Laser Exposure Time Research Articles

Reducing Laser Exposure Time of PBF-LB/P by Providing High Energy Without Thermal Degradation and Its Effect on Part Strength and Process Time

Abstract One of the most promising additive manufacturing technologies for the production of end-use parts is powder bed fusion of polymer with laser beam (PBF-LB/P). This technology can reduce production costs by increasing process efficiency and production speed. As PBF-LB/P is a layer-wise additive manufacturing process, the production speed can be increased by reducing the layering time. Although some operations such as recoating are performed during the layering process, considerable time is spent on laser scanning. To reduce the laser exposure time while maintaining proper powder melting, a high-power beam should be irradiated to the powder layer to prevent energy shortage. However, as the laser beam power increases, the irradiance at the beam center increases significantly, causing powder degradation such as thermal decomposition or sublimation. In this study, an appropriate input energy range was determined by obtaining an input energy limit that does not cause powder deterioration via experimental observations and temperature estimations during the process. Furthermore, the influence of the scanning parameters on the mechanical properties of built specimens was investigated to reduce the layering time within an indicated range. Results show that the mechanical strength of the built parts decreases slightly as the scan spacing increases following the expansion of the beam diameter. This study also validated the effects of scanning parameters on layering time. As a result, by doubling the scan speed and spacing, the layering time can be reduced by up to 1/3.

Time-dependent 532 nm laser irradiation for tuning in optical, structural, and surface wettability changes of Te/In2Se3 thin films for optoelectronic applications

Laser irradiation for tuning the optoelectronic parameters of semiconducting thin films is widely applicable and has many benefits. The aim of the study is 532 nm laser irradiation of Te/In2Se3 film at different laser exposure time scales. The bilayer structure and its conversion to a single layer with laser annealing were confirmed from cross-sectional scanning electron microscopy. At the same time, the element's appearance was found in the EDX analysis. FESEM probed the corresponding surface structure change. XRD and Raman's spectroscopy analyzed the increase in crystallinity with laser irradiation by mixing Te into the In2Se3 layer and related microstructural changes. The shift in Raman peak with lasing time signifies the effect of time of exposure. There is a systematic decrement in the transmittance of the films. Also, the absorption edge shift resulted in the decrement in bandgap with laser irradiation. The static refractive index and optical density increased as well. The skin depth was decreased with a minimal change in the optical electronegativity. The nonlinear refractive index increased from 1.638 × 10–9 esu to 1.773 × 10–9 esu by 60 min laser irradiation. Similarly, there was an increment in 3rd-order nonlinear susceptibility from 1.58 × 10–10 esu to 1.73 × 10–10 esu. The surface wettability test confirmed the hydrophilic nature of the samples with decreasing hydrophilicity by laser irradiation. The tuning in different properties of the Te/In2Se3 film by laser irradiation is suitable for various optoelectronic applications.

Near infrared photothermal inactivation of Candida albicans assisted by plasmonic nanorods

The use of photothermal processes has been proven effective in the control of microbial infections. Simultaneously, the localized surface plasmon resonance phenomena in metallic nanoparticles have been explored as an alternative strategy to achieve highly efficient localized heating. In this work, we propose the use of selected nanoheaters to improve the efficiency of fungal photothermal inactivation of Candida albicans through size optimization of plasmonic gold nanorods. Here, the optical heating of polyethylene glycol coated gold nanorods of varying sizes is evaluated, both theoretically and experimentally. A size-dependent computational approach was applied to identify metallic nanorods with maximized thermal performance at 800 nm, followed by the experimental comparison of optimal and suboptimal nanoheaters. Comparison among samples show temperatures of up to 53.0 °C for 41×10 nm gold nanorods against 32.3 °C for 90×25 nm, a percentage increase of ∼63% in photothermal inactivation assessments. Our findings reveal that gold nanorods of 41×10 nm exhibit superior efficiency in near-infrared (800 nm) photothermal inactivation of fungi, owing to their higher light-thermal conversion efficiency. The identification of high performance metallic nanoheaters may lead to the reduction of the nanoparticle dose used in plasmonic-based procedures and decrease the laser exposure time needed to induce cell death. Moreover, our results provide insights to better exploit plasmonic nanoparticles on photothermal inactivation protocols.

