This study received support from the Research Initiation Grant (RIG) of the Vice President for Research and Economic Development at the University of North Texas (UNT). The authors also thank KCIS Co. Ltd for partially supporting this study. The support from PACCAR Technology Institute at UNT to the success of this publication is greatly appreciated.

1. Planning of Experiment
<ol>
	<li>Draw a sacrificial pattern (an octet truss structure with a sprue system) using computer aided design (CAD) software as shown in Figure 1 and save the CAD model as an STL file format. 
	Note: The sacrificial pattern is an integrated pattern of the octet truss structure with a sprue system that will be eventually melted for casting. Because the sacrificial pattern includes both the octet truss structure and the sprue system, it does not exactly represent the octet truss itself. A STL file of the sacrificial pattern is provided. Record the volume of the sacrificial pattern provided by CAD software, which will be used for calculating metals&#39; mass.</li>
	<li>Open the CAD drawing of the sacrificial pattern on the 3D printing software connected to a 3D printer for printing the pattern.</li>
	<li>Ensure that the 3D printer has enough UV curable/castable acrylic plastic and a support material made of a wax in the printer cartridges.</li>
</ol>
2. Fabrication of Sacrificial Pattern
<ol>
	<li>Manufacture the sacrificial pattern consisting of the octet truss structure and the sprue system using a 3D printer (Figure 2A - C). 
	Note: Processes in 2.1.3 - 2.1.7 are not required if a 3D printer which does not generate supporting materials is used.
	<ol>
		<li>Send an STL file of the sacrificial pattern to the 3D printer to print a sacrificial pattern (Figure 2A).</li>
		<li>Melt out a support material of the sacrificial pattern in an oven at above the melting temperature of the support material (60 -&#160;70 &#778;C) for 2 hr (Figure 2B). 
		Note: The temperature to remove the support material should not be too high. Otherwise, it may cause damage to the sacrificial pattern. The sacrificial pattern starts getting damaged at around 80 &#778;C &#160;in this study. 
		Note: The melting temperature of support materials varies with 3D printers where different support materials may be used.</li>
		<li>Fill out a digital ultrasonic cleaner with baby oil up to 2.5 L, the maximum volume that the cleaner can contain (Figure 2C). 
		Note: It was recommended by the supplier of the 3D printer to use baby oil for dissolving residue of the wax-like support material.</li>
		<li>Put the sacrificial pattern into the digital ultrasonic cleaner and turn on the power of the cleaner (Figure 2C). Make sure that the sacrificial pattern is fully submerged in the oil.</li>
		<li>Remove residue of the support material by dipping the sacrificial pattern into the oil at 65 &#778;C &#160;for 40 min (Figure 2C).</li>
		<li>Take out the sacrificial pattern from the cleaner if the support material is completely removed.</li>
		<li>Have the sacrificial pattern dry with a fan at RT (~20 &#778;C) &#160;(Figure 2C). 
		Note: It takes about 2 hr until the oil on the surface of the sacrificial pattern is fully dried. Consider the sacrificial pattern to be fully dried if the surface is not sticky.</li>
	</ol>
	</li>
</ol>
3. Fabrication of Mold
<ol>
	<li>Pattern Assembly
	<ol>
		<li>Attach a rubber gasket to the sacrificial pattern (the octet truss with the sprue system) and place them on the bottom of a cylinder-shaped flask with a height of 6.35 cm and a diameter of 6.35 cm (Figure 2D). 
		Note: Prepare two flasks for casting each metal; Al and Cu alloys.</li>
		<li>Double check the rubber gasket with the sacrificial pattern is completely attached to the bottom of the flask.</li>
		<li>Wrap the flask with a duct tape so that investment powder-water mixture, whose procedure will be described in the next section, may not leak from the flask.</li>
	</ol>
	</li>
	<li>Preparation of Investment Mold
	<ol>
		<li>Prepare investment powder (CaSO4, &#961; = 1019 kg/m3) of 89 g, which is 87.16 ml. Use a scale for weighing the investment powder. 
		Note: The physical properties of the investment powder are shown in Table 1.</li>
		<li>Pour the investment powder into a mixing bowl (1 L).</li>
		<li>Pour water (114 ml) into the mixing bowl. Use a beaker to measure the volume of water.</li>
		<li>Mix the investment powder with water in the bowl for 3 min. Mix well until there are no lumps in the investment powder-water mixture. Otherwise, it may cause poor surface quality of investment mold. Follow the work-flow, as shown in Figure 3.</li>
		<li>In order to remove air bubbles in the mixture, place the bowl in a vacuum chamber for 90 sec until the air bubbles cannot be seen in the mixture with bare eyes (Figure 3).</li>
		<li>Pour the mixture into a flask embedding the sacrificial pattern and the rubber gasket (Figure 2E).</li>
		<li>Place the flask in the vacuum chamber again for 90 sec to remove the residue of air bubbles inside the mixture (Figure 3).</li>
		<li>Dry the mixture inside the flask until it is hardened at RT (Figure 3). 
		Note: Usually, it takes about 10 - 15 min for the mixture to be hardened at RT.</li>
		<li>Remove the flask and the rubber gasket at the bottom of the mixture in the flask once the mixture is hardened (Figure 3). This product may be called a plaster mold.</li>
	</ol>
	</li>
	<li>Burn-out
	<ol>
		<li>Set up a burn-out time in a furnace while following the heating and cooling schedule (Figure 4) heating from 23 to 150 &#176;C at 2.1 &#778;C/min; &#160;150 to 370 &#778;C &#160;at 3.7 &#778;C/min; &#160;370 to 480 &#778;C &#160;at 1.85 &#778;C/min; &#160;480 to 730 &#778;C at 4.17 &#778;C /min; 730 &#778;C for 1 hr; cooling 730 to 480 &#778;C &#160;at -4.17 &#778;C /min. 
		Note: The time for burn-out varies with size of a flask. In this study, set the burn-out time to 6 hr.</li>
		<li>Place the plaster mold in a furnace (Figure 2F).</li>
		<li>Turn on the furnace and increase temperature in the furnace to remove the sacrificial pattern inside the plaster mold. Follow the temperature condition in Figure 4. 
		Note: Because the UV curable/castable acrylic plastic, the materials of the sacrificial pattern, is a thermosetting acrylic-polymer plastic, it does not flow but is dissociated to a gas phase in the furnace.</li>
	</ol>
	</li>
	<li>Centrifugal Casting (Figure 2G)
	<ol>
		<li>Check that the centrifugal casting machine&#39;s arm spins with an angular velocity of 425 rpm using a tachometer after turning on the power of a centrifugal casting machine.</li>
		<li>Prepare two ceramic crucibles that can hold a 150 g alloy to melt. Use separate crucibles for Al and Cu alloys to keep them from being contaminated with each other.</li>
		<li>Turn on the power of the centrifugal casting machine.</li>
		<li>Using a metal cutter, chop the alloys into pieces with 10 - 20 mm in length. Prepare them enough to fully fill the mold cavity whose volume should be the same as the sacrificial pattern. 
		Note: The mass of metals necessary to fill out the same volume of the mold cavity varies considering varying density for each metal.</li>
		<li>Wear flame retardant cloths and gloves, and goggles. Prepare a bucket of water (30&#160;L) at RT.</li>
		<li>Take the plaster mold temporarily out from the furnace in Section 3.3, install it in the flask cradle and balance the arm of the centrifugal casting machine (Figure 5).</li>
		<li>Place the plaster mold back to the furnace and pre-heat up to 482 &#176;C&#160;before casting.</li>
		<li>Place the crucible in the crucible holder (Figure 5).</li>
		<li>Put the chopped alloy into the crucible.</li>
		<li>Open the valve of an oxygen tank connected with an oxygen-acetylene torch and maintain a pressure level in the tank of 96.5 kPa (14 psi).</li>
		<li>Ignite the oxygen-acetylene torch with a lighter and control the intensity of the flame by adjusting the mix of gases. 
		Note: Caution is needed when using the oxygen-acetylene torch. Its maximum temperature of the torch is around 1,200 &#176;C.</li>
		<li>Melt chopped alloy (Al alloy or Cu alloy) with the torch in the crucible until the alloy completely becomes liquid.</li>
		<li>Stir the alloy in the crucible with a carbon rod until the chopped alloy is completely melted.</li>
		<li>Place the plaster mold in the flask cradle back next to the crucible containing molten alloy (Figure 5).</li>
		<li>Close the cover of the centrifugal casting machine, let the centrifugal arm rotate and wait at least for 3 min. 
		Note: The centrifugal casting machine starts operating as soon as the cover of the casting machine is closed. The centrifugal arm rotates at a speed of 425 rpm which corresponds to the inlet velocity at the mold cavity of the sacrificial pattern, vr = 8.03 m/sec28, 29 in Figure 5 where the inlet-velocity is calculated using the macroscopic particle dynamics from an angular velocity of the centrifugal casting arm28, 29.</li>
		<li>Turn off the power of the centrifugal casting machine after the 3 min rotation of the arm.</li>
		<li>Open the cover of the casting machine.</li>
		<li>Take the plaster mold out of the flask cradle using tongs.</li>
		<li>Keep the mold at RT for 15 - 20 min until the color of molten alloy turns to its original one in the solid phase.</li>
		<li>Using tongs, quench the plaster mold in water placed in a bucket (30 L) at RT for about 5 min. Make sure that the temperature of the plaster mold is close to RT after quenching.</li>
		<li>In order to obtain the lattice metal inside the mold, dissolve the mold in water. The mold made of gypsum dissolves easily in water.</li>
	</ol>
	</li>
</ol>
4. Post Processing for Final Products of Octet Truss Metals
<ol>
	<li>Turn on the power of a sandblaster.</li>
	<li>Place the octet truss metals on the platform inside the sandblaster and close the door of the machine.</li>
	<li>Put on gloves and grab the sandblaster pistol.</li>
	<li>Grab the sprue part of the metal product and blow out the residual plaster from the lattice metal with the sandblaster for 2 hr. 
	Note: The intensity of the sandblaster is automatically fixed approximately at 550 kPa. Once the sandblaster is operated, then the air comes out automatically from the pistol.</li>
	<li>Keep the sandblaster running until the investment plaster residue inside the octet truss metal is completely removed while checking with the naked eye. 
	Note: There is not a microscopic criterion on removal of plaster residue. This is beyond the scope of this study. The removal of the plaster residue is easily determined with the naked eye. Because the octet truss is an open cell structure, it is possible to see through and check if whether or not the plaster residue is completely removed. 
	Note: Caution is needed for the sandblaster to not damage the octet truss metal with a thin wall thickness (0.5 mm) at the high pressure (550 kPa).</li>
	<li>If the investment plaster residue inside the octet truss metal is not fully removed with the sandblaster, use additional post processing methods; e.g., an ultrasonic cleaning or leaving the product in water for a day.</li>
	<li>In case of using an ultrasonic cleaner, fill 0.7 L water into the ultrasonic cleaner and place the octet truss metal with plaster residue in the ultrasonic cleaner.
	<ol>
		<li>Turn on the power of the ultrasonic cleaner.</li>
		<li>Set an operation condition; e.g., 3 hr at 70 &#176;C.</li>
		<li>Take the octet truss metal out of the ultrasonic cleaner once the operation ends.</li>
		<li>Dry the octet truss metal at RT until water on the metal surface is completely removed.</li>
	</ol>
	</li>
	<li>As an alternative post processing method, leave the octet truss metal in water. This causes the plaster residue to be dissolved in water.
	<ol>
		<li>Place the octet truss metal with the plaster residue in water and leave it for one day so that the bonding force between the investment plaster and the metal surface becomes weaken in water.</li>
		<li>Take the octet truss metal out of water.</li>
		<li>Dry the octet truss metal at RT until water on the metal surface is completely removed.</li>
	</ol>
	</li>
	<li>Using a saw or other proper tools, cut the metal filled the cavity of the sprue system part out of the metal product and obtain the final octet truss metal with a size of 25 mm x 25 mm x 25 mm, as shown in Figure 1B.&#160;</li>
</ol>

