Femtosecond-Laser-Assisted Fishbone-Inspired Patterning of Selective Liquid Metal Dewetted Electrodes for Flexible Electronics

Femtosecond-laser-induced selective fishbone-inspired and trapezoidal structures provide low surface energies for liquid metal (LM) and LM-phobic surfaces. This laser-based technique is suitable for processing heat-vulnerable flexible substrates and minimizing changes in their physical properties, which can be analyzed by Fourier-transform infrared spectroscopy. In this study, we developed a femtosecond-laser-assisted fishbone-inspired patterning process for a selective LM wettable surface on a flexible substrate. Because the ribs of the fishbone-inspired structure were developed between laser-ablated lines, the entire LM-phobic pattern was covered without processing the entire surface area. In the fishbone-inspired pattern, the region directly exposed to the femtosecond laser served as the “spines”, while the burrs, which were a byproduct of laser processing, acted as the “ribs”. A minimum line width of ∼40 μm was realized using this structural mechanism. The patterned LM-phobic surface exhibited low surface energy with a 156° contact angle for the LM material. The patterned LM on a flexible poly(dimethylsiloxane) substrate maintained a stable electrical connection with minimal deviations, even under bending, twisting, and stretching conditions. These processes and structures can be used to fabricate flexible, stretchable, and wearable electronic devices

Femtosecond-Laser-Assisted Fishbone-Inspired Patterning of Selective Liquid Metal Dewetted Electrodes for Flexible Electronics

Femtosecond-laser-induced selective fishbone-inspired and trapezoidal structures provide low surface energies for liquid metal (LM) and LM-phobic surfaces. This laser-based technique is suitable for processing heat-vulnerable flexible substrates and minimizing changes in their physical properties, which can be analyzed by Fourier-transform infrared spectroscopy. In this study, we developed a femtosecond-laser-assisted fishbone-inspired patterning process for a selective LM wettable surface on a flexible substrate. Because the ribs of the fishbone-inspired structure were developed between laser-ablated lines, the entire LM-phobic pattern was covered without processing the entire surface area. In the fishbone-inspired pattern, the region directly exposed to the femtosecond laser served as the “spines”, while the burrs, which were a byproduct of laser processing, acted as the “ribs”. A minimum line width of ∼40 μm was realized using this structural mechanism. The patterned LM-phobic surface exhibited low surface energy with a 156° contact angle for the LM material. The patterned LM on a flexible poly(dimethylsiloxane) substrate maintained a stable electrical connection with minimal deviations, even under bending, twisting, and stretching conditions. These processes and structures can be used to fabricate flexible, stretchable, and wearable electronic devices

Femtosecond-Laser-Assisted Fishbone-Inspired Patterning of Selective Liquid Metal Dewetted Electrodes for Flexible Electronics

Femtosecond-laser-induced selective fishbone-inspired and trapezoidal structures provide low surface energies for liquid metal (LM) and LM-phobic surfaces. This laser-based technique is suitable for processing heat-vulnerable flexible substrates and minimizing changes in their physical properties, which can be analyzed by Fourier-transform infrared spectroscopy. In this study, we developed a femtosecond-laser-assisted fishbone-inspired patterning process for a selective LM wettable surface on a flexible substrate. Because the ribs of the fishbone-inspired structure were developed between laser-ablated lines, the entire LM-phobic pattern was covered without processing the entire surface area. In the fishbone-inspired pattern, the region directly exposed to the femtosecond laser served as the “spines”, while the burrs, which were a byproduct of laser processing, acted as the “ribs”. A minimum line width of ∼40 μm was realized using this structural mechanism. The patterned LM-phobic surface exhibited low surface energy with a 156° contact angle for the LM material. The patterned LM on a flexible poly(dimethylsiloxane) substrate maintained a stable electrical connection with minimal deviations, even under bending, twisting, and stretching conditions. These processes and structures can be used to fabricate flexible, stretchable, and wearable electronic devices

Photoactivable Antibody Binding Protein: Site-Selective and Covalent Coupling of Antibody

Here we report new photoactivable antibody binding proteins, which site-selectively capture antibodies and form covalent conjugates with captured antibodies upon irradiation. The proteins allow the site-selective tagging and/or immobilization of antibodies with a highly preferred orientation and omit the need for prior antibody modifications. The minimal Fc-binding domain of protein G, a widely used antibody binding protein, was genetically and chemically engineered to contain a site-specific photo cross-linker, benzophenone. In addition, the domain was further mutated to have an enhanced Fc-targeting ability. This small engineered protein was successfully cross-linked only to the Fc region of the antibody without any nonspecific reactivity. SPR analysis indicated that antibodies can be site-selectively biotinylated through the present photoactivable protein. Furthermore, the system enabled light-induced covalent immobilization of antibodies directly on various solid surfaces, such as those of glass slides, gold chips, and small particles. Antibody coupling via photoactivable antibody binding proteins overcomes several limitations of conventional approaches, such as random chemical reactions or reversible protein binding, and offers a versatile tool for the field of immunosensors

