Name: flow-assisted dielectrophoresis: a low cost method for the fabrication of high performance solution-processable nanowire devices
Uploaded: 2017-12-07T14:00:00
Description: Watch this Scientific Journal Video about Flow-assisted Dielectrophoresis: A Low Cost Method for the Fabrication of High Performance Solution-processable Nanowire Devices at JoVE.com

The authors would like to thank ESPRC and BAE systems for financial support, and Prof. Brian A. Korgel and his group for the supply of SFLS grown silicon nanowires used in this work.

Caution: All procedures unless otherwise stated take place in a clean room environment and risk assessments have been done to ensure safety during nanowires and chemicals handling. Nanomaterials may have a number of health implications which are as of yet unknown, and so should be handled with appropriate care21.
NOTE: The process starts with the preparation of the substrates, followed by the first photolithography and metal deposition steps to define the DEP contacts. ...

<ol>
	<li>Constantinou, M., Rigas, G. P., 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=Simultaneous+Tunable+Selection+and+Self-Assembly+of+Si+Nanowires+from+Heterogeneous+Feedstock.">Simultaneous Tunable Selection and Self-Assembly of Si Nanowires from Heterogeneous Feedstock.</a> ACS Nano. , (2016).</li><li>Constantinou, M., Hoettges, K. F., 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=Rapid+determination+of+nanowires+electrical+properties+using+a+dielectrophoresis-well+based+system.">Rapid determination of nanowires electrical properties using a dielectrophoresis-well based system.</a> App. Phy. Lett. 110 (13), 1-6 (2017).</li><li>Huang, H., Lee, Y. C., Tan, O. K., Zhou, W., Peng, N., Zhang, Q. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High+sensitivity+SnO2+single-nanorod+sensors+for+the+detection+of+H2+gas+at+low+temperature.">High sensitivity SnO2 single-nanorod sensors for the detection of H2 gas at low temperature.</a> Nanotech. 20 (11), 115501 (2009).</li><li>Rutherglen, C., Jain, D., Burke, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nanotube+electronics+for+radiofrequency+applications.">Nanotube electronics for radiofrequency applications.</a> Nat. nanotech. 4 (12), 811-819 (2009).</li><li>Kang, M. G., Hwang, D. H., Kim, B. S., Whang, D., Hwang, S. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=RF+characterization+of+germanium+nanowire+field+effect+transistors.">RF characterization of germanium nanowire field effect transistors.</a> AIP Conf. Proc. 1399 (2011), 319-320 (2011).</li><li>Collet, M., Salomon, S., 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=Large-scale+assembly+of+single+nanowires+through+capillary-assisted+dielectrophoresis.">Large-scale assembly of single nanowires through capillary-assisted dielectrophoresis.</a> Adv. Mat. 27 (7), 1268-1273 (2015).</li><li>Pethig, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dielectrophoresis:+Status+of+the+theory,+technology,+and+applications.">Dielectrophoresis: Status of the theory, technology, and applications.</a> Biomicrofluidics. 4 (2), (2010).</li><li>Jones, T. 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> Electromechanics of particles. (2), (1995).</li><li>El-Ali, J., Sorger, P. K., Jensen, K. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cells+on+chips.">Cells on chips.</a> Nat. 442 (7101), 403-411 (2006).</li><li>Doh, I., Cho, Y. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+continuous+cell+separation+chip+using+hydrodynamic+dielectrophoresis+(DEP)+process.">A continuous cell separation chip using hydrodynamic dielectrophoresis (DEP) process.</a> Sensrs. and Actrs, A: Phys. 121 (1), 59-65 (2005).</li><li>Freer, E. M., Grachev, O., Duan, X., Martin, S., Stumbo, D. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-yield+self-limiting+single-nanowire+assembly+with+dielectrophoresis.">High-yield self-limiting single-nanowire assembly with dielectrophoresis.