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The authors have nothing to disclose.

For conventional metal casting, it is important to keep the molten metal&#39;s flow smooth and streamlined in &#39;laminar&#39; in the mold cavity and rather avoid irregular and agitated flow generally observed in turbulent flow27. Accordingly, it is important to properly design the inlet of the sprue system associated with the rotating speed of a centrifugal arm to maintain the flow of molten metal inside the lattice mold cavity &#39;laminar&#39;.
In this study, the critical steps ...

Cellular metals are the metals made up of an interconnected network of solid struts or plates and have complex micro-architectures with voids1. Examples include both i) randomly structured stochastic foams and ii) periodically ordered two-dimensional (2D) honeycombs and three-dimensional (3D) lattice truss structures. They have received attention due to their high specific stiffness and strength1-3and high specific resilience4-5, excellent energy absorption for impact loading6, acoustic insulation7, possible design of heat dissipaters and heat exchangers8. Especially, periodically ordered lattice structures have the potential to engineer the properties superior with a capability to control the internal porous network geometry.
Due to their complex internal porous network geometry, it is difficult to manufacture cellular metals using the conventional subtractive machining. As such, researchers have started looking for alternative methods to fabricate cellular metals: forming gas in liquid metal or mixing metal powder with blowing agents were explored for manufacturing stochastic metal forms9. Due to the lack of control over cell topology, it is hard to tailor mechanical properties. Alternatively, manufacturing methods for periodically ordered cellular metals were explored: stamping thin sheets of metal into a corrugated shape followed by joining them to create periodic structures10, bonding slotted metal sheets11, extrusion12, weaving and blazing metal filaments to fabricate textiles13. Even though these manufacturing methods offer repeatable patterns, the patterns are still limited in the planar direction. In an effort to generate 3D pattern repetition, researchers started using additive manufacturing (AM); e.g., Selective Laser Melting (SLM)14, Electron Beam Melting (EBM)15, and Direct-Metal Laser Sintering (DMLS)16. Despite their capability to fabricate 3D ordered complex lattice geometries, there still exist some limitations: difficulty using metals with high thermal conductivity and high optical reflectivity17, high thermal residual stress18, poor surface finish with the &#39;balling&#39; phenomenon during laser or electron melting 19, anisotropic properties20-21 of parts caused by a combined effect of the layered manufacturing, anisotropic formation of grains, powder size, power and scanning speed of laser or electron beam15, high energy consumption, etc.
Combining polymer based AM with metal casting may provide an alternative method to manufacture lattice metals. One may call this &#34;indirect AM&#34;. Indirect AM may provide a solution to overcome the technical problems of direct AM of metals mentioned above. Several efforts have been made to manufacture lattice metals using indirect AM combining 3D printing of polymers with gravity based casting22-25; e.g., an investment casting combined with fused deposition modeling (FDM) to fabricate a lattice alloy22-25 or sand casting combined with a sand powder based AM23. The gravity based casting appears to remain a technical challenge to overcome - misrun and porosity caused by sudden solidification of molten metals when they meet network structures with sharp corners of lattice structural molds25-26. Relatively large surface area of lattice structural molds also appears to contribute to sudden cooling, resulting in premature solidification25-26.
In this study, we propose an alternative indirect AM that may overcome the misrun during manufacturing of lattice metals - centrifugal casting to a lattice mold cavity made by a 3D printed lattice sacrificial polymer pattern. We use a digital light processing (DLP) based 3D printing method to build a lattice structural sacrificial pattern followed by centrifugal casting of Al and Cu alloys. The objective of this study is to provide a detailed protocol on fabrication of 3D lattice metals having a complex shape and a thin wall thickness. The main contribution of this process is to provide an opportunity to extend the selection of materials with low manufacturing cost for manufacturing lattice metals.