Low-Temperature Oxidation-Free Selective Laser Sintering of Cu Nanoparticle Paste on a Polymer Substrate for the Flexible Touch Panel Applications

Copper nanomaterials suffer from severe oxidation problem despite the huge cost effectiveness. The effect of two different processes for conventional tube furnace heating and selective laser sintering on copper nanoparticle paste is compared in the aspects of chemical, electrical and surface morphology. The thermal behavior of the copper thin films by furnace and laser is compared by SEM, XRD, FT-IR, and XPS analysis. The selective laser sintering process ensures low annealing temperature, fast processing speed with remarkable oxidation suppression even in air environment while conventional tube furnace heating experiences moderate oxidation even in Ar environment. Moreover, the laser-sintered copper nanoparticle thin film shows good electrical property and reduced oxidation than conventional thermal heating process. Consequently, the proposed selective laser sintering process can be compatible with plastic substrate for copper based flexible electronics applications

Low-Temperature Oxidation-Free Selective Laser Sintering of Cu Nanoparticle Paste on a Polymer Substrate for the Flexible Touch Panel Applications

Copper nanomaterials suffer from severe oxidation problem despite the huge cost effectiveness. The effect of two different processes for conventional tube furnace heating and selective laser sintering on copper nanoparticle paste is compared in the aspects of chemical, electrical and surface morphology. The thermal behavior of the copper thin films by furnace and laser is compared by SEM, XRD, FT-IR, and XPS analysis. The selective laser sintering process ensures low annealing temperature, fast processing speed with remarkable oxidation suppression even in air environment while conventional tube furnace heating experiences moderate oxidation even in Ar environment. Moreover, the laser-sintered copper nanoparticle thin film shows good electrical property and reduced oxidation than conventional thermal heating process. Consequently, the proposed selective laser sintering process can be compatible with plastic substrate for copper based flexible electronics applications

Low-Temperature Oxidation-Free Selective Laser Sintering of Cu Nanoparticle Paste on a Polymer Substrate for the Flexible Touch Panel Applications

Copper nanomaterials suffer from severe oxidation problem despite the huge cost effectiveness. The effect of two different processes for conventional tube furnace heating and selective laser sintering on copper nanoparticle paste is compared in the aspects of chemical, electrical and surface morphology. The thermal behavior of the copper thin films by furnace and laser is compared by SEM, XRD, FT-IR, and XPS analysis. The selective laser sintering process ensures low annealing temperature, fast processing speed with remarkable oxidation suppression even in air environment while conventional tube furnace heating experiences moderate oxidation even in Ar environment. Moreover, the laser-sintered copper nanoparticle thin film shows good electrical property and reduced oxidation than conventional thermal heating process. Consequently, the proposed selective laser sintering process can be compatible with plastic substrate for copper based flexible electronics applications

Self-Assembled TaO_X/2H-TaS₂ as a van der Waals Platform of a Multilevel Memristor Circuit Integrated with a β‑Ga₂O₃ Transistor

Two-dimensional (2D)-layered material tantalum disulfide (2H-TaS2) is known to be a van der Waals conductor at room temperature. Here, 2D-layered TaS2 has been partially oxidized by utraviolet-ozone (UV-O3) annealing to form a 12-nm-thin TaOX on conducting TaS2, so that the TaOX/2H-TaS2 structure might be self-assembled. Utilizing the TaOX/2H-TaS2 structure as a platform, each device of a β-Ga2O3 channel MOSFET and a TaOX memristor has been successfully fabricated. An insulator structure of Pt/TaOX/2H-TaS2 shows good a dielectric constant (k ∼ 21) and strength (∼3 MV/cm) of achieved TaOX, which is enough to support a β-Ga2O3 transistor channel. Based on the quality of TaOX and low trap density of the TaOX/β-Ga2O3 interface, which is achieved via another UV-O3 annealing, excellent device properties such as little hysteresis (<∼0.04 V), band-like transport, and a steep subthreshold swing of ∼85 mV/dec are achieved. With a Cu electrode on top of the TaOX/2H-TaS2 structure, the TaOX acts as a memristor operating around ∼2 V for nonvolatile bipolar and unipolar mode memories. The functionalities of the TaOX/2H-TaS2 platform become more distinguished finally when the Cu/TaOX/2H-TaS2 memristor and β-Ga2O3 MOSFET are integrated to form a resistive memory switching circuit. The circuit nicely demonstrates the multilevel memory functions