A photograph of the large, flexible and transparent touchscreen (20 × 20 cm2) using cross-aligned AgNW TCEs. A photograph of the written letter "A" on the mechanochromic touch screen (left) and its 10 × 10 pixel array of applied force mapping data showing the local force distribution (right).
Introduction
Flexible/stretchable transparent electrodes
- Nanostructured transparent conducting materials
Transparent conductive CNT networks have received increasing attention to replace ITO due to their flexibility, durability and solution processability (Figure 1.2e).17, 25 Single-walled CNTs have been particularly intensively used in flexible optoelectronic devices due to their high optical transparency compared to multi-walled CNTs. . Among the various alternatives to the ITO film, metal nanowires are currently the most promising material due to solution processability and comparable optoelectronic performance to ITO (<30 Ω sq-1 at >90% transmittance) (Figure 1.2g).13 Metal nanowires including copper nanowires (CuNWs )28-30 and silver nanowires (AgNWs)19, 31-33 have been intensively investigated in the last decade for the production of flexible and even stretchable transparent electrodes.
Transparent AgNW networks
- Conductive percolation networks
- Junction resistance
- Alignment of AgNW networks
Recently, a brushing-based liquid transfer technique of a tapered fiber array has been demonstrated to fabricate anisotropic AgNW networks (Fig. 1.7f).57 The brushing-based liquid transfer technique enables precise control over the retraction of a three-phase contact line when. In summary, various alignment techniques have been implemented for the controlled manipulation of AgNW networks, which enable the improvement of the optoelectronic performance of AgNW TCEs.
Flexible and transparent AgNW electrodes and device applications
- Touch screen panels
- Flexible loudspeakers
- Acoustic sensors
Another advantage of the capacitive type touch screen is good stability compared to the resistive type. Moreover, capacitive type touch screen panel provides higher quality of visibility than resistive type for the application in the smart screens.
Stretchable and transparent AgNW electrodes and device applications
- Electroluminescence
With the development of highly transparent and stretchable electrodes, the stretchable ACEL devices have been reported that can withstand large mechanical deformations such as bending, twisting, stretching, and folding. Stretchable ACEL devices based on AgNW electrodes. a) Stretchable and self-deformable ACEL devices (J. Wang et al.
Challenges of current flexible/stretchable transparent electrodes
In Chapter 2, we demonstrated the simple and facile NW alignment technique using the modified rod-coating assembly for the fabrication of large-area (>20 × 20 cm2) cross-aligned AgNW TCEs. In chapter 6, the synchronized generation of audio and vision information is demonstrated for the highly stretchable audio-in-display electronics with the voltage-insensitive AgNW electrodes and field-induced emitting EL layers.
Large-scale AgNW alignment technique for flexible force-sensitive mechanochromic touch
Introduction
Furthermore, force-sensitive response can be added to touch screens by integrating mechanochromic spiropyran-polydimethylsiloxane (SP-PDMS) composite film into the devices. Unlike conventional touchscreens that can only sense writing location, our touchscreens enable monitoring of handwriting patterns with locally different writing forces.
Experimental Details
Fabrication of force-sensitive mechanochromic touchscreen: For the fabrication of mechanochromic composite films on top of the touchscreen, spiropyran mechanophore was completely mixed with a PDMS base (Sylgard 184, Dow Corning) and PDMS curing agent (10:1 ratio for base to curing agent) . Then, the mechanochromic composite film was uniformly deposited on top of the transparent touch screen by a rod coating of the SP-PDMS composite solution using the #15 rod at a coating speed of 10 mm s-1 and thermal curing at 60 °C for 6 hours. The sheet resistances of the cross-aligned and random AgNW networks were measured using a four-point probe measuring device (Kiethley 2400 equipment).
Optical transmittance and absorption spectra of unidirectional, cross-aligned and random AgNW networks were measured with a UV–vis–NIR spectrophotometer (Jasco V-670).
