The authors are grateful for the financial support from Ministry of Science and Technology.

1. Preparation of Silver Precursor Ink
<ol>
	<li>Add 1.85 g of diethanolamine (DEA) in 3.15 ml deionized water.</li>
	<li>Dissolve 0.15 g of silver nitrate in 5 ml deionized water.</li>
	<li>Mix the aqueous silver nitrate solution with DEA at a 1:1 volume ratio to have 10 ml silver precursor ink right before use.</li>
</ol>
2. Fabrication of Stretchable Conductive Thin Films
<ol>
	<li>Preparation of AgNW ink
	<ol>
		<li>Dilute 2 ml of 0.5 wt% AgNWs in isopropanol with 18 ml de...

<ol>
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Interfaces. 4 (4), 1855-1859 (2012).</li><li>Madaria, A., Kumar, A., Ishikawa, F., Zhou, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Uniform,+highly+conductive,+and+patterned+transparent+films+of+a+percolating+silver+nanowire+network+on+rigid+and+flexible+substrates+using+a+dry+transfer+technique.">Uniform, highly conductive, and patterned transparent films of a percolating silver nanowire network on rigid and flexible substrates using a dry transfer technique.</a> Nano Res. 3 (8), 564-573 (2010).</li><li>Lee, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Room-Temperature+Nanosoldering+of+a+Very+Long+Metal+Nanowire+Network+by+Conducting-Polymer-Assisted+Joining+for+a+Flexible+Touch-Panel+Application.">Room-Temperature Nanosoldering of a Very Long Metal Nanowire Network by Conducting-Polymer-Assisted Joining for a Flexible Touch-Panel Application.</a> Adv. 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Mater. 11 (3), 241-249 (2012).</li><li>Zhu, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transferable+self-welding+silver+nanowire+network+as+high+performance+transparent+flexible+electrode.">Transferable self-welding silver nanowire network as high performance transparent flexible electrode.</a> Nanotechnology. 24 (10), 1321-1327 (2013).</li><li>Han, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fast+Plasmonic+Laser+Nanowelding+for+a+Cu-Nanowire+Percolation+Network+for+Flexible+Transparent+Conductors+and+Stretchable+Electronics.">Fast Plasmonic Laser Nanowelding for a Cu-Nanowire Percolation Network for Flexible Transparent Conductors and Stretchable Electronics.</a> Adv. Mater. 26 (33), 5808-5814 (2014).</li><li>Chen, S. P., Liao, Y. 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The authors have nothing to disclose.

The chemical soldering process can help reinforce the contact between silver nanowires. As shown in Figure 4b, the wire/wire junctions are covered with silver after applying the reactive silver ink over the spray coated AgNW thin film. The silver recovery relies strongly on the formaldehyde generated from DEA degradation, and thus the soldering process or silver reduction can be accelerated with increasing temperature.22 Because the metal surfaces of AgNWs provide effective electron exchange s...

Deformable electronic devices with large stretchability have been identified as critical parts to the realization of wearable and portable electronics in the next generation.1 Those stretchable electronic devices not only show great flexibility as those electronic devices on plastic sheets,2, 3 but also exhibit excellent performance under severe stretching or twisting conditions.4 To realize the stretchable electronics, materials with great electric performance under large deformation is needed. Recent advancements in material sciences have shown the possibility to synthesize such functional materials and have used them to design stretchable optoelectronic devices 5-9 with great tolerance to complex shape deformations. Among all the electronic functional materials, stretchable conductors are necessary to supply electrical power to those optoelectronic devices and thus are of critical importance for device performance. Because regular conducting materials, like metal or indium tin oxide, lack of mechanical robustness under large deformation, interconnects made of these materials are unable to exhibit good electrical conductivity under stretching process. Thus, elastic substrates covered with a thin layer of flexible conductive materials, such as carbon nanotube,1 graphene,10 or AgNWs,11-14 are designed for conductors with excellent stretchability. Because of the high bulk conductivity, AgNW thin films have been shown to be the most promising material for composite stretchable conductors.13 The percolating networks of AgNW thin films can effectively accommodate large elastic deformations in stretching process with great electrical conductance, and are considered as a promising stretchable electrode candidate. To implement AgNW thin films as stretchable conductors, it is necessary to have effective electrical contacts between AgNWs. After liquid deposition and drying on substrate surfaces, AgNWs regularly stack together to form a percolating mesh with loose contact points, which yield in large electrical resistances. Thus, one needs to anneal the contacts between nanowires by high-temperature or high-pressure annealing methods15-20 to reduce the contact resistances.
In contrast to these annealing processes in the literature, here, we will demonstrate a simple chemical method to anneal AgNW network connections under regular laboratory conditions.21 The fabrication process is shown in Figure 4A. A reactive ink is used to sinter the spray coated AgNW thin films on a glass plate. After reaction, the contacts between nanowires are covered with silver and hence the AgNW network is soldered chemically together. A cast-and-peel method is then used to transfer the soldered AgNW network to a stretchable PU substrate to form a composite conductor, which can exhibit no obvious change in electrical conductivity even at large tensile strain of 120%.