<table>
	<tbody>
		<tr>
			<td>Motorized centrifugal casting machine</td>
			<td>Rey Motorized Centrifugal Casting Machine, Rey Industries Inc.</td>
			<td></td>
			<td>Made in U.S.A. by Rey industries, Inc. Dallas, TX 75220</td>
		</tr>
		<tr>
			<td>Gypsum powder</td>
			<td>Satin Cast 20, FindingKing Kerr</td>
			<td>7960</td>
			<td>Gypsum powder is used to make the investment mixture</td>
		</tr>
		<tr>
			<td>Ployjet 3D printer</td>
			<td>Projet HD3500 Plus, 3D Systems</td>
			<td></td>
			<td>This polymer based 3D printer to print out sacrificial pattern for casting.</td>
		</tr>
		<tr>
			<td>Cartridge materials - UV curable and castable acrylic plastic</td>
			<td>VisiJet Procast, 3D Systems</td>
			<td></td>
			<td>This is castable material that is going to be burn out before casting</td>
		</tr>
		<tr>
			<td>Cartridge materials- support material</td>
			<td>VijiJet S300, 3D Systems</td>
			<td></td>
			<td>This is support material that is going to be removed before pattern assemble</td>
		</tr>
		<tr>
			<td>Ancient Bronze Casting Grain</td>
			<td>Rio Grande</td>
			<td>706051</td>
			<td>This true bronze grain contains no zinc. Highly fluid, it melts quickly, casts cleanly and provides a good balance between strength and durability. The warm, deep-bronze color has rich red undertones, and the alloy takes a good patina. 
			Composition is 90% copper with an amount of tin; fits into the CDA#90700 category. This grain is sold in 1-lb. packages.</td>
		</tr>
		<tr>
			<td>Aluminum Round Wire, 1/8&#34;, 1-Lb. Spool, Dead Soft</td>
			<td>Rio Grande</td>
			<td>134700</td>
			<td>Lightweight and strong, aluminum wire is an economical and versatile choice. Not as bright-white as silver, aluminum offers a warmer tone much like that of platinum. Solder ONLY with low-temp solders such as Stay-Brite; suitable for both pulse-arc and laser welding. This quality aluminum wire is packaged on 1-lb. spools.</td>
		</tr>
		<tr>
			<td>Computer aided design software (Pro-e)</td>
			<td></td>
			<td></td>
			<td>This software can be replaced with the others such as Auto CAD, Catia, and so on.</td>
		</tr>
		<tr>
			<td>ProJet Finisher 1-A</td>
			<td>3D Systems</td>
			<td></td>
			<td>This machine is used to melt the support material.</td>
		</tr>
		<tr>
			<td>160 Watt 2.5 Liters Digital Ultrasonic Cleaner with Timer Heater Rings Tools</td>
			<td>Chicago, Electric, Power Tools</td>
			<td></td>
			<td>85 oz. capacity, Five cleaning cycles: 90, 180, 280, 380 and 480 seconds, Clean with or without heat, Easy-to-read LED digital timer, Clear-view window</td>
		</tr>
		<tr>
			<td>Fan&#160;</td>
			<td>Honeywell Inc.&#160;</td>
			<td>HT-800</td>
			<td>120V A.C., 60Hz., 0.85A. TP</td>
		</tr>
		<tr>
			<td>Paraffin wax for wax sheet - Modeler&#39;s Pink Wax Sheet, 3&#34; by 6&#34;, 24-Ga.</td>
			<td>Rio Grande</td>
			<td>700075</td>
			<td>Sheet wax is flexible and can be cut or formed into any shape. It&#8217;s ideal for designing since you can draw or trace directly onto the sheet; choose green or pink depending on which will best show your designs. High manufacturing standards ensure exceptional consistency and significant price savings. Value is enhanced by larger package quantities at the same price as the smaller packages available elsewhere. Each 8-oz. package contains approximately 30 sheets.</td>
		</tr>
		<tr>
			<td>Paraffin wax for wax stick - Modeler&#39;s Medium Red Sprue Wax, 8-Ga</td>
			<td>Rio Grande</td>
			<td>700741</td>
			<td>A pliable, softer sprue wax than the firm blue. Good for forming gates and sprues and burns out cleanly with no residue.</td>
		</tr>
		<tr>
			<td>Alcohol Lamp</td>
			<td>Rio Grande</td>
			<td>700008</td>
			<td>Use this lamp to heat wax-working tools or as a flame polisher. The heavy glass reservoir has faceted sides to allow it to be tipped for angling the flame. A screw adjustment for the 7&#34; x 3/16&#34; wick controls the height of the flame. A safety cap snuffs the flame and prevents fuel evaporation. For the best flame, use methyl alcohol fuel. Replacement wicks available. Reservoir holds 5 oz. (150ml) of fuel.</td>
		</tr>
		<tr>
			<td>Wax carving tool set - Soft Grip Wax Carvers, Set of 10</td>
			<td>Rio Grande</td>
			<td>700329</td>
			<td>This boxed set offers the best in cutting and shaping technology. Each of these ten high-quality steel wax-carving tools features a 5/16&#34; PVC covered handle that ensures a sure, comfortable grip through hours of work and all have sharp edges for shaping and fine detailing. Sharpen or custom-shape each tool to fit your needs. These tools provide exceptional tool strength and deliver excellent results. This set comes in a hinged, foam-lined wood box.</td>
		</tr>
		<tr>
			<td>Rubber Mixing Bowl, 1-1/2 Qt.</td>
			<td>Rio Grande</td>
			<td>702131</td>
			<td>This highly-flexible vulcanized rubber bowl is easy to grip, will not be marred by a spatula and cleans with ease.</td>
		</tr>
		<tr>
			<td>Pyrex Beaker, 1,000ml</td>
			<td>Rio Grande</td>
			<td>335040</td>
			<td>Ideal for holding and heating bath plating solutions, this genuine Pyrex glass beaker is sturdy and durable.</td>
		</tr>
		<tr>
			<td>Rio Premium Stainless Steel Flask, 2-1/2&#34; dia.</td>
			<td>Rio Grande</td>
			<td>70201514</td>
			<td>This solid, #304-quality stainless steel flask is corrosion-resistant, durable for a long service life and performs under extreme temperature without distortion.</td>
		</tr>
		<tr>
			<td>CAST/T Ceramic Casting Crucible, 450g</td>
			<td>Rio Grande</td>
			<td>705047</td>
