This research was supported under Australian Research Council's Discovery Projects funding scheme (project number DP120103942). B. T. K. and A. A. are the recipients of an Australian Research Council Future Fellowship (FT0991895) and Australian Research Fellowship (DP1093789) respectively.

Overview
The composite indium/PMMA fiber (Figure 3) is produced by drawing a stack of PMMA fibers including a single indium wire (Figure 2), which themselves have to be prepared from available PMMA tubes and wires. The steps presented are:
<ol class="ualpha">
 <li>Produce a PMMA fiber that contains a single indium wire of diameter appropriate for manual stacking. For this, first prepare a PMMA tube that can accommodate a 1 mm indium wire (Section 1), then include the indium and draw to the required size (Section 2).</li>
 <li>Stack and draw the obtained individual indium-filled PMMA fibers (Section 3) to the required size.</li>
</ol>
Sections 4 and 5 detail the drawing processes used in sections 2 and 3.
1. Fabricating the PMMA Jacketing Tube
The PMMA jacketing tube used to structure the 1 mm indium wire is made by stretching and sleeving standard PMMA tubes in the primary draw process (Section 4) to make a final PMMA jacketing tube of ID 1 mm and OD 12 mm.
<ol>
 <li>Cut PMMA tubes with ID of 6mm and OD of 12 mm to 600 mm lengths. Several PMMA tubes should be prepared for future use during the sleeving process.</li>
 <li>Anneal the PMMA tubes in an annealing oven at 90 &deg;C for a minimum of 5 days.</li>
 <li>Remove one PMMA tube from annealing oven and allow it to cool to room temperature.</li>
 <li>Clean the surface of the PMMA tube with isopropanol wipes and allow to dry.</li>
 <li>Attach the PMMA tube to top extender (Figure 6) using reflective tape (Figure 7).</li>
 <li>Attach the PMMA tube to primary draw bottom extender (Figure 6) using reflective tape (Figure 8).</li>
 <li>Stretch the PMMA tube in the primary drawing process (refer to Section 4). Note that no vacuum is required for this stage. The PMMA tube is stretched from OD 12 mm to 6 mm.</li>
 <li>Remove the stretched tube from the draw tower after drawing.</li>
 <li>Cut the stretched tube into 550 mm lengths.</li>
 <li>Repeat steps 1.3 and 1.4.</li>
 <li>Heat the top side of the stretched tube with a hot air gun until the material softens and crimp seal the hole using pliers (Figure 9).</li>
 <li>Insert the stretched tube into the new PMMA tube to create the PMMA tube assembly (Figure 10). On bottom side of the PMMA tube assembly (i.e. the side which has the inner stretched tube open), wrap polytetrafluoroethylene (PTFE) tape as shown in Figure 10, to seal the gap between the stretched tube and the new PMMA tube.</li>
 <li>Attach top end of the PMMA tube assembly (i.e. the side which has the inner stretched tube sealed) to the top extender (Figure 7), using an inner layer of sticky tape, a middle layer of PTFE tape, and an outer layer of reflective tape. Ensure the PTFE tape is tight and all gaps between the PMMA tube assembly and the top extender are sealed.</li>
 <li>Attach the PMMA tube to the primary draw bottom extender as shown in 1.6.</li>
 <li>Stretch and sleeve the PMMA tube assembly in the primary drawing process with vacuum (refer to Section 4). The PMMA tube assembly is stretched from OD 12 mm to 6 mm.</li>
 <li>The resulting stretched PMMA jacketing tube will have ID/OD of approximately 0.25. Repeat 1.9 to 1.15 until the final PMMA jacketing tube has ID/OD of approximately 0.1 with an ID of 1 mm (Figure 1).</li>
</ol>
2. Fabricating the Indium Filled Fiber
The 1 mm indium wire is sleeved and stretched in the PMMA jacketing tube made in Section 1 using the secondary draw process (Section 5) to produce indium filled fiber with a final OD 1.2 mm.
<ol>
 <li>Prepare and anneal PMMA jacketing tubes as shown in 1.1 - 1.4.</li>
 <li>Cut the indium wire to 550 mm lengths.</li>
 <li>Insert indium wire into the PMMA jacketing tube to create the indium filled preform assembly as shown in Figure 11.</li>
 <li>Seal the bottom side of the PMMA jacketing tube as shown in 1.11.</li>
 <li>Attach indium filled preform assembly to the top extender as shown in 1.13 and the secondary draw bottom extender as shown in 1.14.</li>
 <li>Stretch and sleeve the indium filled preform assembly in the secondary drawing process with vacuum to make indium filled fiber (refer to Section 5) of a final OD 1 mm drawn under 15-20 g tension.</li>
 <li>Remove the spool of indium filled fiber from the tower after the draw process is finished.</li>
 <li>Inspect the endface and along the longitudinal length of the indium filled fiber using a light microscope. Problematic defects can include separation between the indium wire and PMMA tubing interface, fluctuations in the wire diameter or fracture cracks along the length of the fiber. Optical microscope images of the indium filled fiber are presented in Figure 2, showing a continuous 100 &mu;m indium wire in a 1 mm OD PMMA fiber.</li>
 <li>Repeat 2.1 to 2.8 until enough indium filled fiber is produced for the indium stacked preform.</li>
</ol>
3. Fabricating the Indium Stacked Fiber
The indium stacked fiber is fabricated by first stacking the indium filled fibers produced in Secton 2 in a larger PMMA preform jacketing tube, which is then stretched and sleeved to the desired fiber dimensions using the secondary draw process (Section 5).
<ol>
