Extremely Robust and Patternable Electrodes for ... - ACS Publications

Subscriber access provided by UNIV LAVAL

Article

Extremely Robust and Patternable Electrodes for Copy-Paper-Based Electronics Jaeho Ahn, Ji-Won Seo, Tae-Ik Lee, Donguk Kwon, Inkyu Park, Taek-Soo Kim, and Jung-Yong Lee ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.6b05296 • Publication Date (Web): 05 Jul 2016 Downloaded from http://pubs.acs.org on July 9, 2016

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

ACS Applied Materials & Interfaces is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Applied Materials & Interfaces

Extremely Robust and Patternable Electrodes for Copy-Paper-Based Electronics Jaeho Ahn1†, Ji-Won Seo1†, Tae-Ik Lee2, Donguk Kwon3, Inkyu Park3,4, Taek-Soo Kim2, and JungYong Lee1,* 1

Graduate School of Energy, Environment, Water, and Sustainability (EEWS), Graphene Research Center, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Republic of Korea. 2

Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Republic of Korea,

3

Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Republic of Korea.

4

KI for the NanoCentury, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Republic of Korea. †

These two authors contributed equally to this work.

*

All correspondence should be addressed to J.-Y.L. (email: [email protected])

1

ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Abstract We propose a fabrication process for extremely robust and easily patternable silver nanowire (AgNW) electrodes on paper. Using an auxiliary donor layer and a simple laminating process, AgNWs can be easily transferred to copy paper as well as various other substrates using a dry process. Intercalating a polymeric binder between the AgNWs and the substrate through a simple printing technique enhances adhesion, not only guaranteeing high foldability of the electrodes, but also facilitating selective patterning of the AgNWs. Using the proposed process, extremely crease-tolerant electronics based on copy paper can be fabricated, such as a printed circuit board for a 7-segment display, portable heater, and capacitive touch sensor, demonstrating the applicability of the AgNWs-based electrodes to paper electronics.

Keywords: robust electrodes, strong adhesion, patternable electrodes, paper-based electronics, silver nanowires

2


Page 2 of 28

Page 3 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Introduction Developing inexpensive, renewable, and eco-friendly substrates for electronic devices has become increasingly important. Paper, which meets these requirements and has also lightweight and foldable characteristic, is being focused as a great candidate to replace plastic substrates for portable and 3D-structured electronics, but only if electronics can be integrated with it seamlessly.1–4 The most important requirement for paper-based electronics is that electrodes should be able to endure high tension, because tensile and compressive stresses are concentrated at folded joints, cracking electrodes subjected to repeated folding and causing a loss of conduction. As thin metal films cannot endure severe repeated mechanical stress, they may not be appropriate for foldable electronics requiring alternative structure.5 Nanoscale materials such as silver nanowires (AgNWs) have been considered as an alternative for creating robust electrodes, because they can survive high strain upon folding, and also possess excellent optoelectrical performance.6–10 Forming a robust AgNWs network on paper, however, poses challenges. The first issue is the poor adhesion between AgNWs and paper, which must be improved so that they can endure high strain without rupture or exfoliation.11 Various techniques have been introduced to increase the adhesion between AgNWs and substrates, such as inserting an adhesion promoter between the AgNWs and the substrate, overcoating the protective layer on the AgNWs, and embedding the AgNWs into polymer.1,12–15 However, novel techniques still need to be developed that will not damage paper that is vulnerable to solvent wetting. Another proposed option is introducing a nanopaper substrate to enhance the adhesion and foldability of AgNW electrodes.16–19 The adhesion between AgNWs and nanopaper substrate can be enhanced by abundant free hydroxyl groups on nanocellulose surface, which contributes to higher adhesion force. However, preparing such nanopaper may require 3



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

complex annealing, pressing processes, and therefore, higher cost. Therefore, versatile fabrication process that can broaden the selection of substrate even to copy paper while increasing the adhesion between AgNWs and substrates is needed. High lateral resolution patterning of AgNW electrodes under 1 mm is another essential issue for developing various types of electronics, such as touchscreens, printed circuit boards (PCBs), and radio frequency identification (RFID) devices.4 Wet etching with photolithography, laser scribing, spraying with shadow masks, and direct writing of AgNW ink are common choices for patterning AgNWs network.20–30 However, photolithography potentially possesses expensive process, and laser scribing can overheat the substrate, while spraying and direct writing cause direct solvent contact that can damage or wet a paper substrate. In this report, we propose a simple fabrication process for AgNW electrodes on a copy paper substrate, permitting strong adhesion and micrometer scale patterns without causing substrate damage. The AgNW network is dry-transferred onto a paper substrate with the aid of an auxiliary hydrophobic film and a simple lamination process. A desired patterned toner layer printed on target substrate prior to transfer using a laser printer plays a role of smoothening and adhesion-promoting layer as well as selective embedding layer for AgNWs, facilitating below 200 µm resolution patterning of AgNWs electrodes. AgNWs with improved substrate adhesion demonstrate excellent robustness when subjected to repeated folding and twisting stresses. The proposed process enables the fabrication of extremely crease-tolerant electronics based on copy paper, including 7-segment display circuits, portable heaters and capacitive touch sensors.