</a> Nat. nanotech. 5 (7), 525-530 (2010).</li><li>Monica, A. H., Papadakis, S. J., Osiander, R., Paranjape, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Wafer-level+assembly+of+carbon+nanotube+networks+using+dielectrophoresis.">Wafer-level assembly of carbon nanotube networks using dielectrophoresis.</a> Nanotech. 19, 85303 (2008).</li><li>Raychaudhuri, S., Dayeh, S. A., Wang, D., Yu, E. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Precise+semiconductor+nanowire+placement+through+dielectrophoresis.">Precise semiconductor nanowire placement through dielectrophoresis.</a> Nano Lett. 9 (6), 2260-2266 (2009).</li><li>Schmidt, V., Riel, H., Senz, S., Karg, S., Riess, W., G&#246;sele, U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Realization+of+a+silicon+nanowire+vertical+surround-gate+field-effect+transistor.">Realization of a silicon nanowire vertical surround-gate field-effect transistor.</a> Small. 2 (1), 85-88 (2006).</li><li>Hanrath, T., Korgel, B. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Supercritical+fluid-liquid-solid+(SFLS)+synthesis+of+Si+and+Ge+nanowires+seeded+by+colloidal+metal+nanocrystals.">Supercritical fluid-liquid-solid (SFLS) synthesis of Si and Ge nanowires seeded by colloidal metal nanocrystals.</a> Adv. Mat. 15 (5), 437-440 (2003).</li><li>Heitsch, A. T., Akhavan, V. A., Korgel, B. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+SFLS+synthesis+of+Si+nanowires+using+trisilane+with+in+situ+alkyl-amine+passivation.">Rapid SFLS synthesis of Si nanowires using trisilane with in situ alkyl-amine passivation.</a> Chem. of Mat. 23 (11), 2697-2699 (2011).</li><li>Constantinou, M., Stolojan, V., 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=Interface+Passivation+and+Trap+Reduction+via+a+Solution-Based+Method+for+Near-Zero+Hysteresis+Nanowire+Field-Effect+Transistors.">Interface Passivation and Trap Reduction via a Solution-Based Method for Near-Zero Hysteresis Nanowire Field-Effect Transistors.</a> ACS App. Mat. and Intf. 7 (40), 22115-22120 (2015).</li><li>Kim, T. H., Lee, S. Y., 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=Dielectrophoretic+alignment+of+gallium+nitride+nanowires+(GaN+NWs)+for+use+in+device+applications.">Dielectrophoretic alignment of gallium nitride nanowires (GaN NWs) for use in device applications.</a> Nanotech. 17 (14), 3394-3399 (2006).</li><li>Boote, J., Evans, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dielectrophoretic+manipulation+and+electrical+characterization+of+gold+nanowires.">Dielectrophoretic manipulation and electrical characterization of gold nanowires.</a> Nanotech. 16 (9), 1500-1505 (2005).</li><li>Gierhart, B. C., Howitt, D. G., Chen, S. J., Smith, R. L., Collins, S. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Frequency+Dependence+of+Gold+Nanoparticle+Superassembly+by+Dielectrophoresis.">Frequency Dependence of Gold Nanoparticle Superassembly by Dielectrophoresis.</a> Langmuir. 23 (19), 12450-12456 (2007).</li><li>Klaine, S. J., Alvarez, P. J. J., 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=Nanomaterials+in+the+environment:+behavior,+fate,+bioavailability,+and+effects.">Nanomaterials in the environment: behavior, fate, bioavailability, and effects.</a> Environ. tox. and chem. / SETAC. 27 (9), 1825-1851 (2008).</li><li>van Tilburg, J. W. W., Algra, R. E., Immink, W. G. G., Verheijen, M., Bakkers, E. P. A. M., Kouwenhoven, L. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Surface+passivated+InAs/InP+core/shell+nanowires.">Surface passivated InAs/InP core/shell nanowires.</a> Semicond. Sci. and Tech. 25 (2), 24011 (2010).</li><li>Krupke, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Separation+of+Metallic+from+Semiconducting+Single-Walled+Carbon+Nanotubes.">Separation of Metallic from Semiconducting Single-Walled Carbon Nanotubes.</a> Sci. 301 (5631), 344-347 (2003).</li></ol>

