Laser Irradiation Conditions Research Articles

Single-cell transcriptome analysis of fractional CO2 laser efficiency in treating a mouse model of alopecia.

Hair loss, including alopecia, is a common dermatological issue worldwide. At present, the application of fractional carbon dioxide (CO2 ) laser in the treatment of alopecia has been documented; however, the results vary between reports. These varying results may be due to the limited knowledge of cellular action in laser-irradiated skin. The objective of this study was to investigate the molecular and cellular mechanisms of laser treatment under effective conditions for hair cycle initiation. A fractional CO2 laser was applied and optimized to initiate the hair cycle in a mouse model of alopecia. Several cellular markers were analyzed in the irradiated skin using immunofluorescence staining. Cellular populations and their comprehensive gene expression were analyzed using single-cell RNA sequencing and bioinformatics. The effective irradiation condition for initiating the hair cycle was found to be 15 mJ energy/spot, which generates approximately 500 μm depth columns, but does not penetrate the dermis, only reaching approximately 1 spot/mm2 . The proportion of macrophage clusters significantly increased upon irradiation, whereas the proportion of fibroblast clusters decreased. The macrophages strongly expressed C-C chemokine receptor type 2 (Ccr2), which is known to be a key signal for injury-induced hair growth. We found that fractional CO2 laser irradiation recruited Ccr2 positive macrophages, and induced hair regrowth in a mouse alopecia model. These findings may contribute to the development of stable and effective fractional laser irradiation conditions for human alopecia treatment.

Smart paper electronics by laser-induced graphene for biodegradable real-time food spoilage monitoring

In situ monitoring system on the food package based on biodegradable materials to examine the food status is of great significance for practical application since food poisoning and non-degradable package waste have raised critical healthcare and environmental issues recently. Here, we report a laser-induced paper sensor (LIPS) that is comprised of a laser-induced graphene (LIG)/paper hybrid structure for wireless, real-time monitoring of the food status by the chemical- and thermo- sensing capabilities of LIPS. Direct laser irradiation on any type or structure of commercial paper converts the laser-irradiated paper surface into LIPS with a decent sheet resistance of 105 Ω sq−1 and porous structure which enables smart monitoring of key parameters such as gas concentration and temperature for the food spoilage prior to the food intake. Optimized laser irradiation conditions on the paper substrate produced the temperature and chemical gas coefficient of resistance change of 0.15%°C−1 and 0.0041% ppm−1. As a proof-of-concept, we fabricated LIPS on the surface of the paper to both detect the temperature and monitor the chemical degradation of the food, of which data can be directly delivered to the user's mobile device through continuous wireless communication. We believe that LIPS proposed herein will make significant contributions to the next-generation food-related green electronics to provide users with a smart and high-fidelity monitoring platform for simple detection of the real-time status of food products.

Sweep Pulse Excitation Method for Enhancing Photoacoustic Elastic Waves at Different Laser Irradiation Parameters.

Laser remote sensing using a sweep pulse excitation method, in which a laser beam is irradiated at the same repetition frequency as the natural frequency, for enhancing photoacoustic elastic waves through resonance effect has been studied. The sweep pulse excitation method, which is based on the principle of detecting natural frequency fluctuations, such as hammering tests, can detect natural frequencies in the audible sound region with low average laser power and contribute to the convenience and low cost of an installation strength diagnosis of fastening bolts. In this study, we investigated the dynamics of the swept excitation method for optimization by evaluating the dependence of the laser irradiation conditions (pulse width, spot size, and average power) on different metal disc samples. We discovered that the magnitude of the photoacoustic elastic wave is proportional to the absorption of laser power, and the spatiotemporal dynamics can be explained through thermal diffusion phenomena. These findings contribute to the development of laser-sensing technology based on photoacoustic elastic waves.

