Thermal Effect Of Laser Research Articles

Theoretical model and verification of the laser thermal effect on the temperature measurement sensitivity of rare earth

The fluorescence temperature measurement based on rare earth ions has been studied widely. It is quite puzzling that the same thermal coupling energy levels present different relative sensitivities of temperature measurement in reports. Different relative sensitivities indicate that the level spacing of the same thermal coupling energy levels calculated by Boltzmann's formula is different. To solve this problem, a physical model is proposed to explain the influence of the laser thermal effect on the fluorescence temperature measurement. The results show that the additional temperature of the sample imposed by the laser thermal effect has an impact on the relative sensitivity, which is the higher the additional temperature, the lower the relative sensitivity. Furthermore, the source of heat generation from laser irradiation of rare earth is discussed. For Er3+ ions, the laser converted into heat mainly generated by the multiphonon transitions between 2H11/2 and 4S3/2 levels. The results show that the theoretical curve fitted well with the experimental data. It is instructive for the design of new temperature sensors.

Effects of Laser Treatment of Terbium-Doped Indium Oxide Thin Films and Transistors.

In this study, a KrF excimer laser with a high-absorption coefficient in metal oxide films and a wavelength of 248 nm was selected for the post-processing of a film and metal oxide thin film transistor (MOTFT). Due to the poor negative bias illumination stress (NBIS) stability of indium gallium zinc oxide thin film transistor (IGZO-TFT) devices, terbium-doped Tb:In2O3 material was selected as the target of this study. The XPS test revealed the presence of both Tb3+ and Tb4+ ions in the Tb:In2O3 film. It was hypothesized that the peak of the laser thermal effect was reduced and the action time was prolonged by the f-f jump of Tb3+ ions and the C-T jump of Tb4+ ions during the laser treatment. Studies related to the treatment of Tb:In2O3 films with different laser energy densities have been carried out. It is shown that as the laser energy density increases, the film density increases, the thickness decreases, the carrier concentration increases, and the optical band gap widens. Terbium has a low electronegativity (1.1 eV) and a high Tb-O dissociation energy (707 kJ/mol), which brings about a large lattice distortion. The Tb:In2O3 films did not show significant crystallization even under laser energy density treatment of up to 250 mJ/cm2. Compared with pure In2O3-TFT, the doping of Tb ions effectively reduces the off-state current (1.16 × 10-11 A vs. 1.66 × 10-12 A), improves the switching current ratio (1.63 × 106 vs. 1.34 × 107) and improves the NBIS stability (ΔVON = -10.4 V vs. 6.4 V) and positive bias illumination stress (PBIS) stability (ΔVON = 8 V vs. 1.6 V).

Effect of alternating interval of laser power on the element distribution, mechanical, and corrosion performance of electrochemical deposited multilayer Fe–Ni coatings

A new multilayer (ML) Fe–Ni coating was developed by frequently alternating the laser power (5 and 20 W) during electrochemical deposition. Owing to the thermal effect of the laser, the elemental content in each layer changed continuously. As the intervals for adjusting the laser parameters became shorter, the formation of ML Fe–Ni coatings became increasingly challenging due to the laser's thermal effect. This study suggests that a constant laser action exceeding 480 s improves the uniformity of the alternating elemental content distribution in the new coating without visible interlayer boundaries. Moreover, the elemental composition of each layer was affected by various laser parameters during the Fe–Ni reduction process. For a stable ML structure (480 s interval), the range of variation in Fe content reaches approximately 16.6 wt% (from approximately 32.6 to 49.2 wt%). Compared with the overall coating, the bonding force increased by approximately 24.5 %, the microhardness increased by approximately 17.3 % (load of 200 g), the wear rate decreased by approximately 21.6 % (load of 5 N), and the corrosion rate decreased by approximately 53.5 % (3.5 wt% NaCl). The improved wear resistance was attributed to the inhibition of crack extension and spalling. In addition, the ML structure was conducive to inhibiting the propagation of corrosion pits. This study provides guidance for analyzing the structural and performance characteristics of ML coatings formed via laser electrochemical deposition.

