Name: dielectric rheosans &#8212; simultaneous interrogation of impedance, rheology and small angle neutron scattering of complex fluids
Uploaded: 2017-04-10T12:30:00
Description: Watch this Scientific Journal Video about Dielectric RheoSANS â€” Simultaneous Interrogation of Impedance, Rheology and Small Angle Neutron Scattering of Complex Fluids at JoVE.com

The authors would like to acknowledge the NIST Center for Neutron Research CNS cooperative agreement number #70NANB12H239 grant for partial funding during this time period as well as the National Research Council for support. Certain commercial equipment, instruments, or materials are identified in this paper in order to specify the experimental procedure adequately. Such identification is not intended to imply recommendation or endorsement by the National Institute of Standards and Technology, nor is it intended to imply that the materials or equipment identified are necessarily the best available for the purpose.

1. Mounting the Rheometer onto the SANS Beamline
NOTE: See Figure 1 for definitions of named components.
<ol>
	<li>Ensure that the power to the rheometer is off, the transducer is locked and the motor air bearing protector is installed. Turn off the neutron beam, and close the oven door.</li>
	<li>Install the large base plate onto the table, remove the snout, install the window, and secure the 4 eyelets to the mounting brackets on the rheometer&#39;s crane adapter such that ...

<ol>
	<li>Macosko, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rheology:+Principles,+Measurements+and+Applications.">Rheology: Principles, Measurements and Applications.</a> Powder Technology. 86 (3), (1996).</li><li>Barsoukov, E., Macdonald, J. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Impedance Spectroscopy Theory, Experiment, and Applications. , (2010).</li><li>Pelster, R., Simon, U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nanodispersions+of+conducting+particles:+Preparation,+microstructure+and+dielectric+properties.">Nanodispersions of conducting particles: Preparation, microstructure and dielectric properties.</a> Colloid Polym. Sci. 277 (1), 2-14 (1999).</li><li>Hollingsworth, A. 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J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+rheology+and+microstructure+of+branched+micelles+under+shear.">The rheology and microstructure of branched micelles under shear.</a> J. Rheol. 59 (5), 1299-1328 (2015).</li><li>Helgeson, M. E., Vasquez, P. A., Kaler, E. W., Wagner, N. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rheology+and+spatially+resolved+structure+of+cetyltrimethylammonium+bromide+wormlike+micelles+through+the+shear+banding+transition.">Rheology and spatially resolved structure of cetyltrimethylammonium bromide wormlike micelles through the shear banding transition.</a> J. Rheol. 53 (3), 727 (2009).</li><li>Calabrese, M. 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=An+optimized+protocol+for+the+analysis+of+time-resolved+elastic+scattering+experiments.">An optimized protocol for the analysis of time-resolved elastic scattering experiments.</a> Soft Matter. 12 (8), 2301-2308 (2016).</li><li>Eberle, A. P. R., Porcar, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Flow-SANS+and+Rheo-SANS+applied+to+soft+matter.">Flow-SANS and Rheo-SANS applied to soft matter.</a> Curr. Opin. Colloid Interface Sci. 17 (1), 33-43 (2012).</li><li>Campos, J. W., 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=Investigation+of+carbon+materials+for+use+as+a+flowable+electrode+in+electrochemical+flow+capacitors.">Investigation of carbon materials for use as a flowable electrode in electrochemical flow capacitors.</a> Electrochim. Acta. 98, 123-130 (2013).</li><li>Duduta, 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=Semi-solid+lithium+rechargeable+flow+battery.">Semi-solid lithium rechargeable flow battery.</a> Adv. Energy Mater. 1 (4), 511-516 (2011).</li><li>Mewis, J., de Groot, L. M., Helsen, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dielectric+Behaviour+of+Flowing+Thixotropic+Suspensions.">Dielectric Behaviour of Flowing Thixotropic Suspensions.</a> Colloids Surf. 22, (1987).</li><li>Richards, J. J., Wagner, N. J., Butler, P. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Strain-Controlled+RheoSANS+Instrument+for+the+Measurement+of+the+Microstructural,+Electrical+and+Mechanical+Properties+of+Soft+Materials.">A Strain-Controlled RheoSANS Instrument for the Measurement of the Microstructural, Electrical and Mechanical Properties of Soft Materials.</a> Rev. Sci. Instr. , (2016).</li><li>Youssry, 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=Non-aqueous+carbon+black+suspensions+for+lithium-based+redox+flow+batteries:+rheology+and+simultaneous+rheo-electrical+behavior.">Non-aqueous carbon black suspensions for lithium-based redox flow batteries: rheology and simultaneous rheo-electrical behavior.</a> Phys. Chem. Chem. Phys. PCCP. 15 (34), 14476-14486 (2013).</li><li>Cho, B. -. K., Jain, A., Gruner, S. M., Wiesner, U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mesophase+structure-mechanical+and+ionic+transport+correlations+in+extended+amphiphilic+dendrons.">Mesophase structure-mechanical and ionic transport correlations in extended amphiphilic dendrons.</a> Sci. 305 (5690), 1598-1601 (2004).</li><li>Kiel, J. W., MacKay, M. E., Kirby, B. J., Maranville, B. B., Majkrzak, C. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Phase-sensitive+neutron+reflectometry+measurements+applied+in+the+study+of+photovoltaic+films.">Phase-sensitive neutron reflectometry measurements applied in the study of photovoltaic films.</a> J. Chem. Phys. 133 (7), 1-7 (2010).</li><li>L&#243;pez-Barr&#242;n, C. R., Chen, R., Wagner, N. J., Beltramo, P. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Self-Assembly+of+Pluronic+F127+Diacrylate+in+Ethylammonium+Nitrate:+Structure,+Rheology,+and+Ionic+Conductivity+before+and+after+Photo-Cross-Linking.">Self-Assembly of Pluronic F127 Diacrylate in Ethylammonium Nitrate: Structure, Rheology, and Ionic Conductivity before and after Photo-Cross-Linking.</a> Macromolecules. 49 (14), 5179-5189 (2016).</li></ol>

