This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MEST) (No. NRF-2017R1A2A2A05001329). The authors of the manuscript are grateful to the Sogang University, Seoul, Republic of Korea.

1. Experimental requirement
<ol>
	<li>Purchase ion-exchange ionomer polymer, E-550 sulfonated-PEEK polymer fiber to prepare CEM and FAA-3 to prepare AEM. Ensure that all ionomer polymers are stored in a clean, dry, and dust-free environment before use.</li>
	<li>Use high purity (&#62;99%) solvents, including N-Methyl-2- pyrrolidone with molecular weight 99.13 g mol-1 and N, N-Dimethylacetamide with molecular weight 87.12, for preparing homogeneous ionomer solution. Ensure all analytical grade chemicals and solvents are used for membrane preparation as received without any further purification.</li>
	<li>After the membranes&#39; activation process, immediately immerse all membranes in a 0.5 M NaCl solution for better performance. After activation of both membranes, drying is not required. Water with resistivity is 18.2 M&#937; at room temperature was used throughout the synthesis of the membrane.</li>
	<li>Characterize membrane properties using a dry membrane. The detailed description of the characterization techniques and their physicochemical properties such as ion-exchange capacity, ion-conductivity, thickness, thermal analysis, and surface morphology, are as presented in the literatures10,11.</li>
	<li>Use a cutter to shape the membrane for CEM and AEM to the RED stack size with an active area of 49 cm2, as displayed in Figure 2.</li>
	<li>For the RED stack fabrication, make an alternate CEM and AEM arrangement, separated by spacer and gasket; a real picture of the working RED stack is presented in Figure 3a, and its schematic diagram of each layer is illustrated in Figure 3b.
	<ol>
		<li>First, place the PMMA plate facing electrode upside; now, place the rubber gasket and spacer on it, then place the CEM. After that, place the silicone gasket with the spacer on the CEM then place the AEM on it. Similarly, add the silicon gasket and spacer on the top of AEM followed by CEM. Now, place the end PMMA plate, rubber gasket, and spacer followed with tightening using screw and nut bolts.</li>
	</ol>
	</li>
	<li>After assembling the RED stack, check the free flow of the high-concentration (HC), low-concentration (LC), and rinse the solutions one by one. Any crossflow or leakage is required to be eliminated before the measurement.</li>
	<li>Prior to the current and voltage measurement, monitor the flow rate of salt solutions and pressure gauge reading and make sure it gets stabilized. Make sure all the connections are in the exact place before the measurement starts. Avoid touching the RED stack and its connecting tubes while the measurement is running. 
	&#8203;NOTE: HC and LC solution flow from their compartments to discard&#160;compartment through a peristaltic pump, pressure gauge, and RED stack, respectively.</li>
	<li>Use galvanostat method for the measurement of current and voltage, the source meter instrument connected to the RED stack through crocodile clips.</li>
</ol>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/62309/62309fig02.jpg" /> 
Figure 2: Size and shape of the prepared membrane, gasket, and spacer for the fabrication of reverse electrodialysis. (a) outer silicone gasket, (b) outer spacer and inner spacer, (c) inner silicone gasket, (d) cation-exchange membrane, (e) anion-exchange membrane, and (f) gasket and membrane assembly. <a href="https://www.jove.com/files/ftp_upload/62309/62309fig02large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/62309/62309fig03.jpg" /> 
Figure 3:&#160;Reverse electrodialysis stack. (a) setup of reverse electrodialysis stack with connecting tubes, and (b) schematic illustration of different layers, including PMMA endplates, electrodes, gasket, spacer, CEM, and AEM. <a href="https://www.jove.com/files/ftp_upload/62309/62309fig03large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
2. Ion-exchange membrane preparation
NOTE: The amount of precursor material was optimized for obtaining a membrane with 18 cm diameter and ~50 &#181;m thickness.
<ol>
	<li>Cation-exchange membrane
	<ol>
		<li>Take 5 wt% of sulfonated-PEEK fibers in a 250 mL round bottom flask and dissolve the fibers in Dimethylacetamide (DMAc) as a solvent having molecular weight 87.12 g mol-1. Shake the flask for 10 min so that all ionomer polymers settle down.</li>