Effect of Combined Laser Thermal and Shock Wave Effects on the Mechanical and Tribological Properties of Steels.

Herein, we present the results of an experimental study on the mechanical properties of Fe-C alloys with different carbon contents (0.2, 0.45, and 0.8%) in a wide range of deformation rates (10-3-103 s-1) and abrasive wear resistance, which underwent combined laser thermal (laser surface hardening-LSH) and laser shock wave (Laser Shock Peening-LSP) processing. The combined treatment modes included a different sequence of exposure to laser thermal and laser-induced shock pulses on the material. The amplitude and duration of laser-induced shock waves were measured using a laser Michelson interferometer. The mechanical properties of steel samples were studied under conditions of uniaxial tension under static loads on a standard universal testing machine, the LR5KPlus, and under dynamic loading, tests were carried out on a specialized experimental complex according to the H. Kolsky method using a split Hopkinson rod. The abrasive wear resistance of hardened surfaces was studied using the Brinell-Haworth method. Studies have shown that the use of a combination of LSH and LSP treatments leads to an increase in both the mechanical properties of steels and abrasive wear resistance compared to traditional laser hardening. It has been established that in the combinations considered, the most effective is laser treatment, in which LSP treatment is applied twice: before and after LSH. Thus, after processing steels using this mode, an increase in the depth of the hardened layer was recorded-by 1.53 times for steel 20, by 1.41 times for steel 45, and by 1.29 times for steel U8-as well as a maximum increase in microhardness values by 22% for steel 20, by 27% for steel 45, and by 13% for U8 steel. The use of this mode made it possible to obtain the maximum strength properties of the studied materials under static and dynamic loading, which is associated with an increase in the volume fraction of the strengthened metal and high microhardness values of the strengthened layer of traditional LSH. The dependences of abrasive wear of the studied steels after various combinations of LSP and LSH impacts were established. It is shown that the greatest wear resistance of the studied steels is observed in the case when the LSH pulse is located between two LSP pulses. In this case, abrasive wear resistance increases by 1.5-2 times compared to traditional LSH.

Ultra-sensitive flexible pressure sensor with hierarchical structural laser-induced carbon nanosheets/carbon nanotubes composite film

Recently, laser induced carbon nanosheets (LICs) based flexible pressure sensors have received widespread attention. Introducing hierarchical microstructure is an effective method to improve the sensitivity of pressure sensors. However, implementing hierarchical microstructure on LICs film through a simple and low damage process remains a challenge. Herein, taking advantage of the reshaping characteristics of low melting point thermoplastic substrate styrene-isoprene-styrene (SIS) under laser thermal effects, a simple and one-step laser thermoforming process is used to spontaneously form surface microstructure on the LICs film during the formation of LICs. Therefore, a hierarchical structure composed of porous structure and surface microstructure was achieved on the LICs film through the one-step process. Furthermore, a hybrid strategy combining hierarchical microstructure with carbon nanotubes (CNTs)/LICs composite was proposed to improve the sensitivity of LICs based pressure sensor. Benefiting from the hierarchical structure of LICs and the composite conductive network constructed by CNTs and LICs, the LICs/CNTs@SIS sensor exhibits ultrahigh sensitivity of 1089 kPa−1 in 0–5 kPa and ultrahigh gauge factor of 1493 within the strain rate range of 20%–28%. Meanwhile, the sensor has good stability (>1400 cycles), response and recovery times of 23.8 ms and 25.9 ms, excellent reversibility, and 1220% elongation at break. Besides, the application of the sensor in physiological signal monitoring and pressure distribution detection indicates its great potential in flexible electronics.

