We thank A. Sharoni from Bar-Ilan University for providing the superconducting films. This research was supported by European Research Council Grant ERC-2014-STG- 639792, Marie Curie Career Integration Grant FP7-PEOPLE-2012-CIG-333799, and Israel Science Foundation Grant ISF-1102/13.

1. Access to a Scanning SQUID System
<ol>
	<li>Use a scanning SQUID system that includes a SQUID sensor fabricated on a chip9,10, stick slip coarse motion stage, and a piezo-based scanner for fine motion. See Figure 1.</li>
	<li>Polish the SQUID chip into a corner around the pickup loop. The material of the chip needs to be removed all the way to the pickup loop.
	<ol>
		<li>Gently polish the SQUID, using a 5 to 0.5 &#181;m nonmagnetic polishing paper. 
		NOTE: After the polishing stage the pickup loop can be brought into close proximity, or contact, with the sample.</li>
	</ol>
	</li>
</ol>
2. Deposition of Niobium (Nb) Thin Film with Direct Current (DC) Sputtering
<ol>
	<li>Obtain a substrate. In this work, use a boron-doped silicon substrate with 500 nm of silicon oxide. Other substrates such as SrTiO and MgO are possible.</li>
	<li>Reach a base pressure of 10-7 Torr in the chamber. Pre-sputter the evaporation chamber at room temperature with a 99.95% Nb target, in an argon environment at a pressure of 2.4 mTorr with a deposition rate of 1.8 &#197;/s for 10 min. Note that the deposition process can start only when the base pressure in the chamber is less than 10-7 Torr. If pressure is higher repeat the pre-sputtering stage.</li>
	<li>Place substrate in the chamber.</li>
	<li>Deposit Nb thin film by sputtering at room temperature from a 99.95% Nb target, in an argon environment at pressure of 2.4 mTorr with a deposition rate of 1.8 &#197;/s.</li>
</ol>
3. Sample-tip Alignment
<ol>
	<li>In this stage, align the sensor chip with the sample so that the tip of the chip makes contact with the sample when moving the vortices. To achieve this, use an alignment angle of at least 4&#176;.</li>
	<li>Glue a flexible cantilever on a conducting plate with a dielectric layer. Then, glue the SQUID chip on the cantilever. The capacitance between the cantilever and a static plate determines the contact with the sample and the extent of stress applied.</li>
	<li>Load sample on the microscope. Glue the sample to a designated sample mount using a varnish or silver paste. Glue the mount to the Z piezo element (Figure 1a).</li>
	<li>Connect the stick slip coarse motion system to a controller.</li>
	<li>Set up optical imaging from two angles &#8212; the front and the side of the chip. Use two telescopes placed on translation stages, directed to the front of the chip and one of its sides.</li>
	<li>Using the Z stick slip coarse motion stage, move the sample to a distance of 1 &#181;m from the sensor, so that the sensor&#39;s reflection is visible on the sample. 
	NOTE: Contact between the sample and the sensor at this stage may harm the SQUID.</li>
	<li>Move the sample 0.5 - 1 mm away from the sensor using the Z stick slip coarse motion stage to prevent damage to the SQUID.</li>
	<li>Rotate the alignment screws (Figure 1a) to get equal front angles (i.e., angles the sides of the chip&#39;s tip make with its reflection, as seen in Figure 1c).</li>
	<li>Move the sample to a distance of 1 &#181;m from the sensor. Check the angles and repeat step 3.7 and 3.8 if necessary.</li>
	<li>Rotate the alignment screws to get an angle of 4 degrees between the sensor and the sample (Figure 1d). Make sure the tip of the chip is the part which makes contact with the sample.</li>
</ol>
4. Measurements
<ol>
	<li>Load the scanning head (Figure 1a) to a 4 K cooling system. 
	NOTE: Scanning head should be connected to a cold plate, and surrounded by a vacuum can. Wire a coil around the can for applying external magnetic field (low fields of several Gauss are sufficient for this study). Cover this setup with a Mu-metal shield.</li>
	<li>Cool in the presence of magnetic field, by applying current through the coil surrounding the microscope. Choose the field strength carefully to achieve the desired vortex density. Use 1&#934;0 = 20.7 G/&#956;m2 to calculate the cooldown field. For example, for 10 vortices in a 10 &#181;m by 10 &#181;m area, apply 2.07 G.</li>
	<li>For changing to a new vortex density heat sample above the superconducting transition temperature (For Nb, heat above 10 K). Apply the new field.</li>
	<li>Cool sample to 4.2 K.</li>
	<li>Turn magnetic field off. Turn SQUID on.</li>
	<li>Move the sample close to the SQUID using the stick slip coarse motion system.
	<ol>
		<li>Apply increasing voltages on the Z-stick slip cube to move the sample closer to the SQUID chip.</li>
		<li>Apply voltage between the cantilever and the plate for reading the capacitance using a capacitance bridge (0.1-1 V typically).</li>
		<li>Sweep the voltage on the Z piezo element. Measure the capacitance between the cantilever and the plate. If a large change in the capacitance occurs, the sample is in contact with the SQUID chip.</li>
		<li>If the sample did not make contact with the chip, repeat steps 4.6.1-4.6.3 until contact is observed.</li>
		<li>Optional: Use course motion to adjust the spacing between the tip and the sample so that contact occurs at low voltages (0 - 10 V applied on the Z piezo).</li>
		<li>Once there is contact, repeat steps 4.6.2-4.6.3 in several locations in order to determine the tilt angles of the surface and to define the plane of the sample, relative to the sensor.</li>
	</ol>
	</li>
	<li>Sweep the voltage on the X and Y piezo elements in order to move the sample relative to the sensor. Scan at a constant height above the sample, without contact between the tip and the sample, in order to map vortex distribution. Achieve a constant scan height by changing the voltage on the Z piezo according to the X and Y locations, and to the plane defined in 4.6.</li>
	<li>Choose a vortex and scan around it to precisely determine the location of its center. Note that the vortex location is relative to the SQUID&#39;s pickup loop, not to the contact point.</li>
	<li>Turn SQUID off.</li>
	<li>Apply a voltage that is greater than the touchdown voltage to the z piezo and either tap next to the vortex center or sweep the vortex by dragging the sensor (in contact with the sample) slowly on the sample to a desired location. The vortex will move towards the tap or in the sweeping direction. Typical values to add to the applied z piezo voltage are 2-5 V.</li>
	<li>Turn SQUID on.</li>
	<li>Image again at a constant height without contact to locate the new location of the vortex.</li>
</ol>

