Combination Of Laser Irradiation Research Articles

One-step E-Jet printing of loofah-like ZnO nanostructures by real-time laser zone irradiation

Loofah-like nanostructures have been applied in many fields because of their high specific surface area, high porosity, and low density. Developing additive manufacturing methods for loofah-like nanostructures remains a challenge. This paper proposed a novel E-Jet nanoprinting method with real-time laser zone irradiation, for one-step fabricating of loofah-like ZnO nanostructures. The combination of laser irradiation and electrohydrodynamic effect had been proved in detail by adding laser irradiation to the traditional E-Jet printing process. Printable ZnO inks were prepared. The numerical model of the jetting under the combination of flow field and electric field; and the model of the interaction between laser and printing structure were established respectively. The laser beam irradiated the printing structure in real-time to rapidly absorb energy, resulting in thermal expansion and thermal decomposition. The shock wave generated by laser irradiation induced the physical fragmentation and redistribution of particles in the printed structure. Printing at different laser powers was investigated; and the loofah-like ZnO nanostructures, down to the scale of ∼90 nm, have been directly printed without post-processing. The characteristic morphology and hydrophilic characteristics of the printed structure were studied. This study provided a new way for green and efficient additive fabrication of loofah-like nanostructures, which was of significance for the development of nanofabrication and nanodevices.

Effects of topical fluoride on primary tooth enamel microhardness after diode laser treatment

ObjectivesTooth decay is controlled and prevented using fluorides. Specifically, a combination of laser irradiation and topical fluoride application can improve fluoride absorption. Although laser irradiation is recommended in traditional technology for caries prevention, little is known about the efficacy of caries-inhibiting laser diodes. Further, most studies have focused on permanent teeth. The objective of this study was to explore the effect of laser diode radiation mixed with topical fluoride on the enamel surface microhardness of primary teeth. Material and methodThe 60 primary teeth were divided into 60 plates. Baseline Vickers microhardness was established for each enamel surface. The samples were then divided into three groups. 4 % NaF varnish (group A) and 4 % NaF varnish using diode 2 and 3 W lasers (groups B and C, respectively). The final microhardness was measured and statistically evaluated using SPSS version 16. ANOVA was used to compare the means of the tested groups, which had a P-value of 0.05, indicating significance. ResultThe mean and standard deviation of microhardness for the different groups was tested. Group C (4 % NaF with a diode laser at 3 W) showed a higher average Vickers hardness (VHN) than Group B (4 % NaF with a diode laser at 2 W), whereas group A showed the lowest average VHN. There was a significant difference in microhardness between groups (P 0.05). ConclusionThis study explored the effect of laser mixed with topical fluoride on enamel surface microhardness of primary teeth. The use of a diode laser (Quanta System, Italy) with a fluoride varnish applied to the enamel surface has a greater effect on the resistance of the enamel to caries.

Temperature distribution analysis using a combination of near-infrared laser, gold nanorods, and surface cooling equipment: Temperature distribution study

Metastatic diseases are the primary causes of death among cancer patients. Photothermal therapy, which combines near-infrared lasers, gold nanorods (GNRs), and skin surface cooling equipment, is a promising local treatment for breast cancer, as well as head and neck cancer. However, in this treatment, accurate predictions of the temperature distributions within organisms and uniform distributions of GNRs within tumors are often difficult. This study focused on evaluating composite heat transfer characteristics when laser irradiations were combined with GNRs, and a surface cooling method was applied. The temperature distributions were analyzed using agar as a bio-simulated material. The experimental results revealed that the combination of laser irradiation, GNR injection, and surface cooling could achieve higher temperatures near the GNR injection sites at low surface temperatures. The obtained temperature distributions were quantitatively analyzed using the thermal damage function. When the laser power was set to create a tumor area temperature greater than 45 °C, the tumor area could be treated without causing skin damage when injecting GNRs into the tumor area and cooling the surface. This study demonstrates the effectiveness of this therapy in local treatments of cancer.

Enhanced chemical etch rate of borosilicate glass via spatially resolved laser-generated color centers

In this work, it is shown that controllable increases in chemical reactivity of borosilicate glass can be induced through spatially resolved femtosecond laser irradiation at fluence values significantly lower than the damage threshold. The hydrofluoric acid etch rate has been found to be closely correlated to the reduction in optical transmission of the glass at 488 nm, which is, in turn, governed by the production of boron–oxygen hole centers. The combination of laser irradiation below the ablation threshold followed by chemical etching is shown to yield surfaces that have a roughness lower than those achieved by either laser or chemical etching alone. Application of this effect to the manufacture of freeform Laplacian optics is demonstrated.