4


Page 4 of 28

Page 5 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Results and discussion 1. Dry transfer process 1.1. Dry transfer of AgNWs on various substrates First, sprayed AgNWs network on a glass substrate (Figure 1a-i) is chemically reduced to fuse junctions between nanowires, yielding not only high opto-electrical performance, but also enhanced air stability.31The reduced AgNWs network is then immersed in water, and the AgNWs network exfoliates from the substrate and floats because the adhesion force between the AgNWs and the substrate is lowered by byproducts generated during reduction (Figure 1a-ii).31 Compared to other water floating methods, our novel method does not need any additional post-treatments for fusing junctions.32,33 After lifting the floated AgNWs with a hydrophobic film, such as Teflon®, the network can be laid on a film with very low adhesion force (Figure 1a-iii). The film can then act as a versatile donor substrate to transfer the AgNW network to various target substrates. After laminating the AgNW/hydrophobic film with a target substrate under mild heating (Figure 1a-iv), the AgNWs are easily transferred to target substrates such as glass, polyimide (PI), polyethylene terephthalate (PET), polydimethylsiloxane (PDMS), and even copy paper using a dry process as shown in Figure 1b and S1. To the best of our knowledge, transferring the water-floated AgNWs onto various substrates in a dry way is firstly demonstrated. The requirement for successful transfer of material A (e.g., an AgNW network) from substrate B (e.g., Teflon®) to target substrate C can be expressed as EAC > EAB, where EAB and EAC stand respectively for the interfacial binding energy (J/mm2) between materials A and B and materials A and C.34 In order to evaluate the adhesion energy between the layers, a 90° peel test was conducted, as shown in Figure 1c and S2. Peel strength, or fracture energy, was determined from the peel test as a measure of interfacial binding energy.35 AgNWs perfectly detached from Teflon® with a peel strength of approximately 0 N/mm 5



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(immeasurable), while dry-transferred AgNWs on paper detached at 0.013 N/mm. These quantitative results verify the easy transfer of AgNWs from Teflon® to paper. In initial stage, zero load is measured until tape is tightened. Subsequently, higher load is often observed when the peeling configuration stabilizes and the delamination of a target film is initiated. In the case of Figure 1c (AgNWs on Teflon), the front 3 mm of the tape was directly attached to the substrate to maintain a stable test set-up because the AgNW-Teflon adhesion was too weak. To exclude these experimental effects, the data after the initial peak is used when calculating the peel strength as noted by international test standards. (ASTM D6862, ASTM D1876) Scanning electron microscope (SEM) images (Figure S3) reveal that the AgNWs were properly transferred to various substrates. This included hydrophobic surfaces such as PDMS, where an AgNW network could not be uniformly deposited by a spraying or spin-coating process because of low surface energy that would prevents the uniform deposition of AgNWs solution, causing aggregation of the AgNWs without proper surface treatment. The favorable transfer (100 % yield) of AgNWs from Teflon® to PDMS may be attributed to the higher peel strength of AgNWs on PDMS (0.003 N/mm) than that of AgNWs on Teflon®. (Figure S4) Furthermore, utilizing the proposed process, ordinary copy paper can also be a target substrate for the AgNW network, without resulting in damage or wetting. 1.2. Verifying perfect transfer and enhanced sheet resistance and stability of AgNWs To confirm the perfect transfer process for AgNWs, the sheet resistance of AgNWs was measured before and after transfer. Figure S5 shows that the sheet resistance of AgNW electrodes did not change after the dry transfer process, implying that the AgNWs network remained intact. Even on hydrophobic surfaces, AgNWs network can be uniformly transferred without damage. In addition, because the junctions were fully fused by the initial

6


Page 6 of 28

Page 7 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


reduction process, the transferred AgNWs did not require additional post treatments to lower contact resistance and enhance environmental stability, as shown in Figures S5 and S6. The proposed dry transfer process can also be easily manipulated, allowing the selective additive coating of AgNWs. Figure 1d shows the Venn diagram for AgNWs transferred to PDMS. The sheet resistance of each AgNWs circle is 2.3 Ω/□, while the parts overlapping two and three circles are 1.1 Ω/□ and 0.6 Ω/□, respectively, showing that the sheet resistance of AgNWs can be tuned by way of selective transfer of the AgNW network.