MODELING THE IMPACT OF LASER IRRADIATION ON TEMPERATURE CHANGES IN BIOLOGICAL TISSUES

Modeling the impact of laser irradiation (MILI) on biological tissues plays a crucial role in research and the development of laser technologies in biology and medicine. MILI opens a wide spectrum of knowledge for scientists and medical professionals, providing insights into how laser radiation interacts with different types of tissues and organs and determining optimal parameters to achieve the desired outcome. Models can account for various physical processes occurring during irradiation, such as energy absorption, heat propagation, changes in tissue structure, and functions. This enables the prediction of tissue responses to different laser exposure regimes, including intensity, wavelength, and exposure time. In medicine, modeling is used to determine optimal laser exposure parameters for specific diseases or procedures. For example, MILI helps identify the optimal radiation dose during laser therapy or surgical interventions. Additionally, modeling allows for the assessment of potential risks associated with laser radiation, such as tissue overheating or side effects. This, in turn, enhances the development of safer and more effective laser application methods. Moreover, optimizing laser irradiation parameters is relevant for minimizing the risk of damage to surrounding tissues. MILI can be used to develop new laser technologies and devices aimed at improving the outcomes of laser applications in medicine. It also facilitates the faster and more efficient implementation of new methods and technologies into clinical practice. Thus, modeling the impact of laser irradiation on temperature changes in biological tissues plays a vital role in enhancing understanding of processes in biological tissues and contributes to the development of new methods and technologies, as well as the optimization of laser application for achieving effective treatment outcomes and patient safety.

Analysis of printing time components and powder utilisation efficiency of metal selective laser melting process in case of 316L and Ti6Al4V materials

ABSTRACT In selective laser melting technology, the productivity and the efficiency of powder utilisation were examined. Individual components of the printing time were determined by developing a specially designed model. Two main components of the powder recoating and the laser exposure time were given as a function of the filling ratio of the cross-section. Based on the results, the spreading time can increase the printing time by several hours, depending on the filling factor of the cross-section. In the case of a sampling of 70 prints, the individual elements and process of the powder usage were determined, as well as the mass measurement of the different amounts of powder in the case of 316L and Ti6Al4V materials. It turned out that 45–80% of the powder amount is not used to build the model, which is an essential for both printer users and equipment developers for material cost prediction.

Exploring Elemental Powder Approach for Making Al and Ti Containing High-Entropy Alloys by Powder Bed Fusion

This research aimed to produce high-entropy alloys (HEA), namely Mn–Fe–Co–Ni + 5Al and Mn–Fe–Co–Ni + 5Al + 5Ti, through the Powder Bed Fusion technique using elemental powders. Alloy composition has been selected to achieve a HEA matrix with strengthening intermetallic precipitates. Thermo-Calc software has been used to predict solidification behavior and phase stability for non-equilibrium conditions. The experiment involved the execution of an additive manufacturing process with a laser working in point-by-point exposure mode to produce samples using varying laser power and exposure time. The samples underwent investigation via macroscopic examination, porosity analysis, scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and hardness testing. Results have shown that processing parameters and alloy constituents directly influenced processability and sample traits. What is more, a high-energy laser beam introduction to the material during the process has helped mitigate the formation of large Ti or Al oxides. In addition, EDS analysis indicated that higher Volumetric Energy Density values enhanced the uniformity of chemical composition, indicating that homogeneity can be achieved by selecting appropriate melting parameters. The results clearly show that these alloys can be successfully (by means of porosity and homogeneity) manufactured from elemental powders via the powder bed fusion technique.