The successful fabrication and performance of the devices depend on several key factors. These include nanowire density and distribution in the formulation, the choice of solvent, the frequency of DEP, and the control of the number of nanowires present on the device electrodes1.
One of the critical steps in achieving repeatable working devices is the preparation of a nanowire formulation without clusters or clumps. The formulation can be sonicated before DEP to reduce t...

Controllable and reproducible assembly of nanoparticles in pre-defined substrate locations is one of the main challenges in solution-processed electronic and photonic devices utilizing semiconducting or conducting nanoparticles. For high performance devices, it is also highly beneficial to be able to select nanoparticles with preferential sizes, and particular electronic properties, including, for example, high conductivity and low density of surface trap states. Despite significant progress in nanomaterials growth, including nanowire and nanotube materials, some variations of nanoparticle properties are always present, and a selection step can significantly improve nanoparticle-based device performance1,2.
The purpose of the flow-assisted DEP method demonstrated in this work is to address the above challenges by showing controllable semiconducting nanowires assembly onto metallic contacts for high performance nanowire field effect transistors. DEP solves several problems of nanowire device fabrication in a single step including positioning of nanowires, alignment/orientation of nanowires, and selection of nanowires with desired properties via DEP signal frequency selection1. DEP has been used for numerous other devices ranging from gas sensors3, transistors1, and RF switches4,5, to the positioning of bacteria for analysis7.
DEP is the manipulation of polarizable particles via the application of a non-uniform electric field resulting in nanowires self-assembly across the electrodes8. The method was originally developed for the manipulation of bacteria9,10 but has since been expanded to the manipulation of nanowires and nanomaterials.
DEP solution processing of nanoparticles enables semiconductor device fabrication that significantly differs from traditional top-down techniques based on multiple photomasking, ion implantation, high temperature14, annealing, and etching steps. Since DEP manipulates nanoparticles that have already been synthesized, it is a low-temperature, bottom-up fabrication technique11. This approach allows large-scale nanowire devices to be assembled on almost any substrate including temperature-sensitive, flexible plastic substrates6,12,13.
In this work, high performance p-type silicon nanowire field effect transistors are fabricated using flow-assisted DEP, and the FET current-voltage characterization is conducted. The silicon nanowires used in this work are grown via the Super Fluid Liquid Solid (SFLS) method15,16. The nanowires are intentionally&#160;doped, and are approximately 10 - 50 &#181;m in length and 30 - 40 nm in diameter. The SFLS growth method is very attractive since it can offer industry scalable amounts of nanowire materials15. The proposed nanowire assembly methodology is directly applicable to other semiconductor nanowire materials such as InAs13, SnO23, and GaN18. The technique can also be expanded to align conductive nanowires19 and to position nanoparticles across electrode gaps20.