		<li>Place a magnetic bar in the flask and then keep the mixture in the silicon oil bath, followed by vigorously stirring at 500 rpm for 24 h at 80 &#176;C to obtain a homogenous solution.</li>
		<li>Filter the sulfonated-PEEK solution through a 0.45 &#181;m pore size Polytetrafluoroethylene (PTFE) filter.</li>
		<li>After that, pour the filtered solution onto a circular glass dish with a diameter of 18 cm. Ensure that all air bubbles are removed using an air blower before placing the Petri dish in the oven.</li>
		<li>Place the Petri dish inside an oven for drying out the solution at 90 &#176;C for 24 h, resulting in ~50 &#181;m thick free-standing membrane. Do this for extracting free-standing membrane: To peel off the membrane from the Petri dish, fill the Petri dish with warm distill water (~60 &#176;C) and let it stand for 10 min untouched. The free-standing membrane will automatically come out.</li>
		<li>For membrane activation, immerse the prepared free-standing membrane in 1 M sulfuric acid (H2SO4)&#160;aqueous solution, i.e., 98.08 g, in 1 L of distilled water, and incubate for 2 h at 80 &#176;C. 
		NOTE: This step will ensure the removal of foreign particles and other chemicals such as solvents that will reduce the possibility of membrane from fouling.</li>
		<li>Wash the soaked membrane with 1 L of distilled water for 10 min, at least three times at room temperature.</li>
	</ol>
	</li>
	<li>Anion-exchange membrane
	<ol>
		<li>Dissolve FAA-3 ionomer solution 10 wt.% in N-Methyl-2-pyrrolidone (NMP) solvent.</li>
		<li>Keep the solution for stirring at room temperature for 2 h at ~500 rpm.</li>
		<li>After that, filter the solution using the mesh with 100 &#181;m pore size.</li>
		<li>Pour ~30 mL filtered solution into a circular glass Petri dish with a diameter of 18 cm. Ensure that all air bubbles were removed using an air blower before placing the glass Petri dish in the oven. The drying process takes place at 100 &#176;C for 24 h.</li>
		<li>To obtain a free-standing membrane, pour hot distilled water into the glass Petri dish and keep it for at least 10 min. Now peel off the membranes and place in 1 liter of sodium hydroxide (NaOH) solution (concentration 1M and molecular weight 40 g mol-1) for 2 h.</li>
		<li>Then, wash the membrane thoroughly with 1 L of distilled water for 10 min, at least three times in ambient condition. 
		&#8203;NOTE: All prepared membranes were stored in the 0.5 M NaCl solution overnight before using it in the RED stack. So that the membrane conductivity gets enhanced and can achieve stabilized output performance during the measurement of the RED stack. Table 1 describes the membrane properties10,11.</li>
	</ol>
	</li>
</ol>
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Specification</td>
			<td>Unit</td>
			<td>CEM</td>
			<td>AEM</td>
		</tr>
		<tr>
			<td>Swelling degree&#160;</td>
			<td>%</td>
			<td>5&#177;1</td>
			<td>1&#177;0.5</td>
		</tr>
		<tr>
			<td>Charge density or Ion exchange capacity&#160;</td>
			<td>meq/g</td>
			<td>1.8</td>
			<td>~1.6</td>
		</tr>
		<tr>
			<td>Mechanical properties 
			(Tensile strength)</td>
			<td>MPa</td>
			<td>&#62;40</td>
			<td>40-50</td>
		</tr>
		<tr>
			<td>Elongation to Break&#160;</td>
			<td>%</td>
			<td>~42</td>
			<td>30-50</td>
		</tr>
		<tr>
			<td>Young Modulus (MPa)</td>
			<td></td>
			<td>1500&#177;100</td>
			<td>1000-1500</td>
		</tr>
		<tr>
			<td>Conductivity at room temperature</td>
			<td>S/cm</td>
			<td>~0.03</td>
			<td>~0.025</td>
		</tr>
		<tr>
			<td>Permselectivity</td>
			<td>%</td>
			<td>98-99</td>
			<td>94-96</td>
		</tr>
		<tr>
			<td>Thickness</td>
			<td>&#956;m</td>
			<td>50&#177;2</td>
			<td>50&#177;3</td>
		</tr>
		<tr>
			<td>Solvent</td>
			<td>-</td>
			<td>Dimethylacetamide (DMAc)</td>
			<td>N-methyl-2-pyrrolidone (NMP)</td>
		</tr>
	</tbody>
</table>
Table 1: Membranes properties. Summary of both cation-exchange and anion-exchange membrane properties.
3. Fabrication of reverse electrodialysis
<ol>
	<li>Assembly of RED stack
	<ol>
		<li>Prepare a model solution using 0.6 M NaCl for high concentration (HC) and 0.01 M NaCl for low concentration (LC) compartments12. 
		NOTE: Here, river water is considered a low concentration salt solution, and seawater is represented as a high concentration salt solution.</li>
		<li>Prepare 5 L of high concentration and low concentration solution in a large container connected with the tubes. Keep the solutions stirring at ambient conditions (room temperature) for at least 2 h before it is used in the RED stack.</li>
