A Fabrication Method for Highly Stretchable Conductors with Silver Nanowires

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.