 <li>Prepare the PMMA preform jacketing tube as shown in 1.1. For demonstration purposes, we will use a PMMA tube of 12 mm OD and 9 mm ID.</li>
 <li>Cut the indium filled fibers to 550 mm length.</li>
 <li>Clean the surface of the PMMA preform jacketing tube and the indium filled fiber with isopropanol wipes and allow to dry.</li>
 <li>Bundle the indium filled fiber using rubber bands and insert into the PMMA preform jacketing tube, ensuring the fibers are straight and are of a tight fit (Figure 12).</li>
 <li>Anneal the stacked preform assembly in the annealing oven at 90 &deg;C for a minimum of 5 days.</li>
 <li>Remove the stacked preform assembly from the annealing oven and allow it to cool to room temperature.</li>
 <li>Attach indium filled preform assembly to the top extender as shown in 1.13 and the secondary draw bottom extender as shown in 1.14.</li>
 <li>Stretch and sleeve the stacked preform assembly in the secondary drawing process with vacuum to make indium stacked fiber (refer to Section 5). This is stretched to a final OD 0.6 mm drawn under 80 g tension, producing a metamaterial fiber containing 5 mm wires separated by 50 &mu;m. An optical microscope cross-sectional image of the resulting fiber is shown in Figure 3.</li>
 <li>Remove the spool of indium stacked fiber from the tower after the draw process is finished.</li>
 <li>Inspect the endface and along the longitudinal length of the indium stacked fiber as shown in 2.8 (Figure 3).</li>
</ol>
4. Primary Draw Process
The primary draw process is used to stretch preforms to outer diameters greater than 1 mm. The following procedure is used in Section 1: Fabricating the PMMA Jacketing Tube.
<ol>
 <li>Load the preform onto the draw tower by clamping the top extender to the three jaw chuck. Feed the preform into the hot zone of the furnace (Figure 13). Align the preform using the XY micrometer stage. Close the top plate of the furnace.</li>
 <li>The pre-heat stage elevates the temperature of the cross sectional area of the preform to the drawing temperature, using the temperature profile shown in Figure 14.</li>
 <li>Commence the drawing process by increasing the temperature to 185 &deg;C, starting the feed rate at 5 mm/min, draw rate at 6 mm/min and closing the draw unit clamps. Examine the behaviour of draw tension over time (Figure 15).
 <ul>
 <li>If the tension increases exponentially, stop the feed and draw units, wait 1 min to allow the preform to heat up to drawing temperature, before starting the feed and draw units again. Repeat the test until the tension stabilizes.</li>
 <li>If the tension falls, increase the draw rate by 1-2 mm/min. Continue increasing the draw rate in 1-2 mm/min increments (as long as the tension either remains constant or starts falling), until the required draw rate is achieved.</li>
 </ul>
 </li>
 <li>If vacuum is required, attach the vacuum tube to the vacuum sealed top preform extender using Blu-Tac (Figure 13). Turn on the vacuum after the feed and draw units have started to ensure the preform is drawing symmetrically.</li>
 <li>Use the primary drawing condition in Table 1 as a guide when drawing the preform. Note the furnace temperature and the ratio between the feed and draw rate have to be monitored to maintain constant OD and the drawing tension. Note that an indicative outer diameter for the drawn fiber can be obtained from a mass balance equation, 
 Dfinal = Dstart (F/D)1/2 
 where Dfinal- is the final fiber diameter, Dstart is the initial preform diameter, F is the feed rate, and D is the draw rate. Stop the feeding and drawing rate and switch of the furnace when the preform is finished. Remove the preform from the draw tower once the preform cools to room temperature.</li>
</ol>
5. Secondary Draw Process
The secondary draw process is used to stretch preforms to ODs smaller than 1 mm. The following procedure is used in Section 2: Fabricating the indium filled fiber and 3: Fabricating the indium stacked fiber.
<ol>
 <li>Loading the preform for the secondary draw is the same as in the primary draw process (Step 4.1).</li>
 <li>The pre-heating stage for the secondary draw is the same as in the primary draw process (Step 4.2).</li>
 <li>The preform begins to neck-down once the drawing temperature is reached. The drop-down of the preform exits the bottom of the furnace due to the weight of the bottom extender providing the initial drawing force (Figure 16).</li>
 <li>Start the feed rate (2.5 - 5 mm/min) and start increasing the furnace temperature (2.5 - 5 &deg;C) to control the speed of the drop-down. The fiber diameter should be maintained around 250 - 500 &mu;m to prevent the fiber snapping.</li>
 <li>Attach the fiber to the capstan wheel that is spinning at a slow rate of under 1 m/min initially. Wind the fiber around the dancer wheels and attach to the fiber spool.</li>
 <li>If vacuum is required attach the vacuum tube as shown in 4.4.</li>
 <li>The fiber draw will initially be under transient draw conditions. Set the feed rate, draw rate and furnace temperature to the desired draw condition values. Fiber diameter and draw tension will fluctuate until steady state is achieved after a few minutes.</li>
 <li>Use the secondary drawing condition in Table 2 as a guide when drawing the preform. Note the furnace temperature and the ratio between the feed and draw rate have to be monitored to maintain constant OD and the drawing tension.</li>
 <li>Stop the process as shown in 4.5.</li>
</ol>