A novel ultrafast laser ablation fracture polishing method to simultaneously smoothing and improving the surface quality of Al2O3 ceramics with high roughness

Al2O3 ceramics are widely used in industry due to their excellent mechanical and physical properties. However, microcracks, voids and high surface roughness (Sa) on the surface of Al2O3 ceramic parts produced in conventional industrial or additive manufacturing have been one of the technical bottlenecks limiting their high-performance applications. In this paper, a novel method of ultrafast laser ablation fracture polishing (ULAFP) of Al2O3 ceramic parts is proposed for improving the surface quality and enhancing the mechanical properties of the polished surfaces. The ULAFP method is developed with an ultrafast laser, which can be set up as a picosecond (PS) or a femtosecond (FS) laser. The PS laser is used to form a remelting layer on the surface to eliminate surface void defects. Combining laser ablation and laser thermal stress-induced crack extension effects, the FS laser is used to rapidly remove the remelted layer and obtain a surface free of crack defects and finally implement FS laser layer-wise ablation to achieve smoother surface finish. The FS laser energy density is controlled at a critical state close to the ablation threshold of the material to avoid surface defects. This ULAFP can reduce the surface roughness (Sa5.254 μm) polishing of Al2O3 ceramics to 0.80 μm, while controlling the total ablation depth of the polishing process to below 100 μm maintaining the dimensional accuracy of the part and dramatically improving the mechanical properties of the polished surface. Compared with the original surface, the hardness and elastic modulus of the polished surface improved by 104.6% and 63.9%, respectively.

Metasurface-generating high purity narrow linewidth cylindrical vector beams: power scaling and its limitation

1.89 kW cylindrical vector beams (CVBs) at 1,064 nm with the 3 dB linewidth being about 0.08 nm have been generated from a narrow linewidth all-fiber linearly-polarized laser by metasurface extra-cavity conversion. At the maximum output power, the transmission efficiency, mode purity of radially polarized cylindrical vector beams (RP-CVBs) are 97% and 92.7%, respectively. To the best of our knowledge, this is the highest power of narrow linewidth CVBs generated from fiber laser. The temperature of the metasurface is moderate, and the maximum temperature is 75.5°C at 1.89 kW, which means that the system can be further power scaled. The evolution of mode purity has been analyzed numerically, and the influence of high-order modes (HOM) in laser source and thermal effects of metasurface has been calculated, which reveals that the presence of high-order modes and the temperature rise of metasurface degrade the mode purity of the CVBs. Among them, HOM causes a degradation of 1.68%, thermal lensing effect contributes 2.32%, and the microstructure variation of the metasurface contributes the remaining 3.3%.

One-Step Laser Direct-Printing Process of a Hybrid Microstructure for Highly Sensitive Flexible Piezocapacitive Sensors

Microstructures can effectively improve the sensing performance of flexible piezocapacitive sensors. Simple, low-cost fabrication methods for microstructures are key to facilitating the practical application of piezocapacitive sensors. Herein, based on the laser thermal effect and the thermal decomposition of glucose, a rapid, simple, and low-cost laser direct-printing process is proposed for the preparation of a polydimethylsiloxane (PDMS)-based electrode with a hybrid microstructure. Combining the PDMS-based electrode with an ionic gel film, highly sensitive piezocapacitive sensors with different hybrid microstructures are realized. Due to the good mechanical properties brought about by the hybrid microstructure and the double electric layer induced by the ionic gel film, the sensor with a porous X-type microstructure exhibits an ultrahigh sensitivity of 92.87 kPa-1 in the pressure range of 0-1000 Pa, a wide measurement range of 100 kPa, excellent stability (>3000 cycles), fast response time (100 ms) and recovery time (101 ms), and good reversibility. Furthermore, the sensor is used to monitor human physiological signals such as throat vibration, pulse, and facial muscle movement, demonstrating the application potential of the sensor in human health monitoring. Most importantly, the laser direct-printing process provides a new strategy for the one-step preparation of hybrid microstructures on thermal curing polymers.

Quantitative simulation of photothermal effect in laser therapy of hypertrophic scar.