			<td>Made exclusively for the CAST/T centrifugal casting machine, this crucible is designed with an angled base that slides into the hinged bracket on top of the casting machine. This brings the crucible into perfect alignment with the center of the flask ring to ensure an error-free pour.</td>
		</tr>
		<tr>
			<td>MyWeigh iBalance 300 Digital Scale</td>
			<td>Rio Grande</td>
			<td>116850</td>
			<td>This scale is used to measure the weight of the sacrificial and sprue system for metal which is going to be used for centrifugal casting.</td>
		</tr>
		<tr>
			<td>Rubber bottom - CAST/T Flask Ring Base</td>
			<td>Rio Grande</td>
			<td>705025</td>
			<td>Specially made for the CAST/T centrifugal casting machine, this rubber base accommodates all Table King flask ring styles, creating a secure, airtight seal throughout the investment process. The center post fits either of the wax disc styles for complete versatility.</td>
		</tr>
		<tr>
			<td>Scotch&#174; Colored Duct Tape, 1 7/8&#34; x 20 Yd., Blue</td>
			<td>OfficeMax&#160;</td>
			<td>22353766</td>
			<td>This scotch tape is used to make sure that the gypsum-water mixture fully covers the assembled sacrificial pattern inside the flask by allowing for extra material above the flask height</td>
		</tr>
		<tr>
			<td>Vacuum casting machine - V.I.C. 12 Tabletop Solid- and Perforated-Flask Casting Machine with The Rio Assistant, 110-Volt</td>
			<td>Rio Grande</td>
			<td>70511814</td>
			<td>The V.I.C. 12 casting machine offers all the latest technical innovations for efficient, productive vacuum investing and casting. Designed to meet the demands of medium-sized casting operations, this machine includes a powerful 1/2hp, 5cfm vacuum pump for effective vacuuming and outstanding casting results. The V.I.C. 12 casts small or large flasks. Includes an adapter table that accepts standard solid flasks up to 5&#34; x 7&#34; high and is mounted on rubber feet for stability.</td>
		</tr>
		<tr>
			<td>Furnace for burn out sacrificial pattern -Rio Model 1000 Enameling Kiln with Nine Program Controller</td>
			<td>Rio Grande</td>
			<td>703121</td>
			<td>The Rio enameling kiln features three pre-set firing temperatures for enamels and six that you can define. Use the exclusive Rio controller to set and maintain firing temperatures. Perfect for all types of enameling, including tall pieces. Includes ample space for firing and an easy-latch door that will not jar your enamels when opening and closing. Also suitable for metal clay, glass and ceramics. Galvanized steel case with high-temperature insulating firebrick keeps them cool. Element protected in recessed groove. Includes user instructions.</td>
		</tr>
		<tr>
			<td>Smith Complete Little Torch Acetylene and Oxygen System</td>
			<td>Rio Grande</td>
			<td>500030</td>
			<td>Get everything you need to equip your shop for soldering and brazing. Use Little Torch systems for gold 
			or silver soldering, brazing and casting applications. Complete every soldering and melting job with confidence and ease! This system accepts all Little Torch accessory tips for melting, brazing and large soldering jobs and is a staple for every jeweler.</td>
		</tr>
		<tr>
			<td>Heat-Resistant Safety Apron</td>
			<td>Rio Grande</td>
			<td>750160</td>
			<td>The specially designed apron has an 800&#176;F (427&#176;C) temperature resistance. Its reflective finish repels hot metal splashes and helps insulate the wearer from heat.</td>
		</tr>
		<tr>
			<td>Radnor Heat-Resistant Gloves</td>
			<td>Rio Grande</td>
			<td>350050</td>
			<td>These flexible, heat-resistant gloves are ideal for enameling projects, allowing you to grip even small tongs securely. Blue, shoulder-split leather gloves are made of tough cowhide and lined with cotton and foam, and have reinforced thumb wings.</td>
		</tr>
		<tr>
			<td>Platinum Soldering Glasses, #7</td>
			<td>Rio Grande</td>
			<td>113914</td>
			<td>Protect yourself and your employees when soldering platinum. Comfortable glasses feature adjustable earpieces and 52mm IR green polycarbonate #7 lenses. The #7 lens is approved by The Platinum Guild.</td>
		</tr>
		<tr>
			<td>Economy Light-Duty Flask Tongs</td>
			<td>Rio Grande</td>
			<td>704026</td>
			<td>Constructed of bent steel, these tongs are designed to handle flasks 3-1/2&#34; or less in diameter. The small-angle notches grip smaller flask sizes and the larger, rounded contour area securely holds larger flasks.</td>
		</tr>
		<tr>
			<td>Separating Screen Bucket</td>
			<td>Rio Grande</td>
			<td>201360</td>
			<td>15&#34;-diameter, 11-1/2&#34;-deep</td>
		</tr>
		<tr>
			<td>Sand blaster - Econoline - 101701CB-A - Free-Standing Cabinets Workspace Width (Inch): 60 Workspace Depth (Inch): 48</td>
			<td>MSC industrial supply Co.&#160;</td>
			<td>223818</td>
			<td>Ree-Standing Cabinets; Workspace Width (Inch): 60; Workspace Depth (Inch): 48; Workspace Height (Inch): 40; Air Requirement: 12 CFM @ 80 psi; Overall Cabinet Width (Inch): 65; Maximum Cabinet Depth (Inch): 86</td>
		</tr>
		<tr>
			<td>Johnson&#39;s Baby Oil Shea &#38; Cocoa Butter&#160;</td>
			<td>Wal-Mart</td>
			<td>260074132</td>
			<td>This baby&#160; oil is used for removing the residue of the support material for the castable sacrificial pattern using Digital Ultrasonic Cleaner.</td>
		</tr>
		<tr>
			<td>German 4&#34; Saw Frame and Saw Blade Kit</td>
			<td>Rio Grande</td>
			<td>110112</td>
			<td>Quality, German-made frames are our most popular saw frames, and this frame includes a sampler pack of Rio German saw blades! The adjustable saw frame allows you to achieve the blade tension you want. Throat depth is 102mm (4&#34;). Saw blades have rounded backs that make cutting curves and corners easy and are made from hardened, tempered steel.</td>
		</tr>
	</tbody>
</table>