<ol>
	<li>Cai, W., Shalaev, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Optical Metamaterials: Fundamentals and Applications. , (2010).</li><li>Pendry, J. B., Holden, A. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Extremely+Low+Frequency+Plasmons+in+Metallic+Mesostructures.">Extremely Low Frequency Plasmons in Metallic Mesostructures.</a> Phys. Rev. Lett. 76, 4773-4776 (1996).</li><li>Schurig, D., Mock, J. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Metamaterial+Electromagnetic+Cloak+at+Microwave+Frequencies.">Metamaterial Electromagnetic Cloak at Microwave Frequencies.</a> Science. 314, 977-980 (2006).</li><li>Shalaev, V. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optical+negative-index+metamaterials.">Optical negative-index metamaterials.</a> Nat. Photonics. 1, 41-48 (2007).</li><li>Liu, Z., Lee, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Far-field+optical+hyperlens+magnifying+sub-diffraction-limited+objects.">Far-field optical hyperlens magnifying sub-diffraction-limited objects.</a> Science. 315, (2007).</li><li>Boltasseva, A., Shalaev, V. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fabrication+of+optical+negative-index+metamaterials:+Recent+advances+and+outlook.">Fabrication of optical negative-index metamaterials: Recent advances and outlook.</a> Metamaterials. 2, 1-17 (2008).</li><li>Soukoulis, C. M., Wegener, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Past+achievements+and+future+challenges+in+the+development+of+three-dimensional+photonic+metamaterials.">Past achievements and future challenges in the development of three-dimensional photonic metamaterials.</a> Nat. Photonics. 5, 523-530 (2011).</li><li>Tuniz, A., Kuhlmey, B. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Drawn+metamaterials+with+plasmonic+response+at+terahertz+frequencies.">Drawn metamaterials with plasmonic response at terahertz frequencies.</a> Appl. Phys. Lett. 96, 191101 (2010).</li><li>Argyros, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microstructured+polymer+optical+fibers.">Microstructured polymer optical fibers.</a> J. Lightwave Technol. 27, 1571-1579 (2009).</li><li>Donald, I. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Production,+properties+and+applications+of+microwire+and+related+products.">Production, properties and applications of microwire and related products.</a> J. Mater. Sci. 22, 2661-2679 (1987).</li><li>Grischkowsky, D., Keiding, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Far-infrared+time-domain+spectroscopy+with+terahertz+beams+of+dielectrics+and+semiconductors.">Far-infrared time-domain spectroscopy with terahertz beams of dielectrics and semiconductors.</a> J. Opt. Soc. Am. B. 7, 2006-2015 (1990).</li><li>Wang, A., Tuniz, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fiber+metamaterials+with+negative+magnetic+permeability+in+the+terahertz.">Fiber metamaterials with negative magnetic permeability in the terahertz.</a> Opt. Mat. Express. 1, 115-120 (2010).</li><li>Tuniz, A., Lwin, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stacked-and-drawn+metamaterials+with+magnetic+resonances+in+the+terahertz+range.">Stacked-and-drawn metamaterials with magnetic resonances in the terahertz range.</a> Opt. Express. 19, 16480-16490 (2011).</li></ol>

No conflicts of interest declared.

The technique presented here allows the fabrication of kilometers of continuous three-dimensional metamaterials with microscale feature sizes, possessing a plasmonic response (and thus a tailored electric permittivity) in the THz range, effectively behaving as a high-pass filter. This can be experimentally characterized using terahertz time-domain spectroscopy 11. Such fiber-shaped metamaterials can be cut and stacked into bulk materials to realize a large number of devices, or woven into other structures, for...