A photosensitizer-loaded zinc oxide-polydopamine core-shell nanotherapeutic agent for photodynamic and photothermal synergistic therapy of cancer cells

In clinical cancer research, it is quite promising to develop multimodal synergistic therapeutic strategies. Photodynamic and photothermal synergistic therapy is a very desirable multimodal therapy strategy. Herein, we report a facile and simple method to construct a nanotherapeutic agent for photodynamic and photothermal therapy. This nanotherapeutic agent (ZnO@Ce6-PDA) is composed of a ZnO nanoparticle core, an interlayer of photosensitizer chlorin e6 (Ce6) and an outer layer of polydopamine (PDA). Due to the existence of Ce6, the ZnO@Ce6-PDA can efficiently generate singlet oxygen (1O2) under 660 nm laser irradiation. Moreover, the ZnO@Ce6-PDA can serve as a photothermal agent, because of the excellent photothermal conversion efficiency of the PDA coating layer in the presence of 780 nm laser. Experiment results demonstrated that the designed nanotherapeutic agent had outstanding phototoxicity upon the combination of laser irradiation at 660 and 780 nm. Thus, our work proves that the ZnO@Ce6-PDA is a promising photodynamic/photothermal dual-modal nanotherapeutic agent for enhanced cancer therapy.

Effects of Laser Irradiation and Ni Nanoparticles on Biogas Production from Anaerobic Digestion of Slurry

This study investigated the simultaneous effects of nanoparticles (NPs) addition to rumen fluid (archaea source) and laser irradiation of the mixture on biogas production from anaerobic digestion of dairy manure. Where, the previous study reported that the addition of 2 mg L−1 nickel nanoparticles (Ni NPs) significantly (p < 0.05) increased the biogas and methane volumes by 1.74 and 2.01 times compared to the control, respectively. The results indicated that the most efficient irradiation time was 2 h laser with the addition of 2 mg L−1 Ni NPs (p < 0.05), which minimized the lag phase from 4 days to 1 day and the Hydraulic Retention Time (HRT) to attain the peak of biogas production in comparison to the control from 28 days to 16 days. The combination of laser irradiation and nanoparticles addition yielded the highest significant value of the specific biogas and methane production, compared to all treatments (incandescent light, control), which were 679.5 mL biogas g−1 VS and 453.3 mL CH4 g−1 VS. Furthermore, Laser photocatalysis of Ni NPs enhances the photo-reduction/photo-oxidation of CH4 formation pathways. Consequently, this treatment increased the biogas and methane volumes by 1.9 and 2.32 times the biogas and methane volumes resulted from the control, respectively.

A fast fabrication of copper nanowire transparent conductive electrodes by using pulsed laser irradiation

Copper nanowires have shown promise for use in next-generation conducting materials for transparent electrodes owing to their low sheet resistance, natural abundance, and high transmittance properties. Additionally, copper nanowires can be easily synthesized via low-cost solution-based processes. However, copper requires a uniform film to coat the nanowires on the substrate and removing film former residue in the post-treatment process remains a challenge. This lead to the high cost and complexity of fabricating transparent electrode. In this study, we demonstrate a simple, time-saving production method using a combination of laser irradiation and acid dipping to fabricate high-quality copper nanowire transparent electrodes. Preparation of electrodes was achieved by scanning pulsed laser on a copper nanowire film and then dipping in glacial acetic acid. The electrode exhibited excellent properties and the film former was totally erased from the electrode surface. Moreover, to demonstrate their capability, the as-fabricated electrodes were applied in touch-sensor fabrication.

Low-temperature (&amp;lt;200 oC) solid-phase crystallization of high substitutional Sn concentration (∼10%) GeSn on insulator enhanced by weak laser irradiation

Low temperature (&amp;lt;200 oC) crystallization of GeSn (substitutional Sn concentration: &amp;gt;8%) on insulating substrates is essential to realize next generation flexible electronics. To achieve this, a growth method of high quality GeSn films on insulating substrates by combination of laser irradiation and subsequent thermal annealing is developed. Here, the laser fluence is chosen as weak, which is below the critical fluence for crystallization of GeSn. It is clarified that for samples irradiated with weak laser fluence, complete crystallization of GeSn films is achieved by subsequent thermal annealing at ∼170 oC without incubation time. In addition, the quality of GeSn films obtained by this method is higher compared with conventional growth techniques such as melting growth by pulsed laser annealing or solid-phase crystallization (SPC) without pre-laser irradiation. Substitutional Sn concentrations in the grown layers estimated by Raman spectroscopy measurements are 8-10%, which far exceed thermal equilibrium solid-solubility of Sn in Ge (∼2%). These phenomena are explained by generation of a limited number of nuclei by weak laser irradiation and lateral SPC by subsequent thermal annealing. This method will facilitate realization of next-generation high performance devices on flexible insulating substrates.