indirect fabrication of lattice metals with thin sections using centrifugal casting

One of the typical methods to manufacture 3D lattice metals is the direct-metal additive manufacturing (AM) process such as Selective Laser Melting (SLM) and Electron Beam Melting (EBM). In spite of its potential processing capability, the direct AM method has several disadvantages such as high cost, poor surface finish of final products, limitation in material selection, high thermal stress, and anisotropic properties of parts. We propose a cost-effective method to manufacture 3D lattice metals. The objective of this study is to provide a detailed protocol on fabrication of 3D lattice metals having a complex shape and a thin wall thickness; e.g., octet truss made of Al and Cu alloys having a unit cell length of 5 mm and a cell wall thickness of 0.5 mm. An overall experimental procedure is divided into eight sections: (a) 3D printing of sacrificial patterns (b) melt-out of support materials (c) removal of residue of support materials (d) pattern assembly (e) investment (f) burn-out of sacrificial patterns (g) centrifugal casting (h) post-processing for final products. The suggested indirect AM technique provides the potential to manufacture ultra-lightweight lattice metals; e.g., lattice structures with Al alloys. It appears that the process parameters should be properly controlled depending on materials and lattice geometry, observing the final products of octet truss metals by the indirect AM technique.

Using the indirect additive manufacturing described in the protocol section, Al and Cu alloys were used for manufacturing octet truss metals, as shown in Figure 1. The whole casting procedure is summarized in Figure 2. The procedure consists of eight sections: (a) sacrificial pattern printing (b) melting-out of support material (c) removal of residue of support material (d) pattern assembly (e) investment (f) burn-out of sacrificial patterns (g) centrifug...

Watch this Scientific Journal Video about Indirect Fabrication of Lattice Metals with Thin Sections Using Centrifugal Casting at JoVE.com

Indirect Fabrication of Lattice Metals with Thin Sections Using Centrifugal Casting

An indirect additive manufacturing method combining a 3D printing of polymers with a centrifugal casting is outlined for manufacturing 3D octet truss metals (Al and Cu alloys) having a unit cell length of 5 mm with a wall thickness of 0.5 mm.

One of the typical methods to manufacture 3D lattice metals is the direct-metal additive manufacturing (AM) process such as Selective Laser Melting (SLM) ...

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12.4K Views.  University of North Texas. An indirect additive manufacturing method combining a 3D printing of polymers with a centrifugal casting is outlined for manufacturing 3D octet truss metals (Al and Cu alloys) having a unit cell length of 5 mm with a wall thickness of 0.5 mm.