		<li>Prepare the mixture of 0.05 M of [Fe (CN)6]-3/ [Fe (CN)6]-4 and 0.3 M NaCl in 500 mL water as a rinse solution for RED.</li>
		<li>Connect all three solution containers with RED stack using rubber tubes through the peristaltic pump and pressure gauges. Use the tube of size L/S 16 for rinse solution, and use the tube of size L/S 25 for HC and LC solution.</li>
		<li>To make a RED stack, take two endplates made-up of polymethyl methacrylate (PMMA). Connect both endplates horizontally face to face with nuts, bolts, and washers using 25 Nm force using a digital wrench driver. The thickness of PMMA endplates 3 cm, and the path of the flow channels was designed in plates for HC, LC, and rinse solution by a driller2.</li>
		<li>Place two mesh electrodes made from metal Titanium (Ti) coated with a mixture of Iridium (Ir) and Ruthenium (Ru) in a 1:1 ratio and place at the end of the PMMA plates. Both end electrodes are connected with the crocodile clip of the source meter. 
		&#8203;NOTE: Both PMMA end plates are equipped with mesh electrodes, both electrodes were layered with a square shape spacer, and the PMMA endplate covered with a rubber gasket facing inside. After that, CEM and AEM are placed alternatively, separated by silicone gasket and spacer, as shown in Figure 3.</li>
		<li>Install silicon gaskets, polymer spacers, and ion-exchange membranes (CEM and AEM) layer by layer, as presented in the schematic diagram Figure 4 and Figure 5. Ensure the active area of electrodes, both membranes, outer and inner spacer, outer and inner gasket is 7 x 7 = 49 cm2.</li>
		<li>Pass high-concentration and low-concentration solutions from respective compartments by peristaltic pumps, as displayed in the schematic diagram in Figure 4.</li>
		<li>Circulate the rinse solution in the outer electrode and membrane compartments in recirculation mode using peristaltic pumps. The flow rate used for the rinse solution is 50 mL min-1.</li>
		<li>Fixed flow rate is used for analyzing the performance of each membrane. In this experiment, we have used 100 mL min-1 through a peristaltic pump.</li>
	</ol>
	</li>
</ol>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/62309/62309fig04.jpg" /> 
Figure 4: Schematic representation of the tube connection with reverse electrodialysis stack. Connection of reverse electrodialysis with peristaltic pumps, high-concentration solution container, low-concentration solution container, rinse solution container, and discard solution container. It also shows the spacer&#39;s alignment with both an anion exchange membrane (AEM) and cation exchange membrane (CEM). <a href="https://www.jove.com/files/ftp_upload/62309/62309fig04large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/62309/62309fig05.jpg" /> 
Figure 5: Schematic diagram of different layers in the reverse electrodialysis setup. (a) Cross-section view of a schematic illustration of reverse electrodialysis shows the flow direction of the high-concentration solution, low-concentration solution, and electrode rinse solution. Other components such as electrodes, outer and inner gaskets, outer and inner spacers, cation-exchange membrane, and anion-exchange membrane. (b) Front view of the stack, which shows the flow direction of a solution. <a href="https://www.jove.com/files/ftp_upload/62309/62309fig05large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
4. Measurement of reverse electrodialysis
<ol>
	<li>Power calculation
	<ol>
		<li>Let the high concentration, low concentration, and rinse solution, run through the stack at least for 5 min. Measure the RED output performance by a source meter, which is connected to both electrodes of the RED stack13.</li>
		<li>Calculate the RED stack&#39;s current-voltage characteristics in terms of power density using the galvanostat method. 
		NOTE: In the galvanostat method, a constant current is applied across electrodes and measures the resulting current. The resulting current is the current generated due to the electrochemical reaction in the stack. The measurement is carried out under 0.05 V static voltage with a fixed sweep current that is 10 mA.</li>
		<li>The maximum power density for the RED stack is measured with the help of the following equation 1. 
		<img alt="Equation 2" src="/files/ftp_upload/62309/62309eq2.jpg" />&#160;(1) 
		Here, Pmax is the maximum power density of the RED stack (Wm-2), Ustack is the voltage (V) produced by the membrane in the stack, Istack is the recorded current (A), and Amem is the active area of the membranes (m2).</li>
	</ol>
	</li>
</ol>