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	<tbody>
		<tr>
			<td>Silicon/silicon dioxide wafer, CZ method growth, 100mm diameter,&#160; 300 nm oxide thermal growth,&#160; n-doped phosphorus</td>
			<td>Si-Mat (Silicon materials)</td>
			<td>-</td>
			<td>http://si-mat.com/</td>
		</tr>
		<tr>
			<td>Acetone (200ml)</td>
			<td>Sigma Aldrich</td>
			<td>W332615</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Isopropanol (200ml)</td>
			<td>Sigma Aldrich</td>
			<td>W292907</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Deionised water (150ml)</td>
			<td>On site supply</td>
			<td>-</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Photoresist (A) SF6 PMGI under etch photoresit (approx 1 ml per sample)</td>
			<td>Microchem&#160;</td>
			<td>-</td>
			<td>http://microchem.com/pdf/PMGI-Resists-data-sheetV-rhcedit-102206.pdf</td>
		</tr>
		<tr>
			<td>Photoresist (B) S1805 photoresit) (approx 1 ml per sample)</td>
			<td>Microchem&#160;</td>
			<td>-</td>
			<td>http://www.microchem.com/PDFs_Dow/S1800.pdf</td>
		</tr>
		<tr>
			<td>Photoresist developer (A) Microposit&#160; MF319&#160; (100ml)</td>
			<td>Microchem&#160;</td>
			<td>-</td>
			<td>http://microchem.com/products/images/uploads/MF_319_Data_Sheet.pdf</td>
		</tr>
		<tr>
			<td>Photoresist remover (A) Microposit remover 1165 (300ml (2 baths 150 each))</td>
			<td>Microchem&#160;</td>
			<td>-</td>
			<td>http://micromaterialstech.com/wp-content/dow_electronic_materials/datasheets/1165_Remover.pdf</td>
		</tr>
	</tbody>
</table>

flow-assisted dielectrophoresis: a low cost method for the fabrication of high performance solution-processable nanowire devices

Flow-assisted dielectrophoresis (DEP) is an efficient self-assembly method for the controllable and reproducible positioning, alignment, and selection of nanowires. DEP is used for nanowire analysis, characterization, and for solution-based fabrication of semiconducting devices. The method works by applying an alternating electric field between metallic electrodes. The nanowire formulation is then dropped onto the electrodes which are on an inclined surface to create a flow of the formulation using gravity. The nanowires then align along the gradient of the electric field and in the direction of the liquid flow. The frequency of the field can be adjusted to select nanowires with superior conductivity and lower trap density. 
In this work, flow-assisted DEP is used to create nanowire field effect transistors. Flow-assisted DEP has several advantages: it allows selection of nanowire electrical properties; control of nanowire length; placement of nanowires in specific areas; control of orientation of nanowires; and control of nanowire density in the device. 
The technique can be expanded to many other applications such as gas sensors and microwave switches. The technique is efficient, quick, reproducible, and it uses a minimal amount of dilute solution making it ideal for the testing of novel nanomaterials. Wafer scale assembly of nanowire devices can also be achieved using this technique, allowing large numbers of samples for testing and large-area electronic applications.

Bilayer photolithography results in clean sharply defined electrodes. In the example (Figure 1A), inter-digitated finger structure was used with a channel length of 10 &#181;m. These structures allow a large area to assemble the maximum number of nanowires when the DEP force is applied. Figure 1B shows a schematic of a bottom-gate nanowire FET device.
Incorrect nanowire...

Watch this Scientific Journal Video about Flow-assisted Dielectrophoresis: A Low Cost Method for the Fabrication of High Performance Solution-processable Nanowire Devices at JoVE.com

Flow-assisted Dielectrophoresis: A Low Cost Method for the Fabrication of High Performance Solution-processable Nanowire Devices

In this paper, flow assisted dielectrophoresis is demonstrated for the self-assembly of nanowire devices. The fabrication of a silicon nanowire field effect transistor is shown as an example.

Flow-assisted dielectrophoresis (DEP) is an efficient self-assembly method for the controllable and reproducible positioning, alignment, and selection of ...

