Name: experiments on ultrasonic lubrication using a piezoelectrically-assisted tribometer and optical profilometer
Uploaded: 2015-09-28T14:00:00
Description: Watch this Scientific Journal Video about Experiments on Ultrasonic Lubrication Using a Piezoelectrically-assisted Tribometer and Optical Profilometer at JoVE.com

The authors would like to acknowledge Tim Krantz from NASA Glenn and Duane Detwiler from Honda R&#38;D for their technical support and in-kind contributions. Financial support for this research was provided by the member organizations of the Smart Vehicle Concepts Center (www.SmartVehicleCenter.org), a National Science Foundation Industry/University Cooperative Research Center (I/UCRC). S.D. is supported by a Smart Vehicle Concepts Graduate Fellowship and a University Fellowship from The Ohio State University Graduate School.

1. Development of the Modified Tribometer
<ol>
	<li>Install chuck-motor subsystem.
	<ol>
		<li>Level vibration isolation table. Place DC motor on the table; level the motor with shims and fix it with struts and bolts. Place support frame around the motor.</li>
		<li>Connect splined shaft to the motor shaft using a key. Put support plate on the frame with the splined shaft going through the hole in the plate. Set thrust needle-roller bearing on the support plate and around the splined shaft. Lubricate the bearing with c...

<ol>
	<li>Bhushan, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Introduction to tribology. , (2002).</li><li>Severdenko, V., Klubovich, V., Stepanenko, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Ultrasonic rolling and drawing of metals. , (1972).</li><li>Taylor, R., Coy, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Improved+fuel+efficiency+by+lubricant+design:+a+review.">Improved fuel efficiency by lubricant design: a review.</a> Proc. Instit. Mech. Eng., Part J: J Eng. Tribol. 214 (1), 1-15 (2000).</li><li>Littmann, W., Storck, H., Wallaschek, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sliding+friction+in+the+presence+of+ultrasonic+oscillations:+superposition+of+longitudinal+oscillations.">Sliding friction in the presence of ultrasonic oscillations: superposition of longitudinal oscillations.</a> Arch. Appl. Mech. 71 (8), 549-554 (2001).</li><li>Littmann, W., Storck, H., Wallaschek, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reduction+in+friction+using+piezoelectrically+excited+ultrasonic+vibrations.">Reduction in friction using piezoelectrically excited ultrasonic vibrations.</a> Proc. SPIE. 4331, (2001).</li><li>Bharadwaj, S., Dapino, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Friction+control+in+automotive+seat+belt+systems+by+piezoelectrically+generated+ultrasonic+vibrations.">Friction control in automotive seat belt systems by piezoelectrically generated ultrasonic vibrations.</a> Proc. SPIE. 7645, 7645E (2010).</li><li>Bharadwaj, S., Dapino, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+load+on+active+friction+control+using+ultrasonic+vibrations.">Effect of load on active friction control using ultrasonic vibrations.</a> Proc. SPIE. 7290, 7290G (2010).</li><li>Kumar, V., Hutchings, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reduction+of+the+sliding+friction+of+metals+by+the+application+of+longitudinal+or+transverse+ultrasonic+vibration.">Reduction of the sliding friction of metals by the application of longitudinal or transverse ultrasonic vibration.</a> Tribol. Int. 37 (10), 833-840 (2004).</li><li>Pohlman, R., Lehfeldt, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Influence+of+ultrasonic+vibration+on+metallic+friction.">Influence of ultrasonic vibration on metallic friction.