The Effect of Laser Power and Laser Exposure Time for Cavity Created on Al2O3 Ceramic Surface

Al2O3 ceramic materials have many industrial applications, especially because they are wear-resistant. In this study, dimples of different sizes were formed on the surface of ceramic plates with a CO2 laser. The effects of laser power and laser exposure time on the dimensions of the cavity were investigated. For this purpose, laser powers of 40, 52, 65, 78, 91, and 105 W were applied to the ceramic material for 10 seconds. In addition, 80 W laser power was kept constant and the laser beam was sent to the material for 1, 5, 10, 15, 20, 25, and 30 seconds. High-resolution images of the resulting cavities were taken with an optical microscope. Using the images, the dimensions of the cavities were measured and the effects of laser power and laser exposure time on the cavity geometry were observed. The effects of both laser power and laser exposure duration on the cavity and Heat Affected Zone (HAZ) regions showed similar characteristics. The size of the cavities and HAZ increased almost linearly as laser power increased. However, when the effect of laser exposure duration was analyzed, the increase in cavity sizes slowed down after the exposure duration exceeded 10 s. When the laser exposure duration exceeded 15 seconds, it was observed that the dimensions of the cavities did not change.

Spatially Resolved Raman Spectroscopic Investigation of Uranyl Fluoride: A Case Study in the Importance of Instrument Optimization.

Raman spectroscopy is an emerging technique for rapid and nondestructive analysis of nuclear materials for forensic and nonproliferation applications as it is a powerful tool for distinguishing multiple chemical forms of materials with similar stoichiometries. Recent developments in spectroscopic software have enabled rapid data collection with high-speed Raman spectroscopic mapping capabilities. However, some uranium-rich materials are susceptible to degradation in humid air and/or laser-induced phase transformations. To mitigate environmental or measurement-related sample degradation of potential samples of interest, we have taken a systematic approach to define optimized data collection parameters for high-throughput measurements of uranyl fluoride (UO2F2), which is an important intermediate material in the nuclear fuel cycle. First, we systematically describe the influence of optical magnification (5× to 100×), laser power, and exposure time on obtained signal for identical particles of UO2F2 and find that at low laser power and exposure times, comparable signal is obtained regardless of optical magnification. Second, we ensure sample integrity during data collection, and third, collect spectroscopic maps that employ optimized parameters to reduce the time required to obtain spatially resolved spectroscopic information. Reductions of 90% and 99% in measurement times are discussed as they relate to differences in resolving spectroscopic features of particles in identical mapping areas. During this work, we found that additional data processing options were needed and thus developed a customized Python script for importing, processing, analyzing, and visualizing Raman spectroscopic map data.

Bio-thermal response during laser haemorrhoidoplasty: an exclusive analytical and numerical approach for theoretical investigation.

Haemorrhoidal disease is identified by declension of the inflamed and bleeding of vascular tissues of the anal canal. Traditionally, haemorrhoids are associated with chronicconstipation and the most common symptoms are irritation in anus region, pain and discomfort, swelling around anus, tender lumps around the anus and rectal bleeding (depending upon the grade of haemorrhoid). Among the several conventional treatment procedures (commonly mentioned as, rubber band litigation, sclerotherapy and electrotherapy), laser haemorrhoidoplasty is an out-patient and less-invasive laparoscopic procedure. From literature survey it has been observed that an exclusive theoretical model depicting the impact of 1064nm wavelength laser wave on living tissues subjected to haemorrhoid therapy is not available. This research work is a pioneering attempt to develop a theoretical study attributing specifically on laser therapy of haemorrhoid treatment based on Pennes' biological heat transfer model. The corresponding mathematical model has been solved by analytical method to establish thermal response of tissue during the treatment and also the same has been solved a numerical approach based on finite difference method to validate the feasibility of former method due to unavailability of any theoretical model. Impact of variation of blood perfusion term, laser pulse time and optical penetration depth on temperature response of skin tissue is captured. The tissue temperature decreases along with time of laser exposure with increasing the blood perfusion rate as it carries away large amount of heat. With the increase in laser pulse time, tissue temperature declines due to shorter pulse time resulting in higher energy consumed by electrons. The research outcome is successfully validated with less than 1% of error observed between the appointed analytical and numerical scheme.

