Catalogue Search | MBRL
Are you sure you want to remove the book from the shelf?
{{itemTitle}}
269
result(s) for
"Han-Ki Kim"
Sort by:
Deposition Rate Effect on Optical and Electrical Properties of Thermally Evaporated WO3−x/Ag/WO3−x Multilayer Electrode for Transparent and Flexible Thin Film Heaters
We investigated the deposition rate effect on the optical, electrical, and morphological characteristics of thermally evaporated WO
3−x
/Ag/WO
3−x
(WAW) multilayer electrodes. By controlling the deposition rate of the WO
3−x
and Ag layers, we can control the interface structure between WO
3−x
and Ag and improve both the optical and electrical properties of the thermally evaporated WAW multilayer electrodes. At the optimized deposition rate of WO
3−x
(2.5 Å/sec) and Ag (10 Å/sec), the symmetric WAW multilayer exhibited a high optical transmittance of 92.16% at a 550 nm wavelength and low sheet resistance of 3.78 Ω/square. During repeated bending, rolling, and twisting, there was no resistance change indicating the superior flexibility of WAW multilayer electrodes. As a promising application of the WAW multilayer electrodes, we suggested the transparent and flexible thin film heaters (TFHs) to substitute the high cost indium tin oxide-based TFHs. In comparison to the ITO-based TFHs, the WAW based TFHs showed higher convective heat transfer property and higher saturation temperatures are achieved at lower input voltages due to lower sheet resistance. This indicates that the WAW multilayer is suitable as the electrode for high performance transparent and flexible TFHs.
Journal Article
Brush-paintable and highly stretchable Ag nanowire and PEDOT:PSS hybrid electrodes
Highly transparent and stretchable Ag nanowire (NW)/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) hybrid electrodes were prepared on stretchable polyurethane substrates by using simple and cost-effective brush painting technique. The optimized Ag NW/PEDOT:PSS hybrid electrode showed a sheet resistance of 19.7 Ohm/square and a high optical transmittance of 88.64% comparable to conventional ITO electrode. It was found that shear stress of the paintbrush led to an effective lateral alignment of the Ag NWs into the PEDOT:PSS matrix during brush painting process. In addition, we investigated mechanical properties of the brush painted Ag NW/PEDOT:PSS hybrid electrode using inner/outer bending test, stretching tests, twisting test and rolling test in detail. The optimized brush painted Ag NW/PEDOT:PSS electrode showed a higher strain (~30%) than brush painted Ag NW or sputtered ITO electrode. Furthermore, we demonstrated the outstanding stretchability of brush painted Ag NW/PEDOT:PSS hybrid electrode in two applications: stretchable interconnectors and stretchable electrodes for stretchable and wearable thin film heaters. These results provide clear evidence for its potential and widespread applications in next-generation, stretchable displays, solar cells, and electronic devices.
Journal Article
Self-cleanable, waterproof, transparent, and flexible Ag networks covered by hydrophobic polytetrafluoroethylene for multi-functional flexible thin film heaters
We demonstrate a self-cleanable, waterproof, highly transparent, and flexible Ag network covered by a very thin transparent polytetrafluoroethylene (PTFE) layer using typical magnetron sputtering for multi-functional flexible thin film heaters used in smart windows. By passivation of the self-assembled Ag network with very thin PTFE films, we fabricated a multi-functional Ag network suitable for flexible thin film heaters. At a PTFE thickness of 10 nm, the Ag network passivated by hydrophobic PTFE layer showed a low sheet resistance of 11.64 Ohm/square, high optical transmittance of 80.20% at a wavelength of 550 nm, and high contact angle of 102.42°. In addition, sputtering of the PTFE layer on the Ag network improved the mechanical flexibility and reliability of the Ag network electrode. The flexible and transparent thin film heater (TTFH) with Ag network electrode covered by PTFE layer showed a saturation temperature of 120 °C at low voltage of 4.5 V and power of 2.45 W, as well as a hydrophobic surface suited for self-cleaning smart windows. These multi-functional performances of TTFH indicate that the Ag network/PTFE film-based flexible TTFH could be used as self-cleanable, waterproof TTFHs for curved smart windows in smart buildings and automobiles.