Targeted peptide-modified oxidized mesoporous carbon nanospheres for chemo-thermo combined therapy of ovarian cancer in vitro

Ovarian cancer remains one of serious hazards to human health due to many drawbacks of existing available treatment options. In this study, a multifunctional chemo-thermo combined therapy nanoplatform (OMCNPID) was successfully prepared, which is composed of I6P8 peptide as a targeting moiety to interleukin-6 receptors (IL-6Rs), oxidized mesoporous carbon nanospheres (OMCN) as a near infrared (NIR)-triggered drug carrier and doxorubicin (DOX) as a chemotherapeutic drug and fluorescent agent. The synthesized multifunctional nanoplatform displayed high storage capacity for drugs and excellent photothermal properties. Besides, DOX was rapidly released from OMCNPID at the condition of low pH and NIR laser irradiation due to the dissociation of DOX from graphitic cores of OMCN. In vitro experimental results verified that OMCNPID could be markedly taken up by SKOV-3 monolayer cells and tumor spheroids, and revealed a remarkable synergistic chemo-photothermal effect against ovarian cancer. All the results demonstrated that OMCNPID is a pH/NIR dual-stimulus responsive nanoplatform and can achieve efficient chemo-thermo combined therapy.

Structural optimization of femtosecond-laser-written lithium niobate waveguide by Raman spectroscopy

A new optimization method for femtosecond-laser-written lithium niobate (LN) waveguides is proposed and experimentally demonstrated to achieve low propagation loss. In this method, we use Raman spectroscopy to find detailed structural changes in LN crystal. We then use the results to optimize the laser irradiation conditions, including pulse laser energy, and laser irradiation design. In order to confirm the validity of this method, depressed cladding type LN waveguides were formed and their structural and optical characteristics were investigated in detail. Using proposed method, we succeeded in fabricating depressed cladding type LN waveguides with low propagation loss (∼0.64 dB cm−1) in the communications wavelength band. Furthermore, by analyzing the crystal structure of the depressed cladding waveguide cross-section using a Raman spectroscopy mapping system, the asymmetry of the waveguide cladding was newly clarified, providing a new insight for further improvement of the optical properties.

Optimization of Photothermal Therapy Treatment Effect under Various Laser Irradiation Conditions.

The photothermal effect refers to a phenomenon in which light energy is converted into heat energy, and in the medical field, therapeutics based on this phenomenon are used for anticancer treatment. A new treatment technique called photothermal therapy kills tumor tissue through a temperature increase and has the advantages of no bleeding and fast recovery. In this study, the results of photothermal therapy for squamous cell carcinoma in the skin layer were analyzed numerically for different laser profiles, intensities, and radii and various concentrations of gold nanoparticles (AuNPs). According to the heat-transfer theory, the temperature distribution in the tissue was calculated for the conditions under which photothermal therapy was performed, and the therapeutic effect was quantitatively confirmed through three apoptotic variables. In addition, the laser intensity and the volume fraction of AuNPs were optimized, and the results provide useful criteria for optimizing the treatment effects in photothermal therapy.

High-efficiency microdrilling of glass by parallel transient and selective laser processing with spatial light modulator

To use glass as the substrate material in next-generation large-scale integrations and biochips, the high-speed fabrication of high-aspect-ratio microholes is necessary. Transient and selective laser (TSL) processing significantly reduces the processing time per hole. To further improve the processing efficiency, parallel TSL processing using a spatial light modulator is proposed in this study. Two 100-µm depth holes are successfully machined in parallel, in 50 µs. Furthermore, the process control parameters are investigated through high-speed observation and the laser irradiation conditions required for processing are clarified. Parallel processing of three or more holes and depth control of each hole is expected to be realized in future.

Hemorheological alterations of red blood cells induced by 450-nm and 520-nm laser radiation.

Proper rheological properties of red blood cells (RBC) including flexibility and aggregability are essential for healthy blood microcirculation. Excessive RBC aggregation has been observed to be associated with many pathological conditions and is crucial in acute circulatory problems. Low-level laser radiation (LLLR) has been found to have positive effects on the rheology of human blood, however, the detailed mechanisms of blood photobiomodulation remains unclear. In this study, utilizing the single-cell technique optical tweezers (OT) and traditional light microscopy, the influence of photobiomodulation of human RBC was examined under different conditions of laser irradiation. The results revealed that high radiant exposure (over 170.5J/cm2 radiant fluence) caused enhanced RBC aggregation and cell shape transformation while the aggregation force between single RBC remained unchanged. LLLR with radiant fluence below 9.5J/cm2 by 450nm wavelength improved the RBC deformability, weakened the strength of cell-cell interaction in the RBC disaggregation process, and showed rejuvenating effects on RBC suspended in a harsh cell environment.

