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An electric double‐layer capacitor (EDLC), which is one of the pivotal energy storage devices, provides rapid charge–discharge capabilities and an extended cycle life. Areal capacitance, a key indicator of EDLC performance, increases with the specific surface area of its electrodes. This study demonstrates a method for significantly increasing the specific surface area in the laser‐induced graphitization of biodegradable polymers by incorporating NaHCO3 into the composite sheet, generating not only microscale pores but also a large number of nanoscale fine pores. Furthermore, it shows that using these structures as EDLC electrodes leads to a substantial increase in areal capacitance. An increase in the number of fine pores formed in the structure and a corresponding rise in the areal capacitance of the fabricated EDLC are observed with the increase in the NaHCO3 weight ratio. Notably, the composite sheets are composed of natural‐derived, biodegradable materials, while NaHCO3 is known for its low corrosivity and biotoxicity. The proposed method thus offers a pathway for fabricating energy storage devices with minimal environmental impact, ensuring their eco‐friendly disposal post‐use. [ABSTRACT FROM AUTHOR]

Hydrogels have emerged as promising supporting materials for wearable or implantable electronic devices, owing to their high biocompatibility. Among the many techniques for patterning conductive structures on supporting materials, laser‐based graphitization allows the simultaneous synthesis and patterning of conductive structures. Here, it has been demonstrated for the first time, the direct patterning of conductive structures on hydrogels by laser‐based graphitization, and the application of this method to the fabrication of hydrogel‐based supercapacitors. Conductive graphitic carbon is formed on the hydrogel along the trajectory of laser scanning. One‐step fabrication of supercapacitors is achieved by laser irradiation of hydrogels containing both lignin and NaCl electrolyte. Notably, the areal capacitance of the fabricated supercapacitor is retained after drying and swelling, indicating its reusability. The method realizes rapid fabrication of hydrogel‐based supercapacitors that can be stored in a dry state, providing a facile method for storing and delivering energy‐storage devices. [ABSTRACT FROM AUTHOR]

Laser direct-write (LDW) methods offer the rapid, on-demand, and high-resolution patterning of a variety of nanocrystals (NCs). Out of the many LDW methods, the laser-induced modification method is an attractive method as NCs can be directly patterned on polymers without supplementary preparation steps. Previously, it has been indicated that the laser irradiation of polydimethylsiloxane results in composite structures composed of graphitic carbon crystals (GCs) and silicon carbide NCs (SiC-NCs). However, material properties distinctive of SiC-NCs have not been reported for the resulting structures owing to the low formation content relative to those of GCs. In this study by utilizing a high-repetition femtosecond laser, we demonstrate the controlled formation of GCs and SiC-NCs to achieve a composite structure exhibiting a measurable semiconducting behavior for the first time. Moreover, photoluminescence emissions distinctive of fluorescent molecular-sized SiC-NCs were observed from the resulting structures. The presented results will trigger a wave of ideas utilizing ultrashort-pulsed lasers for the laser-induced modification of polymers toward the fabrication of a wide range of electronic and photonic devices, such as memory storage devices, photovoltaics, and optical sensors. [ABSTRACT FROM AUTHOR]

The patterning of electrically conductive structures directly onto the polydimethylsiloxane (PDMS) surface is crucial for the realization of flexible and elastic devices. Herein, defocused femtosecond laser pulses are irradiated for the fabrication of highly crystalline graphitic carbon structures on PDMS and a high electrical conductivity of ≈51.6 S m−1 is achieved. Utilizing the elasticity of PDMS and the high conductivity of fabricated structures, a fingertip‐sized pressure sensor, which can detect pressures as low as ≈0.1 Pa, is realized. Moreover, a novel ring‐shaped heart rate (HR) monitor, capable of measuring the HR from the index finger, is demonstrated, indicating the potential of fabricated structures in miniature and wearable healthcare applications. [ABSTRACT FROM AUTHOR]

