Ablation Region Research Articles

Precise modulation of the debonding behaviours of ultra-thin wafers by laser-induced hot stamping effect and thermoelastic stress wave for advanced packaging of chips

Abstract Laser debonding technology has been widely used in advanced chip packaging, such as fan-out integration, 2.5D/3D ICs, and MEMS devices. Typically, laser debonding of bonded pairs (R/R separation) is typically achieved by completely removing the material from the ablation region within the release material layer at high energy densities. However, this R/R separation method often results in a significant amount of release material and carbonized debris remaining on the surface of the device wafer, severely reducing product yields and cleaning efficiency for ultra-thin device wafers. Here, we proposed an interfacial separation strategy based on laser-induced hot stamping effect and thermoelastic stress wave, which enables stress-free separation of wafer bonding pairs at the interface of the release layer and the adhesive layer (R/A separation). By comprehensively analyzing the micro-morphology and material composition of the release material, we elucidated the laser debonding behavior of bonded pairs under different separation modes. Additionally, we calculated the ablation threshold of the release material in the case of wafer bonding and established the processing window for different separation methods. This work offers a fresh perspective on the development and application of laser debonding technology. The proposed R/A interface separation method is versatile, controllable, and highly reliable, and does not leave release materials and carbonized debris on device wafers, demonstrating strong industrial adaptability, which greatly facilitates the application and development of advanced packaging for ultra-thin chips.

Characterization of weakly nonlinear effects in relationship to transducer parameters in focused ultrasound therapy.

Focused ultrasound therapy has been widely used for the treatment of various diseases, employing different types of transducers. The focused ultrasound pressure fields inevitably exhibit nonlinear effects, which can influence the ablation region. However, the nonlinear effects exhibit noticeable variations across different applications. The characterization of the nonlinear pressure fields of ultrasound is important for the effective implementation of focused ultrasound therapy. The traditional angular spectrum method (ASM) was extended to accurately and efficiently simulate the propagation of weakly nonlinear ultrasound in heterogeneous mediums of clinical model. The nonlinear effects were further analyzed in relationship to the transducer parameters that are different in various applications. The pressure fields were simulated using the extended ASM, incorporating calculations for phase aberration in the frequency domain and magnitude compensation in the spatial domain to account for heterogeneous acoustic impedance mismatch. Validation was performed by comparison to k-Wave simulation results using two simplified clinical models, an abdominal soft tissue and a transcranial skull model. The nonlinear effects were then analyzed in relation to the transducer parameters of f-number and effective source area based on the same acoustic output power. The analysis of nonlinear effects was conducted under both homogeneous medium and the clinical models. The simulation results demonstrated a maximum error of 3.93% in the calculated harmonic pressure of the abdominal model, and a maximum error of 4.89% within the transcranial model when comparing the extended ASM simulation results to those obtained from k-Wave simulations. The characterization of the nonlinear effects reveals a strong correlation with the transducer parameters. Specifically, the results indicate that the nonlinear effects intensify with an increase in the effective source area and f-number, under the same acoustic output power of the transducer. However, the clinical model also showed an influence on the nonlinear effects in relation to the f-number. The extended ASM was demonstrated as an accurate and efficient simulation tool, and the simulation results provide a reference for evaluating the intensity of nonlinear effects in various transducer designs.

Factors that Affect Outcome of Ultrasound-Guided Radiofrequency Ablation of Renal Masses.

The purpose of this study was to examine the factors influencing the efficacy and safety of the ultrasound-guided radiofrequency ablation of renal tumors. Between January 2010 and December 2018, 159 patients with renal tumors treated with ultrasound-guided percutaneous radiofrequency ablation at our institution were included in this study. Biopsies were performed for histopathological analysis prior to each ablation. Patients underwent computed tomography follow-ups at 3, 6, and 12 months and were subsequently observed on an annual basis. The primary efficacy rate (i.e., residual tumor), local tumor progression, morbidity and mortality, and possible outcome predictors (age, body mass index, gender, tumor size, tumor location, tumor characteristics, ablation temperature, and reported technical problems) were analyzed using binary logistic regression. At the first follow-up, 3 months after ablation, the primary efficacy rate was 79%. Two percent of the tumors showed local tumor progression during the whole follow-up. Tumor proximity to the collecting system and the final temperature in the ablation region were associated with the occurrence of residual tumor (OR = 2.85, p = 0.019 and OR = 4.23, p = 0.006, respectively). A similar trend was shown for tumors larger than 3 cm (p = 0.066). A short distance to the collecting system and the ablation temperature were significantly related to the occurrence of residual tumors after the radiofrequency ablation of small renal masses. The ultrasound guidance used in our study has a lower primary efficacy rate than the computed tomography guidance used in comparable studies.