A dielectric RheoSANS experiment measures simultaneously the rheological, electrical and microstructural responses of a material as it undergoes a predefined deformation. The example shown here is an electrically conductive carbon black suspension that forms the conductive additive used in electrochemical flow cells. The dielectric RheoSANS instrument enables the interrogation of the radial plane of shear within a narrow gap Couette cell without compromising the fidelity of either the electrical or rheological measuremen...

Measurement of macroscopic properties are often used to gain fundamental insight into the nature of colloidal materials and self-assembled systems, usually with the goal of developing understanding in order to improve formulation performance. In particular, the field of rheology, which measures a fluid&#39;s dynamic response to an applied stress or deformation, provides valuable insight into colloidal behavior both under equilibrium conditions and also far from equilibrium, such as during processing1 Rheological tests of consumer and industrial fluids, gels, and glasses can also be used to measure rheological parameters, such as viscosity, that are targeted by formulators. While rheology is a powerful probe of material properties, it is an indirect measurement of colloidal information at the microscopic level, such that our understanding of fundamental colloidal behavior can be greatly enhanced by combining rheological measurements with complementary techniques.
One such orthogonal technique is impedance spectroscopy. Impedance spectroscopy is a bulk probe of dielectric relaxation behavior, which measures the response of a material to an applied oscillating electric field.2 The impedance spectrum results from electrical relaxation modes that are active within the material including charge transport and polarization.3,4 These measurements provide additional evidence for colloidal behavior particularly when combined with rheology.5 Therefore, the combination of these techniques is especially relevant when probing charged colloidal dispersions, proteins, ionic surfactants, nanocomposites, and other systems.6,7
A fundamental interest in investigations of colloidal behavior is the material&#39;s microstructure. The microstructure of a colloidal fluid is thought to encode all of the information necessary to reconstitute both its rheological and electrical behavior. Fundamentally, we seek to measure a snapshot of the nanoscale microstructural features that lead to a measured material response. Due to the complicated nature of many complex fluids&#39; dependence on their process history, much of the effort on microstructural characterization has focused on making in situ measurements of the material as it undergoes deformation. This has challenged experimentalists to devise methods to be able to make measurements of nano-sized particles under for example steady shear, where the velocities of the particles have made direct visualization intrinsically challenging. Direct measurement of material microstructure under flow has taken on many forms ranging from rheo-optics, rheo-microscopy and even rheo-NMR.8,9,10 Small angle scattering methods, and in particular small angle neutron scattering (SANS) techniques, have proven themselves effective at measuring the time-averaged microstructure of samples at steady state in a bulk shear field including all three planes of shear.11,12,13 However, new data acquisition techniques have allowed structural transients to be captured with time resolution as fine as 10 ms.14 Indeed combining rheology with various in situ scattering methods has proven invaluable in hundreds of recent studies.15
An emerging engineering challenge is the use of colloidal suspensions as conductive additives in semi-solid flow battery electrodes.16 In this application, conductive colloidal particles must maintain an electrically percolated network while the material is pumped through an electrochemical flow cell. The performance demands on these materials require that they maintain high conductivity without detrimental effect on the rheological performance over a wide range of shear rates.17 It is therefore highly desirable to be able to make measurements of the colloidal behavior under steady and time-dependent shear conditions in order to quantify and characterize the underlying rheological and electrical response of these materials far from their equilibrium state. A significant complicating factor that has hindered further theoretical development in this regard is the thixotropic nature of carbon black slurries.18 These history dependent rheological and electrical properties make experiments notoriously difficult to reproduce; thus, making it difficult to compare data sets measured using varying protocols. Furthermore, to date there is no single geometry capable of performing all three, dielectric, rheological, and microstructural characterizations, simultaneously. Simultaneous measurement is important as the flow can change the structure, such that rest measurements of processed materials may not provide accurate indications of the properties under flow, which are more relevant for their use. Additionally, as many of the measured properties of carbon black slurries are geometry dependent, there are complications with comparing data obtained from the same sample on different instruments.19
In order to meet this challenge in metrology, we have developed a new dielectric RheoSANS geometry at the NIST Center for Neutron Research and the University of Delaware capable of in situ impedance spectroscopy, rheology and SANS measurements of a material under arbitrary deformation on a commercial strain controlled rheometer. This is enabled by developing a Couette geometry capable of measuring the microstructural, electrical and rheological response of a material confined between the gap of two concentric cylinders. As the outer cylinder spins, torque imposed by the deformation of the sample is measured on the inner cylinder and the impedance measurement is made radially across the gap. The cylinders are machined from titanium so as to be transparent to neutrons and robust enough to withstand the shear stress experienced in the rheometer. We perform the SANS measurement through the radial position of the Couette, and have demonstrated that it is possible to measure high quality SANS patterns from the sample undergoing deformation. In this way, all three measurements are made on the same region of interest in the sample as it undergoes a well-defined deformation profile. The goal of this article is to describe the dielectric Couette geometry, its installation onto the RheoSANS instrument, and the successful execution of a simultaneous measurement. This rheometer is available at the NIST Center for Neutron Research at the National Institute of Standards and Technology. It has been designed to work on the NG-7 SANS beam line. We have provided drawings and a detailed description of the custom components that have been machined and assembled in order to enable this measurement.