The overall goal of this procedure is to demonstrate electric field assistance assembly and selection of high quality semi-conducting nanowires including fabrication of metal electrodes and use of these electrodes in flow-assisted dielectrophoresis to create solution-processable nanowire field effect transistors.This method can help us solve one of the main challenges in the field of solution-processable electronics such as placement of semi-conducting nanomaterials, control of the pilation done and field train of superior quality nanowires.The main function of this technique is that it's a fast reproducible method that can be scaled off controllable fabrication of nano material based devices.Although this method can provide insight into the alignment and selection of nanowires, it can also be applied in the alignment of nanotubes, nano flakes and blade-like nanomaterials.Most steps in this protocol take place in a clean room environment.Start with heavily doped four-inch N type silicon/silicon dioxide wafer.Use a diamond scribe to cut the wafer to produce suitably sized samples.Take care not to touch the top surface.Split the wafer along the cuts to yield several samples.The samples for this experiment are 2.5 x 2.5 centimeters.When done, take the samples to an ultrasonic bath.Place the samples on a substrate holder and immerse them in a beaker of deionized water.Sonicate the samples in the beaker for five minutes at full power.Then transfer the samples to a beaker with acetone before sonicating them for five minutes at full power again.Finally, transfer the samples to a beaker with isopropanol and sonicate for an additional five minutes at full power.Remove the samples from the ultrasonic bath and dry them with a nitrogen gun.Next, transfer the samples to a plasma asher to remove any remaining organic residues.For photolithography, move the samples to a yellow room.Work in a fume cupboard with a hotplate at 150

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Engineering

Analysis of Contact Interfaces for Single GaN Nanowire Devices

Single GaN nanowire (NW) devices fabricated on SiO2 can exhibit a strong degradation after annealing due to the occurrence of void formation at the contact/SiO2 interface. This void formation can cause cracking and delamination of the metal film, which can increase the resistance or lead to a complete failure of the NW device. In order to address issues associated with void formation, a technique was developed that removes Ni/Au contact metal films from the substrates to allow for the examination and characterization of the contact/substrate and contact/NW interfaces of single GaN NW devices. This procedure determines the degree of adhesion of the contact films to the substrate and NWs and allows for the characterization of the morphology and composition of the contact interface with the substrate and nanowires. This technique is also useful for assessing the amount of residual contamination that remains from the NW suspension and from photolithographic processes on the NW-SiO2 surface prior to metal deposition. The detailed steps of this procedure are presented for the removal of annealed Ni/Au contacts to Mg-doped GaN NWs on a SiO2 substrate.

A technique was developed that removes Ni/Au contact metal films from their substrate to allow for the examination and characterization of the contact/substrate and contact/NW interfaces of single GaN nanowire devices.

Single GaN nanowire (NW) devices fabricated on SiO2 can exhibit  a strong degradation after annealing due to the  occurrence of void formation at the ...

A High Performance Impedance-based Platform for Evaporation Rate Detection

This paper describes the method of a novel impedance-based platform for the detection of the evaporation rate. The model compound hyaluronic acid was employed here for demonstration purposes. Multiple evaporation tests on the model compound as a humectant with various concentrations in solutions were conducted for comparison purposes. A conventional weight loss approach is known as the most straightforward, but time-consuming, measurement technique for evaporation rate detection. Yet, a clear disadvantage is that a large volume of sample is required and multiple sample tests cannot be conducted at the same time. For the first time in literature, an electrical impedance sensing chip is successfully applied to a real-time evaporation investigation in a time sharing, continuous and automatic manner. Moreover, as little as 0.5 ml of test samples is required in this impedance-based apparatus, and a large impedance variation is demonstrated among various dilute solutions. The proposed high-sensitivity and fast-response impedance sensing system is found to outperform a conventional weight loss approach in terms of evaporation rate detection.

This paper presents an impedance-based apparatus for evaporation rate detection of solutions. It offers clear advantages over a conventional weight loss approach: a fast response, high-sensitivity detection, a small sample requirement, multiple sample measurements, and easy disassembly for cleaning and reuse purposes.

This paper describes the method of a novel impedance-based platform for the detection of the evaporation rate. The model compound hyaluronic acid was ...