Optimizing laser ablation in liquid: The role of ablation region confinement

In the present work, pulsed laser ablation in liquid (PLAL) experiments have been conducted on a disk-shaped copper (Cu) target with a confined ablation region. Nanoparticles (NPs) are synthesized by employing a flat target and targets with valley (channel) widths of 4 and 3 mm to investigate the effect of confinement on properties of NPs. On the flat target, Cu NPs exhibiting bimodal size distribution with average sizes of 8 and 23 nm have been produced. In contrast, monomodal NPs are synthesized in confined valleys, with average sizes decreasing to 4 and 6 nm for 4 and 3 mm valleys, respectively. To understand the influence of confinement on cavitation bubble dynamics, shadowgraphy investigation is employed. The study revealed that the bubble size increases as the valley width decreases. The Gilmore model has been used to estimate the temperature and pressure within the bubble, indicating that both the parameters enhance with confinement. The shadowgraphy results suggest that the reheating of the ablation region due to shockwave interaction with the valley walls is the primary factor influencing the NP properties and cavitation bubble dynamics.

Fast ultrasonic ablation monitoring: An innovative approach using ultrasound RF signals and singular value decomposition

Microwave ablation (MWA) can rapidly lead to tumor cell necrosis by heating local tissues using electromagnetic field energy, making it a highly efficient modality widely utilized in clinical ablation surgeries. However, the lack of timely and accurate intraoperative monitoring methods is a critical issue that urgently needs to be addressed in MWA. This article introduces an innovative approach for real-time monitoring of ablation therapies by the combination of ultrasound radio frequency (RF) signal acquisition and singular value decomposition (SVD), which breaks through the limitations of current monitoring techniques during MWA procedures. Due to the difference in acoustic scattering properties between the gas generated in high-temperature ablated region and the non-ablated tissues, the current new method aimed to apply SVD analyses to ultrasound RF signals scattered from the tissues, through which the range of gas generation could be determined and then the ablation area could be estimated. Eventually, high-precision differentiation between ablated and non-ablated tissues could be achieved, enabling real-time adjustment and improvement of MWA strategies. Validated through ex vivo experiments on pig liver, this technique demonstrated a relative error in monitoring the size of ablation region of approximately 7%, indicating a strong correlation with actual ablation outcomes. The study indicated the proposed method should have great potential to improve the precision and safety of MWA therapy.

Self‐defending mechanism of C/TaC‒SiC composites under 2100°C cyclic ablation environment

AbstractTo achieve the repeatability of aerospace thermal components, C/TaC‒SiC composites were fabricated. Cycle ablation and bending tests were carried out. After 3 × 60 s of ablation beyond 2100°C, the mechanical property retention rate was 80.9%. Interestingly, a reaction similar to “ouroboros ring,” in which the cyclic reactions of “TaC being oxidized to Ta2O5 and Ta2O5 being reduced to TaC,” occurred in the central ablation region of C/TaC‒SiC composites. On the one hand, the continuous generation of TaC could prevent liquid state Ta2O5 from being blown off central ablation region, playing a similar role in “water and soil conservation.” On the other hand, liquid Ta2O5 covered the surface of C/TaC‒SiC composites during ablation process, contributing to block the inward permeation of oxidized gases. In addition, novel “Grotto” structures were detected in the transitional ablation region of C/TaC‒SiC composites. The formation reason of the “Grotto” structure has also been discussed.