</a> Ultrasonics. 4 (4), 178-185 (1966).</li><li>Popov, V., Starcevic, J., Filippov, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Influence+of+Ultrasonic+In-Plane+Oscillations+on+Static+and+Sliding+Friction+and+Intrinsic+Length+Scale+of+Dry+Friction+Processes.">Influence of Ultrasonic In-Plane Oscillations on Static and Sliding Friction and Intrinsic Length Scale of Dry Friction Processes.</a> Tribol. Lett. 39 (1), 25-30 (2010).</li><li>Dong, S., Dapino, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Piezoelectrically-induced+ultrasonic+lubrication+by+way+of+Poisson+effect.">Piezoelectrically-induced ultrasonic lubrication by way of Poisson effect.</a> Proc. SPIE. 8343, 83430L (2012).</li><li>Dong, S., Dapino, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Elastic-plastic+cube+model+for+ultrasonic+friction+reduction+via+Poisson+effect.">Elastic-plastic cube model for ultrasonic friction reduction via Poisson effect.</a> Ultrasonics. 54 (1), 343-350 (2014).</li><li>Dong, S., Dapino, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Wear+Reduction+Through+Piezoelectrically-Assisted+Ultrasonic+Lubrication.">Wear Reduction Through Piezoelectrically-Assisted Ultrasonic Lubrication.</a> Smart. Mater. Struct. 23 (10), 104005 (2014).</li><li>Chowdhury, M., Helali, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+effect+of+frequency+of+vibration+and+humidity+on+the+wear+rate.">The effect of frequency of vibration and humidity on the wear rate.</a> Wear. 262 (1-2), 198-203 (2014).</li><li>Bryant, M., Tewari, A., York, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+Micro+(rocking)+vibrations+and+surface+waviness+on+wear+and+wear+debris.">Effect of Micro (rocking) vibrations and surface waviness on wear and wear debris.</a> Wear. 216 (1), 60-69 (1998).</li><li>Bryant, M., York, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measurements+and+correlations+of+slider+vibrations+and+wear.">Measurements and correlations of slider vibrations and wear.</a> J. Tribol. 122 (1), 374-380 (2000).</li><li>Goto, H., Ashida, M., Terauchi, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+ultrasonic+vibration+on+the+wear+characteristics+of+a+carbon+steel:+analysis+of+the+wear+mechanism.">Effect of ultrasonic vibration on the wear characteristics of a carbon steel: analysis of the wear mechanism.</a> Wear. 94, 13-27 (1984).</li><li>Goto, H., Ashida, M., Terauchi, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Wear+behaviour+of+a+carbon+steel+subjected+to+an+ultrasonic+vibration+effect+superimposed+on+a+static+contact+load.">Wear behaviour of a carbon steel subjected to an ultrasonic vibration effect superimposed on a static contact load.</a> Wear. 110 (2), 169-181 (1986).</li><li>Robinowicz, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> The friction and wear of materials. , (1965).</li><li>Bowden, F., Freitag, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+friction+of+solids+at+very+high+speeds.">The friction of solids at very high speeds.</a> Proc. R. Soc. A. 248 (1254), 350-367 (1985).</li><li>Burwell, J., Rabinowicz, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+nature+of+the+coefficient+of+friction.">The nature of the coefficient of friction.</a> J. Appl. Phys. 24 (2), 136-139 (1953).</li><li>Cocks, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Interaction+of+sliding+metal+surfaces.">Interaction of sliding metal surfaces.</a> J. Appl. Phys. 33 (7), 2152-2161 (1962).</li><li>Rusinko, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Ultrasound and Irrecoverable Deformation in Metals. , (2012).</li></ol>