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	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:283px;">ARES G2 Rheometer</td>
			<td style="width:151px;">TA Instruments</td>
			<td align="right" style="width:119px;">401000.501</td>
			<td style="width:167px;">Rheometer</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:283px;">ARES G2-DETA ACCY Kit</td>
			<td style="width:151px;">TA Instruments</td>
			<td align="right" style="width:119px;">402551.901</td>
			<td>BNC Connectors</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:283px;">Geometry ARES 25mm DETA</td>
			<td style="width:151px;">TA Instruments</td>
			<td align="right" style="width:119px;">402553.901</td>
			<td>Dielectric Geometry</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:283px;">ARES G2 Forced Convection Oven</td>
			<td style="width:151px;">TA Instruments</td>
			<td align="right" style="width:119px;">401892.901</td>
			<td>FCO</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:283px;">Agilent E4980A LCR Meter</td>
			<td style="width:151px;">TA Instruments</td>
			<td align="right" style="width:119px;">613.04946</td>
			<td>LCR Meter</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:283px;">USB-6001</td>
			<td style="width:151px;">National Instruments</td>
			<td style="width:119px;">NI USB-6001</td>
			<td>Data Acquisiton Card</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:283px;">Vulcan XC72R</td>
			<td style="width:151px;">Cabot</td>
			<td style="width:119px;">Vulcan XC72R</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:283px;">Propylene Carbonate</td>
			<td style="width:151px;">Aldrich</td>
			<td align="right" style="width:119px;">310328</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:283px;">LabVIEW&#160; System Design Software</td>
			<td style="width:151px;">National Instruments</td>
			<td>776671-35</td>
			<td>Control Software&#160;</td>
		</tr>
	</tbody>
</table>

dielectric rheosans &#8212; simultaneous interrogation of impedance, rheology and small angle neutron scattering of complex fluids

A procedure for the operation of a new dielectric RheoSANS instrument capable of simultaneous interrogation of the electrical, mechanical and microstructural properties of complex fluids is presented. The instrument consists of a Couette geometry contained within a modified forced convection oven mounted on a commercial rheometer. This instrument is available for use on the small angle neutron scattering (SANS) beamlines at the National Institute of Standards and Technology (NIST) Center for Neutron Research (NCNR). The Couette geometry is machined to be transparent to neutrons and provides for measurement of the electrical properties and microstructural properties of a sample confined between titanium cylinders while the sample undergoes arbitrary deformation. Synchronization of these measurements is enabled through the use of a customizable program that monitors and controls the execution of predetermined experimental protocols. Described here is a protocol to perform a flow sweep experiment where the shear rate is logarithmically stepped from a maximum value to a minimum value holding at each step for a specified period of time while frequency dependent dielectric measurements are made. Representative results are shown from a sample consisting of a gel composed of carbon black aggregates dispersed in propylene carbonate. As the gel undergoes steady shear, the carbon black network is mechanically deformed, which causes an initial decrease in conductivity associated with the breaking of bonds comprising the carbon black network. However, at higher shear rates, the conductivity recovers associated with the onset of shear thickening. Overall, these results demonstrate the utility of the simultaneous measurement of the rheo-electro-microstructural properties of these suspensions using the dielectric RheoSANS geometry.