UV laser-induced nanostructured porous oxide in GaAs crystals

Laser processing is an important tool for inducing local topographical and chemical changes on the surface of technologically important materials to facilitate various device fabrication procedures or to favor chemical reactions. Here, we report that irradiation of GaAs crystal surfaces with c.w. UV laser radiation (λ = 244 nm) in ambient conditions produces a well defined layer of porous oxide with a thickness up to ∼0.4 μm. Under certain laser irradiation conditions the oxidized layer appears to self-organize into periodic features, collectively known as laser-induced periodic surface structures (LIPSS). The topography and composition of the laser grown surface oxide layer is investigated.

Differentiate Thermal Property of Mammary Glands for Precise Photothermal Therapy

AbstractAs an alternative to conventional methods, photothermal therapy is promising in breast cancer therapy. It is essential to prevent overheating of normal tissues and underheating of target tissues, which strongly depends on thermal transport processes. In this work, for the first time, the thermal properties of mammary glands in pubertal and mature mice is accurately measured. Thermal conductivity of mammary gland in pubertal mice is measured as W m−1 K−1, slightly higher than that of fat (0.17 W m−1 K−1), which is the main component of connective tissue in mammary glands. However, with the growth and pregnancy of mature mice, thermal conductivity of mammary gland increases to W m−1 K−1, 66.84% higher than that of pubertal mice. Numerical simulations are conducted to understand the role of thermal conductivity in photothermal therapy. The maximum temperatures in mammary glands of pubertal and mature mice are 49.6 and 44.6 °C, respectively, under the same laser irradiation conditions. This implies that higher thermal conductivity in mature mice mammary glands might lead to ineffectiveness in reaching to the desired temperature. This work suggests that age and pregnancy affect the thermal properties of mammary glands which are not negligible in breast cancer photothermal therapy.

Q-Switched 1,064-nm Neodymium-Doped yttrium aluminum garnet laser irradiation induces collagen remodeling in SKH-1 Hairl ess mice by activating ERK1/2 and p38MAPK signaling pathway

To select the optimal condition of 1064 nm Q-switched Nd:YAG laser irradiation and study the molecular mechanism of laser irradiation for skin rejuvenation. Sixty male, 6-week-old SKH-1 hairless mice were equally divided into 6 groups: 3d, 7d, 21d, 28d, 42d and 56d of 1064 nm laser irradiation at both 0 J/cm2 (left region) and 1.5 J/cm2 (right region) fluence. The basic skin performances were analysed via quantifying hydroxyproline content and skin hydration in the dermis and epidermis. The Collagen I, MMP2 and TIMP1, as well as ERK 1/2, p38MAPK, JNK and ERK5 signaling pathways levels were detected by qRT-PCR. Laser irradiation led to a marked increase in hydroxyproline content and skin hydration in the dermis and epidermis compared to the non-irradiated area. After laser irradiation, collagen I was markedly up-regulated, MMP2 was significantly decreased and TIMP1 was unchanged. Moreover, qRT-PCR results revealed ERK 1/2 and p38MAPK signaling pathways were activated after laser irradiation. we are firstly proves that 1064 nm laser irradiation can inhibit collagen degradation by stimulating the activation of ERK1/2 and p38MAPK signaling pathways. Additionally, the condition of laser irradiation lasting 21d at fluence of 1.5 J/cm2 displays the best effect of skin rejuvenation in our study.

