Nano Res.

Electronic Supplementary Material

Hybrid windshield-glass heater for commercial vehiclesfabricated via enhanced electrostatic interactions amonga substrate, silver nanowires, and an over-coating layer

Sae Mi Lee1,§, Ji Hun Lee1,§, Sora Bak1, Keunsik Lee1, Yang Li1, and Hyoyoung Lee1,2,3 ()

1 2066 Seoburo, Jangan-gu, Center for Smart Molecular Memory, Department of Chemistry, Sungkyunkwan University, Suwon 440-746,

Republic of Korea 2 2066 Seoburo, Jangan-gu, Center for Smart Molecular Memory, Department of Energy Science, Sungkyunkwan University, Suwon 440-746,

Republic of Korea 3 2066 Seoburo, Jangan-gu, Center for Smart Molecular Memory, SKKU Advanced Institute of Nano Technology (SAINT), Sungkyunkwan

University, Suwon 440-746, Republic of Korea § These authors contributed equally to this work.

Supporting information to DOI 10.1007/s12274-014-0696-4

Figure S1 Amethod of drying the solvent, which was used during the dispersion of silver nanowires and

graphene oxide particles. Although we did not anneal the sprayed substrate to reduce the RS, we heated it via

indirect heat from the lamp for several minutes to completely remove the solvent used for the dispersion of

AgNWs and GO. The heat generated from the light bulb was 120 °C, but the surface temperature of the substrate

was measured at 70 °C when heated from a distance of 10 cm. No change was noted in the structure of the AgNW,

such as a break or bend, even after the application of indirect heat from the lamp.

Figure S1 The indirect heating method using a lamp set at 100 °C, 10 cm above the glass substrate.

Figure S2 shows images of the final hybrid film products as compared with pristine substrates. Figure S2(a)–(i)

is O2-plasma-treated, pristine, 5 cm × 5 cm glass. Figure S2(a)–(ii) exhibitsthe final coated film product with PDDA

Address correspondence to Hyoyoung Lee, hyoyoung@skku.edu

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treatment after reaching a target sheet resistance of less than 15 Ω/. Figure S2(b)–(i): an image of the final film

product on a 10 cm × 10 cm glass substrate with a sheet resistance of 13 Ω/, where Figs. S2(b)–(ii) shows an

image of glass with O2 plasma treatment only.

Figure S2 Comparison of the pristine substrate and final hybrid film products of various sizes. (a)–(i) and (a)–(ii) for 5 cm × 5 cm, (b)–(i) and (b)–(ii) for 10 cm × 10 cm for glass substrates, respectively.

Figure S3(a) optical microscopic image of pristine glass without any coatings. Figure S3(b) an image of the coated

glass substrate with AgNW layer only. Figure S3(c) the final layer of GO coating on the surface of the AgNW-

coated layer, showing a slight tint and blurry GO particles on the surface of the AgNWs.

Figure S3 The Optical microscopic image of (a) pristine glass, (b) AgNW-coated glass without GO coating, (c) AgNW-coated glass with GO coating (all images are ×600 magnified).

The prepared hybrid film on the surface of a 10 cm × 10 cm glass substrate with silver paste painted on both

ends was frozen in a refrigerator for 6 hours to generate an even spread of frost on top of the substrate, as seen on

Fig. S4(a). After heating for 300 seconds, a target temperature of 45 °C was easily reached and evenly distributed

throughout the glass substrate. As shown in Fig. S4(b), water droplets were formed from the frost as a result.

Images printed below the glass substrate were not clearly visible when the glass was coated with frost. The

transparency of the substrate increased with the melting of the thinly-formed ice, eventually showing the logo

image placed below the substrate. The experimental set up for the heating test is shown in Fig. S4(c).The voltage

power was generated by Toyotech’s DP 30-05TP 3 Channel Laboratory DC Power Supply. Metal clips were

attached to the area where silver paste was applied, and 12.0 V was given to the resulting sample for heating,

asdisplayed on the machine monitor. Figure S4(d) shows the control panel of the cold chamber as set to 5.5 °C.

Morphologies of the hybrid-film-coated samples were characterized via scanning electron microscopy (JEOL

JSM-7600F and XL30 ESEM FEG). Figures S5(a) and (b) show a top view of the even distribution of the AgNWs

throughout the substrate after exposure to open air in ambient condition for 2 months. No damage was found

on the AgNW network. The sheet resistance measured prior to being left in ambient condition averaged

approximately 15 Ω/, while the sheet resistance measured after 2 months exhibited a value of 18~19 Ω/ with

only slight changes. Figures S5(c) and (d) show the damaged network of AgNWs after a heating test with a

final temperature above 100 °C. The red circled area indicates broken AgNWs with small sphere-like shapes.