Laser technology has been widely used in the treatment of hypertrophic scar (HPS). Due to the lack of effective quantitative relationship between laser doses and thermal effect of lesion tissue, the selection of laser doses in clinical laser treatment of HPS is blind, which cannot guarantee the best treatment effect. The photothermal model of HPS was established by using finite element method. The effects of laser dose parameters such as laser energy density, pulse width, and spot diameter on the thermal effects of laser treatment were analyzed. According to tissue temperature threshold and thermal damage degree of the simulation results, the optimal laser doses of HPS were selected for the laser treatment experiments of rabbit ear HPSs to verify the rationality of the quantitative photothermal model. The temperature rise and thermal damage degree of HPS following laser treatment were directly correlated to the laser doses, which grew with the increase of energy density and laser pulse width. For the different spot diameters, the temperature rise decreased with the increase of spot diameter, whereas the thermal damage degree worsened with the increase of spot diameter. Both simulation and experimental results show that the optimal treatment parameters of HPS were as follows: The laser energy density was 7.5J/cm3 , the pulse width was 4ms, and the spot diameter was 7mm. The laser dose parameters optimized by the photothermal model have achieved good therapeutic effects in the rabbit ear HPS, indicating that the model can be used for quantitative evaluation of laser doses before clinical treatment.

Destructive Effect of High-Temperature Heat Flow of Solid Slow-Release Energetic Materials on a Steel Target

To investigate the high-temperature heat flow's destructive effect of solid slow-release energetic materials on a steel target, we prepared a sample of solid slow-release energetic materials, eruption devices, and a complete test system to conduct the destruction of high-temperature heat flow on the steel target. In addition, we proposed the energy density to characterise the high-temperature heat flow performance and numerically simulated the destructive effect of the high-temperature heat flow on the steel target. The numerical simulation results were in good agreement with the test results, and the error between them was under 8.5%. Based on the test and simulation results, the steady-state melting model of the steel target was established under the action of high-temperature heat flow. Moreover, a time-varying model of the melting hole shape was found. The results showed that the model of destroying the steel target with the high-temperature heat flow of solid slow-release energetic materials was highly accurate. Therefore, the model could provide theoretical guidance for designing and applying solid slow-release energetic materials in ammunition destruction, metal cutting, the simulation of the laser thermal effect, etc.

The Impact of Laser Thermal Effect on Histological Evaluation of Oral Soft Tissue Biopsy: Systematic Review

The aim of the study is to review the literature to observe studies that evaluate the extent of the thermal effect of different laser wavelengths on the histological evaluation of oral soft tissue biopsies. An electronic search for published studies was performed on the PubMed and Scopus databases between July 2020 and November 2022. After the selection process, all the included studies were subjected to quality assessment and data extraction processes. A total of 28 studies met the eligibility criteria. The most studied laser was the carbon dioxide (CO2) laser, followed by the diode laser 940 nm-980 nm. Six studies were focused on each of the Erbium-doped Yttrium Aluminium Garnet (Er:YAG), Neodymium-doped Yttrium Aluminum Garnet (Nd:YAG) lasers, and diode lasers of 808 nm and 445 nm. Three studies were for the Potassium Titanyl Phosphate (KTP) laser, and four studies were for the Erbium, Chromium-doped Yttrium, Scandium, Gallium, and Garnet (Er,Cr:YSGG) laser. The quality and bias assessment revealed that almost all the animal studies were at a low risk of bias (RoB) in the considered domains of the used assessment tool except the allocation concealment domain in the selection bias and the blinding domain in the performance bias, where these domains were awarded an unclear or high score in almost all the included animal studies. For clinical studies, the range of the total RoB score in the comparative studies was 14 to 23, while in the non-comparative studies, it was 11 to 15. Almost all the studies concluded that the thermal effect of different laser wavelengths did not hinder the histological diagnosis. This literature review showed some observations. The thermal effect occurred with different wavelengths and parameters and what should be done is to minimize it by better adjusting the laser parameters. The extension of margins during the collection of laser oral biopsies and the use of laser only in non-suspicious lesions are recommended because of the difficulty of the histopathologist to assess the extension and grade of dysplasia at the surgical margins. The comparison of the thermal effect between different studies was impossible due to the presence of methodological heterogeneity.