The effect of surface treatment with a fractional carbon dioxide laser on shear bond strength of resin cement to a lithium disilicate-based ceramic.

This study investigated the impact of different surface treatments, including fractional carbon dioxide (CO2) laser on shear bond strength (SBS) of resin cement to lithium disilicate ceramic. In this in vitro study, 72 blocks of IPS e.max CAD ceramic were randomly divided into six groups in terms of treatment (n = 12). Group 1 underwent etching with 9.6% hydrofluoric (HF) acid, whereas group 2 was subjected to air abrasion with aluminum oxide particles. Groups 3 and 4 were treated with a fractional CO2 laser for 10 s using 10 W/14 mJ (group 3) or 20 W/10 mJ (group 4). In groups 5 and 6, the CO2 laser was applied similar to that in groups 3 and 4, respectively; then, the specimens were etched by HF acid. After silane application, luting cement was bonded to the specimens. The SBS was assessed with a universal testing machine, and the type of bond failure was determined. Data were analyzed by ANOVA, Duncan, and Fisher's exact tests. Surface conditioning with fractional CO2 laser alone resulted in significantly lower SBS than HF acid treatment (P < 0.05). Bond strengths of the specimens treated with a combination of laser irradiation and acid etching were significantly greater than all the other groups (P < 0.05). No significant difference was found in the distribution of failure modes among the groups (P = 0.337). The combination of fractional CO2 laser irradiation and HF acid etching could be recommended when extra retention is required for lithium disilicate-based restorations, whereas laser treatment alone cannot produce sufficient SBS.

Thermal therapy with magnetic nanoparticles for cell destruction.

In this article we suggest a new concept for cell destruction based upon manipulating magnetic nanoparticles (MNPs) by applying external, low frequency alternating magnetic field (AMF) that oscillates the particles, together with focused laser illumination. Assessment of temperature profiles in a head and neck squamous cell carcinoma sample showed that cells with MNPs, treated with AMF (3 Hz, 300 mW) and laser irradiation (30 mW), reached 42°C after 4.5 min, as opposed to cells treated with laser but without AMF. Moreover, a theoretical model was developed to assess the overall theoretical temperature rise, which was shown to be 50% lower than the experimental temperature. Furthermore, we found that the combination of laser irradiation and AMF decreased the number of live cells by ~50%. Thus, the concentrated assembly of laser heating with AMF-induced MNP oscillations leads to more rapid and efficient cell death. These results suggest that the manipulated MNP technique can serve as a superior agent for PTT, with improved cell death capabilities.

Nanotechnology combined therapy: tyrosine kinase-bound gold nanorod and laser thermal ablation produce a synergistic higher treatment response of renal cell carcinoma in a murine model.

To investigate tyrosine kinase inhibitors (TKI) and gold nanorods (AuNRs) paired with photothermal ablation in a human metastatic clear cell renal cell carcinoma (RCC) mouse model. Nanoparticles have been successful as a platform for targeted drug delivery in the treatment of urological cancers. Likewise, the use of nanoparticles in photothermal tumour ablation, although early in its development, has provided promising results. Our previous in vitro studies of nanoparticles loaded with both TKI and AuNRs and activated with photothermal ablation have shown significant synergistic cell kill greater than each individual arm alone. This study is a translation of our initial findings to an in vivo model. Immunologically naïve nude mice (athymic nude-Foxn1nu ) were injected subcutaneously bilaterally in both flanks (n = 36) with 2.5 × 106 cells of a human metastatic renal cell carcinoma cell line (RCC 786-O). Subcutaneous xenograft tumours developed into 1-cm palpable nodules. AuNRs encapsulated in human serum albumin protein (HSA) nanoparticles were synthesised with or without a TKI and injected directly into the tumour nodule. Irradiation was administered with an 808-nm light-emitting diode laser for 6 min. Mice were humanely killed 14 days after irradiation; tumours were excised, formalin fixed, paraffin embedded, and evaluated for size and the percentage of necrosis by a genitourinary pathologist. The untreated contralateral flank tumours were used as controls. In mice that did not receive irradiation, TKI alone yielded 4.2% tumour necrosis on the injected side and administration of HSA-AuNR-TKI alone yielded 11.1% necrosis. In the laser-ablation models, laser ablation alone yielded 62% necrosis and when paired with HSA-AuNR there was 63.4% necrosis. The combination of laser irradiation and HSA-AuNR-TKI had cell kill rate of 100%. In the absence of laser irradiation, TKI treatment alone or when delivered via nanoparticles produced moderate necrosis. Irradiation with and without gold particles alone also improves tumour necrosis. However, when irradiation is paired with gold particles and drug-loaded nanoparticles, the combined therapy showed the most significant and synergistic complete tumour necrosis of 100% (P < 0.05). This study illustrates the potential of combination nanotechnology as a new approach in the treatment of urological cancers.