<ol><li>Olson Reichhardt, C. J., Hastings, M. B. <a target="_blank" href="https://arxiv.org/abs/cond-mat/0307374">Do Vortices Entangle?</a> Phys. Rev. Lett. 92, 157002(2004).</li>
<li>Milošević, M. V., Berdiyorov, G. R., Peeters, F. M. <a target="_blank" href="http://pubs.acs.org/doi/abs/10.1021/nl301451e">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/pubmed?term=((Scanning+Probe+Manipulation+of+Magnetism+at+the+LaAlO3%2FSrTiO3+Heterointerface%5BTitle%5D)+AND+%22Nano+Lett%22%5BJournal%5D)">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.nature.com/nature/journal/v440/n7084/full/nature04595.html">Controlled multiple reversals of a ratchet effect.</a> Nature. 440, 651-654 (2006).</li>
<li>Kalisky, B., et al. <a target="_blank" href="http://aip.scitation.org/doi/10.1063/1.3137164">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/pubmed?term=((Probing+dynamics+and+pinning+of+single+vortices+in+superconductors+at+nanometer+scales%5BTitle%5D)+AND+%22Sci.+Rep%22%5BJournal%5D)">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.nature.com/nphys/journal/v5/n1/full/nphys1127.html">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="https://arxiv.org/abs/1012.4271">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/pubmed?term=((Gradiometric+micro-SQUID+susceptometer+for+scanning+measurements+of+mesoscopic+samples%5BTitle%5D)+AND+%22Rev.+Sci.+Instrum%22%5BJournal%5D)">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="https://arxiv.org/abs/0901.0308">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/pubmed?term=((Mechanical+Control+of+Individual+Superconducting+Vortices%5BTitle%5D)+AND+%22Nano+Lett%22%5BJournal%5D)">Mechanical Control of Individual Superconducting Vortices.</a> Nano Lett. 16, 1626-1630 (2016).</li>
</ol>

The authors have nothing to disclose.

Successful manipulation of vortices depends on several critical steps. It is important to align the sensor at an angle, such that the tip of the chip will be the first to make contact with the sample. Second, it is important to note that the force exerted on the sample is determined by the mechanical properties of the cantilever that the chip is mounted on. In the elastic regime, the force applied is proportional to the deflection, x, according to Hooke&#39;s law: 
F = -kx
Where k is the ...