Representative results from a dielectric RheoSANS experiment are shown in Figure 5 and 6. These data are taken on a suspension of conductive carbon black in propylene carbonate. These aggregates flocculate due to attractive interactions at relatively low solids loadings forming gels that are electrically conducting. The rheological and conductivity responses of such suspensions are an active area of research and current investigations seek to understand t...

Watch this Scientific Journal Video about Dielectric RheoSANS â€” Simultaneous Interrogation of Impedance, Rheology and Small Angle Neutron Scattering of Complex Fluids at JoVE.com

Dielectric RheoSANS &amp;#8212; Simultaneous Interrogation of Impedance, Rheology and Small Angle Neutron Scattering of Complex Fluids

Here, we present a procedure for the measurement of simultaneous impedance, rheology and neutron scattering from soft matter materials under shear flow.

Dielectric RheoSANS &#8212; Simultaneous Interrogation of Impedance, Rheology and Small Angle Neutron Scattering of Complex Fluids

A procedure for the operation of a new dielectric RheoSANS instrument capable of simultaneous interrogation of the electrical, mechanical and ...

The overall goal of this procedure is to measure the simultaneous impedance, rheology and neutron scattering from a conductive carbon black suspension as it undergoes deformation in response to an applied shear field. This method can help answer key questions in the soft matter and applied materials fields about the intrinsic link between material microstructure and macroscopic properties such as conductivity and rheology. The main advantage of this technique is that the measurements are performed simultaneously, allowing the entire time evolution of mechanical, structural and electrical response to be reconstructed and compared.The implications of this technique extend to the development of advanced conductive materials for electrochemical and optoelectronic applications. Visual demonstration of this method is critical owing to the complex nature of the experimental protocol. NIST professionals will assist in some key aspects of the experiment.Before beginning the procedure, ensure that the neutron beam and the rheometer are both off, the transducer is locked and the motor bearing lock is installed. Clean the dielectric cup and bob assemblies with a detergent solution. Thoroughly rinse the assemblies with deionized water and allow the assembles to air dry.Unlock the transducer and remove the motor bearing lock. Then, turn on the rheometer and start the control software. Mount the dielectric geometry and bob assembly on the lower and upper tool mounts of the rheometer respectively.Use a three milometer allen key to loosen the dielectric geometry set screws. Mount the cup assembly on the dielectric geometry. Then, in the rheometer control software, zero the gap and apply 10 newtons of normal force.Under this axial compression, tighten the set screws to secure the cup assembly to the geometry. Then, set the gap to the measurement gap width. Close the oven door and verify that the oven fully encloses the dielectric cell assembly.With sufficient vertical clearance above and below the geometry to allow a full revolution without contacting the oven walls. Open the oven and remove the dielectric assemblies. Thread the geometry shaft through the slip ring and join the dielectric cup and slip ring connectors.While holding the slip ring, concentric with the shaft above the flange, secure the slip ring adapters on top of the flange. Gently slide the slip ring down to fit over the adapters. Next, mount the rheometer alignment tool on the lower tool head.Install the truncated snout and set the sample aperture to one millimeter by eight millimeters. In the rheometer control software, set the geometry displacement angle to 0.49 radians. Then in the SANS control software, verify that all neutron guides have been removed.Open the oven door to view the beam alignment laser. Use the SANS software to adjust the height and angle of the sample stage until the laser beam is directed along the oven center line and though the sample aperture without intersecting the aperture walls. After rheometer alignment, remove the alignment tool and perform a series of SANS measurements to calibrate the instrument.Then, use the rheometer LCD screen, to set the gap to 100 millimeters. Mount the dielectric cell with the bob assembly on the upper tool head and the cup geometry and slip ring assembly on the lower tool head. Use the instrument software to zero the gap.Next, mount the carbon brush assembly on the brush adapter. Line up the carbon brushes with the grooves on the slip ring and then secure the adapter to the rheometer with screws. Connect the carbon brush assembly to the top bus bar and the dielectric bob assembly to the bottom bus bar.Check the connections of the shielded BNC cables to the bus bars and the LCR meter. Connect the SANS and Trigger BNC cables to the DAQ card. Connect the rheometer to the DAQ card.Verify that the LCR meter and the rheometer are successfully communicating with the computer. Before loading the sample, verify that the gap is set to 100 millimeters. Then, load four millimeters of a carbon black dispersion in propylene carbonate into the dielectric cup assembly, minimizing the amount of sample left on the cup wall.Lower the geometry to 40 millimeter. Then in the rheometer control software, set the motor velocity to one radian per second. Lower the dielectric bob assembly to achieve a gap width of 0.1 millimeters and then set the motor velocity to zero radians per second.Check that the sample levels has reached the Couette wall but is not over filled. Fill the inner dielectric bob assembly with the chosen solvent for the experiment. Place the solvent trap on the rim of the dielectric cup assembly.Next, configure the virtual instrument file for the desired experimental conditions. Set the appropriate run times and procedures for the SANS instrument and the rheometer. Click parameters set to execute the experiment.A conductive carbon black suspension was evaluated by RheoSANS. Rheology, dielectric data and neutron scattering were measured continuously as the shear rate decreased logarithmically in steps, holding at each step for a specific time interval. The steady state, rheological dielectric and SANS data were processed and analyzed at each shear rate step.A period of decreasing conductivity and effective volume fraction with increasing shear rate was attributed to yielding of the microscopic gel. A subsequent period of increasing conductivity and decreasing effective volume fraction with increasing shear rate was attributed to shear thickening caused by hydrodynamic forces drawing aggregated particles together. Micro structural transitions at higher shear rates were represented with two dimensional plots.Dielectric RheoSANS provides a flexible platform capable of the interrogation of nonequilibrium behavior of soft matter systems. Using a wide variety of potential experimental protocols, this instrument is available for broad use by the scientific community at the NCNR.