Results and Discussion
The cross-aligned AgNW array is formed by repeating the rod coating assembly in a perpendicular direction to the previously aligned AgNW arrays. The highly anisotropic optical properties of the highly aligned AgNW array exhibit an optical dichroic characteristic;. The Π value of cross-aligned AgNW arrays (FoM = 479) is much higher than that of random AgNW networks (FoM = 254), confirming the superior optical and electrical properties of cross-aligned AgNW arrays.
All cross-aligned AgNW arrays were fabricated at a deposition rate of 10 mm s-1.
Conclusions
Orthogonal AgNW-embedded hybrid nanomembranes (NMs) for skin-attachable acoustic
Introduction
Hybrid NMs differ from polymeric NMs in that the electrical, optical and mechanical properties of NMs are determined by the type of loading material, which can be metal nanoparticles (NPs), metal nanowires (NWs), carbon nanotubes (CNTs), or graphene In this respect, silver nanowires (AgNW)/polymer composite NMs are attractive candidates because they possess excellent mechanical and electrical/optical properties due to the large aspect ratio of AgNWs used as reinforcement.176, 179 In addition, AgNW networks can be easily prepared by cost-effective and large-scale solution-based processes, such as spin-coating, casting, rod coating, and spray coating. Several studies have addressed the properties mechanical free-standing AgNW/polymer composite NMs formed using a layer-by-layer (LbL) assembly technique.176, 180 Gunawidjaja et al. Furthermore, to our knowledge, there have been no attempts to utilize hybrid NMs with an AgNW network to fabricate NM-based coated electronic devices. Here, we present ultra-thin, conductive, and transparent hybrid NMs that can be applied to the fabrication of skin-attachable NM speakers and microphones, which would be inconspicuous in appearance due to their excellent transparency and contact capability. conform.
Our hybrid NMs consist of an orthogonal AgNW array embedded in a polymer matrix, which significantly enhances the electrical and mechanical properties of ultrathin polymer NMs without any significant loss in optical transparency due to the orthogonal array structure.
Experimental Details
Results and Discussion
We obtained CN=3.2 from the experimental results with the slope of the fitting line shown in Figure 3.12. The Young's modulus of the hybrid NMs increases linearly with an increase in the density of the orthogonal AgNW arrays (Figure 3.10b). We also acquired the bending stiffness of hybrid NMs from the experimentally measured Young's modulus in Figure 3.10b.
The maximum load and displacement that can be applied to the hybrid NMs until failure increases gradually with the density of the orthogonal AgNW array (Figure 3.10e).
Conclusions
High-performance flexible electroluminescent (EL) devices based on high-k nanodielectrics
Introduction
High-performance elastic electroluminescent (EL) devices based on high-grade nanodielectrics and interconnected AgNW electrodes. Here, we present a rational method to synthesize high-k BTO:La nanocuboids (NCs) and fabricate efficient flexible ACEL devices via a simple solution processing method. We synthesized BTO:La NCs with a permittivity greater than pure BTO via local disorder caused by an aliovalent substitution between barium ions (Ba2+) and La3+.204 ACEL devices with high-k BTO:La NCs exhibited significantly enhanced luminescence (4–6 times at 60–320 V, 1 kHz) compared to pristine BTO-based ACEL devices. Furthermore, we fabricated interconnected AgNW electrodes with excellent optical and electrical properties, low surface roughness, and uniform Rsh over a large area, which can further enhance the brightness compared to random AgNW electrodes and avoid the luminance gradient problem in ACEL devices.
To the best of our knowledge, this is the first demonstration of flexible ACEL devices using a solution-processed high-k BTO:La nanodielectric and cross-aligned AgNW electrodes, resulting in high luminance at low operating voltage along with a minimal brightness gradient over a large device area.
Experimental Details
The surface alignment structure of the AgNW arrays was examined with an optical microscope (PSM-1000, Olympus). The surface morphology of the BTO powder was investigated by field emission SEM (FE-SEM, Hitachi S4800) at an operating voltage of 10 kV. The rheological properties of BTO nanodielectric slurries were studied with a rheometer (Haake MARS3, Thermo Fisher).