Controlling cell adhesion and cell differentiation is necessary to fabricate a tissue with arbitrary properties for tissue engineering applications. A substrate with a porous structure as a cell scaffold allows the diffusion of the cell culture medium through the scaffold. In this work, we show that the femtosecond laser fabricated micro through‐holes in biodegradable polymer films, enhance myoblast adhesion, and accelerates proliferation and differentiation. ChR2‐C2C12 and UT‐C2C12 cells were seeded on the films with micro through‐holes each fabricated by a single femtosecond laser pulse. Cell adhesion was enhanced on films with holes fabricated by laser irradiation. In addition, cell proliferation was accelerated on films with micro through‐holes that penetrate the film, compared to on films with micro craters that do not penetrate the film. On films with arrays consisting of micro through‐holes, cells aligned along the arrays and cell fusion was enhanced, indicating the acceleration of cell differentiation. [ABSTRACT FROM AUTHOR]

• Proposed photoacoustic imaging enabled depth profiling of sensitizer and vessels. • Pharmacokinetics in PDT with indocyanine green-lactosome was revealed. • Vascular shutdown effect was shown in PDT with indocyanine green-lactosome. Indocyanine green lactosome (ICG-lactosome) is an attractive new-generation agent for photodynamic therapy (PDT) that is characterized by a near-infrared excitation wavelength and high stability in the bloodstream. Fluorescence imaging has been used to examine its pharmacokinetics in vivo , but no depth-resolved information can be obtained with this method. In this study, we applied photoacoustic (PA) imaging to visualize the depth distribution of ICG-lactosome in a mouse subcutaneous tumor model. With this method, the depth distribution of blood vessels can also be visualized, enabling detection of vascular shutdown effects due to PDT. We performed PA imaging of both the distributions of ICG-lactosome and blood vessels in a tumor before and after PDT, and we found that PA signals originating from ICG-lactosome were greatly increased at 18 h after drug injection but rapidly decreased after PDT. These results indicate efficient accumulation of ICG-lactosome and rapid photobleaching due to the PDT reaction in the tumor, respectively. After PDT, PA amplitudes of hemoglobin were significantly decreased, being attributable to vascular shutdown effects. These results show the usefulness of PA imaging for monitoring not only photosensitizer accumulation and bleaching but also vascular responses in PDT with ICG-lactosome. This method can be applied to the diagnosis of many types of PDT processes. [ABSTRACT FROM AUTHOR]

Biodegradable polymers have attracted increasing attention in tissue engineering and drug delivery systems owing to their high biocompatibility and biodegradability. Among the various methods for shape forming and modification of biodegradable polymers, laser processing has advantages in a dry processing approach that can process complex-shaped surfaces without using toxic chemical components. This review provides an overview of femtosecond laser processing of biodegradable polymers, especially in the last decade. The interaction mechanism of femtosecond laser pulse and biodegradable polymers, e.g., bond dissociation after laser irradiation, affects the degradable property of biodegradable polymers, which has the potential to control the degradation and sustainability of a structure. Applied studies on controlling cell behavior, tissue scaffolding, and drug release are also described. [ABSTRACT FROM AUTHOR]

Micro-/nanosphere-mediated femtosecond laser cell perforation is one of the high throughput technologies used for macro-molecule-delivery into multiple cells. We have demonstrated the delivery of plasmid-DNA/liposome complexes into cells using biodegradable polymer microspheres and a femtosecond laser and investigated the intracellular localization of the complexes by delivering fluorescence-labeled plasmid-DNA/liposome complexes into cells. The utilization of liposomes increases the number of complexes delivered into the cytoplasm by laser illumination, which contributed to the increased transfection rate. In the experiment involving polystyrene (PS) microspheres of different diameters, the fluorescence of the complexes was detected in the nucleus as well as cytoplasm after laser illumination for PS microspheres of 3.0 μm diameter. The direct delivery of complexes into the nucleus is probably attributed to the enhancement of the nuclear membrane permeability by the enhanced optical field obtained close to the nucleus. These revelations on the intracellular localization of foreign DNA would provide effective laser-based transfection. Picture: Intranuclear delivery of plasmid-DNA/liposome complexes by utilizing dielectric microspheres and a femtosecond laser. [ABSTRACT FROM AUTHOR]

In this study, we investigated the change in biodegradability of biodegradable polymer films by deep-ultraviolet laser irradiation with different pulse durations. Measurements of water absorption and mass change as well as microscopic observation revealed that the femtosecond laser irradiation significantly accelerated the degradation rate of the biodegradable polymer films, whereas the nanosecond laser irradiation did not induce a comparable degree of change. Analyses with X-ray photoelectron spectroscopy and X-ray diffraction indicate that the difference in the biodegradability following laser irradiation with different pulse durations is attributable to the difference in chemical structure for amorphous polymers including PLGA, while the difference in chemical structure as well as crystallinity affects the biodegradability for crystalline polymer including PLLA. The obtained results suggest that deep-ultraviolet laser processing enables the fabrication of a tissue scaffold with a desirable degradation rate. [ABSTRACT FROM AUTHOR]