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Engineering

Angle-resolved Photoemission Spectroscopy At Ultra-low Temperatures

The physical properties of a material are defined by its electronic structure. Electrons in solids are characterized by energy (&omega;) and momentum (k) and the probability to find them in a particular state with given &omega; and k is described by the spectral function A(k, &omega;). This function can be directly measured in an experiment based on the well-known photoelectric effect, for the explanation of which Albert Einstein received the Nobel Prize back in 1921. In the photoelectric effect the light shone on a surface ejects electrons from the material. According to Einstein, energy conservation allows one to determine the energy of an electron inside the sample, provided the energy of the light photon and kinetic energy of the outgoing photoelectron are known. Momentum conservation makes it also possible to estimate k relating it to the momentum of the photoelectron by measuring the angle at which the photoelectron left the surface. The modern version of this technique is called Angle-Resolved Photoemission Spectroscopy (ARPES) and exploits both conservation laws in order to determine the electronic structure, i.e. energy and momentum of electrons inside the solid. In order to resolve the details crucial for understanding the topical problems of condensed matter physics, three quantities need to be minimized: uncertainty* in photon energy, uncertainty in kinetic energy of photoelectrons and temperature of the sample.
In our approach we combine three recent achievements in the field of synchrotron radiation, surface science and cryogenics. We use synchrotron radiation with tunable photon energy contributing an uncertainty of the order of 1 meV, an electron energy analyzer which detects the kinetic energies with a precision of the order of 1 meV and a He3 cryostat which allows us to keep the temperature of the sample below 1 K. We discuss the exemplary results obtained on single crystals of Sr2RuO4 and some other materials. The electronic structure of this material can be determined with an unprecedented clarity.

The overall goal of this method is to determine the low-energy electronic structure of solids at ultra-low temperatures using Angle-Resolved Photoemission Spectroscopy with synchrotron radiation.

The physical properties of a material are defined by its  electronic structure. Electrons in solids are characterized by energy (&omega;)  and momentum ...

Measuring Material Microstructure Under Flow Using 1-2 Plane Flow-Small Angle Neutron Scattering

A new small-angle neutron scattering (SANS) sample environment optimized for studying the microstructure of complex fluids under simple shear flow is presented. The SANS shear cell consists of a concentric cylinder Couette geometry that is sealed and rotating about a horizontal axis so that the vorticity direction of the flow field is aligned with the neutron beam enabling scattering from the 1-2 plane of shear (velocity-velocity gradient, respectively). This approach is an advance over previous shear cell sample environments as there is a strong coupling between the bulk rheology and microstructural features in the 1-2 plane of shear. Flow-instabilities, such as shear banding, can also be studied by spatially resolved measurements. This is accomplished in this sample environment by using a narrow aperture for the neutron beam and scanning along the velocity gradient direction. Time resolved experiments, such as flow start-ups and large amplitude oscillatory shear flow are also possible by synchronization of the shear motion and time-resolved detection of scattered neutrons. Representative results using the methods outlined here demonstrate the useful nature of spatial resolution for measuring the microstructure of a wormlike micelle solution that exhibits shear banding, a phenomenon that can only be investigated by resolving the structure along the velocity gradient direction. Finally, potential improvements to the current design are discussed along with suggestions for supplementary experiments as motivation for future experiments on a broad range of complex fluids in a variety of shear motions.