Experiments were conducted using this protocol to study the effect of linear speed on ultrasonic friction and wear reduction. The measurements show that ultrasonic vibrations effectively reduce friction and wear at three linear speeds.&#160;Consistent with prior observations, the amount of friction reduction decreases from 62.2% at 20.3 mm/sec to 29.3% at 87 mm/sec. Wear reduction is negligible with changing linear speed (45.8% to 48.6%).
Material properties such as Young&#8217;s modulus and y...

Friction exists at the interface of two contacting surfaces when they slide or roll relative to each other. Friction usually occurs along with abrasive or adhesive wear.1 Ultrasonics is the science behind high frequency phenomena, that is, waves traveling at frequencies above the acoustic range (20 kHz). The field of ultrasonics encompasses two fundamentally different regimes. One regime involves low intensity waves like those utilized in imaging processes such as medical ultrasound or non-destructive inspection of structures. The other is a high power regime in which high-energy waves are utilized to execute or assist engineering processes such as welding of plastics and metals. It has been shown that application of the latter kind of ultrasonic vibrations at the interface of two surfaces in sliding contact reduces the effective friction force at the interface. This phenomenon is known as ultrasonic lubrication.
To achieve ultrasonic lubrication between two sliding objects, relative vibration at ultrasonic frequencies must be established between them. Vibrations are typically applied to one of the two objects, either in the longitudinal, transverse, or perpendicular direction relative to the sliding velocity. In this study, a tribometer&#8217;s pin is fitted with a piezoelectric actuator so that its tip vibrates in the direction perpendicular to the tribometer&#8217;s rotating disc. Piezoelectric materials are a class of &#8220;smart&#8221; materials that deform when exposed to electric fields, vibrating at the same frequency as the excitation field. Piezoelectric materials can vibrate at frequencies well into the MHz range. Being superimposed to the macroscopic velocity, ultrasonic vibrations have the effect of alternating the direction of the instantaneous friction force and the contact between the surfaces, which in combination leads to a reduction of the effective friction force and surface wear.
Ultrasonic friction reduction has been demonstrated in practical manufacturing systems. For example, this technology has been utilized to reduce the force between tool and work piece in metal machining and forming processes such as drilling, pressing, sheet rolling, and wire drawing. Benefits include improved surface finish2 and a reduced need for expensive and environmentally harmful detergents to remove lubricants from the final product. There are potential applications of ultrasonic lubrication in other areas as well. For example, ultrasonic lubrication can substantially enhance the user experience in personal health care products by eliminating the need for lubricants or coatings. In automobile applications, friction modulation can improve the performance of ball joints whereas friction reduction between vehicle seats and rails facilitates seat movement, saving space and mass that would otherwise be occupied by traditional components and mechanisms. Ultrasonic lubrication can also help to improve fuel efficiency by reducing friction in powertrain and suspension systems.3 In space applications, where traditional lubricants cannot be used, ultrasonic lubrication can be employed to reduce wear and dramatically extend the life of critical components.
Laboratory demonstrations of friction reduction through ultrasonic lubrication are numerous. Friction reduction is quantified as the difference between the friction force measured without ultrasonic lubrication and the friction force with ultrasonic vibrations applied. In either case, the friction force is directly measured with force sensors. Littmann et al. 4-5 connected a piezoelectrically-driven actuator to a slider, on which a force sensor and a frame were installed for measuring friction forces and applying normal loads. A pneumatic actuator was employed to push the slider together with the actuator along a guide rail. Ultrasonic vibrations were applied in the direction longitudinal to the sliding velocity. Bharadwaj and Dapino6-7 conducted similar experiments using a piezoelectric stack actuator connected to a conical waveguide at either end of the stack. Contacts took place between the spherical edges of the cones and the surface of the guide rail. The effects of system parameters such as contact stiffness, normal load, and global stiffness were studied. Kumar and Hutchings8 installed a pin on a sonotrode which was energized by an ultrasonic transducer. Ultrasonic vibrations were generated and transmitted to the pin, which was placed in contact with a tool steel surface. Normal force was applied by a pneumatic cylinder and measured by a load cell. The relative motion between the pin and the disc was created by a reciprocating table.
Pohlman and Lehfeldt9 also implemented a pin-on-disc experiment. Unlike other studies, they employed a magnetostrictive transducer to generate ultrasonic vibrations. To study the optimum direction for ultrasonic friction reduction, the transducer was carefully aligned so that the vibrational direction was longitudinal, transverse, and vertical to the macroscopic velocity. They studied ultrasonic friction reduction on both dry and lubricated surfaces. Popov et al.10 utilized an actuator with conical waveguides. The actuator was placed in contact with a rotating base plate. Cones made of nine materials with various hardnesses were adopted to study the influence of material hardness on ultrasonic friction reduction. Dong and Dapino11-13 used a piezoelectric transducer to generate and transmit ultrasonic vibrations to a prismatic waveguide with rounded edges. The longitudinal vibration causes vertical vibration due to Poisson&#8217;s effect. A slider with a curved top was placed under and in contact the waveguide. A frame was built to apply normal forces at the contact interface. The slider was pulled manually around the center area of the waveguide; the friction force was measured by a load cell that was connected to the slider.
Ultrasonically-induced wear reduction was also investigated and demonstrated. Volume loss, weight loss, and surface roughness changes are employed to quantify the severity of wear.Chowdhury and Helali14 vibrated a rotating disc in a pin-on-disc setup. The vibrations were generated by a support structure of two parallel plates located under the rotating disc. The top plate has a spherical ball installed off-center on the bottom surface, which slides in a slot that was engraved at the top surface of the bottom plate. The slot was machined with a periodically variable depth so that the top plate moves vertically during rotation. The frequencies ranged around 100 Hz according to the rotational speed.
Bryant and York15-16 studied the effect of micro-vibrations on wear reduction. They inserted a carbon cylinder through a holder with one end rested on a spinning steel disc and the other end connected to a coil spring. In one case, the cylinder was snug fitted in the holder so that there was no space for vibration. In other cases, clearances were left to allow micro-vibrations of the cylinder while the cylinder was in contact with the spinning disc. The weight loss of the cylinder was measured to calculate the wear rate. It was shown that the self-generated micro-vibrations helped reduce wear by up to 50%.
Goto and Ashida17-18 also adopted a pin-on-disc experiment. They connected pin samples with a transducer via a tapered cone and a horn. The pin vibrated in the direction perpendicular to the disc surface. A mass was connected to the transducer on its top for applying normal loads. Friction forces were translated from the torque that was applied to rotate the disc. Wear was identified as adhesive because both pin and disc were made of carbon steel. Wear rates were calculated from volume loss measurements.
It has been shown that linear speed plays an important role in ultrasonic lubrication. The experimental component of this research focuses on the dependence of friction and wear reduction on linear speed.