<table border="0" cellpadding="0" cellspacing="0" width="833">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:173px;">Silver nanowire</td>
			<td style="width:195px;">Sigma-Aldrich</td>
			<td style="width:117px;">778095-25ML</td>
			<td style="width:349px;">AgNW, 120 nm in diameter and 20-50 mm in length, 0.5 wt% in IPA</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Silver nitrate crystal</td>
			<td>Macron Fine Chemicals</td>
			<td>MK216903</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Diethanolamine</td>
			<td>Sigma-Aldrich</td>
			<td>D8885-500G</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Polyurethane emulsion</td>
			<td>First Chemical</td>
			<td>20130326036</td>
			<td>35 wt% water-based anionic polyester-polyurethane emulsion</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Airbrush</td>
			<td>Taiwan Airbrush &#38; Equipment</td>
			<td>AFC-sensor&#160;</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Desktop robot</td>
			<td>Dispenser Tech</td>
			<td>DT-200&#160;</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Digital dispenser controller</td>
			<td>Dispenser Tech</td>
			<td>9000E&#160;</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:173px;">Auto-spraying program</td>
			<td style="width:195px;">Dispenser Tech</td>
			<td style="width:117px;">Smart robot edit version 3.0.0.5</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Air compressor&#160;</td>
			<td>PUMA Industrial</td>
			<td>NCS-10&#160;</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Linear motorized stage</td>
			<td>TANLIAN E-O</td>
			<td>Customized</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:173px;">Stage control software</td>
			<td style="width:195px;">TANLIAN E-O</td>
			<td style="width:117px;">Customized</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Digital multimeter</td>
			<td>HILA INTERNATIONAL</td>
			<td>DM-2690TU</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:173px;">Digital multimeter software</td>
			<td style="width:195px;">HILA INTERNATIONAL</td>
			<td style="width:117px;">NA</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Power supply</td>
			<td>CHERN TAIH</td>
			<td>CT-605</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">LED</td>
			<td>PChome</td>
			<td>M08330766</td>
			<td>http://www.pcstore.com.tw/sun-flower/M08330766.htm</td>
		</tr>
	</tbody>
</table>

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%.

The morphology of the AgNW thin film after chemical soldering process is shown in Figure 4B. Recovered AgNPs preferentially grow on the surface of AgNWs and wrap over the wire/wire junctions. Figure 5 shows the variation in sheet resistance with applied elongation strains for the unsoldered and the soldered thin films containing different amount of AgNWs. After the chemical soldering process, AgNW thin film conductors can maintain high conductivity under ...

Watch this Scientific Journal Video about A Fabrication Method for Highly Stretchable Conductors with Silver Nanowires at JoVE.com

A Fabrication Method for Highly Stretchable Conductors with Silver Nanowires

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 ...