2. 1ntercalating adhesion promoter between AgNWs and substrate 2.1. AgNWs embedded in printed pattern on paper using dry transfer The tolerance of mechanical strain in thin films can be enhanced by reinforcing the adhesion between the film and the substrate, because then the thin film can be stretched uniformly without localized strain or delamination.36 Likewise, the AgNW electrodes in robust paper-based electronics should be tightly bounded onto their substrates so they are not damaged by strain at folded joints. Until now, AgNW networks formed by conventional methods, led to weak adhesion to the substrate, allowing the AgNWs to become exfoliated and cracked due to folding. Here we introduce a simple printing method for enhancing adhesion between AgNWs and a substrate. Toner containing a polymer binder can be simply printed on a substrate using an office laser jet printer. Because toner covers copy paper smoothly, the surface morphology is flattened, filling the pores between paper fibers (Figure S7). In addition, printed toner strongly adheres to paper, showing its potential as adhesion promoter (Figure S8). Subsequently, the AgNWs are dry-transferred to the toner-printed substrate via roll lamination with mild heating. The toner becomes temporarily softened at its own glass transition temperature (typically, 50-80°C), so the AgNWs can be embedded into the toner; the toner and AgNWs harden again when the sample is returned to room 7



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

temperature. Top and cross-sectional SEM images demonstrate that this process causes the AgNWs to be well-embedded in the toner (Figure 2a-b and S7). The AgNWs embedded in toner were strongly bonded to the substrate, showing no detachment in the peel test; no sheet resistance difference was measured in the AgNWs before and after peeling. The measured peel strength of toner embedded AgNWs on paper was 0.078 N/mm (Figure S9a), which was much higher than that of dry-transferred AgNWs on paper without toner (0.013 N/mm). In contrast, AgNWs sprayed on paper were easily detached at a very low peel strength of 0.001 N/mm, showing the weak adhesion of AgNWs on paper (Figure S9b). Furthermore, AgNWs with overcoated graphene oxide (GO) (a useful method for enhancing adhesion between AgNWs and a substrate) also completely detach from paper, demonstrating weak adhesion (Figure S9c).1 The peel strength result here is summarized in Figure 2c. To verify the mechanical stability of adhesion-promoted AgNWs, a repeated folding test was performed. Figure 2d shows the test results of folding metal thin film evaporated on copy paper, as well as AgNWs transferred to copy paper with and without toner. Each film on paper is completely folded, as shown in the inset of Figure 2d, and the resistance change of the electrode measured over the folding cycles. After folding the electrode 5 times, the resistance of evaporated metal film sharply increased, indicating failure to survive high strain in the folded areas. AgNWs transferred to paper without toner also became detached and cracked at fold joints after 20 cycles, due to rupture of the paper and weak adhesion between it and the AgNWs.11 Figure 2e shows the cracked and exfoliated AgNW network at a folded joint (AgNWs are blue and the paper is brown). In contrast, the resistance of AgNWs embedded in toner showed less than a two-fold increase even after 1,000 repetitions of concave and convex folding, without exfoliation.

8


Page 8 of 28

Page 9 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


The strain on the top surface of a two-layer film surface can be calculated by the equation (1),37

εtop = (

d f + ds (1+ 2η + χη 2 ) , ) 2R (1+ η )(1+ χη )

(1)

where f and s stand for film and substrate, respectively; R is the bending radius; and η=df/ds and χ=Yf/Ys, where d is the thickness and Y is Young’s modulus. Because the thickness of AgNWs is much smaller than that of paper, εtop can be approximated by ds/2R. If the bending radius is 500 µm (see Figure 2e, 2f, and S10) and the thickness of copy paper is 100 µm, εtop is 10 %. Because the Young’s modulus of toner and paper is similar and the thickness of the toner (4 µm) is much smaller than that of the paper, the strain on top of the AgNW film with toner is similar to that found without toner.38,39 (Figure S11) The reason for the higher foldability of AgNWs embedded in toner despite the similar strain levels can be ascribed to enhanced adhesion. An SEM image confirms that the AgNWs embedded in toner still have conducting paths when folded because of the high adhesion between AgNW-embedded toner and paper. (Figure 2f and Figure S12) 2.2. Selective patterning of AgNWs The AgNWs transferred to paper without toner exhibit very weak adhesion, while those embedded in toner are strongly bound to the substrate. Finely selective patterning of AgNWs can thus be realized by simply printing the pattern using a laser printer. First, the AgNWs are dry-transferred to the desired pattern-printed paper. AgNWs without toner can then be easily detached from the substrate through a process such as swabbing, taping or stamping with polymer. For example, if a sticky material like PDMS is stamped onto AgNW-transferred paper, AgNWs on printed areas remain, while the AgNWs on unprinted areas become detached. Figure 3a-i and a-ii illustrate the pattern-printing and dry-transferring process. Figure 3a-iii shows the detachment process, demonstrating selective patterning in that the 9