A shear cell is developed for small-angle neutron scattering measurements in the velocity-velocity gradient plane of shear and is used to characterize complex fluids. Spatially resolved measurements in the velocity gradient direction are possible for studying shear-banding materials. Applications include investigations of colloidal dispersions, polymer solutions, and self-assembled structures.

A new small-angle neutron scattering (SANS) sample environment optimized for studying the microstructure of complex fluids under simple shear flow is ...

Using Neutron Spin Echo Resolved Grazing Incidence Scattering to Investigate Organic Solar Cell Materials

The spin echo resolved grazing incidence scattering (SERGIS) technique has been used to probe the length-scales associated with irregularly shaped crystallites. Neutrons are passed through two well defined regions of magnetic field; one before and one after the sample. The two magnetic field regions have opposite polarity and are tuned such that neutrons travelling through both regions, without being perturbed, will undergo the same number of precessions in opposing directions. In this case the neutron precession in the second arm is said to &#34;echo&#34; the first, and the original polarization of the beam is preserved. If the neutron interacts with a sample and scatters elastically the path through the second arm is not the same as the first and the original polarization is not recovered. Depolarization of the neutron beam is a highly sensitive probe at very small angles (&#60;50&#160;&#956;rad) but still allows a high intensity, divergent beam to be used. The decrease in polarization of the beam reflected from the sample as compared to that from the reference sample can be directly related to structure within the sample.
In comparison to scattering observed in neutron reflection measurements the SERGIS signals are often weak and are unlikely to be observed if the in-plane structures within the sample under investigation are dilute, disordered, small in size and polydisperse or the neutron scattering contrast is low. Therefore, good results will most likely be obtained using the SERGIS technique if the sample being measured consist of thin films on a flat substrate and contain scattering features that contains a high density of moderately sized features (30 nm to 5 &#181;m) which scatter neutrons strongly or the features are arranged on a lattice. An advantage of the SERGIS technique is that it can probe structures in the plane of the sample.

Progress has been made in utilizing spin echo resolved grazing incidence scattering (SERGIS) as a neutron scattering technique to probe the length-scales in irregular samples. Crystallites of [6,6]-phenyl-C61-butyric acid methyl ester have been probed using the SERGIS technique and the results confirmed by optical and atomic force microscopy.

The spin echo resolved grazing incidence scattering (SERGIS) technique has been used to probe the length-scales associated with irregularly shaped ...

Fabrication Process of Silicone-based Dielectric Elastomer Actuators

This contribution demonstrates the fabrication process of dielectric elastomer transducers (DETs). DETs are stretchable capacitors consisting of an elastomeric dielectric membrane sandwiched between two compliant electrodes. The large actuation strains of these transducers when used as actuators (over 300% area strain) and their soft and compliant nature has been exploited for a wide range of applications, including electrically tunable optics, haptic feedback devices, wave-energy harvesting, deformable cell-culture devices, compliant grippers, and propulsion of a bio-inspired fish-like airship. In most cases, DETs are made with a commercial proprietary acrylic elastomer and with hand-applied electrodes of carbon powder or carbon grease. This combination leads to non-reproducible and slow actuators exhibiting viscoelastic creep and a short lifetime. We present here a complete process flow for the reproducible fabrication of DETs based on thin elastomeric silicone films, including casting of thin silicone membranes, membrane release and prestretching, patterning of robust compliant electrodes, assembly and testing. The membranes are cast on flexible polyethylene terephthalate (PET) substrates coated with a water-soluble sacrificial layer for ease of release. The electrodes consist of carbon black particles dispersed into a silicone matrix and patterned using a stamping technique, which leads to precisely-defined compliant electrodes that present a high adhesion to the dielectric membrane on which they are applied.

This manuscript shows the fabrication process for the manufacture of dielectric elastomer soft actuators based on silicone membranes. The three key stages of production are presented in detail: blade casting of thin silicone membranes; pad printing of compliant electrodes; and the assembly of all the components.

This contribution demonstrates the fabrication process of dielectric elastomer transducers (DETs). DETs are stretchable capacitors consisting of an ...