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	<tbody>
		<tr>
			<td>DC Motor&#160;</td>
			<td>Minarik&#160;</td>
			<td>SL14</td>
		</tr>
		<tr>
			<td>Electrical amplifier</td>
			<td>AE Techron</td>
			<td>LVC5050</td>
		</tr>
		<tr>
			<td>Signal conditioner&#160;</td>
			<td>Vishay Measurements Group</td>
			<td>2310</td>
		</tr>
		<tr>
			<td>Signal generator</td>
			<td>Agilent&#160;</td>
			<td>33120A</td>
		</tr>
		<tr>
			<td>Piezoelectric stack</td>
			<td>EDO corporation</td>
			<td>EP200-62</td>
		</tr>
		<tr>
			<td>Load cell</td>
			<td>Transducer Techniques</td>
			<td>MLP-50</td>
		</tr>
		<tr>
			<td>Load sensor pad</td>
			<td>FlexiForce</td>
			<td>A201</td>
		</tr>
		<tr>
			<td>Laser meter</td>
			<td>Keyence corporation&#160;</td>
			<td>LK-G32</td>
		</tr>
		<tr>
			<td>Hall-effect probe and gaussmeter</td>
			<td>Walker Scientific, Inc.</td>
			<td>MG-4D</td>
		</tr>
		<tr>
			<td>Data acquisition module</td>
			<td>Data Physics</td>
			<td>Quattro</td>
		</tr>
		<tr>
			<td>Data acquisition software</td>
			<td>Data Physics</td>
			<td>SignalCalc Ace</td>
		</tr>
		<tr>
			<td>Thermocouple reader</td>
			<td>Omega</td>
			<td>HH22</td>
		</tr>
		<tr>
			<td>Optical profilometer</td>
			<td>Bruker</td>
			<td>Contour GT</td>
		</tr>
		<tr>
			<td>Profilometer operation software</td>
			<td>Bruker&#160;</td>
			<td>Vision 64</td>
		</tr>
	</tbody>
</table>

experiments on ultrasonic lubrication using a piezoelectrically-assisted tribometer and optical profilometer

Friction and wear are detrimental to engineered systems. Ultrasonic lubrication is achieved when the interface between two sliding surfaces is vibrated at a frequency above the acoustic range (20 kHz). As a solid-state technology, ultrasonic lubrication can be used where conventional lubricants are unfeasible or undesirable. Further, ultrasonic lubrication allows for electrical modulation of the effective friction coefficient between two sliding surfaces. This property enables adaptive systems that modify their frictional state and associated dynamic response as the operating conditions change. Surface wear can also be reduced through ultrasonic lubrication. We developed a protocol to investigate the dependence of friction force reduction and wear reduction on the linear sliding velocity between ultrasonically lubricated surfaces. A pin-on-disc tribometer was built which differs from commercial units in that a piezoelectric stack is used to vibrate the pin at 22 kHz normal to the rotating disc surface. Friction and wear metrics including effective friction force, volume loss, and surface roughness are measured without and with ultrasonic vibrations at a constant pressure of 1 to 4 MPa and three different sliding velocities: 20.3, 40.6, and 87 mm/sec. An optical profilometer is utilized to characterize the wear surfaces. The effective friction force is reduced by 62% at 20.3 mm/sec. Consistently with existing theories for ultrasonic lubrication, the percent reduction in friction force diminishes with increasing speed, down to 29% friction force reduction at 87 mm/sec. Wear reduction remains essentially constant (49%) at the three speeds considered.

The representative measurements presented here were obtained from the modified tribometer shown in Figure 1. The piezoelectric actuator generates vibrations with amplitude of 2.5 &#956;m at a frequency of 22 kHz. To study the dependence of friction and wear reduction on linear velocity, three different speeds (20.3, 40.6, and 87 mm/sec) were applied to the disc by changing the rotational speed of the motor. For all three groups, the number of disc revolutions and the travel distance of the pin were chose...

Watch this Scientific Journal Video about Experiments on Ultrasonic Lubrication Using a Piezoelectrically-assisted Tribometer and Optical Profilometer at JoVE.com

Experiments on Ultrasonic Lubrication Using a Piezoelectrically-assisted Tribometer and Optical Profilometer

We present a protocol for using a piezoelectrically-assisted tribometer and optical profilometer to investigate the dependence of ultrasonic wear and friction reduction on linear velocity, contact pressure, and surface properties.