Direct laser patterning of ruthenium below the optical diffraction limit

We describe a method that can be used to produce ruthenium/ruthenium oxide patterns starting from a ruthenium thin film. The method is based on highly localized oxidation of a small surface area of a ruthenium film by means of exposure to a pulsed laser under ambient conditions. Laser exposure is followed by dissolution of the un-exposed ruthenium in a NaClO solution, which leaves the conductive, partially oxidized ruthenium area on the substrate. Spatially selective oxidation, material removal, and, by implication, patterning, are, therefore, achieved without the need for a photoresist layer. Varying the exposure laser parameters, such as fluence, focus diameter, and repetition rate, allows us to optimize the process. In particular, it enables us to obtain circular Ru/RuO2 islands with a sub-diffraction-limited diameter of about 500 nm, for laser exposure times as short as 50 ms. The capability to obtain such small islands suggests that heat-diffusion is not a limiting factor to pattern Ru by laser heating on a (sub-)micron scale. In fact, heat diffusion helps in that it limits the area where a sufficiently high temperature is reached and maintained for a sufficiently long time for oxidation to occur. Our method provides an easy way to produce metallic Ru/RuO2 (sub-)micron structures and has possible applications in semiconductor manufacturing.

Revolutionizing Antibacterial Surfaces: 3D Printed Nanoscale and Microscale Topographies through Two-Photon Polymerization

The evolving bacteria defense mechanism against antimicrobial agents due to the overuse and misuse of antimicrobial chemicals has led to a catastrophic problem - antimicrobial resistance, this has spurred the quest for innovative antibacterial approach to inhibit bacterial growth effectively without using any chemicals. Tailored nano- and microstructured architecture, inspired by natural nanotopography such as those found on cicada wings, hold great promise in antibacterial activity due to their unique mechano-antibacterial properties. Among the various nano-/microfabrication techniques, the two-photon polymerisation (TPP) stands out as a versatile and precise approach to fabricate arbitrarily functional three-dimensional structures with sub-micrometre resolution. The process involves the use of femtosecond laser pulses to induce polymerization of a biocompatible acrylate-based photoresin in a precise spatial pattern to generate the nano-/microarchitecture. In this study, we investigated the influence of key fabrication parameters, such as laser power, exposure time, and interface value to achieve the final pre-defined nano-/microarchitecture. Microscopy analysis showed that nanostructure of heights between 350-650 nm; 300-400 nm diameter; and increasing center-to-center distances of 700-2000 nm were successfully fabricated. The mechano-antibacterial feasibility of the two photon-designed nanoarchitecture were tested against P. aeruginosa pathogenic bacteria commonly encountered in healthcare settings. Our results showed that the TPP nano-/microarchitecture demonstrated intriguing antibacterial activity through physico-mechanical interactions between the nano-/microarchitectures and bacteria, creating surfaces that exhibit bactericidal activity. This study paves the way for advanced antibacterial applications in the field of nanotechnology and biomedicine, making a significant contribution to the ongoing efforts in combating antimicrobial resistance and promoting global health.

Determination of Laser Parameters in Thermomechanical Treatment of Skin Based on Response Surface Methodology

An investigation was conducted to examine the photothermal and thermomechanical effects of short-pulse laser irradiation on normal tissues. This study analyzed the impact of short-pulse laser radiation on the heat-affected region within tissues, taking into consideration a set of laser variables, namely wavelength, intensity, beam size, and exposure time. The beam size ranged between 0.5 and 3 mm, and the intensity of the laser radiation ranged from 1 to 5 W/mm2 at wavelengths of 532 and 800 nm. A three-layered, three-dimensional model was implemented and studied in a polar coordinate system (r = 10 mm, z = 12 mm) in COMSOL Multiphysics (version 5.4, COMSOL Inc., Stockholm, Sweden) to perform numerical simulations. The Pennes bioheat transfer model, Beer-Lambert, and Hooke’s law are integrated to simulate the coupled biophysics problem. Temperature and stress distributions resulting from laser radiation were produced and analyzed. The accuracy of the developed model was qualitatively verified by comparing temperature and mechanical variations following the variations of laser parameters with relevant studies. The results of Box-Behnken analysis showed that beam size (S) had no significant impact on the response variables, with p-values exceeding 0.05. Temperature (Tmax) demonstrates sensitivity to both beam intensity (I) and exposure time (T), jointly contributing to 89.6% of the observed variation. Conversely, while beam size (S) has no significant effect on stress value (Smax), wavelength (W), beam intensity (I), and exposure time (T) collectively account for 71.6% of the observed variation in Smax. It is recommended to use this model to obtain the optimal values of the laser treatment corresponding to tissue with specified dimensions and properties.