<table border="1">
	<tbody>
		<tr>
			<td>Name of Reagent/Material</td>
			<td>Company</td>
			<td>Catalogue Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Indium 99.99% Wire, 1 mm diameter</td>
			<td>AIM Specialty</td>
			<td>Available on request</td>
			<td><a href="http://www.aimspecialty.com" target="_blank">www.aimspecialty.com</a> 
			<a href="http://www.aimspecialty.com/Portals/0/Files/Indium.pdf" target="_blank">http://www.aimspecialty.com/Portals/0/Files/Indium.pdf</a></td>
		</tr>
		<tr>
			<td>2-Propanol(Isopropanol)</td>
			<td>Sigma-Aldrich</td>
			<td>Product Number 
			190764</td>
			<td><a href="http://www.sigmaaldrich.com/chemistry/solvents/products.html?TablePage=17292086" target="_blank">http://www.sigmaaldrich.com/chemistry/solvents/products.html?TablePage=17292086</a></td>
		</tr>
		<tr>
			<td>Adhesive tape</td>
			<td>Staples</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>One Wrap PTFE Tape, 5 ml x 12 mmW x 0.2 mmT</td>
			<td>RS Components</td>
			<td>RS Stock Number 
			231-964</td>
			<td><a href="http://uk.rs-online.com/web/p/ptfe-tapes/0231964/" target="_blank">http://uk.rs-online.com/web/p/ptfe-tapes/0231964/</a></td>
		</tr>
		<tr>
			<td>50 Micron Aluminium Foil Tape</td>
			<td>Advance Adhesive Tapes</td>
			<td>AT506</td>
			<td><a href="http://www.advancetapes.com/Products/types/9/page1/81" target="_blank">http://www.advancetapes.com/Products/types/9/page1/81</a></td>
		</tr>
		<tr>
			<td>Blu-tak</td>
			<td>Bostik</td>
			<td>&nbsp;</td>
			<td><a href="http://www.blutack.com/index.html" target="_blank">http://www.blutack.com/index.html</a></td>
		</tr>
		<tr>
			<td>Araldite Quick Set</td>
			<td>Selleys</td>
			<td>&nbsp;</td>
			<td><a href="http://selleys.com.au/adhesives/household-adhesive/araldite/quick-set" target="_blank">http://selleys.com.au/adhesives/household-adhesive/araldite/quick-set</a></td>
		</tr>
		<tr>
			<td>PMMA tubes: 
			- ID 6 mm, OD 12 mm 
			- ID 9 mm, OD 12 mm</td>
			<td>B &amp; M Plastics: Plastic Fabrication</td>
			<td>Available on request</td>
			<td><a href="http://www.bmplastics.com.au/about-us.htm" target="_blank">http://www.bmplastics.com.au/about-us.htm</a></td>
		</tr>
		<tr>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
			<td>Equipment Requirements</td>
		</tr>
		<tr>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
			<td>
			<ul>
				<li>Fibre draw tower with furnaces of maximum temperatures of at least 200 &deg;C (Heathway Polymer Draw Tower with Preform and Fibre draw facilities). A photograph of the draw tower is shown in Figure 5.</li>
				<li>Annealing oven of maximum temperatures of at least 90 &deg;C.</li>
				<li>Optical microscope.</li>
				<li>Hot air gun.</li>
				<li>Vacuum pump.</li>
				<li>Top preform extender (metal tube of 30 cm length and 12 mm diameter).</li>
				<li>Primary draw bottom extender (metal tube of 100 cm length and 12 mm diameter).</li>
				<li>Secondary draw bottom extender (PMMA tube of 20 cm length and 12 mm diameter).</li>
			</ul>
			</td>
		</tr>
	</tbody>
</table>

fabricating metamaterials using the fiber drawing method

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

Metamaterial fibers were produced using the technique described. They was assembled from a preform of 1 mm PMMA fibers containing 100 &mu;m diameter continuous indium wires, shown in Figure 2, which in turn had themselves been drawn from a preform of 1 mm indium wires contained inside a 10 mm polymer jacket, which was produced by sleeving appropriately sized polymer tubes, as shown in the schematic of Figure 1. A microscope image of the cross section of an example of a metamaterial fiber...

Watch this Scientific Journal Video about Fabricating Metamaterials Using the Fiber Drawing Method at JoVE.com

Fabricating Metamaterials Using the Fiber Drawing Method

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

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

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13.7K Views.  University of Sydney. Metamaterials at terahertz frequencies offer unique opportunities, but are challenging to fabricate in bulk. We adapt the fabrication procedure for microstructured polymer optical fibers to inexpensively fabricate metamaterials potentially on an industrial scale. We produce polymethylmethacrylate fibers containing ~10 μm diameter indium wires separated by ~100 μm, which exhibit a terahertz plasmonic response.