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E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Salt+concentration+differences+alter+membrane+resistance+in+reverse+electrodialysis+stacks.">Salt concentration differences alter membrane resistance in reverse electrodialysis stacks.</a> Environmental Science &amp; Technology Letters. 1, 36-39 (2014).</li></ol>

The authors declare no conflicts of interest.

The RED&#39;s working principle is mainly dominated by the membrane&#39;s physicochemical properties, which is a crucial part of the RED system, as illustrated in Figure 3. Here, we describe the fundamental characteristics of the membrane for delivering a high-performance RED system. Membrane&#39;s specific ion permeability makes it pass one type of ions through their polymer nanochannel. As the name suggests, CEM can pass cation from one side to another and restricts anion, whereas AEM can ...

Energy harvesting from natural resources is an economical method that is environmentally friendly, thereby making our planet green and clean. Several processes have been proposed until now to extract energy, but reverse electrodialysis (RED) has an enormous potential to overcome the energy crisis issue1. Power production from Reverse electrodialysis is a technological breakthrough for the decarbonization of global energy. As the name suggests, RED is a reverse process, where the alternate cell compartment is filled with the high-concentrated salt solution and low-concentrated salt solution2. The chemical potential generated by the salt concentration difference across the ion-exchange membranes, collected from the electrodes at the compartment end.
Since the year 2000, many research articles have been published, providing insight into the RED theoretically and experimentally3,4. Systematic studies on the operation conditions and reliability studies under stress conditions improved the stack architecture and enhanced the overall cell performance. Several research groups have diverted their attention toward RED&#39;s hybrid application, such as RED with desalination process5, RED with solar power6, RED with reverse osmosis (RO) process5, RED with the microbial fuel cell7, and RED with the radiative cooling process8. As mentioned earlier, there is a lot of scope in implementing RED&#39;s hybrid application to solve the energy and clean water problem.
Several methods have been adopted to enhance the RED cell&#39;s performance and the membrane&#39;s ion-exchange capacity. Tailoring the cation-exchange membranes with different types of ions using sulfonic acid group (-SO3H), phosphonic acid group (-PO3H2), and carboxylic acid group (-COOH) is one of the effective ways to alter the physicochemical properties of the membrane. Anion-exchange membranes are tailored with ammonium groups (<img alt="Equation 1" src="/files/ftp_upload/62309/62209eq1.jpg" />)9. The high ionic conductivity of AEM and CEM without deteriorating the membrane&#39;s mechanical strength is the essential parameter for selecting an appropriate membrane for device application. The robust membrane under stress conditions provides mechanical stability to the membrane and enhances the device&#39;s durability. Here, a unique combination of high-performance free-standing sulfonated poly (ether ether ketone) (sPEEK) as cation-exchange membranes with FAA-3 as anion-exchange membranes are used in the RED application. Figure 1 shows the flow chart of the experimental procedure.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/62309/62309fig01.jpg" /> 
Figure 1: Procedure chart. The flow chart presents the procedure adopted for the preparation of ion-exchange membrane followed by the process for measurement of reverse electrodialysis. <a href="https://www.jove.com/files/ftp_upload/62309/62309fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>AEM based membrane</td>
			<td>Fumion</td>
			<td>P1810-194</td>
			<td>Ionomer</td>
		</tr>
		<tr>
			<td>CEM based membrane</td>
			<td>Fumion</td>
			<td>E550</td>
			<td>Ionomer</td>
		</tr>
		<tr>
			<td>Digital torque wrench</td>
			<td>Torqueworld</td>
			<td>WP2-030-09000251</td>
			<td>wrench</td>
		</tr>
		<tr>
			<td>Labview software</td>
			<td>Natiaonal Instrument</td>
			<td>-</td>
			<td>Software</td>
		</tr>
		<tr>
			<td>Laptop</td>
			<td>LG</td>
			<td>-</td>
			<td>PC</td>
		</tr>
		<tr>
			<td>Magnetic stirrer</td>
			<td>Lab Companion</td>
			<td>-</td>
			<td>MS-17BB</td>
		</tr>
		<tr>
			<td>N, N-Dimethylacetamide</td>
			<td>Sigma aldrich</td>
			<td>271012</td>
			<td>Chemical</td>
		</tr>
		<tr>
			<td>N-Methyl-2- pyrrolidone</td>
			<td>Daejung</td>
			<td>872-50-4</td>
			<td>Chemical</td>
		</tr>
		<tr>
			<td>Peristaltic pump</td>
			<td>EMS tech Inc</td>
			<td>-</td>
			<td>EMP 2000W</td>
		</tr>
		<tr>
			<td>Potassium hexacyanoferrate(II) trihydrate</td>
			<td>Sigma aldrich</td>
			<td>P3289</td>
			<td>Chemical</td>
		</tr>
		<tr>
			<td>Potassium hexacyanoferrate(III)</td>
			<td>Sigma aldrich</td>
			<td>244023</td>
			<td>Chemical</td>
		</tr>
		<tr>
			<td>Pressure Gauge</td>
			<td>Swagelok</td>
			<td>-</td>
			<td>Guage</td>
		</tr>
		<tr>
			<td>Reverse electrodialysis setup</td>
			<td>fabricated in lab</td>
			<td>-</td>
			<td>Device</td>
		</tr>
		<tr>
			<td>RO system pure water</td>
			<td>KOTITI</td>
			<td>-</td>
			<td>Water</td>
		</tr>
		<tr>
			<td>Rotary evaporator</td>
			<td>Hitachi</td>
			<td>YEFO-KTPM</td>
			<td>Induction motor</td>
		</tr>
		<tr>
			<td>Sodium Chloride</td>
			<td>Sigma aldrich</td>
			<td>S9888</td>
			<td>Chemical</td>
		</tr>
		<tr>
			<td>Sodium Hydroxide</td>
			<td>Merk</td>
			<td>1310-73-2</td>
			<td>Chemical</td>
		</tr>
		<tr>
			<td>Source meter</td>
			<td>Keithley</td>
			<td>-</td>
			<td>2410</td>
		</tr>
		<tr>
			<td>Spacer</td>
			<td>Nitex, SEFAR</td>
			<td>06-250/34</td>
			<td>Spacer</td>
		</tr>
		<tr>
			<td>Sulfuric acid</td>
			<td>Daejung</td>
			<td>7664-93-9</td>
			<td>Chemical</td>
		</tr>
		<tr>
			<td>Tube</td>
			<td>Masterflex tube</td>
			<td>96410-25</td>
			<td>Rubber tube</td>
		</tr>
	</tbody>
</table>