Optical transformation characteristic of silicone resin matrix composite coatings under high-energy laser ablation

The easy destruction of most conventional materials by high-energy lasers is a great concern. Anti-laser coatings with ablative heat absorption capabilities are effective in preventing laser damage. However, their extremely low reflectivity implies a high energy absorption rate, which can result in rapid failure. In this study, silicone resin matrix composite coatings were designed and prepared by incorporating ceramic modification components to realize desired optical transformation characteristics. The modification effects on ZrC/SiC, ZrSi2, TiC/SiC, and TiSi2 were specifically studied with a high-energy continuous-wave laser (1080 nm). The results showed that oxidation reactions during laser ablation play a significant role in phase change and optical transformation. The element analysis proved that the composition rapidly changed from carbide and silicide to oxide, leading to the formation of oxide layer with relatively high reflectivity in laser ablation region. In particularly, oxidation and ablation of ZrSi2 facilitated the exposure, gathering, and sintering of ZrO2, which realized an increase in reflection from 6.2 % to 34.9 % during laser ablation (500 W/cm2, 60 s). The optical transformation characteristics were compared with the evolution of diffuse reflection intensity and its corresponding differential curve, which indicates that ZrSi2 exhibited the best performance.

Accurate two-dimensional simulation model and experimental demonstration in ultraviolet picosecond laser scribing ablation.

Laser patterning of copper thin films is essential for the electronics manufacturing industry. In this work, to efficiently and accurately describe the physics process of UV-ps laser ablating copper thin film, a two-temperature model (TTM) consisting of the electron-lattice system and phase explosion mechanism was proposed. The process of electron heating and electron-lattice heat transfer in single pulse ablation were revealed. The average relative errors (ARE) of simulated ablation depth and width were 6.24% and 4.82%, respectively. The process of laser scribing ablation presents the characteristics of repeated ablation in the overlapping ablation region and new ablation in the non-overlapping region. The physics essence of laser scribing is the multiple laser ablations with different energies on the cross-section. The laser scribing cross-section ablation was simulated on 2D TTM. Compared with 3D simulation, though the ARE of ablation depth and width of 2D simulation slightly increased from 15.81% and 5.69% to 18.96% and 8.76%, respectively, the average solving time decreased significantly, from 81960 s to 2140 s. This comprehensive study aims to offer some insights into the characteristics of UV-ps laser ablation of copper thin film.

Multi-pulse femtosecond laser ablation of SiC/SiC composites: Morphological evolution, oxidation mechanisms and component characterization

SiC fiber reinforced SiC matrix (SiosC/SiC) composites processed by femtosecond laser play a pivotal role in thermal protection systems. This paper reveals the ablation characteristics of multi-pulse femtosecond laser ablation of SiC/SiC composites, including morphological evolution, oxidation mechanisms and component characterization by heat accumulation simulation and advanced experimental analysis. The results show that the ablation depth induced by the heat accumulation effect is an exponential function of laser parameters. Morphological analysis and component characterization indicate that two types of ablation regions are formed, normal ablation region is an oxidized zone induced by passive oxidation mechanism, and central ablation region is a non-oxidized zone induced by active oxidation mechanism. The increase of single pulse energy and decrease of scanning speed enhance the driving force of chemical reactions, thus dramatically affecting the gas hole and graphite properties in the normal ablation region. Furthermore, the propagation path of thermal stress-induced cracks is determined which emerges from the center ablation region, extending through gas holes to the normal ablation region.

Improved procedural workflow for catheter ablation of paroxysmal AF with high density mapping system and advanced technology: insights from a multicenter, international study