Journal Article
Thermally evaporated indium-free, transparent, flexible SnO2/AgPdCu/SnO2 electrodes for flexible and transparent thin film heaters
We investigated the characteristics of themally evaporated SnO
2
/Ag-Pd-Cu (APC)/SnO
2
multilayer films for applications as damage-free, indium-free, flexible, and transparent electrodes for high performance flexible and transparent thin film heaters (TFHs). The top and bottom SnO
2
layers and APC interlayer were prepared by a multi-source evaporation process, and the effect of the thickness of each layer on the resistivity, optical transmittance, and mechanical flexibility of the SnO
2
/APC/SnO
2
electrodes was investigated in detail. Based on a figure of merit value, we obtained a SnO
2
/APC/SnO
2
electrode with a low sheet resistance of 9.42 Ohm/square and a high optical transmittance of 91.14%. In addition, we examined the mechanical properties of the SnO
2
/APC/SnO
2
electrode using various bending tests such as inner bending, outer bending, dynamic fatigue, and a twisting test. By comparing the crack shape of the SnO
2
/APC/SnO
2
electrode bent beyond the critical bending radius (2~3 mm), we suggest a possible crack formation mechanism for the SnO
2
/APC/SnO
2
electrodes. Furthermore, we evaluated the feasibility of the SnO
2
/APC/SnO
2
electrodes for flexible and transparent TFHs. By correlating the sheet resistance of the SnO
2
/APC/SnO
2
electrode and the performance of TFHs, we show the importance of transparent electrodes for high performance flexible and transparent TFHs.
Journal Article
Effective passivation of Ag nanowire network by transparent tetrahedral amorphous carbon film for flexible and transparent thin film heaters
We developed effective passivation method of flexible Ag nanowire (NW) network electrodes using transparent tetrahedral amorphous carbon (ta-C) film prepared by filtered cathode vacuum arc (FCVA) coating. Even at room temperature process of FCVA, the ta-C passivation layer effectively protect Ag NW network electrode and improved the ambient stability of Ag NW network without change of sheet resistance of Ag NW network. In addition, ta-C coated Ag NW electrode showed identical critical inner and outer bending radius to bare Ag NW due to the thin thickness of ta-C passivation layer. The time-temperature profiles demonstrate that the performance of the transparent and flexible thin film heater (TFH) with the ta-C/Ag NW network is better than that of a TFH with Ag NW electrodes due to thermal stability of FCVA grown ta-C layer. In addition, the transparent and flexible TFHs with ta-C/Ag NW showed robustness against external force due to its high hardness and wear resistance. This indicates that the FCVA coated ta-C is promising passivation and protective layer for chemically weak Ag NW network electrodes against sulfur in ambient.
Journal Article
Roll-to-Roll sputtered ITO/Cu/ITO multilayer electrode for flexible, transparent thin film heaters and electrochromic applications
We fabricate high-performance, flexible, transparent electrochromic (EC) films and thin film heaters (TFHs) on an ITO/Cu/ITO (ICI) multilayer electrode prepared by continuous roll-to-roll (RTR) sputtering of ITO and Cu targets. The RTR-sputtered ICI multilayer on a 700 mm wide PET substrate at room temperature exhibits a sheet resistance of 11.8 Ω/square and optical transmittance of 73.9%, which are acceptable for the fabrication of flexible and transparent EC films and TFHs. The effect of the Cu interlayer thickness on the electrical and optical properties of the ICI multilayer was investigated in detail. The bending and cycling fatigue tests demonstrate that the RTR-sputtered ICI multilayer was more flexible than a single ITO film because of high strain failure of the Cu interlayer. The flexible and transparent EC films and TFHs fabricated on the ICI electrode show better performances than reference EC films and TFHs with a single ITO electrode. Therefore, the RTR-sputtered ICI multilayer is the best substitute for the conventional ITO film electrode in order to realize flexible, transparent, cost-effective and large-area EC devices and TFHs that can be used as flexible and smart windows.