Luminescence spectra from the flexible AXEL devices were recorded with a spectroradiometer (PR-655, Photo Research, Inc.).
Results and Discussion
As a result, the adaptive ACEL device with cross-aligned AgNW electrodes shows improved brightness compared to the adaptive ACEL devices based on random AgNW electrodes (Figure 4.12). Although the dielectric constant increased with increasing filler concentration, high filler loadings above 26% resulted in agglomeration and phase separation of NCs (Figure 4.14). This field strength of the BTO:La ACEL device was further verified by simulating the electric field distribution using finite element methods, as shown in Figure 4.18.
The flexible ACEL devices showed a small (5 %) increase in device brightness as the radius of curvature was increased (Figure 4.21c), which can be attributed to the reduced thickness of the active layer during bending, resulting in a reduction in the inter-electrode distance.
Conclusions
Self-healable and flexible thermoacoustic loudspeakers with AgNW/poly(urethane-hindered
Introduction
Through the use of self-healing polymers, the TA loudspeaker can become fault-tolerant, durable, recyclable and shape-retaining. Moreover, each self-healing material has advantages and disadvantages depending on its chain dynamics and modulus. Self-healing polymers with high modulus such as Diels-Alder polymers and PUHU require high temperature for self-healing.
Transparent and conductive AgNW networks are fabricated on the PUHU film by a simple solution-based process as a highly transparent and self-healing material.
Experimental Details
Fabrication of the self-healable AgNW/PUHU electrodes: First, the surface of the substrate is pretreated with O2 plasma at a radio frequency (RF) power of 18 W for 10 minutes before applying the AgNW solution to the self-healable PUHU substrate. Fabrication of the self-healable TA speaker: First, the self-healable PUHU substrate was pretreated with O2 plasma for 10 minutes, and the AgNW solution was spin-coated on the area of 1.5 × 2.5 cm2. SPL test of self-recoverable TA speaker: 1 V DC voltage and 7 V AC voltage are applied to the fabricated TA speaker and the distance between TA speaker and commercial microphone was 2 cm.
Characterization: The surface morphology of the self-healing electrodes was investigated using an OM (PSM-1000, Olympus) and a field emission SEM (FE-SEM, Hitachi S4800) at an operating voltage of 10 kV.
Results and Discussion
The detailed scheme of the self-healing process of AgNW/PUHU electrodes is illustrated in Figure 5.8a. The surface height profiles from the AFM results confirm the successful reconstruction of the interrupted AgNW network after the self-healing process (Figure 5.8c). Therefore, the resistance of the self-healing AgNW/PUHU electrodes is perfectly interrupted after surface scratching.
In addition, the resistance recovery of the AgNW/PUHU film after the self-healing process is demonstrated by its use in an electrode for an LED lamp (Figure 5.14).
Conclusions
Highly stretchable sound-in-display electronic devices with strain-insensitive AgNW
- Introduction
- Experimental Details
- Results and Discussion
- Conclusions
The concept of integrating a color module and a speaker into a single stretchable unit, enabling a so-called stretchable sound-on-screen device capable of synchronizing light and sound, is shown in Figure 6.1a. The homogeneous size distribution (average size ≈ 18.2 µm; Fig. 6.2) of the ZnS:Cu particles and their good dispersion in the PDMS matrix layer resulted in uniform light emission without device failure under strong electric fields. The softness and tackiness of the partially cured PDMS enabled strong and conformal attachment of the AgNW networks to the periodic folds of the stretchable electrodes (Figure 6.7a,b).
On the contrary, using the less sticky and less elastic fully cured PDMS resulted in the poor adhesion of AgNW networks on wrinkles, and protruding nanowires were observed along with abundant cracks (Figure 6.7c,d).
Summary and Future perspective
Summary
Future perspective