The impact of Er:YAG laser enamel conditioning on the microleakage of a new hydrophilic sealant--UltraSeal XT hydro.

UltraSeal XT® hydro™ is a new hydrophilic, light-cured, methacrylate-based pit and fissure sealant which has been developed by Ultradent Products, USA. The sealant is highly filled with a 53 wt.% mixture of inorganic particles which confer both thixotropy and radiopacity. The principal purpose of this study was to investigate the microleakage of UltraSeal XT® hydro™ as a function of different enamel etching techniques. The occlusal surfaces of sound, extracted human molars were either acid etched, Er:YAG laser irradiated or successively laser irradiated and acid etched. UltraSeal XT® hydro™ was applied to each group of teeth (n = 10) which were subjected to a thermocycling process consisting of 2500 cycles between 5 and 50 °C with a dwell time of 30 s. Microleakage assessments were then carried out using 0.5 % fuchsin dye and optical microscopy. The microleakage score data were analysed using the Kruskal-Wallis, Mann–Whitney U test with Bonferroni adjustment. No significant differences in microleakage were noted between the individually acid etched and laser-irradiated groups (p > 0.05); however, teeth treated with a combination of laser irradiation and acid etching demonstrated significantly lower microleakage scores (p < 0.001). Electron microscopy with energy-dispersive X-ray analysis revealed that the mineral filler component of UltraSeal XT® hydro™ essentially comprises micrometre-sized particles of inorganic silicon-, aluminium- and barium-bearing phases. Laser etching increases the roughness of the enamel surface which causes a concentrated zoning of the filler particles at the enamel-sealant interface.

Nd:YAG Laser Irradiation of the Tooth Root Surface Inhibits Demineralization and Root Surface Softening Caused by Minocycline Application

The aim of this study was to investigate the effect of laser irradiation on root surface demineralization caused by local drug delivery systems (DDS), and to evaluate the effect of sealing on drug retention. The duration of supportive periodontal treatment (SPT) has increased with increasing life expectancy. Repeated root planing and DDS application during SPT should be reconsidered with regard to their effects on the root surface. Extracted human teeth were collected, cut into 3 × 3 × 2 mm root dentin specimens, and divided randomly into eight groups with various combinations of Nd:YAG laser power (0, 0.5, 1, and 2 W), with and without DDS (minocycline HCl). Specimen microhardness and calcium (Ca) solubility were measured after treatment. The specimens (control and laser and DDS groups) were examined by scanning electron microscopy. Forty SPT patients were recruited, to assess the effect of periodontal pocket sealing on drug retention. Laser irradiation increased the microhardness of root specimens in an energy-dependent manner. Calcium solubilities decreased from the 0 W+DDS group to the 2.0 W+DDS group. The mean Ca solubilities in the 1.0 W+DDS and 2.0 W+DDS groups were significantly lower than in the 0 W+DDS group (p<0.01, p<0.001, respectively). Laser irradiation counteracted the softening effect of DDS. Morphologic change was observed in the 2 W+DDS group; however, no morphologic changes were observed in the control and the 1 W+DDS groups. The mean concentration of minocycline in the periodontal pocket 24 h after application was 252.79 ± 67.50 μg/mL. Laser irradiation of the root surface inhibited the softening and decalcification caused by minocycline HCl. Sealing the periodontal pockets effectively improved drug retention. These results suggest that the combination of laser irradiation and DDS could benefit patients receiving repeated SPT.