Solvent Bonding for Fabrication of PMMA and COP Microfluidic Devices

Thermoplastic microfluidic devices offer many advantages over those made from silicone elastomers, but bonding procedures must be developed for each thermoplastic of interest. Solvent bonding is a simple and versatile method that can be used to fabricate devices from a variety of plastics. An appropriate solvent is added between two device layers to be bonded, and heat and pressure are applied to the device to facilitate the bonding. By using an appropriate combination of solvent, plastic, heat, and pressure, the device can be sealed with a high quality bond, characterized as having high bond coverage, bond strength, optical clarity, durability over time, and low deformation or damage to microfeature geometry. We describe the procedure for bonding devices made from two popular thermoplastics, poly(methyl-methacrylate) (PMMA), and cyclo-olefin polymer (COP), as well as a variety of methods to characterize the quality of the resulting bonds, and strategies to troubleshoot low quality bonds. These methods can be used to develop new solvent bonding protocols for other plastic-solvent systems.

Solvent bonding is a simple and versatile method for fabricating thermoplastic microfluidic devices with high quality bonds. We describe a protocol to achieve strong, optically clear bonds in PMMA and COP microfluidic devices that preserve microfeature details, by a judicious combination of pressure, temperature, an appropriate solvent, and device geometry.

Thermoplastic microfluidic devices offer many advantages over those made from silicone elastomers, but bonding procedures must be developed for each ...

Scalable Solution-processed Fabrication Strategy for High-performance, Flexible, Transparent Electrodes with Embedded Metal Mesh

Here, the authors report the embedded metal-mesh transparent electrode (EMTE), a new transparent electrode (TE) with a metal mesh completely embedded in a polymer film. This paper also presents a low-cost, vacuum-free fabrication method for this novel TE; the approach combines lithography, electroplating, and imprint transfer (LEIT) processing. The embedded nature of the EMTEs offers many advantages, such as high surface smoothness, which is essential for organic electronic device production; superior mechanical stability during bending; favorable resistance to chemicals and moisture; and strong adhesion with plastic film. LEIT fabrication features an electroplating process for vacuum-free metal deposition and is favorable for industrial mass production. Furthermore, LEIT allows for the fabrication of metal mesh with a high aspect ratio (i.e., thickness to linewidth), significantly enhancing its electrical conductance without adversely losing optical transmittance. We demonstrate several prototypes of flexible EMTEs, with sheet resistances lower than 1 &#937;/sq and transmittances greater than 90%, resulting in very high figures of merit (FoM) &#8211; up to 1.5 x 104 &#8211; which are amongst the best values in the published literature.

This protocol describes a solution-based fabrication strategy for high-performance, flexible, transparent electrodes with fully-embedded, thick metal mesh. Flexible transparent electrodes fabricated by this process demonstrate among the highest reported performances, including ultra-low sheet resistance, high optical transmittance, mechanical stability under bending, strong substrate adhesion, surface smoothness, and environmental stability.

Here, the authors report the embedded metal-mesh transparent electrode (EMTE), a new transparent electrode (TE) with a metal mesh completely embedded in a ...

Detecting the Water-soluble Chloride Distribution of Cement Paste in a High-precision Way

To improve the accuracy of the chloride distribution along the depth of cement paste under cyclic wet-dry conditions, a new method is proposed to obtain a high-precision chloride profile. Firstly, paste specimens are molded, cured, and exposed to cyclic wet-dry conditions. Then, powder samples at different specimen depths are grinded when the exposure age is reached. Finally, the water-soluble chloride content is detected using a silver nitrate titration method, and chloride profiles are plotted. The key to improving the accuracy of the chloride distribution along the depth is to exclude the error in the powderization, which is the most critical step for testing the distribution of chloride. Based on the above concept, the grinding method in this protocol can be used to grind powder samples automatically layer by layer from the surface inward, and it should be noted that a very thin grinding thickness (less than 0.5 mm) with a minimum error less than 0.04 mm can be obtained. The chloride profile obtained by this method better reflects the chloride distribution in specimens, which helps researchers to capture the distribution features that are often overlooked. Furthermore, this method can be applied to studies in the field of cement-based materials, which require high chloride distribution accuracy.