ion-exchange membranes for the fabrication of reverse electrodialysis device

Reverse electrodialysis (RED) is an effective way to generate power by mixing two different salt concentrations in water using cation-exchange membranes (CEM) and anion-exchange membranes (AEM). The RED stack is composed of an alternating arrangement of the cation-exchange membrane and anion-exchange membrane. The RED device acts as a potential candidate for fulfilling the universal demand for future energy crises. Here, in this article, we demonstrate a procedure to fabricate a reverse electrodialysis device using laboratory-scale CEM and AEM for power production. The active area of the ion-exchange membrane is 49 cm2. In this article, we provide a step-by-step procedure for synthesizing the membrane, followed by the stack&#39;s assembly and power measurement. The measurement conditions and net power output calculation have also been explained. Furthermore, we describe the fundamental parameters that are taken into consideration for obtaining a reliable outcome. We also provide a theoretical parameter that affects the overall cell performance relating to the membrane and the feed solution. In short, this experiment describes how to assemble and measure RED cells on the same platform. It also contains the working principle and calculation used for estimating the net power output of the RED stack using CEM and AEM membranes.

Net power output 
RED cell generally generates electrical energy from the salinity gradient of the salt solution, i.e., ions&#39; movement in the opposite direction through the membrane. To assemble the RED stack correctly, one needs to align all the layers, including electrodes, gaskets, membranes, and spacers in the stack carefully, as demonstrated in the schematic diagram in Figure 4 and Figure 5. If the stack is not perfectly aligned, t...

Watch this Scientific Journal Video about Ion-Exchange Membranes for the Fabrication of Reverse Electrodialysis Device at JoVE.com

Ion-Exchange Membranes for the Fabrication of Reverse Electrodialysis Device

We demonstrate the fabrication of a reverse electrodialysis device using a cation-exchange membrane (CEM) and anion-exchange membrane (AEM) for power generation.

Reverse electrodialysis (RED) is an effective way to generate power by mixing two different salt concentrations in water using cation-exchange membranes ...

ion-exchange-membranes-for-fabrication-reverse-electrodialysis

Research

JoVE Journal

Engineering

10.1K Views.  Energy Engineering Lab, Sogang University. We demonstrate the fabrication of a reverse electrodialysis device using a cation-exchange membrane (CEM) and anion-exchange membrane (AEM) for power generation.