Video: Fabricating Metamaterials Using the Fiber Drawing Method

Colloidal Synthesis of Nanopatch Antennas for Applications in Plasmonics and Nanophotonics

We present a method for colloidal synthesis of silver nanocubes and the use of these in combination with a smooth gold film, to fabricate plasmonic nanoscale patch antennas. This includes a detailed procedure for the fabrication of thin films with a well-controlled thickness over macroscopic areas using layer-by-layer deposition of polyelectrolyte polymers, namely poly(allylamine) hydrochloride (PAH) and polystyrene sulfonate (PSS). These polyelectrolyte spacer layers serve as a dielectric gap in between silver nanocubes and a gold film. By controlling the size of the nanocubes or the gap thickness, the plasmon resonance can be tuned from about 500 nm to 700 nm. Next, we demonstrate how to incorporate organic sulfo-cyanine5 carboxylic acid (Cy5) dye molecules into the dielectric polymer gap region of the nanopatch antennas. Finally, we show greatly enhanced fluorescence of the Cy5 dyes by spectrally matching the plasmon resonance with the excitation energy and the Cy5 absorption peak. The method presented here enables the fabrication of plasmonic nanopatch antennas with well-controlled dimensions utilizing colloidal synthesis and a layer-by-layer dip-coating process with the potential for low cost and large-scale production. These nanopatch antennas hold great promise for practical applications, for example in sensing, ultrafast optoelectronic devices and for high-efficiency photodetectors.

A protocol for the colloidal synthesis of silver nanocubes and fabrication of plasmonic nanoscale patch antennas with sub-10 nm gaps is presented.

We present a method for colloidal synthesis of silver nanocubes and the use of these in combination with a smooth gold film, to fabricate plasmonic ...

Fabrication of Nanopillar-Based Split Ring Resonators for Displacement Current Mediated Resonances in Terahertz Metamaterials

Terahertz (THz) split ring resonator (SRR) metamaterials (MMs) has been studied for gas, chemical, and biomolecular sensing applications because the SRR is not affected by environmental characteristics such as the temperature and pressure surrounding the resonator. Electromagnetic radiation in THz frequencies is biocompatible, which is a critical condition especially for the application of the biomolecular sensing. However, the quality factor (Q-factor) and frequency responses of traditional thin-film based split ring resonator (SRR) MMs are very low, which limits their sensitivities and selectivity as sensors. In this work, novel nanopillar-based SRR MMs, utilizing displacement current, are designed to enhance the Q-factor up to 450, which is around 45 times higher than that of traditional thin-film-based MMs. In addition to the enhanced Q-factor, the nanopillar-based MMs induce a larger frequency shifts (17 times compared to the shift obtained by the traditional thin-film based MMs). Because of the significantly enhanced Q-factors and frequency shifts as well as the property of biocompatible radiation, the THz nanopillar-based SRR are ideal MMs for the development of biomolecular sensors with high sensitivity and selectivity without inducing damage or distortion to biomaterials. A novel fabrication process has been demonstrated to build the nanopillar-based SRRs for displacement current mediated THz MMs. A two-step gold (Au) electroplating process and an atomic layer deposition (ALD) process are used to create sub-10 nm scale gaps between Au nanopillars. Since the ALD process is a conformal coating process, a uniform aluminum oxide (Al2O3) layer with nanometer-scale thickness can be achieved. By sequentially electroplating another Au thin film to fill the spaces between Al2O3 and Au, a close-packed Au-Al2O3-Au structure with nano-scale Al2O3 gaps can be fabricated. The size of the nano-gaps can be well defined by precisely controlling the deposition cycles of the ALD process, which has an accuracy of 0.1 nm.

A protocol for the design and fabrication of a novel nanopillar-based split ring resonator (SRR) is presented.

Terahertz (THz) split ring resonator (SRR) metamaterials (MMs) has been studied for gas, chemical, and biomolecular sensing applications because the SRR ...

Installation Method to Enhance Quality Control for Fiber Reinforced Polymer Spike Anchors

Fiber reinforced polymer (FRP) anchors are a promising way to enhance the performance of externally-bonded FRPs applied to existing structures, as they can delay or even prevent debonding failure. However, a major concern faced by designers is the premature failure of the anchors due to stress concentration. Poor installation quality and preparation of the clearance holes can result in stress concentration that provokes this premature failure. This paper deals with an installation method that aims to reduce the impact of the stress concentration and to provide a proper quality control of the preparation of the drill hole. The method involves three parts: the drilling and cleaning of the holes, the smoothing of the hole edges with a customized drill bit, and the installation of the anchor itself, including the impregnation of the anchor dowel and its insertion. Anchor fans (the free length of the spikes) are then bonded to the external FRP reinforcement. For the end anchorage, and in the case of reinforcements with multiple plies, it is recommended that the anchor fan be inserted between two plies to assist the stress-transfer mechanism. 
The proposed procedure is complemented with a design approach for spike anchors, based on an extensive database. It is proposed that the design follow a number of steps, namely: selection of the anchor diameter and subsequent tensile strength of the connector (that is to say, the anchor before fanning out the free end), evaluation of the reduction in the tensile strength due to bending, provision of enough embedment to prevent slippage failure, and consideration of the number and spacing of anchors for a given reinforcement. In this sense, it should be noted that further research is needed in order to obtain a general expression for the contribution of spike anchors to overall bond strength of FRP reinforcements.