Video: Indirect Fabrication of Lattice Metals with Thin Sections Using Centrifugal Casting

Polycrystalline Silicon Thin-film Solar cells with Plasmonic-enhanced Light-trapping

One of major approaches to cheaper solar cells is reducing the amount of semiconductor material used for their fabrication and making cells thinner. To compensate for lower light absorption such physically thin devices have to incorporate light-trapping which increases their optical thickness. Light scattering by textured surfaces is a common technique but it cannot be universally applied to all solar cell technologies. Some cells, for example those made of evaporated silicon, are planar as produced and they require an alternative light-trapping means suitable for planar devices. Metal nanoparticles formed on planar silicon cell surface and capable of light scattering due to surface plasmon resonance is an effective approach.
The paper presents a fabrication procedure of evaporated polycrystalline silicon solar cells with plasmonic light-trapping and demonstrates how the cell quantum efficiency improves due to presence of metal nanoparticles.
To fabricate the cells a film consisting of alternative boron and phosphorous doped silicon layers is deposited on glass substrate by electron beam evaporation. An Initially amorphous film is crystallised and electronic defects are mitigated by annealing and hydrogen passivation. Metal grid contacts are applied to the layers of opposite polarity to extract electricity generated by the cell. Typically, such a ~2 &mu;m thick cell has a short-circuit current density (Jsc) of 14-16 mA/cm2, which can be increased up to 17-18 mA/cm2 (~25% higher) after application of a simple diffuse back reflector made of a white paint.
To implement plasmonic light-trapping a silver nanoparticle array is formed on the metallised cell silicon surface. A precursor silver film is deposited on the cell by thermal evaporation and annealed at 23&deg;C to form silver nanoparticles. Nanoparticle size and coverage, which affect plasmonic light-scattering, can be tuned for enhanced cell performance by varying the precursor film thickness and its annealing conditions. An optimised nanoparticle array alone results in cell Jsc enhancement of about 28%, similar to the effect of the diffuse reflector. The photocurrent can be further increased by coating the nanoparticles by a low refractive index dielectric, like MgF2, and applying the diffused reflector. The complete plasmonic cell structure comprises the polycrystalline silicon film, a silver nanoparticle array, a layer of MgF2, and a diffuse reflector. The Jsc for such cell is 21-23 mA/cm2, up to 45% higher than Jsc of the original cell without light-trapping or ~25% higher than Jsc for the cell with the diffuse reflector only.
Introduction
Light-trapping in silicon solar cells is commonly achieved via light scattering at textured interfaces. Scattered light travels through a cell at oblique angles for a longer distance and when such angles exceed the critical angle at the cell interfaces the light is permanently trapped in the cell by total internal reflection (Animation 1: Light-trapping). Although this scheme works well for most solar cells, there are developing technologies where ultra-thin Si layers are produced planar (e.g. layer-transfer technologies and epitaxial c-Si layers) 1 and or when such layers are not compatible with textures substrates (e.g. evaporated silicon) 2. For such originally planar Si layer alternative light trapping approaches, such as diffuse white paint reflector 3, silicon plasma texturing 4 or high refractive index nanoparticle reflector 5 have been suggested.
Metal nanoparticles can effectively scatter incident light into a higher refractive index material, like silicon, due to the surface plasmon resonance effect 6. They also can be easily formed on the planar silicon cell surface thus offering a light-trapping approach alternative to texturing. For a nanoparticle located at the air-silicon interface the scattered light fraction coupled into silicon exceeds 95% and a large faction of that light is scattered at angles above critical providing nearly ideal light-trapping condition (Animation 2: Plasmons on NP). The resonance can be tuned to the wavelength region, which is most important for a particular cell material and design, by varying the nanoparticle average size, surface coverage and local dielectric environment 6,7. Theoretical design principles of plasmonic nanoparticle solar cells have been suggested 8. In practice, Ag nanoparticle array is an ideal light-trapping partner for poly-Si thin-film solar cells because most of these design principle are naturally met. The simplest way of forming nanoparticles by thermal annealing of a thin precursor Ag film results in a random array with a relatively wide size and shape distribution, which is particularly suitable for light-trapping because such an array has a wide resonance peak, covering the wavelength range of 700-900 nm, important for poly-Si solar cell performance. The nanoparticle array can only be located on the rear poly-Si cell surface thus avoiding destructive interference between incident and scattered light which occurs for front-located nanoparticles 9. Moreover, poly-Si thin-film cells do not requires a passivating layer and the flat base-shaped nanoparticles (that naturally result from thermal annealing of a metal film) can be directly placed on silicon further increases plasmonic scattering efficiency due to surface plasmon-polariton resonance 10.
The cell with the plasmonic nanoparticle array as described above can have a photocurrent about 28% higher than the original cell. However, the array still transmits a significant amount of light which escapes through the rear of the cell and does not contribute into the current. This loss can be mitigated by adding a rear reflector to allow catching transmitted light and re-directing it back to the cell. Providing sufficient distance between the reflector and the nanoparticles (a few hundred nanometers) the reflected light will then experience one more plasmonic scattering event while passing through the nanoparticle array on re-entering the cell and the reflector itself can be made diffuse - both effects further facilitating light scattering and hence light-trapping. Importantly, the Ag nanoparticles have to be encapsulated with an inert and low refractive index dielectric, like MgF2 or SiO2, from the rear reflector to avoid mechanical and chemical damage 7. Low refractive index for this cladding layer is required to maintain a high coupling fraction into silicon and larger scattering angles, which are ensured by the high optical contrast between the media on both sides of the nanoparticle, silicon and dielectric 6. The photocurrent of the plasmonic cell with the diffuse rear reflector can be up to 45% higher than the current of the original cell or up to 25% higher than the current of an equivalent cell with the diffuse reflector only.

Polycrystalline silicon thin-film solar cells on glass are fabricated by deposition of boron and phosphorous doped silicon layers followed by crystallisation, defect passivation and metallisation. Plasmonic light-trapping is introduced by forming Ag nanoparticles on the silicon cell surface capped with a diffused reflector resulting in ~45% photocurrent enhancement.

One of major approaches to cheaper solar cells is reducing the amount of semiconductor material used for their fabrication and making cells thinner. To ...

