Agradecemos a A. Sharoni da Universidade de Bar-Ilan para a prestação dos filmes supercondutores. Esta pesquisa foi apoiada pelo Conselho Europeu de Investigação Grant ERC-2014-STG- 639.792, Integração Marie Curie Career Grant FP7-PEOPLE-2012-CIG-333799, e Israel Science Foundation Grant ISF-1102/13.

1. O acesso a um Sistema de Digitalização SQUID <ol><li> Use um sistema de SQUID de digitalização que inclui um sensor SQUID fabricado num chip de 9, 10, vara deslizamento estágio movimento grosseiro, e um scanner baseado em piezo para o movimento bem. Veja a Figura 1. </li><li> Polir o chip SQUID em um canto em torno do laço de recolhimento. O material do chip tem de ser removido todo o caminho para o circuito de captação. <ol><li> Gentilmente polir o SQUID, usando um 5-0,5 mm de papel de polimento não magnético. NOTA: Após a fase de polimento do circuito de captação pode ser posta em proximidade ou contato, com a amostra. </li></ol></li></ol> 2. Deposição de nióbio (Nb) Thin Film com Corrente contínua (CC) Sputtering <ol><li> Obter um substrato. Neste trabalho, utilizar um substrato de silício dopado com boro, com 500 nm de óxido de silício. Outros substratos tais como SrTiO e MgO são possíveis. </li><li> Chegar a um pressu de basere de 10 -7 Torr na câmara. Pré-sputter da câmara de evaporação à temperatura ambiente com um alvo Nb 99,95%, em ambiente de árgon, a uma pressão de 2,4 mTorr com uma velocidade de deposição de 1,8 Ã / s para 10 min. Note-se que o processo de deposição pode começar apenas quando a pressão de base da câmara é inferior a 10 -7 Torr. Se a pressão é maior repita a fase de pré-pulverização catódica. </li><li> Coloque substrato na câmara. </li><li> Depósito Nb película fina por pulverização catódica à temperatura ambiente a partir de um alvo Nb 99,95%, em ambiente de árgon, à pressão de 2,4 mTorr com uma velocidade de deposição de 1,8 Ã / s. </li></ol> Alinhamento 3. Sample-tip <ol><li> Nesta etapa, o chip sensor alinhar com a amostra de forma que a ponta do chip faz contacto com a amostra quando se deslocam os vórtices. Para conseguir isso, usar um ângulo de alinhamento de pelo menos 4 ° C. </li><li> Cole um braço de suporte flexível em uma placa condutora com uma camada de dieléctrico. Em seguida, cole o chi SQUIDp sobre o cantilever. A capacitância entre o cantilever e uma placa estática determina o contato com a amostra e a extensão da tensão aplicada. </li><li> amostra de carga sobre o microscópio. Cole a amostra a uma amostra designada montagem usando um verniz ou prata colar. Cole a montagem ao elemento Z piezo (Figura 1a). </li><li> Ligue o sistema de movimento grossa vara de deslizamento para um controlador. </li><li> Configurar imageamento óptico de dois ângulos - a frente eo lado do chip. Usar dois telescópios colocados em estágios de translação, dirigido para a frente de o chip e um dos seus lados. </li><li> Utilizando a vara Z deslizamento fase grosseira movimento, mover-se a amostra a uma distância de 1 uM a partir do sensor, de modo que a reflexão do sensor é visível na amostra. NOTA: Entre em contato entre a amostra e o sensor nesta fase pode prejudicar o SQUID. </li><li> Mova a amostra de 0,5 - 1 mm de distância do sensor utilizando a fase Z vara deslizamento movimento grossa para evitar danos ao SLIBRA. </li><li> Girar a parafusos de alinhamento (Figura 1a) para obter ângulos frontais iguais (ou seja, os ângulos dos lados da ponta do chip fazer com sua reflexão, como pode ser visto na Figura 1c). </li><li> Mover a amostra a uma distância de 1 uM a partir