Friction and wear are detrimental to engineered systems. Ultrasonic lubrication is achieved when the interface between two sliding surfaces is vibrated at ...

experiments-on-ultrasonic-lubrication-using-piezoelectrically

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Engineering

Construction and Testing of Coin Cells of Lithium Ion Batteries

Rechargeable lithium ion batteries have wide applications in electronics, where customers always demand more capacity and longer lifetime. Lithium ion batteries have also been considered to be used in electric and hybrid vehicles1 or even electrical grid stabilization systems2. All these applications simulate a dramatic increase in the research and development of battery materials3-7, including new materials3,8, doping9, nanostructuring10-13, coatings or surface modifications14-17 and novel binders18. Consequently, an increasing number of physicists, chemists and materials scientists have recently ventured into this area. Coin cells are widely used in research laboratories to test new battery materials; even for the research and development that target large-scale and high-power applications, small coin cells are often used to test the capacities and rate capabilities of new materials in the initial stage. 
 In 2010, we started a National Science Foundation (NSF) sponsored research project to investigate the surface adsorption and disordering in battery materials (grant no. DMR-1006515). In the initial stage of this project, we have struggled to learn the techniques of assembling and testing coin cells, which cannot be achieved without numerous help of other researchers in other universities (through frequent calls, email exchanges and two site visits). Thus, we feel that it is beneficial to document, by both text and video, a protocol of assembling and testing a coin cell, which will help other new researchers in this field. This effort represents the "Broader Impact" activities of our NSF project, and it will also help to educate and inspire students.
In this video article, we document a protocol to assemble a CR2032 coin cell with a LiCoO2 working electrode, a Li counter electrode, and (the mostly commonly used) polyvinylidene fluoride (PVDF) binder. To ensure new learners to readily repeat the protocol, we keep the protocol as specific and explicit as we can. However, it is important to note that in specific research and development work, many parameters adopted here can be varied. First, one can make coin cells of different sizes and test the working electrode against a counter electrode other than Li. Second, the amounts of C black and binder added into the working electrodes are often varied to suit the particular purpose of research; for example, large amounts of C black or even inert powder were added to the working electrode to test the "intrinsic" performance of cathode materials14. Third, better binders (other than PVDF) have also developed and used18. Finally, other types of electrolytes (instead of LiPF6) can also be used; in fact, certain high-voltage electrode materials will require the uses of special electrolytes7.

A protocol to construct and test coin cells of lithium ion batteries is described. The specific procedures of making a working electrode, preparing a counter electrode, assembling a cell inside a glovebox and testing the cell are presented.

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

Fabricating Metamaterials Using the Fiber Drawing Method

Metamaterials are man-made composite materials, fabricated by assembling components much smaller than the wavelength at which they operate 1. They owe their electromagnetic properties to the structure of their constituents, instead of the atoms that compose them. For example, sub-wavelength metal wires can be arranged to possess an effective electric permittivity that is either positive or negative at a given frequency, in contrast to the metals themselves 2. This unprecedented control over the behaviour of light can potentially lead to a number of novel devices, such as invisibility cloaks 3, negative refractive index materials 4, and lenses that resolve objects below the diffraction limit 5. However, metamaterials operating at optical, mid-infrared and terahertz frequencies are conventionally made using nano- and micro-fabrication techniques that are expensive and produce samples that are at most a few centimetres in size 6-7. Here we present a fabrication method to produce hundreds of meters of metal wire metamaterials in fiber form, which exhibit a terahertz plasmonic response 8. We combine the stack-and-draw technique used to produce microstructured polymer optical fiber 9 with the Taylor-wire process 10, using indium wires inside polymethylmethacrylate (PMMA) tubes. PMMA is chosen because it is an easy to handle, drawable dielectric with suitable optical properties in the terahertz region; indium because it has a melting temperature of 156.6 &deg;C which is appropriate for codrawing with PMMA. We include an indium wire of 1 mm diameter and 99.99% purity in a PMMA tube with 1 mm inner diameter (ID) and 12 mm outside diameter (OD) which is sealed at one end. The tube is evacuated and drawn down to an outer diameter of 1.2 mm. The resulting fiber is then cut into smaller pieces, and stacked into a larger PMMA tube. This stack is sealed at one end and fed into a furnace while being rapidly drawn, reducing the diameter of the structure by a factor of 10, and increasing the length by a factor of 100. Such fibers possess features on the micro- and nano- scale, are inherently flexible, mass-producible, and can be woven to exhibit electromagnetic properties that are not found in nature. They represent a promising platform for a number of novel devices from terahertz to optical frequencies, such as invisible fibers, woven negative refractive index cloths, and super-resolving lenses.

Metamaterials at terahertz frequencies offer unique opportunities, but are challenging to fabricate in bulk. We adapt the fabrication procedure for microstructured polymer optical fibers to inexpensively fabricate metamaterials potentially on an industrial scale. We produce polymethylmethacrylate fibers containing ~10 &mu;m diameter indium wires separated by ~100 &mu;m, which exhibit a terahertz plasmonic response.

Metamaterials are man-made composite materials, fabricated by assembling components much smaller than the wavelength at which they operate 1. They owe ...