Research on optical camera imaging quality evaluation method under the condition of laser irradiation

Research on optical camera imaging quality evaluation method under the condition of laser irradiation

Effect of a helium gas atmosphere on the mechanical properties of Ti-6Al-4V alloy built with laser powder bed fusion: A comparative study with argon gas

In metal additive manufacturing, the microstructures and associated mechanical properties of metal specimens can be controlled over a wide range. Although process parameters are considered important in the fabrication of functional parts, the effect of atmospheric gas has not been comprehensively documented. In laser powder bed fusion (LPBF), gas flow is used to eliminate fumes generated by laser irradiation. Simultaneously, the gas removes heat from the laser-irradiated part, which is exposed to high temperature. In this study, we investigated the capacity of helium as an alternative to argon, which is conventionally used as the LPBF atmosphere gas. He has a higher thermal conductivity and lower gas density than Ar, which may result in enhanced heat removal from the Ti-6Al-4V alloy during fabrication. Numerical simulations suggest a greater cooling rate under He flow. Further, the material built under He flow contained finer α' martensite grains and showed improved mechanical properties compared to those fabricated under Ar flow, despite the identical laser irradiation conditions. Thus, He gas is advantageous in LPBF for fabricating products with superior mechanical performance through microstructural refinement, and this is a result of its capacity for cooling and fume generation inhibition. Therefore, this study reveals the importance of the choice of atmospheric gas because of its effects on the characteristics of metallic specimens fabricated using LPBF.

Atomic resolution in situ observation on photon-induced reshaping and phase transitions of CsPbBr3 nanocube and quantum dot

Controlling the photon-induced reshaping and phase transitions of low-dimensional halide perovskites is a significant and challenging task. Using in situ Cs-corrected transmission electron microscopy with a nanosecond pulsed laser source, we traced CsPbBr3 nanocubes and quantum dots under different laser irradiation conditions, through a low-dose observation mode. We found that a high laser fluence with a short irradiation time (e.g., 300 mJ/cm2 in the range of seconds) triggers defect growth and a cubic-to-orthorhombic phase transition in perovskite nanocubes; however, a low laser fluence with a long irradiation time (e.g., 30 mJ/cm2 in the range of minutes) is actually like an annealing process that removes defects and gradually reshapes the perovskite samples into a round morphology, with the cubic phase well stabilized by the strong surface tension. Based on the in situ studies, we present a feasible and effective laser engineering approach for low-dimensional halide perovskite materials.

Pure copper layer formation on stainless-steel and aluminum substrate with a multibeam laser metal deposition system with blue diode laser

Laser metal deposition (LMD), which is one of the additive manufacturing technologies, is suitable for making 3D objects with complex shapes. In this method, a blue diode laser is used to explore the formation of pure copper parts because of the high light absorption of pure copper in blue light. Inspired by this method, in this study, we developed a high-power blue diode laser with a wavelength of 450 nm. This laser had an output power of 100 W and a fiber core diameter of 100 μm. We also developed a multibeam LMD system with the blue diode laser in which metal powder was supplied perpendicularly to the processing point and multiple lasers were irradiated from the surroundings for additively manufactured pure copper. We investigated the differences in copper layer formation that are dependent on the properties of substrates. Upon using the multibeam LMD system, a pure copper layer formed on pure aluminum and stainless-steel substrates. The interaction of pure copper powder and the substrates was observed using a high-speed video camera. After laser irradiation, copper cladding samples were observed with an optical microscope and scanning electron microscope and energy dispersive x-ray spectroscopy to evaluate the cross-sectional area of the pure copper layer and the dilution zone. As a result, a pure copper layer formed on the aluminum surface under the laser irradiation condition under which the aluminum substrate was not subjected to melting by heating with the blue laser. It was suggested that the pure copper powder heated by the laser melted the aluminum and formed a copper layer on the aluminum substrate.

Surface characterization of laser-induced molten area in micro-grooving of silicon by ultraviolet (UV) laser

The objective of this research is to understand the fundamental mechanisms that govern the formation of laser-induced molten area during the micro-grooved fabrication on silicon material. In this research work, micro grooves were fabricated on silicon wafer by using ultraviolet (UV) laser of 248nm wavelength. Influence of lasing parameters such as pulse duration, laser pulse energy and scanning speed on the surface of micro-grooved was characterized. It is found that, the width of the micro grooves become wider with increasing laser pulse energy when ultraviolet laser was irradiated on silicon material. On the other hand, heat affected zone (HAZ) can be found at the surface of micro groove line at high pulse energy, high pulse repetition rate and lower scanning speed irradiation condition. This is considered due to the excessive heat input of the laser irradiation condition. It is concluded that proper selection of laser processing parameters of pulse energy, E, pulse repetition rate, R p , and scanning speed is necessary to achieve high quality micro-grooves.