do sensor. Verifique os ângulos e repita o passo 3.7 e 3.8, se necessário. </li><li> Rodar os parafusos de alinhamento para obter um ângulo de 4 graus entre o sensor e a amostra (Figura 1D). Certifique-se a ponta do chip é a parte que entra em contato com a amostra. </li></ol> 4. medições <ol><li> Coloque a cabeça de digitalização (Figura 1a) para um sistema de 4 K de resfriamento. NOTA: cabeça de digitalização deve ser conectado a uma placa fria, e rodeado por uma lata de vácuo. Ligar uma bobina em torno da lata para aplicação de um campo magnético externo (baixos campos de vários Gauss são suficientes para este estudo). Cubra essa configuração com um escudo Mu-metal. </li><li> Legal, na presença de magneTic campo, através da aplicação de corrente através da bobina em torno do microscópio. Escolha a intensidade do campo cuidadosamente para conseguir a densidade desejada vórtice. Use 1Φ = 0 20,7 g / uM 2 para calcular o campo de recarga. Por exemplo, para 10 vórtices em um 10 um por 10 uM área, aplicam-se 2,07 G. </li><li> Para alterar para a nova amostra de calor densidade vórtice acima da temperatura de transição supercondutora (Para Nb, aqueça acima de 10 K). Aplicar o novo campo. </li><li> amostra legal para 4,2 K. </li><li> Vire campo magnético fora. Vire SQUID diante. </li><li> Mova a amostra perto do SQUID usando o sistema de movimento grossa vara de deslizamento. <ol><li> Aplique tensões crescentes no cubo Z-stick deslizamento para mover a amostra mais próxima do chip SQUID. </li><li> Aplicar a tensão entre o braço de suporte e a placa de leitura a capacitância usando uma ponte de capacitância (0,1-1 V tipicamente). </li><li> Varrer a tensão no elemento piezo Z. Medir a capacitância entre o cantilever ea plate. Se uma grande alteração na capacitância ocorre, a amostra está em contacto com o chip SQUID. </li><li> Se a amostra não fazer contato com o chip, repita os passos 4.6.1-4.6.3 até que o contato é observado. </li><li> Opcional: Use curso de movimento para ajustar o espaçamento entre a ponta e a amostra de modo que o contacto ocorre a baixas tensões (0 - 10 V aplicada na Z piezo). </li><li> Uma vez que não há contacto, repetir os passos 4.6.2-4.6.3 em vários locais, a fim de determinar os ângulos de inclinação da superfície e para definir o plano da amostra, em relação ao sensor. </li></ol></li><li> Varrer a tensão nos elementos piezoeléctricos X e Y de modo a mover-se a amostra em relação ao sensor. Digitalizar a uma altura constante acima da amostra, sem contacto entre a ponta e a amostra, a fim de mapear a distribuição de vórtice. Atingir uma altura constante de digitalização, alterando a tensão sobre o piezo Z de acordo com os locais X e Y, e ao plano definido em 4.6. </li><li> Escolha um vórtice e digitalizar around-lo para determinar com precisão a localização do seu centro. Note-se que a localização vortex é relativo ao ciclo de captação da lula, não ao ponto de contacto. </li><li> Vire SQUID off. </li><li> Aplicar uma tensão que é maior do que a tensão de aterragem ao piezo e ou z torneira ao lado do centro do vórtice ou varrer o vórtice, arrastando o sensor (em contacto com a amostra) lentamente sobre a amostra a um local desejado. O vórtice vai avançar para a torneira ou na direção de varredura. Os valores típicos para adicionar à tensão piezoeléctrica aplicada z são 2-5 V. </li><li> Vire SQUID diante. </li><li> Imagem novamente a uma altura constante, sem contacto para localizar a nova localização do vórtice. </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.