A protocol for obtaining a water-soluble chloride profile by using a high precision milling method is presented.

To improve the accuracy of the chloride distribution along the depth of cement paste under cyclic wet-dry conditions, a new method is proposed to obtain a ...

Method for Recording Broadband High Resolution Emission Spectra of Laboratory Lightning Arcs

Lightning is one of the most common and destructive forces in nature and has long been studied using spectroscopic techniques, first with traditional camera film methods and then digital camera technology, from which several important characteristics have been derived. However, such work has always been limited due to the inherently random and non-repeatable nature of natural lightning events in the field. Recent developments in lightning test facilities now allow the reproducible generation of lightning arcs within controlled laboratory environments, providing a test bed for the development of new sensors and diagnostic techniques to understand lightning mechanisms better. One such technique is a spectroscopic system using digital camera technology capable of identifying the chemical elements with which the lightning arc interacts, with these data then being used to derive further characteristics. In this paper, the spectroscopic system is used to obtain the emission spectrum from a 100 kA peak, 100 &#181;s duration lightning arc generated across a pair of hemispherical tungsten electrodes separated by a small air gap. To maintain a spectral resolution of less than 1 nm, several individual spectra were recorded across discrete wavelength ranges, averaged, stitched, and corrected to produce a final composite spectrum in the 450 nm (blue light) to 890 nm (near infrared light) range. Characteristic peaks within the data were then compared to an established publicly available database to identify the chemical element interactions. This method is readily applicable to a variety of other light emitting events, such as fast electrical discharges, partial discharges, and sparking in electrical equipment, apparatus, and systems.

Emission spectroscopy techniques have traditionally been used to analyze inherently random lightning arcs occurring in nature. In this paper, a method developed to obtain the emission spectroscopy from reproducible lightning arcs generated within a laboratory environment is described.

Lightning is one of the most common and destructive forces in nature and has long been studied using spectroscopic techniques, first with traditional ...

A Fabrication and Measurement Method for a Flexible Ferroelectric Element Based on Van Der Waals Heteroepitaxy

Flexible non-volatile memories have received much attention as they are applicable for portable smart electronic device in the future, relying on high-density data storage and low-power consumption capabilities. However, the high-quality oxide based nonvolatile memory on flexible substrates is often constrained by the material characteristics and the inevitable high-temperature fabrication process. In this paper, a protocol is proposed to directly grow an epitaxial yet flexible lead zirconium titanate memory element on muscovite mica. The versatile deposition technique and measurement method enable the fabrication of flexible yet single-crystalline non-volatile memory elements necessary for the next generation of smart devices.

In this paper, we present a protocol to directly grow an epitaxial yet flexible lead zirconium titanate memory element on muscovite mica.

Flexible non-volatile memories have received much attention as they are applicable for portable smart electronic device in the future, relying on ...

Fabrication of Refractive-index-matched Devices for Biomedical Microfluidics

The use of microfluidic devices has emerged as a defining tool for biomedical applications. When combined with modern microscopy techniques, these devices can be implemented as part of a robust platform capable of making simultaneous complementary measurements. The primary challenge created by the combination of these two techniques is the mismatch in refractive index between the materials traditionally used to make microfluidic devices and the aqueous solutions typically used in biomedicine. This mismatch can create optical artifacts near the channel or device edges. One solution is to reduce the refractive index of the material used to fabricate the device by using a fluorinated polymer such as MY133-V2000 whose refractive index is similar to that of water (n = 1.33). Here, the construction of a microfluidic device made out of MY133-V2000 using soft lithography techniques is demonstrated, using O2 plasma in conjunction with an acrylic holder to increase the adhesion between the MY133-V2000 fabricated device and the polydimethylsiloxane (PDMS) substrate. The device is then tested by incubating it filled with cell culture media for 24 h to demonstrate the ability of the device to maintain cell culture conditions during the course of a typical imaging experiment. Finally, quantitative phase microscopy (QPM) is used to measure the distribution of mass within the live adherent cells in the microchannel. This way, the increased precision, enabled by fabricating the device from a low index of refraction polymer such as MY133-V2000 in lieu of traditional soft lithography materials such as PDMS, is demonstrated. Overall, this approach for fabricating microfluidic devices can be readily integrated into existing soft lithography workflows in order to reduce optical artifacts and increase measurement precision.