Video: Ion-Exchange Membranes for the Fabrication of Reverse Electrodialysis Device

Fabrication of VB2/Air Cells for Electrochemical Testing

A technique to investigate the properties and performance of new multi-electron metal/air battery systems is proposed and presented. A method for synthesizing nanoscopic VB2 is presented as well as step-by-step procedure for applying a zirconium oxide coating to the VB2 particles for stabilization upon discharge. The process for disassembling existing zinc/air cells is shown, in addition construction of the new working electrode to replace the conventional zinc/air cell anode with a the nanoscopic VB2 anode. Finally, discharge of the completed VB2/air battery is reported. We show that using the zinc/air cell as a test bed is useful to provide a consistent configuration to study the performance of the high-energy high capacity nanoscopic VB2 anode.

Fabrication of VB2/Air Cells for Electrochemical Testing

A protocol is presented to study multi-electron metal/air battery systems by using previous technology developed for the zinc/air cell. Electrochemical testing is then performed on fabricated batteries to evaluate performance.

A technique to investigate the properties and performance of new multi-electron metal/air battery systems is proposed and presented. A method for ...

Fabrication of Uniform Nanoscale Cavities via Silicon Direct Wafer Bonding

Measurements of the heat capacity and superfluid fraction of confined 4He have been performed near the lambda transition using lithographically patterned and bonded silicon wafers. Unlike confinements in porous materials often used for these types of experiments3, bonded wafers provide predesigned uniform spaces for confinement. The geometry of each cell is well known, which removes a large source of ambiguity in the interpretation of data.
Exceptionally flat, 5 cm diameter, 375 &#181;m thick Si wafers with about 1 &#181;m variation over the entire wafer can be obtained commercially (from Semiconductor Processing Company, for example). Thermal oxide is grown on the wafers to define the confinement dimension in the z-direction. A pattern is then etched in the oxide using lithographic techniques so as to create a desired enclosure upon bonding. A hole is drilled in one of the wafers (the top) to allow for the introduction of the liquid to be measured. The wafers are cleaned2 in RCA solutions and then put in a microclean chamber where they are rinsed with deionized water4. The wafers are bonded at RT and then annealed at ~1,100 &#176;C. This forms a strong and permanent bond. This process can be used to make uniform enclosures for measuring thermal and hydrodynamic properties of confined liquids from the nanometer to the micrometer scale.

A method for permanently bonding two silicon wafers so as to realize a uniform enclosure is described. This includes wafer preparation, cleaning, RT bonding, and annealing processes. The resulting bonded wafers (cells) have uniformity of enclosure ~1%1,2. The resulting geometry allows for measurements of confined liquids and gasses.

Measurements of the heat capacity and superfluid fraction of confined 4He have been performed near the lambda transition using lithographically patterned ...

Patterning via Optical Saturable Transitions - Fabrication and Characterization

This protocol describes the fabrication and characterization of nanostructures using a novel nanolithographic technique called Patterning via Optical Saturable Transitions (POST). In this technique the chemical properties of organic photochromic molecules that undergo single-photon reactions are exploited, enabling rapid top-down nanopatterning over large areas at low light intensities, thereby, allowing for the circumvention of the far-field diffraction barrier.4 Simple, cost-effective, high throughput and resolution alternatives to nanopatterning are being explored, such as, two-photon polymerization5,6, beam pen lithography (BPL)7, scanning electron beam lithography (SEBL), and focused ion beam (FIB) patterning. However, multi-photon approaches require high light intensities, which limit their potential for high throughput and offer low image contrast. Although, electron and ion beam lithographic processes offer increased resolution, the serial nature of the process is limited to slow writing speeds, which also prevents patterning of features over large areas. Beam-pen lithography is an approach towards parallel near-field optical lithography. However, the gap between the source of the beam and the surface of the photoresist needs to be controlled extremely precisely for good pattern uniformity and this is very challenging to accomplish for large arrays of beams. Patterning via Optical Saturable Transitions (POST) is an alternative optical nanopatterning technique for patterning sub-wavelength features1-3. Since this technique uses single photons instead of electrons, it is extremely fast and does not require high light intensities1-3, opening the door to massive parallelization.