manipulação bem sucedida de vórtices depende de vários passos críticos. É importante para alinhar o sensor a um ângulo, de tal modo que a ponta do chip será o primeiro a fazer o contacto com a amostra. Em segundo lugar, é importante notar que a força exercida sobre a amostra é determinada pelas propriedades mecânicas do cantilever que o chip é montado. No regime elástica, a força exercida é proporcional à deflexão, X, de acordo com a lei de Hooke: F = -kx Onde k é a...

Vórtices são objetos magnéticos em nanoescala, formada em tipo 2 supercondutores na presença de um campo magnético externo. Em uma amostra livre de defeitos, vórtices podem se mover livremente. No entanto, diferentes defeitos no resultado de material nas regiões da supercondutividade reduzida que são energeticamente favorável para vórtices. Vórtices tendem a decorar estas regiões, também conhecidos como os locais de fixação. Neste caso, a força necessária para mover um vórtice deve ser maior do que a força de fixação. Propriedades de vórtices, tais como a densidade de vórtice, a força interacção e gama, pode ser facilmente determinada por um campo externo, a temperatura, ou a geometria da amostra. A capacidade de controlar estas propriedades que os torna um bom sistema modelo para o comportamento da matéria condensada que pode ser facilmente afinado, bem como candidatos adequados para aplicações electrónicas 1, 2. O controlo da localização dos vórtices individuais é essencial para a concepção de tais Loelementos gicos. controle mecânico de nanopartículas magnéticas tinha sido alcançado antes. Kalisky et ai. recentemente utilizado digitalização supercondutores quantum interference device (SQUID) para estudar a influência do estresse mecânico local no manchas ferromagnéticos nas interfaces de óxido complexo 3. Eles foram capazes de alterar a orientação do penso por varrimento em contacto, pressionar a ponta da lula na amostra, aplicando uma força de 1 até μN no processo. Temos utilizado um método semelhante em nosso protocolo, a fim de mover vórtices. Em estudos existentes sobre a manipulação do vortex, movimento foi conseguido através da aplicação de corrente com a amostra, assim criando força de Lorentz 4, 5, 6. Enquanto este método é eficaz, não é local, e, a fim de controlar uma única vórtice, fabricação adicional é necessária. Vórtices também pode ser manippovoadas por aplicação de um campo magnético externo, por exemplo com um microscópio de força magnética (MFM) ou com uma bobina de campo SQUID 7, 8. Este método é eficaz e local, mas a força exercida por estas ferramentas é pequena, e pode superar a força fixando-se apenas com altas temperaturas, próximas da temperatura crítica do supercondutor. Nosso protocolo permite uma manipulação eficaz, local, a baixas temperaturas (4 K) sem fabricação adicional da amostra. Nós imagem vórtices usando microscopia de varredura SQUID. O sensor é fabricado num chip de silício, que é polida para um canto, e colado sobre um braço de suporte flexível. O braço de suporte é utilizado para detecção capacitiva da superfície. O chip é colocado em ângulo com a amostra, de modo que o ponto de contacto está na ponta do chip. Nós aplicar forças de até 2 μN empurrando o chip na amostra. Movemo-nos a amostra em relação ao SQUID por elementos piezo. Nós movemoso vórtice tocando a ponta de silício ao lado de um vórtice, ou por varrendo-o, tocar o vórtice.

<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.

O protocolo foi testado com sucesso em milhares de vórtices individuais, bem separadas em duas amostras de Nb, e nove amostras de NBN. Geramos novos vórtices sobre a mesma amostra por aquecimento da amostra acima de Tc, e arrefecendo-o de volta para 4,2 K na presença de um campo magnético. Nós escolhemos o campo magnético externo para atingir a densidade desejada vórtice. Mostramos aqui dados a partir destas experiências. Estes resultados foram descritos em detalhe por Kremen <em...

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.

Digitalizar Estudo SQUID de Manipulação Vortex por contato local

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 visualizações.  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. 

Vídeo: 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.

Medir quantitativamente In situ Fluxos usando um Aparelho Autônomo de Velocimetria Underwater (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 ...

Bioengenharia

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.

O exame quantitativo e qualitativo dos Interações partícula-partícula coloidal Usando Probe Nanoscopia

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

Química

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.

Métodos para medir a orientação e rotação Taxa de partículas em Turbulência 3D-impressos

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

Engenharia

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.

Mão Controlado Manipulação de solteiro moléculas através de um Scanning Probe Microscope com uma interface de realidade virtual 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.

Investigando a separação de fluxo tridimensional induzida por um polip de dobra vocal modelo

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.

Visualização do campo de fluxo em torno de um encanamento vibratório dentro de um furo de Scour do equilíbrio

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.

Fabricação de nanoestruturas magnéticas nas membranas de nitreto de silício para estudos de vórtice magnético utilizando técnicas de microscopia de transmissão

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.

Medições de força direta de mecânica subcelular em confinamento usando pinças ópticas

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

Biologia do Desenvolvimento

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.

Utilizando um dispositivo microfluídica para estimulação mecânica e alta resolução de imagem de c. elegans

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

Neurociência

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.

Visualizando a formação de babados de membrana usando microscopia eletrônica de varredura

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