Abstract Background A high incidence of pulmonary vein (PV) reconnection has been reported in patients with clinical recurrences of AF. Low-voltage activity beyond PVs (e.g. antral activity potentials, RAP) likely represent vulnerabilities in antral lesion sets and they may contribute to ablation failures. Purpose The aim of this study is to validate a structured application of an approach that includes the complete abolition of any antral potential achieving electrical quiescence in antral regions. Methods DELETE AF is a prospective, single-arm, international post-market cohort study. Consecutive patients from 10 centers who were undergoing radiofrequency ablation of paroxysmal AF were included. The Lumipoint map-analysis tool was used sequentially on each PV component. Post-ablation, all patients were monitored with ambulatory event monitoring, starting within 30 days post-ablation to proactively detect and manage any recurrences within the 90-day blanking period, as well as Holter monitoring at 3, 6, 9, and 12 months post-ablation. Additional ECG monitoring were performed as indicated by patient symptoms. The ablation endpoint was PV isolation (PVI). Long-term outcome was the recurrence of AF over follow-up. Data are reported as median [IQ range]. Results One-hundred ten cases of AF ablation were analyzed: 28 (25.5%) females, age=63[56-69] years, 24 (21.8%) patients with a history of AT/AFL. The procedure duration was 58[24-76] min (RF delivery time=18[12-28] min, number of ablation spots=77[44-101]) and the fluoroscopy time was 13[9-19] min. Thirty-eight (34.5%) were repeat ablation: in these patients after initial mapping a total of 114 PV gaps (PVGs) in 29 (76.3%) patients and 69 RAPs in 15 patients (39.5%) were found. After ablation, a total of 5 early PVGs in 2 (1.8%) patients (all in de novo procedures) and a total of 10 RAPs in 7 (6.3%) patients (3 out 38 -7.9%- of repeat ablations vs 4 out 72 -5.6%- of de novo cases, p=0.690) were detected after first remapping. Each residual PVG was first targeted and additional focal ablations were performed at any low-voltage propagation suspected within the region of previous antral ablation. Acute procedural success was 100%, with all PVs successfully isolated and RAPs completely abolished in all study patients except for one that still exhibited a residual low-voltage antral signal after adenosine infusion with no PV conduction. Eighty-six (78.2%) patients had complete follow-up information. During the 90-day blanking period, 8 (9.2%) patients experienced an early recurrence. After the blanking period, over a follow-up of 357[190-380] days, 13 patients (15.1%) suffered an AF recurrence (time to recurrence: 207[144-300] days). No major complications or adverse events occurred. Conclusion A structured ablation workflow for catheter ablation, with consistent high-density mapping and improved diagnostic tools to guide the ablation, proved to be safe and effective in paroxysmal AF.

Enhancement of laser ablation via high-frequency electromagnetic induction heating

The efficiency of pulsed laser ablation has always been the focus point of research. A novel high-frequency electromagnetic induction heating-assisted laser ablation scheme is proposed and investigated to enhance the efficiency and improve the surface processing quality during the nanosecond laser ablation of metal substrates. To reduce laser energy required to reach the ablation threshold of metal, this method utilizes the electromagnetic induction to rapidly elevate substrate temperature, making the metal easier to be ablated. The results show that ablation width increases 16% and ablation depth increases 31% with the assistance of electromagnetic induction heating at a laser fluence of 1.32 J/cm2, which increases 90% of the laser-ablated volume. Meanwhile, the surface ablation quality is significantly improved due to the smaller temperature gradient around the ablation region. This new method has great potentials in the laser micromachining at a higher processing efficiency and better laser-processed surface quality.

The Enhancement of Tumor Ablation Effect by the Combination of High-Frequency and Low-Voltage Bipolar Electroporation Pulses.

Recently, combining short high-voltage IRE monopolar pulses with long low-voltage IRE monopolar pulses was shown to enlarge the ablation region. This finding indicates that combining HFBPs with low-voltage bipolar pulses (LVBPs), which are called composited bipolar pulses (CBPs), may enhance the ablation effect. This study designed a pulse generator by modifying a full-bridge inverter. The cell suspension and 3D tumor mimic experiments (U251 cells) were performed to examine the enhancement of the ablation effect. The generator outputs HFBPs with 0-±2.5 kV and LVBPs with 0-±0.3 kV in one period. The pulse parameters are adjustable by programming on a human-computer interface. The cell suspension experiments showed that CBPs could enhance cytotoxicity, as compared to HFBPs with no cell-killing effect. Even at lower electric energy, the cell viability by CBPs was significantly lower than that of the HFBPs protocol. The ablation experiments on the 3D tumor mimic showed that the CBPs could create a larger connected ablation area. In contrast, the HFBPs protocol with a similar dose generated a nonconnected ablation area. Results indicate that the CBPs protocol can enhance the ablation effect of HFBPs protocol. This proposed generator that uses the CBPs principle may be a useful tool for tumor ablation.