This protocol describes the fabrication of microfluidic devices from MY133-V2000 to eliminate artifacts that often arise in microchannels due to the mismatching refractive indices between microchannel structures and an aqueous solution. This protocol uses an acrylic holder to compress the encapsulated device, improving adhesion both chemically and mechanically.

The use of microfluidic devices has emerged as a defining tool for biomedical applications. When combined with modern microscopy techniques, these devices ...

Low-cost Custom Fabrication and Mode-locked Operation of an All-normal-dispersion Femtosecond Fiber Laser for Multiphoton Microscopy

A protocol is presented to build a custom low-cost yet high-performance femtosecond (fs) fiber laser. This all-normal-dispersion (ANDi) ytterbium-doped fiber laser is built completely using commercially available parts, including $8,000 in fiber optic and pump laser components, plus $4,800 in standard optical components and extra-cavity accessories. Researchers new to fiber optic device fabrication may also consider investing in basic fiber splicing and laser pulse characterization equipment (~$63,000). Important for optimal laser operation, methods to verify true versus apparent (partial or noise-like) mode-locked performance are presented. This system achieves 70 fs pulse duration with a center wavelength of approximately 1,070 nm and a pulse repetition rate of 31 MHz. This fiber laser exhibits the peak performance that may be obtained for an easily assembled fiber laser system, which makes this design ideal for research laboratories aiming to develop compact and portable fs laser technologies that enable new implementations of clinical multiphoton microscopy and fs surgery.

A method is presented to build a custom low-cost, mode-locked femtosecond fiber laser for potential applications in multiphoton microscopy, endoscopy, and photomedicine. This laser is built using commercially available parts and basic splicing techniques.

A protocol is presented to build a custom low-cost yet high-performance femtosecond (fs) fiber laser. This all-normal-dispersion (ANDi) ytterbium-doped ...

Determination of Aggregate Surface Morphology at the Interfacial Transition Zone (ITZ)

Here, we present a comprehensive method to illustrate the uneven distribution of the interfacial transition zone (ITZ) around the aggregate and the effect of aggregate surface morphology on the formation of ITZ. First, a model concrete sample is prepared with a spherical ceramic particle in roughly the central part of the cement matrix, acting as a coarse aggregate used in common concrete/mortar. After curing until the designed age, the sample is scanned by X-ray computed tomography to determine the relative location of the ceramic particle inside the cement matrix. Three locations of the ITZ are chosen: above the aggregate, on the side of the aggregate, and below the aggregate. After a series of treatments, the samples are scanned with a SEM-BSE detector. The resultant images were further processed using a digital image processing method (DIP) to obtain quantitative characteristics of the ITZ. The surface morphology is characterized at the pixel level based on the digital image. Thereafter, K-means clustering method is used to illustrate the effect of surface roughness on ITZ formation.

Determination of Aggregate Surface Morphology at the Interfacial Transition Zone ITZ

Hereby, we proposed a protocol to illustrate the effect of aggregate surface morphology on the ITZ microstructure. The SEM-BSE image were quantitatively analyzed to obtain ITZ's porosity gradient via digital image processing and a K-means clustering algorithm was further employed to establish a relationship between porosity gradient and surface roughness.

Here, we present a comprehensive method to illustrate the uneven distribution of the interfacial transition zone (ITZ) around the aggregate and the effect ...