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

dry-transferred AgNWs remain only on the flower pattern with the simple stamping process. No AgNWs were observed on paper without toner after stamping. (Figure S13) To confirm the conduction of the patterned AgNWs on toner, line pads were printed and AgNWs transferred to them (Figure 3b-d). The patterning resolution can be investigated by measuring the conduction from 1 to 2 and 2 to 3; if the conduction from 1 to 2 is secured without crosstalk from 2 to 3, the patterning resolution can be guaranteed. From the experiment, a minimum line spacing of 91 µm and line width of 124 µm were obtained (Figure S14). Note that the resolution of the pattern can be determined by that of the printer, suggesting that resolution can be enhanced by increasing the printer’s resolution performance. As shown in optical microscope images before (Figure 3c) and after (Figure 3d) dry transfer to a patterned line, the proposed process results in AgNWs transferred properly and with fine patterns. The AgNW-embedded toner layer can also be transferred to 3D objects using a water soluble layer. As shown in Figure S15, both AgNWs and the toner layer are floated on water and transferred to a glass vial. After a simple drying process, the transferred patterns adhered to the vial firmly; even taping or swabbing would not detach the AgNW/toner layer from the substrate (Movie S1).

3. Device application 3.1. Paper-based printed circuit board using AgNWs To demonstrate the proposed process for fabricating AgNW electrodes on a copy paper substrate, a 7-segment circuit was designed and printed using an office laser printer (Figure S16), and AgNWs were dry-transferred to this printed pattern as explained above. On the AgNW-embedded PCB, a decoder, switch, resistors and a 7-segment display were connected, illustrating the functionality of a paper-based AgNW PCB (Figure 4a-b and Figure S17). 10


Page 10 of 28

Page 11 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 4c shows the AgNW-based PCB operating well even while being deformed by finger pressure, demonstrating that AgNW-embedded toner electrodes have extreme foldability. By folding the wiring part, an 3D structure was also realized and only display part can be shown on top (inset of Figure 4c). Even after creasing or repeated folding, the PCB worked without any disconnections or failures (Figure 4d and Movie S2). 3.2. Paper-based portable heater A portable paper-based heater was also fabricated using the proposed process. The temperature of the heater was increased up to 90°C at 3V (Figure 4e) with uniform heating. Even after folding and unfolding, the paper-based heater operated well (Figure 4f). To demonstrate the portable heater, a water-filled bottle was placed on the heater connected to 2 AA batteries connected (3V). The temperature of water in bottle was 20°C before heating commenced. After the heater was turned on, the temperature of the water in the bottle increased to 32°C (Figure 4g). A letter-shaped heater was also demonstrated and operated, illustrating the potential for fabrication of patterned heaters (Figure S18). 3.3. Paper-based capacitive touch sensor Finally, we illustrated the ability to fabricate a foldable paper-based capacitive touch sensor. As shown in Figure S19, AgNWs were embedded in four-lined circuit arrays printed perpendicularly on both the front and back sides of paper, forming a 4×4 array configuration with each pixelated sensor having an area of 13 mm2. Figure S20 illustrates the working principle of the paper-based capacitive touch sensor. The capacitance change in response to the gentle touch of a human finger was clearly observed, as seen in Figure 4h, showing the on/off touch sensing capability of the device. To investigate crosstalk in the sensor array, a small metallic ball was placed on one pixel of the sensor array and capacitance responses measured at each pixel (inset of Figure 4i). The 2D mapping result of the capacitance response to the metallic ball is presented in Figure 4i, 11



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

showing the capacitance change at the touched pixel with negligible crosstalk signals at other pixels. The paper-based capacitive touch sensor also exhibited excellent mechanical stability against folding, as shown in Figure 4j and inset. Even after 100 folding cycles, the capacitive response remained intact.

12


Page 12 of 28

Page 13 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Conclusion AgNW electrodes were fabricated utilizing a simple printing and transfer process, resulting in strong adhesion and high patterning resolution on a copy paper substrate. The patterned toner was simply applied to the paper by a laser printer, which also enhanced the flatness of the paper surface. With a dry transfer technique, AgNWs were embedded in toner and transferred to a pattern-printed copy paper substrate without becoming wet or causing substrate damage. The AgNWs embedded in toner showed greatly enhanced adhesion to copy paper, allowing extreme foldability of the electrodes. Exploiting the enhanced adhesion of AgNWs with toner on paper allowed AgNWs to be selectively patterned with micrometer scale resolution. With the proposed fabrication process, a robust 7-segment display circuit, heater, and touch sensor were fabricated on copy paper, which operated consistently even after repeated extreme folding and creasing.