Journal Article
Optimizing stent retrievers for mechanical enhancement and in vitro testing in acute ischemic stroke models
Background
Acute ischemic stroke (AIS) remains a major cause of morbidity and mortality worldwide. Mechanical thrombectomy, especially with stent retrievers, offers a promising treatment, particularly for patients ineligible for intravenous tissue plasminogen activator (IV tPA) therapy. This study aimed to develop and evaluate novel stent retriever designs to enhance mechanical properties and vessel compatibility.
Results
We evaluated four stent designs using finite-element analysis (FEA) to assess their mechanical properties. Based on these evaluations, Stent D emerged as the optimal design due to its superior elasticity and adaptability. Comparative testing of Stent D against commercial stents, Solitaire FR and Trevo XP ProVue, revealed the following metrics: radial forces of 3.77 ± 0.01 N for Solitaire FR, 3.92 ± 0.08 N for Trevo XP ProVue, and 4.10 ± 0.07 N for Stent D; flexibility measurements of 0.38 ± 0.11 N for Solitaire FR, 0.91 ± 0.11 N for Trevo XP ProVue, and 0.59 ± 0.05 N for Stent D; deployment forces of 0.37 ± 0.02 N for Solitaire FR, 0.42 ± 0.04 N for Trevo XP ProVue, and 0.32 ± 0.02 N for Stent D; and recapture forces of 0.38 ± 0.01 N for Solitaire FR, 0.45 ± 0.02 N for Trevo XP ProVue, and 0.35 ± 0.01 N for Stent D. Thrombus retrieval rates were 96.16% for Solitaire FR and 95.51% for Stent D.
Conclusions
These findings demonstrate that Stent D performs comparably to commercial stents, highlighting its effective performance in AIS treatment. Stent D shows promise as a candidate for further clinical evaluation due to its superior mechanical properties and effective thrombus retrieval capabilities.
Journal Article
Stretchable and Flexible Snake Skin Patterned Electrodes for Wearable Electronics Inspired by Kirigami Structure
Herein, snake‐skin‐patterned electrodes, with high versatility and excellent biocompatibility, are developed by combining the Kirigami structure and biomimicry. The snake‐skin electrode has excellent stretchability owing to the integration of the Kirigami structure and patterning. The snake skin patterns are optimized through finite element analysis (FEA) simulations to determine the most stretchable pattern structure. Based on the FEA results, we fabricated the optimal pattern on a polyurethane (PU) substrate by sputtering the AgPdCu alloy target. Even at high strains of 30% and 50%, the electrode exhibits much better stretchability compared with the electrode without the snake skin pattern. The best stretchable electrode exhibits a resistance change (ΔR) of less than 1.5 when it is severely stretched at up to 50% strain. Additionally, the dynamic stretching fatigue test, reveals that it exhibits stable conductivity, thus proving the effectiveness of using snake‐skin pattern for stretchable electrodes. The bending, rolling, folding and twisting tests confirm that the electrode has outstanding flexibility, too. A wearable temperature sensor with a snake‐skin‐patterned electrode exhibits stable and highly sensitive temperature sensing properties. In addition, light emitting diodes connected to the stretchable electrode exhibits stable brightness despite severe deformation of the electrodes. Snake‐skin electrodes are developed by combining the Kirigami structure and biomimicry. The snake‐skin electrode has excellent stretchability owing to the Kirigami structure based snake‐skin patterning. The snake‐skin‐patterned wearable temperature sensor exhibits stable and highly sensitive temperature sensing properties. In addition, light emitting diodes (LED) connected to stretchable snake‐skin electrodes exhibit stable brightness despite severe deformation of the electrodes.
Journal Article