This manuscript presents a method for controlling the quality of installation for spike anchors designed to delay delamination of externally bonded fiber reinforced polymers. The protocol includes the preparation of the drill hole and the insertion process. The most influential parameters on the efficiency of the anchors are discussed.

Fiber reinforced polymer (FRP) anchors are a promising way to enhance the performance of externally-bonded FRPs applied to existing structures, as they ...

Fabricating Reactive Surfaces with Brush-like and Crosslinked Films of Azlactone-Functionalized Block Co-Polymers

In this paper, fabrication methods that generate novel surfaces using the azlactone-based block co-polymer, poly (glycidyl methacrylate)-block-poly (vinyl dimethyl azlactone) (PGMA-b-PVDMA), are presented. Due to the high reactivity of azlactone groups towards amine, thiol, and hydroxyl groups, PGMA-b-PVDMA surfaces can be modified with secondary molecules to create chemically or biologically functionalized interfaces for a variety of applications. Previous reports of patterned PGMA-b-PVDMA interfaces have used traditional top-down patterning techniques that generate non-uniform films and poorly controlled background chemistries. Here, we describe customized patterning techniques that enable precise deposition of highly uniform PGMA-b-PVDMA films in backgrounds that are chemically inert or that have biomolecule-repellent properties. Importantly, these methods are designed to deposit PGMA-b-PVDMA films in a manner that completely preserves azlactone functionality through each processing step. Patterned films show well-controlled thicknesses that correspond to polymer brushes (~90 nm) or to highly crosslinked structures (~1-10 &#956;m). Brush patterns are generated using either the parylene lift-off or interface directed assembly methods described and are useful for precise modulation of overall chemical surface reactivity by adjusting either the PGMA-b-PVDMA pattern density or the length of the VDMA block. In contrast, the thick, crosslinked PGMA-b-PVDMA patterns are obtained using a customized micro-contact printing technique and offer the benefit of higher loading or capture of secondary material due to higher surface area to volume ratios. Detailed experimental steps, critical film characterizations, and trouble-shooting guides for each fabrication method are discussed.

Surface fabrication methods for patterned deposition of nanometer thick brushes or micron thick, crosslinked films of an azlactone block co-polymer are reported. Critical experimental steps, representative results, and limitations of each method are discussed. These methods are useful for creating functional interfaces with tailored physical features and tunable surface reactivity.

In this paper, fabrication methods that generate novel surfaces using the azlactone-based block co-polymer, poly (glycidyl methacrylate)-block-poly (vinyl ...

Drawing and Hydrophobicity-patterning Long Polydimethylsiloxane Silicone Filaments

Polydimethylsiloxane (PDMS) silicone is a versatile polymer that cannot readily be formed into long filaments. Traditional spinning methods fail because PDMS does not exhibit long-range fluidity at melting. We introduce an improved method to produce filaments of PDMS by a stepped temperature profile of the polymer as it cross-links from a fluid to an elastomer. By monitoring its warm-temperature viscosity, we estimate a window of time when its material properties are amendable to drawing into long filaments. The filaments pass through a high-temperature tube oven, curing them sufficiently to be harvested. These filaments are on the order of hundreds of micrometers in diameter and tens of centimeters in length, and even longer and thinner filaments are possible. These filaments retain many of the material properties of bulk PDMS, including switchable hydrophobicity. We demonstrate this capability with an automated corona-discharge patterning method. These patternable PDMS silicone filaments have applications in silicone weavings, gas-permeable sensor components, and model microscale foldamers.

Here, we present a protocol to produce long filaments of polydimethylsiloxane (PDMS) silicone by gravity-drawing through a furnace. Filaments are on the order of hundreds of micrometers in diameter and tens of centimeters in length and are hydrophobically patternable via an Arduino-controlled corona discharge system.

Polydimethylsiloxane (PDMS) silicone is a versatile polymer that cannot readily be formed into long filaments. Traditional spinning methods fail because ...

Fabricating van der Waals Heterostructures with Precise Rotational Alignment

In this work we describe a technique for creating new crystals (van der Waals heterostructures) by stacking distinct ultrathin layered 2D materials. We demonstrate not only lateral control but, importantly, also control over the angular alignment of adjacent layers. The core of the technique is represented by a home-built transfer setup which allows the user to control the position of the individual crystals involved in the transfer. This is achieved with sub-micrometer (translational) and sub-degree (angular) precision. Prior to stacking them together, the isolated crystals are individually manipulated by custom-designed moving stages that are controlled by a programmed software interface. Moreover, since the entire transfer setup is computer controlled, the user can remotely create precise heterostructures without coming into direct contact with the transfer setup, labeling this technique as &#8220;hands-free&#8221;. In addition to presenting the transfer set-up, we also describe two techniques for preparing the crystals that are subsequently stacked.