13



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Experimental Procedures Sample preparation: An AgNW electrode was fabricated by spraying the AgNWs solution, synthesized by a modified polyol process, using a lab-built spray system.3 Reduction of AgNWs: As-sprayed AgNWs were put into a beaker with 1 ml of hydrazine hydrate solution (45% in DI water, Sigma-Aldrich) in a water bath heated at 80°C.31 Then, the generated water by a reduction process is formed between the AgNWs and substrate, lowering the adhesion between AgNWs and the substrate. After 7 minutes, samples were pulled out and soaked in water to float the AgNWs. Peeling test: The 90° peel test was conducted using a high precision mechanical testing machine composed of two linear stages in Y-axis and Z-axis. A 12 mm wide tape (3M 810D) was attached to the top of the material, and detached at a 90° angle with a peeling speed of 1 mm/s. The sample moved along the Y-axis while the tape was detached along the Z-axis at the same speed. The peel strength is estimated by dividing the measured peeling force by the tape width (12 mm). Folding test: Electrodes on copy paper (Double A 80G) measuring 50 mm × 10 mm were fully folded and unfolded manually. The resistance was measured by a multimeter in unfolded status. Preparation of paper-based PCB: A circuit for operating the 7-segment display was printed on copy paper using an office laser printer (Canon LBP 6300dn). The toner (Canon Q2612A-AC-AD-AF-L) consists of styrene acrylate copolymer (< 55%), iron oxide (< 50%), and amorphous silica (< 3%), and styrene acrylate copolymer may act as a polymer binder. On the printed circuit, AgNWs were dry-transferred by the lamination process at 80°C. Each component was then connected to the AgNW embedded circuit using silver paste. The 7segment display PCB was operated using a voltage of 5V.

14


Page 14 of 28

Page 15 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Transfer of AgNWs / toner: A water soluble layer (PEDOT:PSS) was coated on PET and a toner pattern printed on it. AgNWs were then dry-transferred to the pattern, and the AgNW pattern floated on water by dipping the sample. Finally, the layer containing the AgNWs and toner was scooped from the water with the target substrate and annealed in an oven at 70°C for 1 minute. Preparation of paper-based heater: A rectangular pattern was printed on copy paper and AgNWs were dry-transferred to it. With a biased voltage, the temperature of the heater was measured by infrared camera (FLIR T400). To demonstrate the portable heater, two 1.5 V batteries (Energizer LR6/2B) were connected in series. Capacitive touch sensor measurement: Circuit lines were printed on both sides of copy paper perpendicularly and AgNWs were dry-transferred to both. The capacitance was measured by a precision LCR meter (Agilent E4980A) at a frequency of 1 MHz. Characterization: SEM images were acquired using field-emission scanning electron microscopy (FE-SEM, Nova230, FEI Co.) and sheet resistance measured with a 4-point probe sheet resistance meter.

Supporting Information Photograph of dry transfer process; Photograph of peel test setup; SEM images of drytransferred AgNWs on various substrates; Force-displacement curves of a 90° peel test for AgNWs on PDMS; Sheet resistance change before and after reduction; Environmental stability of reduced AgNWs; SEM images of AgNWs transferred on toner printed paper; Force-displacement curve of 90° peel test for toner on paper; Tapes and samples after peel test; Cross-sectional SEM image of the folded paper; Thickness measurement for toner; SEM images of AgNWs embedded in toner before and after folding; SEM images before and after stamping process; Optical microscope images of printed line with different pixels; Water15



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

floated AgNWs/toner pattern; Schematic illustration of 7-segment display circuit; Operation of 7-segments display on copy paper; Letter-patterned heater; Schematic illustration of a paper-based capacitive touch sensor; Schematic illustration of principle of direct capacitive touch sensor Video S1: Floating and transferring the AgNWs / toner layer Video S2: Folding test of paper-based 7-segment display circuit

16


Page 16 of 28

Page 17 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Author Information Corresponding Author *E-mail: [email protected]

Author Contributions †

These authors contributed equally to this work.

Notes The authors declare no competing financial interest.

17



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Acknowledgments We gratefully acknowledge the support from the New & Renewable Energy Core Technology Program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP), granted financial resource from the Ministry of Trade, Industry & Energy (No. 20133030000130), Graphene Materials and Components Development Program of MOTIE/KEIT (10044412), Climate Change Research Hub of KAIST (EEWS-2014N01140052). J. Ahn and J. Seo contributed equally to this work.