Optical Trapping of Nanoparticles

Optical trapping is a technique for immobilizing and manipulating small objects in a gentle way using light, and it has been widely applied in trapping and manipulating small biological particles. Ashkin and co-workers first demonstrated optical tweezers using a single focused beam1. The single beam trap can be described accurately using the perturbative gradient force formulation in the case of small Rayleigh regime particles1. In the perturbative regime, the optical power required for trapping a particle scales as the inverse fourth power of the particle size. High optical powers can damage dielectric particles and cause heating. For instance, trapped latex spheres of 109 nm in diameter were destroyed by a 15 mW beam in 25 sec1, which has serious implications for biological matter2,3.
A self-induced back-action (SIBA) optical trapping was proposed to trap 50 nm polystyrene spheres in the non-perturbative regime4. In a non-perturbative regime, even a small particle with little permittivity contrast to the background can influence significantly the ambient electromagnetic field and induce a large optical force. As a particle enters an illuminated aperture, light transmission increases dramatically because of dielectric loading. If the particle attempts to leave the aperture, decreased transmission causes a change in momentum outwards from the hole and, by Newton's Third Law, results in a force on the particle inwards into the hole, trapping the particle. The light transmission can be monitored; hence, the trap can become a sensor. The SIBA trapping technique can be further improved by using a double-nanohole structure.
The double-nanohole structure has been shown to give a strong local field enhancement5,6. Between the two sharp tips of the double-nanohole, a small particle can cause a large change in optical transmission, thereby inducing a large optical force. As a result, smaller nanoparticles can be trapped, such as 12 nm silicate spheres7 and 3.4 nm hydrodynamic radius bovine serum albumin proteins8. In this work, the experimental configuration used for nanoparticle trapping is outlined. First, we detail the assembly of the trapping setup which is based on a Thorlabs Optical Tweezer Kit. Next, we explain the nanofabrication procedure of the double-nanohole in a metal film, the fabrication of the microfluidic chamber and the sample preparation. Finally, we detail the data acquisition procedure and provide typical results for trapping 20 nm polystyrene nanospheres.

The following setup approach details low power optical trapping of dielectric nanoparticles using a double-nanohole in metal film.

Optical trapping is a technique for immobilizing and manipulating small objects in a gentle way using light, and it has been widely applied in trapping ...

Characterization of Surface Modifications by White Light Interferometry: Applications in Ion Sputtering, Laser Ablation, and Tribology Experiments

In materials science and engineering it is often necessary to obtain quantitative measurements of surface topography with micrometer lateral resolution. From the measured surface, 3D topographic maps can be subsequently analyzed using a variety of software packages to extract the information that is needed.
In this article we describe how white light interferometry, and optical profilometry (OP) in general, combined with generic surface analysis software, can be used for materials science and engineering tasks. In this article, a number of applications of white light interferometry for investigation of surface modifications in mass spectrometry, and wear phenomena in tribology and lubrication are demonstrated. We characterize the products of the interaction of semiconductors and metals with energetic ions (sputtering), and laser irradiation (ablation), as well as ex situ measurements of wear of tribological test specimens.
Specifically, we will discuss:
<ol class="lroman">
	<li>Aspects of traditional ion sputtering-based mass spectrometry such as sputtering rates/yields measurements on Si and Cu and subsequent time-to-depth conversion.</li>
	<li>Results of quantitative characterization of the interaction of femtosecond laser irradiation with a semiconductor surface. These results are important for applications such as ablation mass spectrometry, where the quantities of evaporated material can be studied and controlled via pulse duration and energy per pulse. Thus, by determining the crater geometry one can define depth and lateral resolution versus experimental setup conditions.</li>
	<li>Measurements of surface roughness parameters in two dimensions, and quantitative measurements of the surface wear that occur as a result of friction and wear tests.</li>
</ol>
Some inherent drawbacks, possible artifacts, and uncertainty assessments of the white light interferometry approach will be discussed and explained.

White light microscope interferometry is an optical, noncontact and quick method for measuring the topography of surfaces. It is shown how the method can be applied toward mechanical wear analysis, where wear scars on tribological test samples are analyzed; and in materials science to determine ion beam sputtering or laser ablation volumes and depths.

In materials science and engineering it is often necessary to obtain quantitative measurements of surface topography with micrometer lateral resolution. ...