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The breakage appears to occur near the edge of each nanowire. Figure S5(e) displays GO particles on top of the

AgNW network. The sample featured in this image was fabricated by spraying a large amount of GO solution.

This solution was produced by increasing the concentration three times. The blurry area of the image indicates

the presence of GO particles covering up the majority of the AgNWs. Lastly, Fig. S5(f) shows a magnified image

of the sample after the heating test with a final recorded temperature of 48 °C. The test was performed without

a GO layer to investigate the effect of PDDA treatment and verify the stability of the AgNWs after polymer

treatment. To achieve a clear result, we magnified the top view 100,000 times to observe the networks, and

conclude that PDDA treatment under the target temperature of 50 °C was able to stabilize the sample.

Figure S4 The images of (a) frost on the hybrid film before a heating test, (b) after the heating test, (c) experimentalset up of the heating test, (d) control panel of the cold chamber where the heating test was conducted.

Figure S5 SEM images of final film product after exposure in ambient conditions for 2 months. (a) ×10,000, (b) ×50,000 magnified, (c) damaged AgNWs after heating to over 100 °C, where red-circled areas indicate the damaged areas of the AgNWs. ×10,000 magnified, (d) damaged AgNWs after heating to over 100 °C. ×50,000 magnified, (e) GO-covered area of the hybrid film. ×30,000 magnified, (f) AgNW with PDDA coating after heating to under 50 °C. ×100,000 magnified.

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To demonstrate the role of the polymer solution in hybrid film fabrication, we compared the AFM (SPI3800N,

SII) data of the AgNW-coated substrate without PDDA immersion to that of the AgNW with PDDA immersion.

The PDDA solution was clearly observed to strengthen the adhesion of the overall coating by pressing the

AgNWs from the top. The samples were prepared with the same amount of AgNWs, and the same number of

sprays, though only half of the samples were immersed in the PDDA solution for purposes of comparison with

the AgNWs applied on the surface. The AFM image in Fig. S6 shows a Z value ranging from 69.65535 nm to

74.97303 nm without PDDA coating, and a Z value ranging from 43.42827 nm to 48.52073 nm with PDDA

coating. We confirmed that the PDDA solution coating was able to reduce the total coating height by 26 nm,

which resulted in a lower sheet resistance value, as shown in Fig. S6.

Figure S6 AFM images of the film (a) without immersion in PDDA solution and (b), (c) without an immersion of GO over coating.

The heating test was performed to investigate the possible use of AgNW-based transparent electrodes on the

surface of glass substrates for use as vehicle windshield heaters. 12 V were applied, and the temperature of the

air where the test was performed was at 23.8 °C, as shown in Fig. S7(p). Images of Figs. S7(a)–(o) showed an even

Figure S7 Thermal infrared images during the heat test of the 10 cm × 10 cm glass substrate with hybrid transparent electrode film and 12 V applied under ambient condition.

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distribution of heat on the surface of the substrate during temperature increase. The purple/blue area at the

edge of each image represents the room-temperature area. The orange/red areas represent the 10 cm × 10 cm

glass substrate’s square planer shape, and we can conclude visually via IR monitoring that the final product

wasable to evenly heat every surface. The experimental set up for this heating test was identical to that shown

in Fig. S4(s).

During the heating test of the transparent AgNW glass hybrid film, we can observe that not only the size but

also the thickness of the substrate affects the rate of temperature increase during testing under identical

conditions. To check such phenomena, we conducted additional heating tests on a 2 cm × 6 cm glass slide using

the same experimental method for the coating of the hybrid film, and measured the increase in temperature.

This small substrate had a sheet resistance of 13 Ω/, but a smaller area of silver paste painted on each edge due

to its size and shape, and exhibited a dramatic increase in temperature during the test conducted in a room

temperatureenvironment.

Figure S8 Thermal infrared images during the heat test of the 2 cm × 6 cm glass substrate with transparent AgNW glass electrodes, with 12 V applied in ambient conditions.

Figure S9 Graph showing sheet resistance change of 10 cm × 10 cm glass substrate after UV light exposure.

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Figure S10 Graph of changes in sheet resistance (Ω/) vs time (hr) of the 2 cm × 6 cm × 0.05 cm glass substrate with transparent AgNW glass hybrid electrode film when immersed in deionized water under ambient conditions.