Thermal Effect of Laser on Silver Nanoparticles Synthesized by the Cold Plasma Method on Cancer Cells

In this study, silver nanoparticles (AgNPs) were synthesized using a cold plasma technique and a plasma jet. They were then used to explore how photothermal treatment may be used to treat lung cancer (A549) and normal cells (REF) <i>in vitro</i>. The anti-proliferative activity of these nanoparticles was studied after A549 cells were treated with (AgNPs) at various concentrations (100%, 50%, or 25%) and exposure times (6 or 8 min) of laser after 1 h or 24 h from exposed AgNPs. The highest growth inhibition for cancer cells is (75%) at (AgNPs) concentration (100%) and the period of exposure to the laser is (8 min). Particle size for the prepared samples varied according to the diameter of the electrode and was within the range AgNPs according to FE-SEM was 38-65 nm, where the crystal size calculated using Debye Scherrer from XRD was 24-27 nm. The results of this study suggest that AgNPs have strong activity and has an effective role in the treatment of cancer cells.

A simple and fast strategy for rare earth doped phosphors prepared by 980 nm laser thermal effect

The phosphors synthesize by the sol-gel method show low cost and good homogeneity, but it also requires furnace annealing at high-temperatures. This report uses a 980 nm laser annealing strategy to replace the furnace annealing in the sol-gel combustion synthesis. The fast laser annealing can improve the preparation efficiency of rare earth doped phosphor. Er3+/Li+ co-doped Y2O3 nanocrystals are synthesized by laser annealing strategy. The structures and spectral properties of the phosphors prepared by laser annealing are studied. The phosphors prepared by laser annealing have the same crystal structure and spectral properties as those organized by furnace annealing. In addition, phosphors can be heated into crystals using a high-power 980 nm laser. Under 980 nm excitation, the crystal prepared by laser annealing shows a much stronger fluorescence intensity than phosphors.

Laser-Induced Heating in GdVO4: Yb3+/Er3+ Nanocrystals for Thermometry

Photoluminescent temperature sensors based on gadolinium orthovanadate (GdVO4) doped with 10% ytterbium and 2% erbium are developed and dispersed in different media (lubricant fluid, sol–gel glass, and PDMS) to evaluate the best conditions for temperature measurement. Two excitation modes are considered: (i) visible excitation by a downshifting (DS) process or (ii) NIR excitation by energy transfer upconversion (UC) between Yb and Er. The luminescence intensity ratio (LIR) of the thermally coupled Er3+ emission peaks varies linearly with temperature in the range of 25–300 °C, and this variation is reversible. The impact of the laser power density on thermometry via the UC process that has been verified with GdVO4: Yb3+/Er3+ powders and with its different dilutions (low and high concentration) shows that the LIR is highly dependent on the laser source intensity, the environmental temperature, and the dispersed medium. When GdVO4: Yb3+/Er3+ powders are dispersed at high concentration, high laser power density leads to significant laser-induced thermal heating. However, at low concentration, this laser thermal effect is no longer influenced by the laser intensity. In this paper, we propose a method to directly measure the laser-induced heating temperature and to correct the error caused by this effect on temperature measurement. According to these results, GdVO4: Yb3+/Er3+ upconversion nanoparticles can be applied for temperature sensing even if the laser-induced thermal effect occurs in the system.