Optical Trap Loading of Dielectric Microparticles In Air

We demonstrate a method to trap a selected dielectric microparticle in air using radiation pressure from a single-beam gradient optical trap. Randomly scattered dielectric microparticles adhered to a glass substrate are momentarily detached using ultrasonic vibrations generated by a piezoelectric transducer (PZT). Then, the optical beam focused on a selected particle lifts it up to the optical trap while the vibrationally excited microparticles fall back to the substrate. A particle may be trapped at the nominal focus of the trapping beam or at a position above the focus (referred to here as the levitation position) where gravity provides the restoring force. After the measurement, the trapped particle can be placed at a desired position on the substrate in a controlled manner. 
In this protocol, an experimental procedure for selective optical trap loading in air is outlined. First, the experimental setup is briefly introduced. Second, the design and fabrication of a PZT holder and a sample enclosure are illustrated in detail. The optical trap loading of a selected microparticle is then demonstrated with step-by-step instructions including sample preparation, launching into the trap, and use of electrostatic force to excite particle motion in the trap and measure charge. Finally, we present recorded particle trajectories of Brownian and ballistic motions of a trapped microparticle in air. These trajectories can be used to measure stiffness or to verify optical alignment through time domain and frequency domain analysis. Selective trap loading enables optical tweezers to track a particle and its changes over repeated trap loadings in a reversible manner, thereby enabling studies of particle-surface interaction.

A protocol for launching and stably trapping selected dielectric microparticles in air is presented.

We demonstrate a method to trap a selected dielectric microparticle in air using radiation pressure from a single-beam gradient optical trap. Randomly ...

Scanning Light Scattering Profiler (SLPS) Based Methodology to Quantitatively Evaluate Forward and Backward Light Scattering from Intraocular Lenses

The scanning light scattering profiler (SLSP) methodology has been developed for the full-angle quantitative evaluation of forward and backward light scattering from intraocular lenses (IOLs) using goniophotometer principles. This protocol describes the SLSP platform and how it employs a 360&#176; rotational photodetector sensor that is scanned around an IOL sample while recording the intensity and location of scattered light as it passes through the IOL medium. The SLSP platform can be used to predict, non-clinically, the propensity for current and novel IOL designs and materials to induce light scatter. Non-clinical evaluation of light scattering properties of IOLs can significantly reduce the number of patient complaints related to unwanted glare, glistening, optical defects, poor image quality, and other phenomena associated with the unintended light scattering. Future studies should be conducted to correlate SLSP data with clinical results to help identify which measured light scatter is most problematic for patients that have undergone cataract surgery subsequent to IOL implantation.

Scanning Light Scattering Profiler SLPS Based Methodology to Quantitatively Evaluate Forward and Backward Light Scattering from Intraocular Lenses

This protocol describes the scanning light scattering profiler (SLSP) that enables the full-angle quantitative evaluation of forward and backward scattering of light from intraocular lenses (IOLs) using goniophotometer principles.

The scanning light scattering profiler (SLSP) methodology has been developed for the full-angle quantitative evaluation of forward and backward light ...

Demonstration of Equal-Intensity Beam Generation by Dielectric Metasurfaces

The fabrication and characterization protocol for a metasurface beam splitter, enabling equal-intensity beam generation, is demonstrated. Hydrogenated amorphous silicon (a-Si:H) is deposited on the fused silica substrate, using plasma-enhanced chemical vapor deposition (PECVD). Typical amorphous silicon deposited by evaporation causes severe optical loss, impinging the operation at visible frequencies. Hydrogen atoms inside the amorphous silicon thin film can reduce the structural defects, improving optical loss. Nanostructures of a few hundreds of nanometers are required for the operation of metasurfaces in the visible frequencies. Conventional photolithography or direct laser writing is not feasible when fabricating such small structures, due to the diffraction limit. Hence, electron beam lithography (EBL) is utilized to define a chromium (Cr) mask on the thin film. During this process, the exposed resist is developed at a cold temperature to slow down the chemical reaction and make the pattern edges sharper. Finally, a-Si:H is etched along the mask, using inductively coupled plasma&#8211;reactive ion etching (ICP-RIE). The demonstrated method is not feasible for large-scale fabrication due to the low throughput of EBL, but it can be improved upon by combining it with nanoimprint lithography. The fabricated device is characterized by a customized optical setup consisting of a laser, polarizer, lens, power meter, and charge-coupled device (CCD). By changing the laser wavelength and polarization, the diffraction properties are measured. The measured diffracted beam powers are always equal, regardless of the incident polarization, as well as wavelength.

A protocol for the fabrication and optical characterization of dielectric metasurfaces is presented. This method can be applied to the fabrication of not only beam splitters, but also of general dielectric metasurfaces, such as lenses, holograms, and optical cloaks.

The fabrication and characterization protocol for a metasurface beam splitter, enabling equal-intensity beam generation, is demonstrated. Hydrogenated ...