The overall goal of this procedure is to provide a simple method to fabricate highly stretchable conductors for applications in stretchable electronics. This method can help answer key questions in developing stretchable electronics such as the mechanical of connecting conductors. The main advantage of this technique is that it's a simple fabrication method.And the amount of silver there was in the fabrication of the conductors can be greatly reduced. To begin, prepare 10 milliliters of fresh aqueous silver nitrate solution, with DEA at a one to one volume ratio. Next, fabricate the stretchable conductive thin films.First, make the silver nanowire ink by diluting two milliliters of 0.5%silver nanowire in isopropanol, into 18 milliliters of water. Sonicate this mixture for 30 seconds. Next, use a pipette to transfer 16 milliliters of this mixture to an airbrush.Mount the loaded airbrush to a computer-controlled robot. Then, on the heated airbrushing stage, arrange eight glass rectangles to cover a four by five centimeter area. Use heat-resistant tape to fix the slides in place.Then, set the stage to 100 degrees Celsius, and set the airbrush to three bars. Now, in the software control of the robot, select the brush motion command sequence under the command column. Then, input the necessary parameters to complete the auto spraying program, and run the program.Consult the text protocol for more details. After spraycoating the glass, bake the silver nanowire thin films on a hot plate at 120 degrees Celsius for 10 minutes. Once baked, cast 400 microliters of the prepared silver precursor ink over the thin film.Then bake the films on a hot plate set to 100 degrees Celsius for 40 minutes. Later, carefully rinse the coatings under deionized water to remove the unreacted chemical residues. Then, air-dry the coated films.The next step is to cast 200 microliters of water-based PU emulsion over the silver nano-composite thin films. Then, let the films air-dry for 10 hours so they are fully solidified. Once fully solidified, peel the samples off the glass using forceps, and proceed with testing them.First, execute a stretch test. Begin by warming up a linear motorized stage. Now, in the software control of the stage, set the number of the moving steps for the motor to 8000.Then, click X+in the stage control software to move the mobile stage until it touches the fixed stage. When contact is made, click Set 0"in the stage control software. Then, click X-to move the mobile stage backward.Move the stage until there is a one centimeter gap between the two stages. Now, secure the sample across the gap with wired holders. This creates a testable one by one centimeter area.Next, connect the alligator clips to the digital multimeter, and record the resistance across the test area. Then, set the number of the moving steps of the motor to 800 and click X-to move the mobile stage one millimeter further away from the fixed stage to create a 10%strain on the sample. After producing a 10%strain, record the resistance.Repeat this step until the resistance increases significantly, which may require a strain of 150%Then, proceed with the next sample or the next test. Next, conduct a stability test. Setup is like the stretch test, however, for this test, connect the multimeter to a computer so the computer can record the data.In the stage control software, key in the number of cycles, and click on run 1 2 3"in the program panel to execute the stability test. This moves the mobile stage in a reciprocating motion to stretch the sample, with elongation cycles in triangular wave form. The final test is the LED lighting test.Set up the test material as before, and connect the wired holders in series with an LED and a power supply. Now, increase the power supply from zero to nine volts. This should light up the LED.Then, in the software, create strain as done for the strain test, until the LED becomes dim. Once a sample passes all these tests, it can be considered an effective conductor in the applications of stretchable electronics. The morphology of the silver nanowire thin film after the chemical soldering process shows that the recovered silver nanoparticles preferentially grow on the surface of silver nanowire and wrap over the wire-wire junctions.Elongation strain was placed on unsoldered and soldered thin films, containing different amounts of silver nanowire. Both showed sheet resistance below 100 ohms, when strains below 120%were applied. The composite stretchable conducting thin films showed great mechanical stability in this dynamic deformation process.When subjecting the thin film to elongation cycles in a triangular waveform at a fast strain rate, no obvious resistance changes were observed at strain amplitudes of 50%When the strain amplitude was 100%the peak resistance increased with the pulsation cycles. After the pulsation stopped, the resistance of the film returned to the original value. This method can produce highly stretchable conductors to serve us in effective interconnect for next generation stretchable electronics.

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9.8K visualizações.  National Taiwan University. The overall goal of this procedure is to provide a simple method to fabricate highly stretchable conductors for applications in stretchable electronics. This method can help answer key questions in developing stretchable electronics such as the mechanical of connecting conductors. The main advantage of this technique is that it's a simple fabrication method.And the amount of silver there was in the fabrication of the conductors can be greatly reduced. To begin, prepare 10 milliliters o...