18


Page 18 of 28

Page 19 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


References (1)

Moon, I. K.; Kim, J. Il; Lee, H.; Hur, K.; Kim, W. C.; Lee, H. 2D Graphene Oxide Nanosheets as an Adhesive Over-Coating Layer for Flexible Transparent Conductive Electrodes. Sci. Rep. 2013, 3, 1112.

(2)

Chang, Y.-M.; Yeh, W.-Y.; Chen, P.-C. Highly Foldable Transparent Conductive Films Composed of Silver Nanowire Junctions Prepared by Chemical Metal Reduction. Nanotechnology 2014, 25 (28), 285601.

(3)

Lee, J.; Lee, I.; Kim, T.-S.; Lee, J.-Y. Efficient Welding of Silver Nanowire Networks without Post-Processing. Small 2013, 9 (17), 2887–2894.

(4)

Tobjörk, D.; Österbacka, R. Paper Electronics. Adv. Mater. 2011, 23 (17), 1935–1961.

(5)

Siegel, A. C.; Phillips, S. T.; Dickey, M. D.; Lu, N.; Suo, Z.; Whitesides, G. M. Foldable Printed Circuit Boards on Paper Substrates. Adv. Funct. Mater. 2010, 20 (1), 28–35.

(6)

Hu, L.; Kim, H. S.; Lee, J.-Y.; Peumans, P.; Cui, Y. Scalable Coating and Properties of Transparent, Flexible, Silver Nanowire Electrodes. ACS Nano 2010, 4 (5), 2955–2963.

(7)

Huang, G.-W.; Xiao, H.-M.; Fu, S.-Y. Paper-Based Silver-Nanowire Electronic Circuits with Outstanding Electrical Conductivity and Extreme Bending Stability. Nanoscale 2014, 6 (15), 8495–8502.

(8)

Lee, M.-S.; Kim, J.; Park, J.; Park, J.-U. Studies on the Mechanical Stretchability of Transparent Conductive Film Based on Graphene-Metal Nanowire Structures. Nanoscale Res. Lett. 2015, 10 (1), 27.

(9)

Kim, M.; Park, J.; Ji, S.; Shin, S.-H.; Kim, S.-Y.; Kim, Y.-C.; Kim, J.-Y.; Park, J.-U. Fully-Integrated, Bezel-Less Transistor Arrays Using Reversibly Foldable Interconnects and Stretchable Origami Substrates. Nanoscale 2016, 8 (18), 9504–9510.

19



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(10)

An, B. W.; Kim, K.; Lee, H.; Kim, S. Y.; Shim, Y.; Lee, D. Y.; Song, J. Y.; Park, J. U. High-Resolution Printing of 3D Structures Using an Electrohydrodynamic Inkjet with Multiple Functional Inks. Adv. Mater. 2015, 27 (29), 4322–4328.

(11)

Yang, C.; Gu, H.; Lin, W.; Yuen, M. M.; Wong, C. P.; Xiong, M.; Gao, B. Silver Nanowires: From Scalable Synthesis to Recyclable Foldable Electronics. Adv. Mater. 2011, 23 (27), 3052–3056.

(12)

Jin, J.; Lee, J.; Jeong, S.; Yang, S.; Ko, J.-H.; Im, H.-G.; Baek, S.-W.; Lee, J.-Y.; Bae, B.-S. High-Performance Hybrid Plastic Films: A Robust Electrode Platform for ThinFilm Optoelectronics. Energy Environ. Sci. 2013, 6 (6), 1811–1817.

(13)

Sun, Q.; Lee, S. J.; Kang, H.; Gim, Y.; Park, H. S.; Cho, J. H. Positively-Charged Reduced Graphene Oxide as an Adhesion Promoter for Preparing a Highly-Stable Silver Nanowire Film. Nanoscale 2015, 7 (15), 6798–6804.

(14)

Nam, S.; Song, M.; Kim, D.-H.; Cho, B.; Lee, H. M.; Kwon, J.-D.; Park, S.-G.; Nam, K.-S.; Jeong, Y.; Kwon, S.-H.; Park, Y. C.; Jin, S.-H.; Kang, J.-W.; Jo, S.; Kim, C. S. Ultrasmooth, Extremely Deformable and Shape Recoverable Ag Nanowire Embedded Transparent Electrode. Sci. Rep. 2014, 4, 4788.

(15)

Akter, T.; Kim, W. S. Reversibly Stretchable Transparent Conductive Coatings of Spray-Deposited Silver Nanowires. ACS Appl. Mater. Interfaces 2012, 4 (4), 1855– 1859.

(16)

Kang, W.; Yan, C.; Foo, C. Y.; Lee, P. S. Foldable Electrochromics Enabled by Nanopaper Transfer Method. Adv. Funct. Mater. 2015, 25 (27), 4203–4210.