Improvement of electrochemical deposition performance and design of Fe–Ni multilayer structure by nanosecond laser

Multilayer (ML) coatings obtained by adjusting the alternating changes in electrical parameters are typically accompanied by a high internal tensile stress. In this study, Fe–Ni ML coatings were electrodeposited by frequent changes in duty cycles between 55 (50 mA/cm2) and 30% (25 mA/cm2). The surface quality, internal structure, mechanical, and corrosion resistance of the electrodeposited ML coatings were evaluated with and without laser irradiation. After the laser was introduced, the surface quality of the ML coating improved, accompanied by fewer surface defects and smaller grain sizes. The Fe content of the electrochemical deposited coating alternated between 40 (25 mA/cm2) and 54 wt% (50 mA/cm2), and that of the coating prepared by laser-assisted electrochemical deposition alternated between 18 (25 mA/cm2) and 42 wt% (50 mA/cm2). This difference is due to the laser thermal and force effects on the abnormal Fe–Ni co-deposited coating. In addition, the residual internal stress changed from tensile to compressive, and the surface microhardness improved. The friction coefficient decreased from 0.34 to 0.27, indicating better wear resistance. In addition, the electrochemical test results show that the ML coating prepared by LECD has better corrosion resistance. Finally, the strengthening mechanism of the laser in the preparation of the Fe–Ni ML coating is summarized. Combined with the abnormal co-deposition reduction characteristics of Fe–Ni, an ML structure with controllable elemental contents (horizontal and vertical) and better quality can be obtained by adjusting the laser parameters without changing the electrochemical parameters.

Laser-enhanced electrodeposition preparation technology of superhydrophobic micro-nano structure coating

The superhydrophobic surface has functions such as anti-wetting, self-cleaning, and anti-icing, which is widely used in aerospace, pipeline transportation, medical equipment and other fields. In this study, a combination of laser and electrodeposition (ECD) is used to prepare a coating with sponge-like micro-nano line structures by using the principle that laser thermal effect can enhance the local electrodeposition rate, and then treated with 1 H,1 H,2 H,2 H-perfluorodecyltriethoxysilane to obtain the function of superhydrophobic. This method achieves the simultaneous preparation of the coating and the micro-nano structures without destroying the substrate, and the micro-nano structures are uniform and controllable. The effects of current density, laser scanning line spacing, laser power density, and laser scanning speed on the line structures and the wettability of the coating were investigated experimentally, and the wear resistance and anti-icing properties were tested. The experiment results show that when the line spacing is 150 µm, the contact angle (CA) can reach 155°, and the sliding angle (SA) is less than 1°, which has good superhydrophobic performance. Moreover, the coefficient of friction (COF) of the prepared superhydrophobic coating is 0.606, and the CA gradually decreases to 147° after rubbing the superhydrophobic surface 20 times with 1000 # sandpaper at a pressure of 10 kPa, and the SA exceeds 10° after rubbing 35 times, showing good wear resistance. In addition, the water drop freezing experiment shows that the freezing time of this superhydrophobic coating is 200 s, which is about 13 times longer than that of the hydrophobic coating (CA: 102°) prepared at a line spacing of 300 µm, therefore, the coating has excellent anti-icing performance.

Investigation on the machinability of nitriding mold steel by applying in-situ laser assisted diamond cutting

Mold steel is a typical material in precision molding for the massive production of optical lenses. It has the outstanding mechanical properties and superior corrosion resistance. However, it is a huge challenge for ultra-precision diamond cutting mold steel due to the active chemical affinity between the diamond tool and steel, which causes the deteriorated surface integrity and catastrophic tool wear. In this research, we adopted a novel hybrid machining technology, which is in-situ laser assisted diamond cutting (In-situ LADC), for ultra-precision machining nitriding mold steel. Pulsed plasma nitriding treatment provides a dense nitrided compounds layer in workpiece surface to suppress the chemical reaction between the iron atom of steel and carbon atom of diamond. Furthermore, the surface nitriding layer is softened by the laser radiating to improve the machinability of workpiece. Experimental results showed that the laser thermal effect obviously decreased the hardness and elastic modulus of nitrided layer, which enhanced the material removing in ductile mode. Compared with the ordinary cutting (OC), the machined surface roughness Ra is decreased from 29 nm to 12 nm. The maximum profile error PV is also decreased from 161 nm to 64 nm. The mechanism of tool wear was changed from the rapidly abrasive wear to mildly adhesive wear, which significantly increased working life by 29 %.