Flame Experiments at the Advanced Light Source: New Insights into Soot Formation Processes

The following experimental protocols and the accompanying video are concerned with the flame experiments that are performed at the Chemical Dynamics Beamline of the Advanced Light Source (ALS) of the Lawrence Berkeley National Laboratory1-4. This video demonstrates how the complex chemical structures of laboratory-based model flames are analyzed using flame-sampling mass spectrometry with tunable synchrotron-generated vacuum-ultraviolet (VUV) radiation. This experimental approach combines isomer-resolving capabilities with high sensitivity and a large dynamic range5,6. The first part of the video describes experiments involving burner-stabilized, reduced-pressure (20-80 mbar) laminar premixed flames. A small hydrocarbon fuel was used for the selected flame to demonstrate the general experimental approach. It is shown how species&#8217; profiles are acquired as a function of distance from the burner surface and how the tunability of the VUV photon energy is used advantageously to identify many combustion intermediates based on their ionization energies. For example, this technique has been used to study gas-phase aspects of the soot-formation processes, and the video shows how the resonance-stabilized radicals, such as C3H3, C3H5, and i-C4H5, are identified as important intermediates7. The work has been focused on soot formation processes, and, from the chemical point of view, this process is very intriguing because chemical structures containing millions of carbon atoms are assembled from a fuel molecule possessing only a few carbon atoms in just milliseconds. The second part of the video highlights a new experiment, in which an opposed-flow diffusion flame and synchrotron-based aerosol mass spectrometry are used to study the chemical composition of the combustion-generated soot particles4. The experimental results indicate that the widely accepted H-abstraction-C2H2-addition (HACA) mechanism is not the sole molecular growth process responsible for the formation of the observed large polycyclic aromatic hydrocarbons (PAHs).

Gas sampling from laboratory-scale flames with online analysis of all species by mass spectrometry is a powerful method to investigate the complex mixture of chemical compounds occurring during combustion processes. Coupled with tunable soft ionization via synchrotron-generated vacuum-ultraviolet radiation, this technique provides isomer-resolved information and potentially fragment-free mass spectra.

The following experimental protocols and the accompanying video are concerned with the flame experiments that are performed at the Chemical Dynamics ...

Fabrication and Operation of a Nano-Optical Conveyor Belt

The technique of using focused laser beams to trap and exert forces on small particles has enabled many pivotal discoveries in the nanoscale biological and physical sciences over the past few decades. The progress made in this field invites further study of even smaller systems and at a larger scale, with tools that could be distributed more easily and made more widely available. Unfortunately, the fundamental laws of diffraction limit the minimum size of the focal spot of a laser beam, which makes particles smaller than a half-wavelength in diameter hard to trap and generally prevents an operator from discriminating between particles which are closer together than one half-wavelength. This precludes the optical manipulation of many closely-spaced nanoparticles and&#160;limits the&#160;resolution of optical-mechanical systems. Furthermore, manipulation using focused beams requires beam-forming or steering optics, which can be very bulky and expensive. To address these limitations in the system scalability of conventional optical trapping our lab has devised an alternative technique which utilizes near-field optics to move particles across a chip. Instead of focusing laser beams in the far-field, the optical near field of plasmonic resonators produces the necessary local optical intensity enhancement to overcome the restrictions of diffraction and manipulate particles at higher resolution. Closely-spaced resonators produce strong optical traps which can be addressed to mediate the hand-off of particles from one to the next in a conveyor-belt-like fashion. Here, we describe how to design and produce a conveyor belt using a gold surface patterned with plasmonic C-shaped resonators and how to operate it with polarized laser light to achieve super-resolution nanoparticle manipulation and transport. The nano-optical conveyor belt chip can be produced using lithography techniques and easily packaged and distributed.

The scalability and resolution of conventional optical manipulation techniques are limited by diffraction. We circumvent the diffraction limit and describe a method of optically transporting nanoparticles across a chip using a gold surface patterned with a path of closely spaced C-shaped plasmonic resonators.

The technique of using focused laser beams to trap and exert forces on small particles has enabled many pivotal discoveries in the nanoscale biological ...

Visualizing Hyporheic Flow Through Bedforms Using Dye Experiments and Simulation

Advective exchange between the pore space of sediments and the overlying water column, called hyporheic exchange in fluvial environments, drives solute transport in rivers and many important biogeochemical processes. To improve understanding of these processes through visual demonstration, we created a hyporheic flow simulation in the multi-agent computer modeling platform NetLogo. The simulation shows virtual tracer flowing through a streambed covered with two-dimensional bedforms. Sediment, flow, and bedform characteristics are used as input variables for the model. We illustrate how these simulations match experimental observations from laboratory flume experiments based on measured input parameters. Dye is injected into the flume sediments to visualize the porewater flow. For comparison virtual tracer particles are placed at the same locations in the simulation. This coupled simulation and lab experiment has been used successfully in undergraduate and graduate laboratories to directly visualize river-porewater interactions and show how physically-based flow simulations can reproduce environmental phenomena. Students took photographs of the bed through the transparent flume walls and compared them to shapes of the dye at the same times in the simulation. This resulted in very similar trends, which allowed the students to better understand both the flow patterns and the mathematical model. The simulations also allow the user to quickly visualize the impact of each input parameter by running multiple simulations. This process can also be used in research applications to illustrate basic processes, relate interfacial fluxes and porewater transport, and support quantitative process-based modeling.