Vortices are magnetic objects at the nanoscale, formed in type 2 superconductors in the presence of external magnetic field. In a defect free sample, vortices can move freely. However, different defects in the material result in regions of reduced superconductivity which are energetically favorable for vortices. Vortices tend to decorate these regions, also known as the pinning sites. In this case, the force required to move a vortex must be greater than the pinning force. Properties of vortices, such as vortex density, interaction strength and range, can be easily determined by external field, temperature, or geometry of the sample. The ability to control these properties makes them a good model system for condensed matter behavior that can be easily tuned, as well as suitable candidates for electronic applications1,2. Control of the location of individual vortices is essential for the design of such logical elements.
Mechanical control of magnetic nanoparticles had been achieved before. Kalisky et al. recently used scanning superconducting quantum interference device (SQUID) to study the influence of local mechanical stress on ferromagnetic patches in complex oxide interfaces3. They were able to change the orientation of the patch by scanning in contact, pressing the tip of the SQUID into the sample, applying a force of up to 1 &#181;N in the process. We have used a similar method in our protocol in order to move vortices.
In existing studies of vortex manipulation, motion was achieved by applying current to the sample, thus creating Lorentz force4,5,6. While this method is effective, it is not local, and in order to control a single vortex, additional fabrication is required. Vortices can also be manipulated by applying external magnetic field, for example with a magnetic force microscope (MFM) or with a SQUID field coil7,8. This method is effective and local, but the force applied by these tools is small, and can overcome the pinning force only at high temperatures, close to the critical temperature of the superconductor. Our protocol allows effective, local manipulation at low temperatures (4 K) without additional fabrication of the sample.
We image vortices using scanning SQUID microscopy. The sensor is fabricated on a silicon chip which is polished into a corner, and glued on a flexible cantilever. The cantilever is used for capacitive sensing of the surface. The chip is placed at an angle to the sample, so that the contact point is at the tip of the chip. We apply forces of up to 2 &#181;N by pushing the chip into the sample. We move the sample relative to the SQUID by piezo elements. We move the vortex by tapping the silicon tip next to a vortex, or by sweeping it, touching the vortex.

<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.

Our protocol was successfully tested on thousands of individual, well separated vortices in two samples of Nb, and nine samples of NbN. We generate new vortices on the same sample by heating the sample above Tc, and cooling it back to 4.2 K in the presence of a magnetic field. We chose the external magnetic field to achieve the desired vortex density. We show here data from these experiments. These results have been described in detail by Kremen et al.11.<...

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.

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.

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

Bioengineering

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.

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

Chemistry

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.

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

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.

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

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.

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.

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.

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

Environment

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.

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

In Vitro Reconstitution of Spatial Cell Contact Patterns with Isolated Caenorhabditis elegans Embryo Blastomeres and Adhesive Polystyrene Beads

In multicellular systems, individual cells are surrounded by the various physical and chemical cues coming from neighboring cells and the environment. This tissue complexity confounds the identification of causal link between extrinsic cues and cellular dynamics. A synthetically reconstituted multicellular system overcomes this problem by enabling researchers to test for a specific cue while eliminating others. Here, we present a method to reconstitute cell contact patterns with isolated Caenorhabditis elegans blastomere and adhesive polystyrene beads. The procedures involve eggshell removal, blastomere isolation by disrupting cell-cell adhesion, preparation of adhesive polystyrene beads, and reconstitution of cell-cell or cell-bead contact. Finally, we present the application of this method to investigate the orientation of cellular division axes that contributes to the regulation of spatial cellular patterning and cell fate specification in developing embryos. This robust, reproducible, and versatile in vitro method enables the study of direct relationships between spatial cell contact patterns and cellular responses.

In Vitro Reconstitution of Spatial Cell Contact Patterns with Isolated Caenorhabditis elegans Embryo Blastomeres and Adhesive Polystyrene Beads

Tissue complexities of multicellular systems confound the identification of causal relationship between extracellular cues and individual cellular behaviors. Here, we present a method to study the direct link between contact-dependent cues and division axes using C. elegans embryo blastomeres and adhesive polystyrene beads.

In multicellular systems, individual cells are surrounded by the various physical and chemical cues coming from neighboring cells and the environment. ...

Developmental Biology

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.

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

Scanning SQUID Study of Vortex Manipulation by Local Contact

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