Study of the kinetics of accumulation and distribution of the photosensitizer photoditazin in the oral mucosa in patients with lichen planus

Was to explore the accumulation and distribution of the photosensitizer Photoditazine in the oral mucosa when applied to pathological lesions in patients with severe forms of lichen planus. A clinical and laboratory examination was carried out in 50 patients with severe forms of lichen planus (bullous and erosive-ulcerative) aged 18 to 70 years, including 6 men and 44 women. For autofluorescent imaging a LED device with a wavelength in the violet region of the spectrum (400±10 nm) was used. Quantitative registration of the kinetics of accumulation and distribution of the photosensitizer was carried out using the method of local fluorescence spectroscopy by measuring the fluorescence spectra. The measurements were made before applying the photosensitizer, 10, 20 and 30 minutes after application. The study showed that in most patients with erosive-ulcerative and bullous forms of lichen planus, the accumulation of the photosensitizer in the lesions on the oral mucosa increased as the exposure time increased from 20 to 30 minutes. The fastest accumulation of the photosensitizer occurred in the areas of mucosal lesions with the most pronounced vascularization, namely, in the area of the tongue and the bottom of the oral cavity. Using the method of local fluorescence spectroscopy, the kinetics of accumulation and destruction of photosensitizer in pathological areas of the oral mucosa was determined, and therefore the optimal time of laser exposure to the lesion was determined.

Using CO2 Laser, Optimization of Laser Power, Exposure Time and Frequency for Cavity Formation on Hardox Steel Plate

The texture of the surfaces of materials causes changes in mechanical properties such as friction. Micro-scale cavities have been created on Hardox steel plate, which has recently been the focus of attention in demanding applications with its hardness, toughness and wear resistance. CO2 laser was used in the cavitation process on the surface and the power, exposure and frequency of the laser used were optimized to obtain a cavity with the desired geometry. Taguchi method was used in the optimization process. In addition to obtaining the optimum parameters, the effect ratios of the parameters were also calculated. Optimum laser parameters were obtained as 5 s for laser exposure duration, 60 W for laser power, and 50 kHz for laser frequency. According to the optimization calculations, the parameter with the highest effect on the result was laser exposure duration with a rate of 71,86 %. Laser power and laser frequency affected the result by 23.02 % and 5.12 % respectively.

Influence of process parameters on the quality of powder bed fusion-fabricated Ni-Co-Fe-Mn-Ti high entropy alloy prints using elemental powders

Ni-Co-Fe-Mn-Ti high entropy alloys (HEA) were fabricated via powder bed fusion using elemental powders. Based on thermodynamic calculations, 3 alloys were designed with medium to high entropy (from 3 to 5 components) and printed. Additive manufacturing (AM) was performed, while varying the laser power and exposure time (point-by-point exposure laser working mode). The obtained samples were characterised by means of macroscopic observations combined with porosity analysis, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), electron backscatter diffraction (EBSD), X-ray diffraction (XRD), as well as compression and hardness tests. The varied process parameters and the content of individual alloying elements directly impacted alloy processability and sample properties. We proved that it is possible to produce HEAs (Ni-Co-Fe-Mn-Ti) with low porosity and good chemical homogeneity from elemental powders. By comparing the processes of producing 3-, 4-, and 5-component alloys, it was observed that it is not the quantity of the components but the melting temperatures of the individual elemental powders and their tendency to oxidise that affect obtaining good 3D prints. The most promising results for 5-component HEAs were obtained for 145 µs of laser exposure time combined with laser powers of 250 and 300 W.