Abstract: The scattering physics of photons is traced back to Rayleigh scattering theory in 1871 and Mie scattering theory in 1908. However, the scattering near field and far field have recently emerged again as a new fundamental physics and innovative nanoprocessing technology in quantum electronics and photonic devices. An enhanced near field generated by plasmonic particles can concentrate optical energy into a nanoscale space as a nanolens even with near infrared laser pumping. This plasmonic nanophotonics extends the existing optical science to a new class of photonics inclusive of surface enhanced Raman scattering, nanoprocessing of advanced electronic and photonic materials, etc. The Mie scattering near field also opens up new fields. The Anderson localization of light in a planar random photonic crystal laser is also a new class of quantum electronics devices, where Slow Bloch Mode is scattered by artificial structural randomness in a photonic crystal. In this contribution we will review the recent efforts of our scattering photonics research, which have resulted in significant advances in the plasmonic surface photonics of near-field and far-field nano/micro photonics and the Anderson localization in random lasing. [Copyright &y& Elsevier]

We investigate the dependence of the size parameter in the Mie scattering theory on the near-field enhanced Raman scattering properties for high dielectric constant ZnO nanorods grown randomly by PLD (pulsed laser deposition). High Raman signals of Rhodamine 6G (R6G) at 532 nm excitation wavelength were observed with nanorods of 400 nm average diameter. This experimental result was explained theoretically by the size parameter described in the Mie scattering theory, not by surface plasmon polaritons. This was also confirmed by the near-field distribution calculated by the FDTD (Finite-Difference Time Domain) method. The ZnO nanorods with 400 nm average diameter can detect as low as 1 μM of R6G. This near-field enhancement factor is equivalent to that with 10-nm-thick gold-coated ZnO nanorods (nanoshells) with an average core diameter of 100 nm. Controlling the diameter of bare ZnO nanorods is effective for obtaining large enhancement factors without an additional process of gold thin film coating on them. [ABSTRACT FROM AUTHOR]

We have directly observed the interference ripple pattern between surface plasmon far field by gold nanosphere and the incident laser on silicon substrate. We explained the ripple formation using three-dimensional finite-difference time-domain simulation method. Nanosphere is an origin for regular ripple formation due to Mie scattering. We present a new method to control the plasmonic far-field pattern using an arbitrary gold nanostructure on the silicon substrate. Previously, the formed ripples were not regular but wavy because they were formed incoherently through the self organization process originating from the random surface roughness. The ripple structure was well controlled coherently. [ABSTRACT FROM AUTHOR]

We demonstrate near-field nanohole patterning using a Mie resonance, small size parameter particle for nanofabrication technology regardless of substrate’s refractive index. Maximal enhancement factor and nearly smallest spot diameter among the same size dielectric particles are simultaneously obtainable on both low-refractive-index SiO2 and high-refractive-index Si substrates with a 200 nm particle of magnetic quadrupole resonance scattering mode (n∼2.7) at 400 nm excitation wavelength. Circular nanoholes with approximately 100 nm in diameter were fabricated on both substrates using a 200 nm amorphous TiO2 particle (n=2.66+0.024i) even with lower laser fluences than a half ablation threshold of the bare substrates. [ABSTRACT FROM AUTHOR]

The fabrication of hollow channels surrounded by gold nanoparticles in poly(ethylene glycol) diacrylate (PEGDA) is demonstrated. The absorption spectra show that gold nanoparticles were formed at the periphery of the focus by reduction of gold ions. The microscope observation and Raman spectroscopy analyses indicate that the center of the channels were void of PEGDA, which can be attributed to the femtosecond laser-induced degradation of the hydrogel. Since both the hydrogel and gold nanoparticles are biocompatible, this technique of fabricating hollow channels surrounded by gold nanoparticles is promising for tissue engineering, drug screening, and lab-on-a-chip devices. [ABSTRACT FROM AUTHOR]