studies Using Transmission Microscopy Techniques

Electron and x-ray magnetic microscopies allow for high-resolution magnetic imaging down to tens of nanometers. However, the samples need to be prepared on transparent membranes which are very fragile and difficult to manipulate. We present processes for the fabrication of samples with magnetic micro- and nanostructures with spin configurations forming magnetic vortices suitable for Lorentz transmission electron microscopy and magnetic transmission x-ray microscopy studies. The samples are prepared on silicon nitride membranes and the fabrication consists of a spin coating, UV and electron-beam lithography, the chemical development of the resist, and the evaporation of the magnetic material followed by a lift-off process forming the final magnetic structures. The samples for the Lorentz transmission electron microscopy consist of magnetic nanodiscs prepared in a single lithography step. The samples for the magnetic x-ray transmission microscopy are used for time-resolved magnetization dynamic experiments, and magnetic nanodiscs are placed on a waveguide which is used for the generation of repeatable magnetic field pulses by passing an electric current through the waveguide. The waveguide is created in an extra lithography step.

A protocol for the fabrication of magnetic micro- and nanostructures with spin configurations forming magnetic vortices suitable for transmission electron microscopy (TEM) and magnetic transmission x-ray microscopy (MTXM) studies is presented.

Fabbricazione di nanostrutture magnetiche sulle membrane di nitruro di silicio per studi di vortice magnetico utilizzando tecniche di microscopia di trasmissione

Electron and x-ray magnetic microscopies allow for high-resolution magnetic imaging down to tens of nanometers. However, the samples need to be prepared ...

Direct Force Measurements of Subcellular Mechanics in Confinement using Optical Tweezers

During the development of a multicellular organism, a single fertilized cell divides and gives rise to multiple tissues with diverse functions. Tissue morphogenesis goes in hand with molecular and structural changes at the single cell level that result in variations of subcellular mechanical properties. As a consequence, even within the same cell, different organelles and compartments resist differently to mechanical stresses; and mechanotransduction pathways can actively regulate their mechanical properties. The ability of a cell to adapt to the microenvironment of the tissue niche thus is in part due to the ability to sense and respond to mechanical stresses. We recently proposed a new mechanosensation paradigm in which nuclear deformation and positioning enables a cell to gauge the physical 3D environment and endows the cell with a sense of proprioception to decode changes in cell shape. In this article, we describe a new method to measure the forces and material properties that shape the cell nucleus inside living cells, exemplified on adherent cells and mechanically confined cells. The measurements can be performed non-invasively with optical traps inside cells, and the forces are directly accessible through calibration-free detection of light momentum. This allows measuring the mechanics of the nucleus independently from cell surface deformations and allowing dissection of exteroceptive and interoceptive mechanotransduction pathways. Importantly, the trapping experiment can be combined with optical microscopy to investigate the cellular response and subcellular dynamics using fluorescence imaging of the cytoskeleton, calcium ions, or nuclear morphology. The presented method is straightforward to apply, compatible with commercial solutions for force measurements, and can easily be extended to investigate the mechanics of other subcellular compartments, e.g., mitochondria, stress-fibers, and endosomes.

Here, we present a protocol to investigate the intracellular mechanical properties of isolated embryonic zebrafish cells in three-dimensional confinement with direct force measurement by an optical trap.

Misure di forza diretta della meccanica subcellulare nel confinamento mediante pinzette ottiche

During the development of a multicellular organism, a single fertilized cell divides and gives rise to multiple tissues with diverse functions. Tissue ...

Biologia dello sviluppo

Using a Microfluidics Device for Mechanical Stimulation and High Resolution Imaging of C. elegans

One central goal of mechanobiology is to understand the reciprocal effect of mechanical stress on proteins and cells. Despite its importance, the influence of mechanical stress on cellular function is still poorly understood. In part, this knowledge gap exists because few tools enable simultaneous deformation of tissue and cells, imaging of cellular activity in live animals, and efficient restriction of motility in otherwise highly mobile model organisms, such as the nematode Caenorhabditis elegans. The small size of C. elegans makes them an excellent match to microfluidics-based research devices, and solutions for immobilization have been presented using microfluidic devices. Although these devices allow for high-resolution imaging, the animal is fully encased in polydimethylsiloxane (PDMS) and glass, limiting physical access for delivery of mechanical force or electrophysiological recordings. Recently, we created a device that integrates pneumatic actuators with a trapping design that is compatible with high-resolution fluorescence microscopy. The actuation channel is separated from the worm-trapping channel by a thin PDMS diaphragm. This diaphragm is deflected into the side of a worm by applying pressure from an external source. The device can target individual mechanosensitive neurons. The activation of these neurons is imaged at high-resolution with genetically-encoded calcium indicators. This article presents the general method using C. elegans strains expressing calcium-sensitive activity indicator (GCaMP6s) in their touch receptor neurons (TRNs). The method, however, is not limited to TRNs nor to calcium sensors as a probe, but can be expanded to other mechanically-sensitive cells or sensors.

Using a Microfluidics Device for Mechanical Stimulation and High Resolution Imaging of C. elegans

New tools for mechanobiology research are needed to understand how mechanical stress activates biochemical pathways and elicits biological responses. Here, we showcase a new method for selective mechanical stimulation of immobilized animals with a microfluidic trap allowing high-resolution imaging of cellular responses.

Utilizzando un dispositivo di microfluidica per stimolazione meccanica e alta risoluzione Imaging di c. elegans

One central goal of mechanobiology is to understand the reciprocal effect of mechanical stress on proteins and cells. Despite its importance, the ...

Neuroscienze

Visualizing Membrane Ruffle Formation using Scanning Electron Microscopy

Membrane ruffling is the formation of motile plasma membrane protrusions containing a meshwork of newly polymerized actin filaments. Membrane ruffles may form spontaneously or in response to growth factors, inflammatory cytokines, and phorbol esters. Some of the membrane protrusions may reorganize into circular membrane ruffles that fuse at their distal margins and form cups that close and separate into the cytoplasm as large, heterogeneous vacuoles called macropinosomes. During the process, ruffles trap extracellular fluid and solutes that internalize within macropinosomes. High-resolution scanning electron microscopy (SEM) is a commonly used imaging technique to visualize and quantify membrane ruffle formation, circular protrusions, and closed macropinocytic cups on the cell surface. The following protocol describes the cell culture conditions, stimulation of the membrane ruffle formation in vitro, and how to fix, dehydrate, and prepare cells for imaging using SEM. Quantification of membrane ruffling, data normalization, and stimulators and inhibitors of membrane ruffle formation are also described. This method can help answer key questions about the role of macropinocytosis in physiological and pathological processes, investigate new targets that regulate membrane ruffle formation, and identify yet uncharacterized physiological stimulators as well as novel pharmacological inhibitors of macropinocytosis.

Macropinocytosis is a highly conserved endocytic process initiated by the formation of F-actin-rich sheet-like membrane projections, also known as membrane ruffles. Increased rate of macropinocytotic solute internalization has been implicated in various pathological conditions. This protocol presents a method to quantify membrane ruffle formation in vitro using scanning electron microscopy.

Visualizzazione della formazione di increspature a membrana utilizzando la microscopia elettronica a scansione

Membrane ruffling is the formation of motile plasma membrane protrusions containing a meshwork of newly polymerized actin filaments. Membrane ruffles may ...