(17)

Nogi, M.; Komoda, N.; Otsuka, K.; Suganuma, K. Foldable Nanopaper Antennas for Origami Electronics. Nanoscale 2013, 5 (10), 4395–4399.

20


Page 20 of 28

Page 21 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(18)

Koga, H.; Nogi, M.; Komoda, N.; Nge, T. T.; Sugahara, T.; Suganuma, K. Uniformly Connected Conductive Networks on Cellulose Nanofiber Paper for Transparent Paper Electronics. NPG Asia Mater. 2014, 6 (3), e93.

(19)

Nogi, M.; Karakawa, M.; Komoda, N.; Yagyu, H.; Nge, T. T. Transparent Conductive Nanofiber Paper for Foldable Solar Cells. Sci. Rep. 2015, 5, 17254.

(20)

Asadpoordarvish, A.; Sandström, A.; Larsen, C.; Bollström, R.; Toivakka, M.; Österbacka, R.; Edman, L. Light-Emitting Paper. Adv. Funct. Mater. 2015, 25 (21), 3238–3245.

(21)

Li, R.-Z.; Hu, A.; Zhang, T.; Oakes, K. D. Direct Writing on Paper of Foldable Capacitive Touch Pads with Silver Nanowire Inks. ACS Appl. Mater. Interfaces 2014, 6 (23), 21721–21729.

(22)

Wei, Y.; Chen, S.; Li, F.; Lin, Y.; Zhang, Y.; Liu, L. Highly Stable and Sensitive Paper-Based Bending Sensor Using Silver Nanowires/Layered Double Hydroxides Hybrids. ACS Appl. Mater. Interfaces 2015, 7 (26), 14182–14191.

(23)

Ahn, Y.; Lee, H.; Lee, D.; Lee, Y. Highly Conductive and Flexible Silver NanowireBased Microelectrodes on Biocompatible Hydrogel. ACS Appl. Mater. Interfaces 2014, 6 (21), 18401–18407.

(24)

Henley, S. J.; Cann, M.; Jurewicz, I.; Dalton, A.; Milne, D. Laser Patterning of Transparent Conductive Metal Nanowire Coatings: Simulation and Experiment. Nanoscale 2014, 6 (2), 946–952.

(25)

Liang, J.; Li, L.; Niu, X.; Yu, Z.; Pei, Q. Elastomeric Polymer Light-Emitting Devices and Displays. Nat. Photonics 2013, 7 (10), 817–824.

(26)

Hong, S.; Yeo, J.; Lee, J.; Lee, H.; Lee, P.; Lee, S. S.; Ko, S. H. Selective Laser Direct Patterning of Silver Nanowire Percolation Network Transparent Conductor for Capacitive Touch Panel. J. Nanosci. Nanotechnol. 2015, 15 (3), 2317–2323. 21



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(27)

Pothoven, T. Laser Patterning of Silver Nanowire. Inf. Disp. 2012, 28 (9), 20–24.

(28)

Wu, J.-T.; Hsu, S. L.-C.; Tsai, M.-H.; Hwang, W.-S. Direct Inkjet Printing of Silver Nitrate/Poly( N -Vinyl-2-Pyrrolidone) Inks To Fabricate Silver Conductive Lines. J. Phys. Chem. C 2010, 114 (10), 4659–4662.

(29)

Park, S.-E.; Kim, S.; Lee, D.-Y.; Kim, E.; Hwang, J. Fabrication of Silver Nanowire Transparent Electrodes Using Electrohydrodynamic Spray Deposition for Flexible Organic Solar Cells. J. Mater. Chem. A 2013, 1 (45), 14286-14293.

(30)

Wang, P.-H.; Chen, S.-P.; Su, C.-H.; Liao, Y.-C. Direct Printed Silver Nanowire Thin Film Patterns for Flexible Transparent Heaters with Temperature Gradients. RSC Adv. 2015, 5 (119), 98412–98418.

(31)

Ahn, J.; Seo, J.-W.; Kim, J. Y.; Lee, J.; Cho, C.; Kang, J.; Choi, S.-Y.; Lee, J.-Y. SelfSupplied Nano-Fusing and Transferring Metal Nanostructures via Surface Oxide Reduction. ACS Appl. Mater. Interfaces 2016, 8 (2), 1112–1119.

(32)

Pyo, J. B.; Kim, B. S.; Park, H.; Kim, T. A.; Koo, C. M.; Lee, J.; Son, J. G.; Lee, S.-S; Park, J. H. Floating Compression of Ag Nanowire Networks for Effective Strain Release of Stretchable Transparent Electrodes. Nanoscale 2015, 7 (39), 16434–16441.