Detection and Recovery of Palladium, Gold and Cobalt Metals from the Urban Mine Using Novel Sensors/Adsorbents Designated with Nanoscale Wagon-wheel-shaped Pores

Developing low-cost, efficient processes for recovering and recycling palladium, gold and cobalt metals from urban mine remains a significant challenge in industrialized countries. Here, the development of optical mesosensors/adsorbents (MSAs) for efficient recognition and selective recovery of Pd(II), Au(III), and Co(II) from urban mine was achieved. A simple, general method for preparing MSAs based on using high-order mesoporous monolithic scaffolds was described. Hierarchical cubic Ia3d wagon-wheel-shaped MSAs were fabricated by anchoring chelating agents (colorants) into three-dimensional pores and micrometric particle surfaces of the mesoporous monolithic scaffolds. Findings show, for the first time, evidence of controlled optical recognition of Pd(II), Au(III), and Co(II) ions and a highly selective system for recovery of Pd(II) ions (up to ~95%) in ores and industrial wastes. Furthermore, the controlled assessment processes described herein involve evaluation of intrinsic properties (e.g., visual signal change, long-term stability, adsorption efficiency, extraordinary sensitivity, selectivity, and reusability); thus, expensive, sophisticated instruments are not required. Results show evidence that MSAs will attract worldwide attention as a promising technological means of recovering and recycling palladium, gold and cobalt metals.

Because of the importance and extensive use of palladium, gold and cobalt metals in high-technology equipment, their recovery and recycling constitute an important industrial challenge. The metal recovery system described herein is a simple, low-cost means for the effective detection, removal, and recovery of these metals from the urban mine.

Developing low-cost, efficient processes for recovering and recycling palladium, gold and cobalt metals from urban mine remains a significant challenge in ...

Speciation and Bioavailability Measurements of Environmental Plutonium Using Diffusion in Thin Films

The biological uptake of plutonium (Pu) in aquatic ecosystems is of particular concern since it is an alpha-particle emitter with long half-life which can potentially contribute to the exposure of biota and humans. The diffusive gradients in thin films technique is introduced here for in-situ measurements of Pu bioavailability and speciation. A diffusion cell constructed for laboratory experiments with Pu and the newly developed protocol make it possible to simulate the environmental behavior of Pu in model solutions of various chemical compositions. Adjustment of the oxidation states to Pu(IV) and Pu(V) described in this protocol is essential in order to investigate the complex redox chemistry of plutonium in the environment. The calibration of this technique and the results obtained in the laboratory experiments enable to develop a specific DGT device for in-situ Pu measurements in freshwaters. Accelerator-based mass-spectrometry measurements of Pu accumulated by DGTs in a karst spring allowed determining the bioavailability of Pu in a mineral freshwater environment. Application of this protocol for Pu measurements using DGT devices has a large potential to improve our understanding of the speciation and the biological transfer of Pu in aquatic ecosystems.

The technique of diffusive gradients in thin films (DGT) is proposed for speciation studies of plutonium. This protocol describes diffusion experiments probing the behavior of Pu(IV) and Pu(V) in presence of organic matter. DGTs deployed in a karstic spring allow assessment of the bioavailability of Pu.

The biological uptake of plutonium (Pu) in aquatic ecosystems is of particular concern since it is an alpha-particle emitter with long half-life which can ...

Fabrication of Low Temperature Carbon Nanotube Vertical Interconnects Compatible with Semiconductor Technology

We demonstrate a method for the low temperature growth (350 &#176;C) of vertically-aligned carbon nanotubes (CNT) bundles on electrically conductive thin-films. Due to the low growth temperature, the process allows integration with modern low-&#954; dielectrics and some flexible substrates. The process is compatible with standard semiconductor fabrication, and a method for the fabrication of electrical 4-point probe test structures for vertical interconnect test structures is presented. Using scanning electron microscopy the morphology of the CNT bundles is investigated, which demonstrates vertical alignment of the CNT and can be used to tune the CNT growth time. With Raman spectroscopy the crystallinity of the CNT is investigated. It was found that the CNT have many defects, due to the low growth temperature. The electrical current-voltage measurements of the test vertical interconnects displays a linear response, indicating good ohmic contact was achieved between the CNT bundle and the top and bottom metal electrodes. The obtained resistivities of the CNT bundle are among the average values in the literature, while a record-low CNT growth temperature was used.

A method for the growth of low temperature vertically-aligned carbon nanotubes, and the subsequent fabrication of vertical interconnect electrical test structures using semiconductor fabrication is presented.

We demonstrate a method for the low temperature growth (350 &#176;C) of vertically-aligned carbon nanotubes (CNT) bundles on electrically conductive ...

A Fabrication Method for Highly Stretchable Conductors with Silver Nanowires

Stretchable electronics are identified as a key technology for electronic applications in the next generation. One of the challenges in fabrication of stretchable electronic devices is the preparation of stretchable conductors with great mechanical stability. In this study, we developed a simple fabrication method to chemically solder the contact points between silver nanowire (AgNW) networks. AgNW nanomesh was first deposited on a glass slide via spray coating method. A reactive ink composed of silver nanoparticle (AgNPs) precursors was applied over the spray coated AgNW thin films. After heating for 40 min, AgNPs were preferentially generated over the nanowire junctions to solder the AgNW nanomesh, and reinforced the conducting network. The chemically modified AgNW thin film was then transferred to polyurethane (PU) substrates by casting method. The soldered AgNW thin films on PU exhibited no obvious change in electrical conductivity under stretching or rolling process with elongation strains up to 120%.

A simple synthesis method is used to chemically solder silver nanowire thin film to fabricate highly stretchable and conductive metal conductors.

Stretchable electronics are identified as a key technology for electronic applications in the next generation. One of the challenges in fabrication of ...

Capillary-based Centrifugal Microfluidic Device for Size-controllable Formation of Monodisperse Microdroplets

Here, we demonstrate a simple method for the rapid production of size-controllable, monodisperse, W/O microdroplets using a capillary-based centrifugal microfluidic device. W/O microdroplets have recently been used in powerful methods that enable miniaturized chemical experiments. Therefore, developing a versatile method to yield monodisperse W/O microdroplets is needed. We have developed a method for generating monodisperse W/O microdroplets based on a capillary-based centrifugal axisymmetric co-flowing microfluidic device. We succeeded in controlling the size of microdroplets by adjusting the capillary orifice. Our method requires equipment that is easier-to-use than with other microfluidic techniques, requires only a small volume (0.1-1 &#181;l) of sample solution for encapsulation, and enables the production of hundreds of thousands number of W/O microdroplets per second. We expect this method will assist biological studies that require precious biological samples by conserving the volume of the samples for rapid quantitative analysis biochemical and biological studies.

Here, we demonstrate a simple production method for size-controllable, monodisperse, water-in-oil (W/O) microdroplets using a capillary-based centrifugal microfluidic device. This method requires only a small sample volume and enables high-yield production. We expect this method will be useful for rapid biochemical and cellular analyses.