AN IMPACT OF THE LASER IRRADIATION TIME ON PROPERTIES OF COLLOIDAL SOLUTIONS OF SILICON NANOPARTICLES

The design of semiconductor-metallic nanostructures using pulsed laser ablation in liquids (PLAL) is a very demanding task for biomedical applications being at an early stage of its development. Only few recent papers show the possibility of such a synthesis of composite nanoparticles as well as their perspectives for biosensing applications. However, mechanisms of the laser-stimulated formation of semiconductor-metallic nanoparticles involving several processes are not clarified yet being considerably depended on experimental conditions. In this work, we demonstrated an impact of the laser irradiation of colloidal solutions of silicon nanoparticles at different exposure time in the presence/absence of a gold target. In particular, longer ablation of the metal led to a stronger plasmonic maximum in silicon nanoparticles at around 520 nm. It also decreased the hydrodynamic size from 165 nm to 85 nm as well as the ξ-potential from –46 mV to –30 mV by increasing the ablation time from 0 s to 600 s. At the same time, the lowest electrical conductivity value (~1.5 µS/cm) of the plasmonic nanocomposites was detected at 120 s irradiation time. The highest concentration of synthesized composite nanoparticles (~3·1011 NPs/mL) was achieved at 180 s ablation time. Another purpose of the paper was to reveal an influence of the used laser irradiation on properties of the colloidal solutions of silicon nanoparticles themselves. It was found a considerable decrease of their absorbance with the increase of the laser exposure time that can be associated with the change of their properties (e.g. concentration, size, oxidation state etc.). Thus, the laser irradiation strongly affects properties of colloidal solutions of silicon nanoparticles that must also be taken into account considering possible mechanisms of the formation of composite nanostructures. Presented in the paper fast optical diagnostic can help to determine properties of colloidal solutions of nanocomposites formed by PLAL prior their biomedical or catalytic applications.

Classification and analysis of common simplifications in part-scale thermal modelling of metal additive manufacturing processes

Computational process modelling of metal additive manufacturing has gained significant research attention in recent past. The cornerstone of many process models is the transient thermal response during the AM process. Since deposition-scale modelling of the thermal conditions in AM is computationally expensive, spatial and temporal simplifications, such as simulating deposition of an entire layer or multiple layers, and extending the laser exposure times, are commonly employed in the literature. Although beneficial in reducing computational costs, the influence of these simplifications on the accuracy of temperature history is reported on a case-by-case basis. In this paper, the simplifications from the existing literature are first classified in a normalised simplification space based on assumptions made in spatial and temporal domains. Subsequently, all types of simplifications are investigated with numerical examples and compared with a high-fidelity reference model. The required numerical discretisation for each simplification is established, leading to a fair comparison of computational times. The holistic approach to the suitability of different modelling simplifications for capturing thermal history provides guidelines for the suitability of simplifications while setting up a thermal AM model.

Fabrication of microneedles using two photon-polymerization with low numerical aperture

Three-dimensional (3D) micro-nano fabrication through two-photon polymerization (TPP) is a prominent approach for fabricating complex 3D structures. However, the existing techniques face limitations, such as small fabrication area, dependence on high numerical aperture (e.g., oil immersion) objective lenses, which are more expensive. We developed a 780 nm fs laser system integrated with a 2D galvanometer system and Z axis to create a 3D micro-nano printing system. A method to print arbitrarily complex 3D structures while maintaining an extremely high lateral spatial resolution of sub-100nm is proposed by using a cheap low numerical aperture objective lens with the laser power and exposure time precisely controlled. The impact of the laser power and exposure time on the resolution of 3D micro-nano processing is investigated, and we identify the optimal processing environment for achieving the best resolution. The printed linewidth of 62 nm was achieved without the use of an oil immersed objective lens, and only one laser beam was used instead of stimulated emission depletion. Microneedle arrays for animal injection were fabricated using this strategy, which can improve the performance of animal organoid repair. Our results suggest that TPP micro-nano fabrication is an effective method for processing microneedle arrays for biomedical engineering, with the ability to improve the processing resolution with a cheap low numerical aperture objectives lens (e.g., NA = 0.4) through meticulous control of laser power and exposure time. This approach opens up possibilities for affordable and scalable fabrication in sub-100nm structures.