Selective electrodeposition of copper on stainless steel using laser irradiation

This paper proposes a novel selective metal deposition process that uses a combination of laser irradiation and electrodeposition. Via the selective electrodeposition using laser irradiation (SELI) process, metal can be deposited selectively on a metal surface without a special mask, which is in contrast to conventional deposition processes that routinely require a metal mask or a photo-resist. The SELI process consists of three steps: laser irradiation, electrodeposition, and ultrasonic vibration cleaning. In the course of experimentation, a recast layer was formed via the laser irradiation process, which acts as the sacrificial layer in the SELI process. The sacrificial layer was removed after the cleaning step. The separation of the sacrificial layer was due to the hydrogen evolution effects of the hydrogen embrittlement via the hydrogen bubbles and the hydrogen absorption. The results were observed via focused ion beam (FIB) analysis of the cross-sectional images. Electron probe X-ray micro-analyzer (EPMA) analysis was used to detect the surface components. Through the SELI process, selective copper deposition was successfully performed with various micro-patterns of the approximately 4μm thick deposited copper.

Laser-induced Propagation and Destruction of Amyloid β Fibrils

The amyloid deposition of amyloid beta (Abeta) peptides is a critical pathological event in Alzheimer disease (AD). Preventing the formation of amyloid deposits and removing preformed fibrils in tissues are important therapeutic strategies against AD. Previously, we reported the destruction of amyloid fibrils of beta(2)-microglobulin K3 fragments by laser irradiation coupled with the binding of amyloid-specific thioflavin T. Here, we studied the effects of a laser beam on Abeta fibrils. As was the case for K3 fibrils, extensive irradiation destroyed the preformed Abeta fibrils. However, irradiation during spontaneous fibril formation resulted in only the partial destruction of growing fibrils and a subsequent explosive propagation of fibrils. The explosive propagation was caused by an increase in the number of active ends due to breakage. The results not only reveal a case of fragmentation-induced propagation of fibrils but also provide insights into therapeutic strategies for AD.

Laboratory simulations of sulfur depletion at Eros

The X-ray spectrometer of the Near-Earth Asteroid Rendezvous (NEAR) mission discovered a low abundance of sulfur on the surface of asteroid Eros, which is seemingly inconsistent with the match of the overall surface composition to that of ordinary chondrites. Since troilite, FeS, is the primary sulfur-bearing mineral in ordinary chondrites, we investigated the hypothesis that sulfur loss from surface FeS could result from ‘space weathering’ by impact of solar wind ions and micrometeorites. We performed laboratory studies on the chemical alteration of FeS by 4 keV ions simulating exposure to the solar wind and by nanosecond laser pulses simulating pulsed heating by micrometeorite impact. We found that the combination of laser irradiation followed by ion impact lowers the S:Fe atomic ratio on the surface by a factor of up to 2.5, which is consistent with the value of at least 1.5 deduced from the NEAR measurements. Thus, our results support the hypothesis that the low abundance of sulfur at the surface of Eros is caused by space weathering.

Degradation Dynamics of Polymeric Housing Materials Used for HV Line and Station Apparatus

A combination of laser irradiation and thermogravimetric analysis has been utilized to understand the degradation dynamics of polymeric materials used for housings of outdoor high voltage (HV) line and apparatus insulators, namely, silicone rubber, ethylene propylene diene monomer rubber and cycloaliphatic epoxy. The induced temperature rise was calculated using laser photo-thermal models and the results were found to be in good agreement with experimental findings. It has been shown that there are significant differences in the degradation dynamics of silicone rubber when compared with ethylene propylene diene monomer and epoxy. It has also been shown that the laser irradiation technique can be used as an efficient method to rank polymers materials for arc tracking and erosion resistance, especially for present day materials that will easily pass the screening tests prescribed in the ASTM and IEC standards.

Lateral Crystalline Grain Growth by Combination of Laser Irradiation with Rapid Substrate Heating

Lateral Crystalline Grain Growth by Combination of Laser Irradiation with Rapid Substrate Heating

Advanced Laser Therapy. Photodynamic Therapy for Vascular Disease.

Photodynamic therapy is a new approach to treat the cardio-vascular diseases. Several photosensitizers were selectively accumulated in atherosclerotic plaques. A tunable diode laser was developed and was useful to activate the photosensitizer. Atheroma could be destroyed by photodynamic therapy. Intimal hyperplasia of the artery could also be suppressed by the combination of laser irradiation and a photosensitizer. We reviewed a new trend of photodynamic therapy in the field of atherosclerosis and vascular intimal hyperplasia.