Effect of Laser on Abnormal Reduction Process and Properties Evaluation of Electrodeposited Soft Magnetic Fe-Ni Coating

Electrodeposition (ECD) process of Fe-Ni coating belongs to abnormal co-deposition according to Brenner’s classification, in which Ni is mainly affected by activation, and Fe is mainly affected by diffusion. In this paper, Fe-Ni coating was prepared by laser-assisted electrodeposition (LECD) technology. The regulation of Fe and Ni contents and coating properties is achieved by using the influence of laser thermal and force effects on the abnormal co-deposition process. The results show that the laser positively shifts the reduction potential and increases the current density. At the laser single-pulse energy is 15 μJ and the laser scanning speed 3000 mm s−1, the Fe content of the coating is the lowest, and the Ni content is the highest, which refines the average grain size and reduces surface roughness. Under these parameters, the coating has a small corrosion current density of 5.8 × 10−7 A cm−2 and a large impedance of 4.3 × 104 Ω·cm2, its coercivity increases by 0.7 Oe, and its saturation magnetic induction intensity declines by 4.7 emu g−1. Compared with the electrodeposited Fe-Ni coating, the corrosion resistance is improved, and the soft magnetic properties is slightly weakened.

Therapeutic processes for eradicating cancerous or benign tumours by laser beams using the excitonic approach of peptide groups

The aim of the present study was to develop a protocol for the treatment of cancerous or benign tumours making use of laser rays, also demonstrating that the destruction process remains exclusively confined in the defective organ. Thermal effects of lasers on biological tissue have been elucidated using vibrational excitations approach of peptide groups (PGs). It was proposed a Hamiltonian which integrate excitations induced by laser pulses and it was shown that the system is governed by a nonlinear equation with strong nonlinearity. It was also exactly described what happens in polypeptide chain once the unwanted organ is irradiated by the Neodymium-doped yttrium aluminium garnet, chosen as incident laser. It was shown that, the advent of incident laser beams contributes to a sudden reinforcement of the vibrational excitations of PGs frequencies and amplitudes. It was also demonstrated that the heating process leads to transverse and longitudinal deformation of the polypeptide chain and these sudden changes lead to the denaturation and subsequently to the destruction of the bulky organ. The drawn curves make it possible to estimate the spatial expansion of the denaturation, in order to effectively control the spread of the heat. Laser irradiation leads to a drastic increase in the vibration amplitudes of the PGs and subsequently results in the destruction of the undesirable tissue. An appropriate choice of the laser can make it possible to circumscribe the destruction only in the defective zone and to protect healthy cells.

A study on preparation of ultra-thin localized Au coating by laser-induced electrodeposition

Traditional electrodeposition requires auxiliary technologies such as mask to realize localized deposited layer. In this paper, ultra-thin Au coating can be obtained selectively by laser-induced electrodeposition without mask, which has advantages in dimensional accuracy, brightness, good compactness. The deposition rate, dimensional accuracy, density, roughness, and corrosion resistance were evaluated under different laser single pulse energy (4.5, 5, 5.5, 6, 6.5, 7, 7.5, and 8 μJ). Furthermore, the spatial distribution of the transient temperature field and the change law of the cathode substrate current under laser irradiation were detected to explore the mechanism induced by laser thermal effect. The results show that laser irradiation can increase the cathode limit current density to reach the Au precipitation potential. Besides, the electrodeposition rate increases with the increase of laser single pulse energy. When the laser single pulse energy is 6 µJ, the electrodeposition rate reaches 0.167 mg/min. Meanwhile, the electrodeposition accuracy and surface density are better, and surface roughness (Sa) is 0.98 μm. Moreover, compared with the Au coating product provided by an electroplating enterprise, the coating prepared by laser-induced electrodeposition has better corrosion resistance. When the laser single pulse energy is 6 µJ, self-corrosion potential (φcorr) is −0.3059 V, and self-corrosion current density (jcorr) is 5.066 × 10−5 A/cm2.