In this work we describe a technique that is used to create new crystals (van der Waals heterostructures) by stacking ultrathin layered 2D materials with precise control over position and relative orientation.

In this work we describe a technique for creating new crystals (van der Waals heterostructures) by stacking distinct ultrathin layered 2D materials. We ...

Etalon Assembly and Fiber-Etalon Alignment

To begin, place the 3D-printed cell on the table with the etalon pit facing upward. Insert an O-ring into the etalon pit and press it slightly into the designated groove. Place the beam splitter with the reflective surface facing upward onto the O-ring in the etalon pit.Using a tweezer, carefully place the two spacers onto the beam splitter to generate a clear aperture for the gas and excitation laser, which enters the air cavity via the through-hole running from one side of the cell to the other. Align the mirror on top of the spacers with the reflective side facing down so that the beam splitter, spacers, and mirror are aligned concentrically. Take the 3D-printed etalon cap and put the O-rings into the designated grooves.Align the cap to the rectangular groove of the cell, lift the cell, and apply pressure on the cap to fix the spacers in place while simultaneously inserting four M4 screws through the designated holes from the back side. Mount the screws with four M4 nuts on the front side and tighten them until the pressure from the cap is enough to hold the spacers in place and the O-rings are sufficiently compressed. For fiber-etalon alignment, mount the pigtailed ferrule and the GRIN lens system with the ferrule clamp and ensure that the translation stage in the Z direction is moved to its maximum height.Align the 3D-printed cell underneath this system, fixing its position at a height slightly below the GRIN lens, pointing directly to the center of the opening. Apply one or two drops of adhesive on the front end of the GRIN lens with a pipette. Lower down the translation stage in the Z direction until contact with the anti-reflection coated surface of the beam splitter is insured.Continue to lower the GRIN lens until sufficient pressure is applied and the springs are under enough tension. Turn on the modulated laser and the oscilloscope. Ensure the oscilloscope has the highest possible resolution when starting the alignment process.Then, set the time resolution so that the two to three periods of the modulation are visible. To start the alignment process, ensure that the GRIN lens points normally on the beam splitter surface. Step by step, deflect the first goniometric stage slightly and then move the other goniometric stage around the zero position.If no change is observed on the oscilloscope, deflect the first goniometric stage slightly more and repeat this iterative process until the triangular modulation becomes visible on the oscilloscope. Once a strong back-reflection is observed, adjust the oscilloscope's resolution and ensure the peak of the etalon's reflectance function sits centrally on the triangular modulation slopes. Tune the etalon's peak by changing the temperature of the laser until the peak is centered on the slope.With slight movements of the goniometric stages, try to maximize the peak strength while simultaneously maximizing the peak-to-peak ratio of the triangular modulation. When the alignment is finished, mount the UV lamp close to the GRIN lens mounted at a 45-degree angle. Next, cure the adhesive applied on the front end of the GRIN lens.After 5 to 10 minutes, turn off the UV lamp and apply more adhesive around the GRIN lens without touching it. Expose the adhesive to UV light for another five to 10 minutes. Repeat this step until the opening of the cell is completely filled with a homogenous layer of adhesive and perform the final cure for at least one hour.The representative image shows a good and worse alignment. The better the alignment, the higher the peak-to-peak ratio of the triangular modulation and the more the reflectance peak approaches zero.

Fabrication and Mechanical Property Assessment of Fiber Composite Laminates

Measuring the Mechanical Properties of Glass Fiber Reinforcement Polymer Composite Laminates Obtained by Different Fabrication Processes

The traditional wet hand lay-up process (WL) has been widely applied in the manufacturing of fiber composite laminates. However, due insufficiency in the forming pressure, the mass fraction of fiber is reduced and lots of air bubbles are trapped inside, resulting in low-quality laminates (low stiffness and strength). The wet hand lay-up/vacuum bag (WLVB) process for the fabrication of composite laminates is based on the traditional wet hand lay-up process, using a vacuum bag to remove air bubbles and provide pressure, and then carrying out the heating and curing process. 
Compared with the traditional hand lay-up process, laminates manufactured by the WLVB process show superior mechanical properties, including better strength and stiffness, higher fiber volume fraction, and lower void volume fraction, which are all benefits for composite laminates. This process is completely manual, and it is greatly influenced by the skills of the preparation personnel. Therefore, the products are prone to defects such as voids and uneven thickness, leading to unstable qualities and mechanical properties of the laminate. Hence, it is necessary to finely describe the WLVB process, finely control steps, and quantify material ratios, in order to ensure the mechanical properties of laminates. 
This paper describes the meticulous process of the WLVB process for preparing woven plain patterned glass fiber reinforcement composite laminates (GFRPs). The fiber volume content of laminates was calculated using the formula method, and the calculated results showed that the fiber volume content of WL laminates was 42.04%, while that of WLVB laminates was 57.82%, increasing by 15.78%. The mechanical properties of the laminates were characterized using tensile and impact tests. The experimental results revealed that with the WLVB process, the strength and modulus of the laminates were enhanced by 17.4% and 16.35%, respectively, and the specific absorbed energy was increased by 19.48%.