Substrate Cleaning Threshold for Various Coated Al Alloys Using a Continuous-Wave Laser

In this study, different coatings (gray epoxy primer, white epoxy varnish and red alkyd paint) of 7075 aluminum alloy are cleaned with a 500 W continuous-wave (CW) fiber laser. We analyzed the influence of the laser power density on the temperature evolution and target surface morphology. Under the condition of continuous laser irradiation for 1 s, the experimental results indicated that the suitable cleaning thresholds of epoxy primer, epoxy primer and epoxy varnish, as well as epoxy primer, epoxy varnish and alkyd paint were 177.74, 192.89 and 147.44 W/mm2. The results show that the cleaning threshold of thicker three-layer paint target was smaller than the single-layer paint layer, and we analyze the mechanism of this phenomenon.

The influence of laser irradiation conditions on the bulk damage of JGS1 fused silica

The fused silica is an important optical material in the large laser devices, which are often subject to laser induced damage in the laser systems. In this work we studied nanosecond laser induced damage in JGS1 fused silica at the three harmonic wavelengths of the 1064 nm, 355 nm and 248 nm. Under 1064nm/10ns, 355nm/10ns and 248nm/22.8ns laser irradiation, the bulk damage threshold is 150 J/cm2, 15 J/cm2 and 7 J/cm2, respectively. The results showed that the weakest point of bulk damage threshold among the three tested wavelengths is 248 nm. And the damage threshold decreases sharply with the decrease of wavelength.

Cracking behavior and microstructural, mechanical and thermal characteristics of tungsten–rhenium binary alloys fabricated by laser powder bed fusion

In this study, the cracking behavior and microstructural, mechanical and thermal characteristics of tungsten–rhenium (W–Re) binary alloys fabricated by laser powder bed fusion (L-PBF) were investigated. Four bulk specimens were prepared by L-PBF: pure W, W–1%Re, W–3%Re and W–10%Re (percentages indicate the mass percent of Re). High-density bulk specimens (relative density > 98.0%) were obtained for pure W and W–Re alloys under the same laser irradiation conditions. The columnar grains elongated along the building direction were gradually refined as the Re content increased. The most remarkable grain refinement was observed for the W–10%Re alloy. Hardness under a high-temperature environment increased with increasing Re content; the micro-Vickers hardnesses of pure W and W–10%Re at 400 °C were 179 ± 4 HV0.1/30 and 281 ± 5 HV0.1/30, respectively. Observations with a scanning electron microscope revealed that the 10 mass% Re addition resulted in a shorter and narrower crack morphology in comparison with pure W and consequently reduced crack area by 59%. Furthermore, the anisotropy of the thermal diffusivity was mitigated in the high Re content specimens, suggesting that, at high Re content, thermal diffusivity is affected less by cracks than by the effect of Re atoms on heat carrier transfer via isotropic scattering.

Microstructure and Mechanical Properties of AlSi12CuNi Alloy Fabricated by Laser Powder Bed Fusion Process

The microstructure and mechanical properties of the AlSi12CuNi alloy fabricated by the additive manufacturing technique, laser powder bed fusion (L-PBF), were investigated. Several laser irradiation conditions were examined to optimize the manufacturing process to obtain a high volume density of the fabricated alloy. Good fabricated samples with a relative density of 99% or higher were obtained with no cracks. The fabricated samples exhibited significantly good mechanical properties, such as ultimate tensile strength, breaking elongation, and micro-hardness, compared to the conventional die casting AlSi12CuNi alloy. Fine microstructures consisting of the α-Al phase and a nano-sized eutectic Al-Si network were observed. The dimensions of the microstructures were smaller than those of the conventional die-casting AlSi12CuNi alloy. The superior mechanical properties were attributed to the microstructure associated with the rapid solidification in the L-PBF process. Furthermore, the influence of the building direction on the mechanical properties of the fabricated samples was evaluated. The ultimate tensile strength and breaking elongation were significantly affected by the building direction; mechanical properties parallel to the roller moving direction were significantly better than those perpendicular to the roller moving direction. In conclusion, AlSi12CuNi alloys with good characteristics were successfully fabricated by the L-PBF process.