We report that the diffraction limit of conventional optical lithography can be overcome by exploiting the transitions of organic photochromic derivatives induced by their photoisomerization at low light intensities.1-3 This paper outlines our fabrication technique and two locking mechanisms, namely: dissolution of one photoisomer and electrochemical oxidation.

This protocol describes the fabrication and characterization of nanostructures using a novel nanolithographic technique called Patterning via Optical ...

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 ...

Preparation of Large-area Vertical 2D Crystal Hetero-structures Through the Sulfurization of Transition Metal Films for Device Fabrication

We have demonstrated that through the sulfurization of transition metal films such as molybdenum (Mo) and tungsten (W), large-area and uniform transition metal dichalcogenides (TMDs) MoS2 and WS2 can be prepared on sapphire substrates. By controlling the metal film thicknesses, good layer number controllability, down to a single layer of TMDs, can be obtained using this growth technique. Based on the results obtained from the Mo film sulfurized under the sulfur deficient condition, there are two mechanisms of (a) planar MoS2 growth and (b) Mo oxide segregation observed during the sulfurization procedure. When the background sulfur is sufficient, planar TMD growth is the dominant growth mechanism, which will result in a uniform MoS2 film after the sulfurization procedure. If the background sulfur is deficient, Mo oxide segregation will be the dominant growth mechanism at the initial stage of the sulfurization procedure. In this case, the sample with Mo oxide clusters covered with few-layer MoS2 will be obtained. After sequential Mo deposition/sulfurization and W deposition/sulfurization procedures, vertical WS2/MoS2 hetero-structures are established using this growth technique. Raman peaks corresponding to WS2 and MoS2, respectively, and the identical layer number of the hetero-structure with the summation of individual 2D materials have confirmed the successful establishment of the vertical 2D crystal hetero-structure. After transferring the WS2/MoS2 film onto a SiO2/Si substrate with pre-patterned source/drain electrodes, a bottom-gate transistor is fabricated. Compared with the transistor with only MoS2 channels, the higher drain currents of the device with the WS2/MoS2 hetero-structure have exhibited that with the introduction of 2D crystal hetero-structures, superior device performance can be obtained. The results have revealed the potential of this growth technique for the practical application of 2D crystals.

Through the sulfurization of pre-deposited transition metals, large-area and vertical 2D crystal hetero-structures can be fabricated. The film transferring and device fabrication procedures are also demonstrated in this report.

We have demonstrated that through the sulfurization of transition metal films such as molybdenum (Mo) and tungsten (W), large-area and uniform transition ...

Fabrication of Magnetic Nanostructures on Silicon Nitride Membranes for Magnetic Vortex Studies Using Transmission Microscopy Techniques

Electron and x-ray magnetic microscopies allow for high-resolution magnetic imaging down to tens of nanometers. However, the samples need to be prepared on transparent membranes which are very fragile and difficult to manipulate. We present processes for the fabrication of samples with magnetic micro- and nanostructures with spin configurations forming magnetic vortices suitable for Lorentz transmission electron microscopy and magnetic transmission x-ray microscopy studies. The samples are prepared on silicon nitride membranes and the fabrication consists of a spin coating, UV and electron-beam lithography, the chemical development of the resist, and the evaporation of the magnetic material followed by a lift-off process forming the final magnetic structures. The samples for the Lorentz transmission electron microscopy consist of magnetic nanodiscs prepared in a single lithography step. The samples for the magnetic x-ray transmission microscopy are used for time-resolved magnetization dynamic experiments, and magnetic nanodiscs are placed on a waveguide which is used for the generation of repeatable magnetic field pulses by passing an electric current through the waveguide. The waveguide is created in an extra lithography step.

A protocol for the fabrication of magnetic micro- and nanostructures with spin configurations forming magnetic vortices suitable for transmission electron microscopy (TEM) and magnetic transmission x-ray microscopy (MTXM) studies is presented.

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

Fabrication of an Optical Cell Dryer for the Spectroscopic Analysis Cells

Optical cells, which are experimental instruments, are small, square tubes sealed on one side. A sample is placed in this tube, and a measurement is performed with a spectroscope. The materials used for optical cells generally include quartz glass or plastic, but expensive quartz glass is reused by removing substances, other than liquids, to be analyzed that adhere to the interior of the container. In such a case, the optical cells are washed with water or ethanol and dried. Then, the next sample is added and measured. Optical cells are dried naturally or with a manual hairdryer. However, drying takes time, which makes it one of the factors that increase the experiment time. In this study, the objective is to drastically reduce the drying time with a dedicated automatic dryer that can dry multiple optical cells at once. To realize this, a circuit was designed for a microcomputer, and the hardware using it was independently designed and manufactured.