Here, we demonstrate a simple method for the rapid production of size-controllable, monodisperse, W/O microdroplets using a capillary-based centrifugal ...

Fabrication of White Light-emitting Electrochemical Cells with Stable Emission from Exciplexes

The authors present an approach for fabricating stable white light emission from polymer light-emitting electrochemical cells (PLECs) having an active layer which consists of blue-fluorescent poly(9,9-di-n-dodecylfluorenyl-2,7-diyl) (PFD) and &#960;-conjugated triphenylamine molecules. This white light emission originates from exciplexes formed between PFD and amines in electronically excited states. A device containing PFD, 4,4&#39;,4&#39;&#39;-tris[2-naphthyl(phenyl)amino]triphenylamine (2-TNATA), Poly(ethylene oxide) and K2CF3SO3 showed white light emission with Commission internationale de l&#39;&#233;clairage (CIE) coordinates of (0.33, 0.43) and a Color Rendering Index (CRI) of Ra = 73 at an applied voltage of 3.5 V. Constant voltage measurements showed that the CIE coordinates of (0.27, 0.37), Ra of 67, and the emission color observed immediately after application of a voltage of 5 V were nearly unchanged and stable after 300 sec.

The authors present a method for fabricating stable white-light-emitting electrochemical cells utilizing emission from exciplexes formed between a blue-emitting fluorene polymer and aromatic amines.

The authors present an approach for fabricating stable white light emission from polymer light-emitting electrochemical cells (PLECs) having an active ...

In Situ Monitoring of the Accelerated Performance Degradation of Solar Cells and Modules: A Case Study for Cu(In,Ga)Se2 Solar Cells

The levelized cost of electricity (LCOE) of photovoltaic (PV) systems is determined by, among other factors, the PV module reliability. Better prediction of degradation mechanisms and prevention of module field failure can consequently decrease investment risks as well as increase the electricity yield. An improved knowledge level can for these reasons significantly decrease the total costs of PV electricity. 
In order to better understand and minimize the degradation of PV modules, the occurring degradation mechanisms and conditions should be identified. This should preferably happen under combined stresses, since modules in the field are also simultaneously exposed to multiple stress factors. Therefore, two 'Combined Stress test with in situ measurement' setups have been designed and constructed. These setups allow the simultaneous use of humidity, temperature, illumination, and electrical biases as independently controlled stress factors on solar cells and minimodules. The setups also allow real-time monitoring of the electrical properties of these samples. This protocol presents these setups and describes the experimental possibilities. Moreover, results obtained with these setups are also presented: various examples about the influence of both deposition and degradation conditions on the stability of thin film Cu(In,Ga)Se2 (CIGS) as well as Cu2ZnSnSe4 (CZTS) solar cells are described. Results on the temperature dependency of CIGS solar cells are also presented.

In Situ Monitoring of the Accelerated Performance Degradation of Solar Cells and Modules: A Case Study for CuIn,GaSe2 Solar Cells

Two &#39;Combined Stress test with in situ measurement&#39; setups, which allow real-time monitoring of accelerated degradation of solar cells and modules, were designed and constructed. These setups allow the simultaneous use of humidity, temperature, electrical biases, and illumination as independently controlled stress factors. The setups and various experiments executed are presented.

The levelized cost of electricity (LCOE) of photovoltaic (PV) systems is determined by, among other factors, the PV module reliability. Better prediction ...

Fabrication of Periodic Gold Nanocup Arrays Using Colloidal Lithography

Within recent years, the field of plasmonics has exploded as researchers have demonstrated exciting applications related to chemical and optical sensing in combination with new nanofabrication techniques. A plasmon is a quantum of charge density oscillation that lends nanoscale metals such as gold and silver unique optical properties. In particular, gold and silver nanoparticles exhibit localized surface plasmon resonances-collective charge density oscillations on the surface of the nanoparticle-in the visible spectrum. Here, we focus on the fabrication of periodic arrays of anisotropic plasmonic nanostructures. These half-shell (or nanocup) structures can exhibit additional unique light-bending and polarization-dependent optical properties that simple isotropic nanostructures cannot. Researchers are interested in the fabrication of periodic arrays of nanocups for a wide variety of applications such as low-cost optical devices, surface-enhanced Raman scattering, and tamper indication. We present a scalable technique based on colloidal lithography in which it is possible to easily fabricate large periodic arrays of nanocups using spin-coating and self-assembled commercially available polymeric nanospheres. Electron microscopy and optical spectroscopy from the visible to near-infrared (near-IR) was performed to confirm successful nanocup fabrication. We conclude with a demonstration of the transfer of nanocups to a flexible, conformal adhesive film.

We demonstrate the fabrication of periodic gold nanocup arrays using colloidal lithographic techniques and discuss the importance of nanoplasmonic films.

Within recent years, the field of plasmonics has exploded as researchers have demonstrated exciting applications related to chemical and optical sensing ...

Fabrication of Ultra-thin Color Films with Highly Absorbing Media Using Oblique Angle Deposition

Ultra-thin film structures have been studied extensively for use as optical coatings, but performance and fabrication challenges remain.&#160; We present an advanced method for fabricating ultra-thin color films with improved characteristics. The proposed process addresses several fabrication issues, including large area processing. Specifically, the protocol describes a process for fabricating ultra-thin color films using an electron beam evaporator for oblique angle deposition of germanium (Ge) and gold (Au) on silicon (Si) substrates.&#160; Film porosity produced by the oblique angle deposition induces color changes in the ultra-thin film. The degree of color change depends on factors such as deposition angle and film thickness. Fabricated samples of the ultra-thin color films showed improved color tunability and color purity. In addition, the measured reflectance of the fabricated samples was converted into chromatic values and analyzed in terms of color. Our ultra-thin film fabricating method is expected to be used for various ultra-thin film applications such as flexible color electrodes, thin film solar cells, and optical filters. Also, the process developed here for analyzing the color of the fabricated samples is broadly useful for studying various color structures.

We present a detailed method for fabricating ultra-thin color films with improved characteristics for optical coatings. The oblique angle deposition technique using an electron beam evaporator allows improved color tunability and purity. Fabricated films of Ge and Au on Si substrates were analyzed by reflectance measurements and color information conversion.

Ultra-thin film structures have been studied extensively for use as optical coatings, but performance and fabrication challenges remain.&#160; We present ...