Author Spotlight: Enhancing Fiber Composite Laminate Quality with the Wet Hand Lay-Up/Vacuum Bag Process 

This paper describes a fabrication process for fiber-reinforced polymer matrix composite laminates obtained using the wet hand lay-up/vacuum bag method.

The traditional wet hand lay-up process (WL) has been widely applied in the manufacturing of fiber composite laminates. However, due insufficiency in the ...

Micro-Embossed Fabrication of Nanocellulose Paper-Based Analytical Devices  

Microembossing: A Convenient Process for Fabricating Microchannels on Nanocellulose Paper-Based Microfluidics

Nanopaper, derived from nanofibrillated cellulose, has generated considerable interest as a promising material for microfluidic applications. Its appeal lies in a range of excellent&#160;qualities, including an exceptionally smooth surface, outstanding optical transparency, a uniform nanofiber matrix with nanoscale porosity, and customizable chemical properties. Despite the rapid growth of nanopaper-based microfluidics, the current techniques used to create microchannels on nanopaper, such as 3D printing, spray coating, or manual cutting and assembly, which are crucial for practical applications, still possess certain limitations, notably susceptibility to contamination. Furthermore, these methods are restricted to the production of millimeter-sized channels. This study introduces a straightforward process that utilizes convenient plastic micro-molds for simple microembossing operations to fabricate microchannels on nanopaper, achieving a minimum width of 200 &#181;m. The developed microchannel outperforms existing approaches, achieving a fourfold improvement, and can be fabricated within 45 min. Furthermore, fabrication parameters have been optimized, and a convenient quick-reference table is provided for application developers. The proof-of-concept for a laminar mixer, droplet generator, and functional nanopaper-based analytical devices (NanoPADs) designed for Rhodamine B sensing using surface-enhanced Raman spectroscopy was demonstrated. Notably, the NanoPADs exhibited exceptional performance with improved limits of detection. These outstanding results can be attributed to the superior optical properties of nanopaper and the recently developed accurate microembossing method, enabling the integration and fine-tuning of the NanoPADs.

Author Spotlight: Revolutionizing Microfluidics Through Microchannel Fabrication on Nanopaper 

This protocol describes a straightforward process that utilizes convenient plastic micro-molds for simple microembossing operations to fabricate microchannels on nanofibrillated cellulose paper, achieving a minimum width of 200 &#181;m.

Nanopaper, derived from nanofibrillated cellulose, has generated considerable interest as a promising material for microfluidic applications. Its appeal ...

﻿Fabrication of Glass Fiber-Reinforced Polymer (GFRP) Composite Laminates by Wet Hand Lay-Up/Vacuum Bag (WLVB) Method

Fabrication of Glass Fiber-Reinforced Polymer (GFRP) Composite Laminates by Wet Hand Lay-Up/Vacuum Bag (WLVB) Method  

Begin by heating the glass fiber fabric at 60 degrees Celsius for eight hours. Then, paste an isolation film on the acrylic sheet to prevent the resin from bonding. Position the mold in the laying area.Gently mix the resin and hardener for five minutes before placing it in a vacuum chamber to remove air bubbles. Place a non-porous release film on the mold and secure it with tape. Then, lay one Peel Ply on the non-porous release film.Pour epoxy resin on the film and evenly distribute it throughout using a scraper. Next, ply the first fiber fabric on the resin. Roll the fabric with a naked roller to ensure bubble removal and complete resin infiltration into the fabric.Again, pour and evenly spread the resin on the fabric using a scraper and continue till all the fabric has been used. Place a Peel Ply on the fabric and manually remove air bubbles by scraping in one direction. Lay a perforated release film followed by a breather fabric.Position the suction channel and breathable pad to one side. Secure a circular heat-resistant tape with an acrylic sheet outside the mold and attach the vacuum bag at the top of the device to create a closed space. Apply vacuum for 10 hours at room temperature, then switch off the vacuum pump and maintain quiescence for 14 hours.Cure the laminates completely at 80 degrees Celsius for 16 hours before measuring the fiber volume fraction. Comparison of laminates fabricated by the wet hand layup method with and without the vacuum bag process revealed that the vacuum bag assistance, the fiber volume fraction of the laminates increased by 15.78%and their average thickness reduced to 2.11 millimeters.