Solvent-Assisted Laser Desorption Flexible Microtube Plasma Mass Spectrometry for Direct Analysis of Dried Samples on Paper.

The present study investigated the potential for solvent-assisted laser desorption coupled with flexible microtube plasma ionization mass spectrometry (SALD-FμTP-MS) as a rapid analytical technique for direct analysis of surface-deposited samples. Paper was used as the demonstrative substrate, and an infrared hand-held laser was employed for sample desorption, aiming to explore cost-effective sampling and analysis methods. SALD-FμTP-MS offers several advantages, particularly for biofluid analysis, including affordability, the ability to analyze low sample volumes (<10 μL), expanded chemical coverage, sample and substrate stability, and in situ analysis and high throughput potential. The optimization process involved exploring the use of viscous solvents with high boiling points as liquid matrices. This approach aimed to enhance desorption and ionization efficiencies. Ethylene glycol (EG) was identified as a suitable solvent, which not only improved sensitivity but also ensured substrate stability during analysis. Furthermore, the addition of cosolvents such as acetonitrile/water (1:1) and ethyl acetate further enhanced sensitivity and reproducibility for a standard solution containing amphetamine, imazalil, and cholesterol. Optimized conditions for reproducible and sensitive analysis were determined as 1000 ms of laser exposure time using a 1 μL solvent mixture of 60% EG and 40% acetonitrile (ACN)/water (1:1). A mixture of 60% EG and 40% ACN/water (1:1) resulted in signal enhancements and relative standard deviations of 12, 20, and 13% for the evaluated standards, respectively. The applicability of SALD-FμTP-MS was further evaluated by successfully analyzing food, water, and biological samples, highlighting the potential of SALD-FμTP-MS analysis, particularly for thermolabile and polarity diverse compounds.

Comparative Effects of Er:YAG Laser, Sodium Hypochlorite, and QMix on Root Canals Infected With Enterococcus faecalis and Candida albicans.

Introduction: During endodontic treatment, the smear layer can reduce disinfectant efficacy. The aim of this study was to evaluate the antimicrobial efficacy of Er:YAG laser radiation and its combination with NaOCl and QMix against Enterococcus faecalis and Candida albicans and their comparison with conventional irrigation with only NaOCl and QMix. Methods: Two hundred extracted single-rooted teeth after root canal preparation were divided into two groups and inoculated with E. faecalis and C. albicans. According to the treatment method, all samples were divided into five treatment groups: (1) Er:YAG laser, (2) NaOCl, (3) QMix, (4) Er:YAG laser plus NaOCl, and (5) Er:YAG laser plus QMix. After 24 hours of agar plate cultivation, cell viability was recorded with a flow cytometer. Results: All treatment modalities showed efficiency in the reduction of microbial cells. For laser treatment alone after exposure for 90 seconds, significantly fewer non-death cells were seen, compared to 30-second treatment. For both timings (30 and 90 seconds), irrigation with NaOCl or QMix after laser application resulted in significantly fewer vital cells of E. faecalis and C. albicans, compared with laser treatment alone (P<0.001). The samples treated with only NaOCl showed a significantly higher percentage of vital E. faecalis and Candida albicans cells, compared to the samples treated with only QMix (P<0.001). Conclusion: Higher Er: YAG laser exposure time (90 seconds) after its combination with QMix and NaOCl improves the efficacy in the reduction of E. faecalis and C. albicans from the root canal, compared to 30-second laser exposure time and conventional irrigation methods with NaOCl and QMix.