A protocol for fabricating a device for simultaneously drying multiple optical cells is presented.

Optical cells, which are experimental instruments, are small, square tubes sealed on one side. A sample is placed in this tube, and a measurement is ...

Hybrid Printing for the Fabrication of Smart Sensors

A method to combine additively manufactured substrates or foils and multilayer inkjet printing for the fabrication of sensor devices is presented. First, three substrates (acrylate, ceramics, and copper) are prepared. To determine the resulting material properties of these substrates, profilometer, contact angle, scanning electron microscope (SEM), and focused ion beam (FIB) measurements are done. The achievable printing resolution and suitable drop volume for each substrate are, then, found through the drop size tests. Then, layers of insulating and conductive ink are inkjet printed alternately to fabricate the target sensor structures. After each printing step, the respective layers are individually treated by photonic curing. The parameters used for the curing of each layer are adapted depending on the printed ink, as well as on the surface properties of the respective substrate. To confirm the resulting conductivity and to determine the quality of the printed surface, four-point probe and profilometer measurements are done. Finally, a measurement set-up and results achieved by such an all-printed sensor system are shown to demonstrate the achievable quality.

Here we present a protocol for the fabrication of inkjet-printed multilayer sensor structures on additively manufactured substrates and foil.

A method to combine additively manufactured substrates or foils and multilayer inkjet printing for the fabrication of sensor devices is presented. First, ...

Fabrication of Nanoheight Channels Incorporating Surface Acoustic Wave Actuation via Lithium Niobate for Acoustic Nanofluidics

Controlled nanoscale manipulation of fluids is known to be exceptionally difficult due to the dominance of surface and viscous forces. Megahertz-order surface acoustic wave (SAW) devices generate tremendous acceleration on their surface, up to 108 m/s2, in turn responsible for many of the observed effects that have come to define acoustofluidics: acoustic streaming and acoustic radiation forces. These effects have been used for particle, cell, and fluid manipulation at the microscale, although more recently SAW has been used to produce similar phenomena at the nanoscale through an entirely different set of mechanisms. Controllable nanoscale fluid manipulation offers a broad range of opportunities in ultrafast fluid pumping and biomacromolecule dynamics useful for physical and biological applications. Here, we demonstrate nanoscale-height channel fabrication via room-temperature lithium niobate (LN) bonding integrated with a SAW device. We describe the entire experimental process including nano-height channel fabrication via dry etching, plasma-activated bonding on lithium niobate, the appropriate optical setup for subsequent imaging, and SAW actuation. We show representative results for fluid capillary filling and fluid draining in a nanoscale channel induced by SAW. This procedure offers a practical protocol for nanoscale channel fabrication and integration with SAW devices useful to build upon for future nanofluidics applications.

We demonstrate fabrication of nanoheight channels with the integration of surface acoustic wave actuation devices upon lithium niobate for acoustic nanofluidics via liftoff photolithography, nano-depth reactive ion etching, and room-temperature plasma surface-activated multilayer bonding of single-crystal lithium niobate, a process similarly useful for bonding lithium niobate to oxides.

Controlled nanoscale manipulation of fluids is known to be exceptionally difficult due to the dominance of surface and viscous forces. Megahertz-order ...

Pneumatically Driven Microfluidic Platform for Micro-Particle Concentration

The present article introduces a method for fabricating and operating a pneumatic valve to control particle concentration using a microfluidic platform. This platform has a three-dimensional (3D) network with curved fluid channels and three pneumatic valves, which create networks, channels, and spaces through duplex replication with polydimethylsiloxane (PDMS). The device operates based on the transient response of a fluid flow rate controlled by a pneumatic valve in the following order: (1) sample loading, (2) sample blocking, (3) sample concentration, and (4) sample release. The particles are blocked by thin diaphragm layer deformation of the sieve valve (Vs) plate and accumulate in the curved microfluidic channel. The working fluid is discharged by the actuation of two on/off valves. As a result of the operation, all particles of various magnifications were successfully intercepted and disengaged. When this technology is applied, the operating pressure, the time required for concentration, and the concentration rate may vary depending on the device dimensions and particle size magnification.

The present protocol describes a pneumatic microfluidic platform that can be used for efficient microparticle concentration.

The present article introduces a method for fabricating and operating a pneumatic valve to control particle concentration using a microfluidic platform. ...