(33)

Kim, B. S.; Shin, K. Y.; Pyo, J. B.; Lee, J.; Son, J. G.; Lee, S.-S.; Park, J. H. Reversibly Stretchable, Optically Transparent Radio-Frequency Antennas Based on Wavy Ag Nanowire Networks. ACS Appl. Mater. Interfaces 2016, 8 (4), 2582–2590.

(34)

Hines, D. R.; Mezhenny, S.; Breban, M.; Williams, E. D.; Ballarotto, V. W.; Esen, G.; Southard, A.; Fuhrer, M. S. Nanotransfer Printing of Organic and Carbon Nanotube Thin-Film Transistors on Plastic Substrates. Appl. Phys. Lett. 2005, 86 (16), 163101.

(35)

Pallas, A.; Larsson, K. Effect of Terminating Species on the Initial Growth of BN on Diamond Substrates. J. Phys. Chem. C 2014, 118 (7), 3490–3503.

22


Page 22 of 28

Page 23 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(36)

Xiang, Y.; Li, T.; Suo, Z.; Vlassak, J. J. High Ductility of a Metal Film Adherent on a Polymer Substrate. Appl. Phys. Lett. 2005, 87 (16), 161910.

(37)

Suo, Z.; Gleskova, H.; Wagner, S. Mechanics of Rollable and Foldable Film-on-Foil Electronics. Appl. Phys. Lett. 1999, 74 (8), 1177–1179.

(38)

Zhou, H. Investigation of Toner Adhesion in the Electrophotographic Process, Cuvillier Verlag, 2008.

(39)

Yokoyama, T.; Nakai, K. Evaluation In Plane Orthotropic Elastic Constants Paper and Paperboard. 2007 SEM Annu. Conf. 2007.

23



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 1. a) Schematic illustration of a dry transfer process for AgNWs. (i) Spraying the AgNWs on the substrate; (ii) Floating the AgNWs by immersing the reduced AgNW/substrate sample in water; (iii) Lifting the AgNWs with hydrophobic film; (iv) AgNW/hydrophobic film is laminated with pattern-printed target substrate and the AgNW network is transferred onto the target substrate. b) Dry transfer of AgNWs to paper, glass, PET, PI, and PDMS. c) Force-displacement curves of a 90° peel test; dry-transferred AgNWs to Teflon® and paper. d) Venn diagram of AgNW circles on PDMS, showing the additive coating for the AgNW network. The numbers marked are sheet resistance levels. The inset microscope image shows AgNWs are clearly overlapped. Scale bars for (d) and inset are 10 mm and 100 µm, respectively.

24


Page 24 of 28

Page 25 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 2. a) Top view and b) cross-sectional SEM images of AgNWs embedded in toner on paper. Toner is colored red in (b). Scale bars for (a) and (b) are 2 µm and 500 nm, respectively. c) Peel strength of AgNW network on paper formed by various methods. d) Resistance change of Ag metal film and AgNWs with and without toner on paper after repeated folding. Inset is a photograph of a folded electrode; scale bar of inset is 10 mm. SEM images of dry transferred AgNWs on paper e) without and f) with toner upon folding. AgNWs without toner are torn and exfoliated at the fold joint, while AgNWs on toner tolerate the strain. The AgNW network is blue and the paper red colored. The scale bars for (e) and (f) are 500 µm.

25



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 3. a) Schematic illustration and photographs of selective patterning process for AgNWs. (i) Before and (ii) after dry transfer of AgNWs to paper printed with a flower pattern; (iii) after PDMS stamping. b) Illustration of line pads printed by an office printer. Optical microscope images c) before and d) after dry-transferring AgNWs to pattern-printed paper. Scale bars of (c) and (d) are 100 µm.

26


Page 26 of 28

Page 27 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 4. a) Bottom and b) top view of paper-based PCB for a 7-segment display. Operational PCB circuit c) under extreme folding and d) creasing conditions. Insets of (c) and (d) are 3D-structured and spread paper-based PCBs, respectively. e) Paper-based heater and its infrared image, before and after voltage application.f) Operational paper-based heater after folding and unfolding. Scale bars for (e) and (f) are 2 cm. g) Photograph of portable heater operated by batteries and its infrared images after turning on the heater. h) Capacitive response to finger touch as a function of measuring time. Insets: touching the sensor using an index finger. i) Capacitive response distribution of a touch sensor with a small metallic ball on (4, 3) pixel. Inset is photograph of the touch sensor with metallic ball. Scale bar of inset is 2 cm. j) Capacitive response as a function of measuring time before and after a folding/unfolding cycle. On and off state stands for putting and removing the metallic ball on the pixel, respectively. Inset is photograph of folded touch sensor.

27



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Table of Contents Graphic

28


Page 28 of 28

Extremely Robust and Patternable Electrodes for ... - ACS Publications

Recommend Documents