This manuscript describes how to create regular bedforms in a flume, visualize flow through the bedforms, and use computer simulations to simulate the hyporheic flow. The computer simulations compare well with the experimental observations. This coupled simulation and experiment is well-suited for both research and educational purposes.

Advective exchange between the pore space of sediments and the overlying water column, called hyporheic exchange in fluvial environments, drives solute ...

Writing Bragg Gratings in Multicore Fibers

Fiber Bragg gratings in multicore fibers can be used as compact and robust filters in astronomical and other research and commercial applications. Strong suppression at a single wavelength requires that all cores have matching transmission profiles. These gratings cannot be inscribed using the same method as for single-core fibers because the curved surface of the cladding acts as a lens, focusing the incoming UV laser beam and causing variations in exposure between cores. Therefore we use an additional optical element to ensure that the beam shape does not change while passing through the cross-section of the multicore fiber. This consists of a glass capillary tube which has been polished flat on one side, which is then placed over the section of the fiber to be inscribed. The laser beam enters the fiber through the flat surface of the capillary tube and hence maintains its original dimensions. This paper demonstrates the improvements in core-to-core uniformity for a 7-core fiber using this method. The technique can be generalized to larger multicore fibers.

We describe a technique for inscribing identical fiber Bragg gratings into each core of a multicore fiber. This is achieved by introducing an additional surface into the optical path to mitigate lensing by the curved surface of the fiber cladding.

Fiber Bragg gratings in multicore fibers can be used as compact and robust filters in astronomical and other research and commercial applications. Strong ...

Compact Lens-less Digital Holographic Microscope for MEMS Inspection and Characterization

A micro-electro-mechanical-system (MEMS) is a widely used component in many industries, including energy, biotechnology, medical, communications, and automotive. However, effective inspection and characterization metrology systems are needed to ensure the functional reliability of MEMS. This study presents a system based on digital holography as a tool for MEMS metrology. Digital holography has gained increasing attention in the past 20 years. With the fast development and decreasing cost of sensor arrays, resolution of such systems has increased broadening potential applications. Thus, it has attracted attention from both research and industry sides as a potential reliable tool for industrial metrology. Indeed, by recording the interference pattern between an object beam (which contains sample height information) and a reference beam on a CCD camera, one can retrieve the quantitative phase information of an object. However, most of digital holographic systems are bulky and thus not easy to implement on industry production lines. The novelty of the system presented is that it is lens-less and thus very compact. In this study, it is shown that the Compact Digital Holographic Microscope (CDHM) can be used to evaluate several characteristics typically consider as criteria in MEMS inspections. The surface profiles of MEMS in both static and dynamic conditions are presented. Comparison with AFM is investigated to validate the accuracy of the CDHM.

We present a compact reflection digital holographic system (CDHM) for inspection and characterization of MEMS devices. A lens-less design using a diverging input wave providing natural geometrical magnification is demonstrated. Both static and dynamic studies are presented.

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

Ultrasonic Fatigue Testing in the Tension-Compression Mode

Ultrasonic fatigue testing is one of a few methods which allow investigating fatigue properties in the ultra-high cycle region. The method is based on exposing the specimen to longitudinal vibrations on its resonance frequency close to 20 kHz. With use of this method, it is possible to significantly decrease the time required for the test, when compared to conventional testing devices usually working at frequencies under 200 Hz. It is also used to simulate loading of material during operation in high speed conditions, such as those experienced by components of jet engines or car turbo pumps. It is necessary to operate only in the high and ultra-high cycle region, due to the possibility of extremely high deformation rates, which can have a significant influence on the test results. Specimen shape and dimensions have to be carefully selected and calculated to fulfill the resonance condition of the ultrasonic system; thus, it is not possible to test the full components or specimens of arbitrary shape. Before each test, it is necessary to harmonize the specimen with the frequency of the ultrasonic system to compensate for deviations of the real shape from the ideal one. It is not possible to run a test until a total fracture of the specimen, since the test is automatically terminated after initiation and propagation of the crack to a certain length, when the stiffness of the system changes enough to shift the system out of the resonance frequency. This manuscript describes the process of evaluation of materials' fatigue properties at high-frequency ultrasonic fatigue loading with use of mechanical resonance at a frequency close to 20 kHz. The protocol includes a detailed description of all steps required for a correct test, including specimen design, stress calculation, harmonizing with the resonance frequency, performing the test, and final static fracture.

A protocol for ultrasonic fatigue testing in the high and ultra-high cycle region in axial tension-compression loading mode.

Ultrasonic fatigue testing is one of a few methods which allow investigating fatigue properties in the ultra-high cycle region. The method is based on ...