Scattering And Absorption of Light in Planetary Regoliths

Theoretical, numerical, and experimental methods are presented for multiple scattering of light in macroscopic discrete random media of densely-packed microscopic particles. The theoretical and numerical methods constitute a framework of Radiative Transfer with Reciprocal Transactions (R2T2). The R2T2 framework entails Monte Carlo order-of-scattering tracing of interactions in the frequency space, assuming that the fundamental scatterers and absorbers are wavelength-scale volume elements composed of large numbers of randomly distributed particles. The discrete random media are fully packed with the volume elements. For spherical and nonspherical particles, the interactions within the volume elements are computed exactly using the Superposition T-Matrix Method (STMM) and the Volume Integral Equation Method (VIEM), respectively. For both particle types, the interactions between different volume elements are computed exactly using the STMM. As the tracing takes place within the discrete random media, incoherent electromagnetic fields are utilized, that is, the coherent field of the volume elements is removed from the interactions. The experimental methods are based on acoustic levitation of the samples for non-contact, non-destructive scattering measurements. The levitation entails full ultrasonic control of the sample position and orientation, that is, six degrees of freedom. The light source is a laser-driven white-light source with a monochromator and polarizer. The detector is a mini-photomultiplier tube on a rotating wheel, equipped with polarizers. The R2T2 is validated using measurements for a mm-scale spherical sample of densely-packed spherical silica particles. After validation, the methods are applied to interpret astronomical observations for asteroid (4) Vesta and comet 67P/Churyumov-Gerasimenko (Figure 1) recently visited by the NASA Dawn mission and the ESA Rosetta mission, respectively.

Numerical and experimental methods are presented for multiple scattering of light in discrete random media of densely-packed particles. The methods are utilized to interpret the observations of asteroid (4) Vesta and comet 67P/Churyumov-Gerasimenko.

Theoretical, numerical, and experimental methods are presented for multiple scattering of light in macroscopic discrete random media of densely-packed ...

Spectral and Angle-Resolved Magneto-Optical Characterization of Photonic Nanostructures

Photonic crystals are periodic nanostructures that can support a variety of confined electromagnetic modes. Such confined modes are usually accompanied by local enhancement of electric field intensity that strengthens light-matter interactions, enabling applications such as surface-enhanced Raman scattering (SERS) and surface plasmon enhanced sensing. In the presence of magneto-optically active materials, the local field enhancement gives rise to anomalous magneto-optical activity. Typically, the confined modes of a given photonic crystal depend strongly on the wavelength and incidence angle of the incident electromagnetic radiation. Thus, spectral and angular-resolved measurements are needed to fully identify them as well as to establish their relationship with the magneto-optical activity of the crystal. In this article, we describe how to use a Fourier-plane (back focal plane) microscope to characterize magneto-optically active samples. As a model system, here we use a plasmonic grating built out of magneto-optically active Au/Co/Au multilayer. In the experiments, we apply a magnetic field on the grating in situ and measure its reciprocal space response, obtaining the magneto-optical response of the grating over a range of wavelengths and incident angles. This information enables us to build a complete map of the plasmonic band structure of the grating and the angle and wavelength dependent magneto-optical activity. These two images allow us to pinpoint the effect that the plasmon resonances have on the magneto-optical response of the grating. The relatively small magnitude of magneto-optical effects requires a careful treatment of the acquired optical signals. To this end, an image processing protocol for obtaining magneto-optical response from the acquired raw data is laid out.

Photonic band structure enables understanding how confined electromagnetic modes propagate within a photonic crystal. In photonic crystals that incorporate magnetic elements, such confined and resonant optical modes are accompanied by enhanced and modified magneto-optical activity. We describe a measurement procedure to extract the magneto-optical band structure by Fourier space microscopy.

Photonic crystals are periodic nanostructures that can support a variety of confined electromagnetic modes. Such confined modes are usually accompanied by ...

Application of a Coupling Agent to Improve the Dielectric Properties of Polymer-Based Nanocomposites

In this work, an easy, low-cost, and widely applicable method was developed to improve the compatibility between the ceramic fillers and the polymer matrix by adding 3-aminopropyltriethoxysilane (KH550) as a coupling agent during the fabrication process of BaTiO3-P(VDF-CTFE) nanocomposites through solution casting. Results show that the use of KH550 can modify the surface of ceramic nanofillers; therefore, good wettability on the ceramic-polymer interface was achieved, and the enhanced energy storage performances were obtained by a suitable amount of the coupling agent. This method can be used to prepare flexible composites, which is highly desirable for the production of high-performance film capacitors. If an excessive amount of coupling agent is used in the process, the non-attached coupling agent can participate in complex reactions, which leads to a decrease in dielectric constant and an increase in dielectric loss.

Here, we demonstrate a simple and low-cost solution-casting process to improve the compatibility between the filler and the matrix of polymer-based nanocomposites using surface modified BaTiO3 fillers, which can effectively enhance the energy density of the composites.

In this work, an easy, low-cost, and widely applicable method was developed to improve the compatibility between the ceramic fillers and the polymer ...