1130 Anatomical Features Predicting Outcome From Stereotactic Laser Amygdalohippocampotomy

INTRODUCTION: Stereotactic laser amygdalohippocampotomy (SLAH) is a novel procedure which is effective and safe for the treatment of temporal lobe epilepsy. Optimal operative ablation location and extent, however, is uncertain, as are the neuroanatomical features guiding successful ablations. METHODS: Patients treated with SLAH for MTS at Emory University between 2011 and 2019 (n = 65) were considered in this retrospective study. Post-procedure T1 MRI scans of patients were used to create manual segmentations of the ablation region of each patient. Ablations were assessed in relation to 1) whether they crossed the coronal plane of the lateral mesencephalic sulcus (LMS), 2) the extent to which the ablation extended posterior to the LMS, and 3) extent of ablation of the uncus. Wilcoxon ranked-sign test was performed for each variable between groups of patients with Engel score 1 versus Engel score 2-4. RESULTS: Distance of ablation past the LMS was not different between Engel class 1 (mean 6.32 ± 4.16 mm), and Engel class 2-4 (7.93 ± 3.75 mm) (p = 0.099). Ratio of ablations extending posterior to the LMS was 0.82 (SD = 0.39) in Engel 1, and 0.90 (SD = 0.30) in Engel 2-4 (p = 0.370). Volume of ablation showed little correlation with outcome, with average ablation of Engel 1 = 6064 ± 2128 mm3, Engel 2-4 = 5828 ± 3031 mm3, and no significant difference with Wilcoxon ranked-sign test (p = 0.239). Ablation of the uncus showed a strong association with better surgical outcome, with ratio of uncus ablation for Engel 1 at 0.71(SD = 0.31), and Engel 2-4 at 0.37 (SD = 0.36); p < 0.001). CONCLUSIONS: Larger ablation alone was not associated with better surgical outcomes. Ablation of the uncus was shown to result in better outcomes. Contrary to current practice, extension of SLAH ablation posterior to the lateral mesencephalic sulcus did not demonstrate improved post-operative outcomes.

The influence of microwave ablation parameters on the positioning of trocar in different cancerous tissues: a numerical study

ABSTRACT The present study analyzed the microwave ablation of cancerous tumors located in six major cancer-prone organs and estimated the significance of input power and treatment time parameters in the apt positioning of the trocar into the tissue during microwave ablation. The present study has considered a three-dimensional two-compartment tumour-embedded tissue model. FEA based COMSOL Multiphysics software with inbuilt bioheat transfer, electromagnetic waves, heat transfer in solids and fluids, and laminar flow physics has been used to obtain the numerical results. Based on the mortality rates caused by cancer, the present study has considered six major organs affected by cancer, viz. lung, breast, stomach/gastric, liver, liver (with colon metastasis), and kidney for MWA analysis. The input power (100 W) and ablation times (4 minutes) with apt and inapt positioning of the trocar have been considered to compare the ablation volume of various cancerous tissues. The present study addresses one of the major problems clinicians face, i.e. the proper placement of the trocar due to poor imaging techniques and human error, resulting in incomplete tumor ablation and increased surgical procedures. The highest values of the ablation region have been observed for the liver, colon metastatic liver and breast cancerous tissues compared with other organs at the same operating conditions.

Habitat-based radiomics analysis for evaluating immediate response in colorectal cancer lung metastases treated by radiofrequency ablation

PurposeTo create radiomics signatures based on habitat to assess the instant response in lung metastases of colorectal cancer (CRC) after radiofrequency ablation (RFA).MethodsBetween August 2016 and June 2019, we retrospectively included 515 lung metastases in 233 CRC patients who received RFA (412 in the training group and 103 in the test group). Multivariable analysis was performed to identify independent risk factors for developing the clinical model. Tumor and ablation regions of interest (ROI) were split into three spatial habitats through K-means clustering and dilated with 5 mm and 10 mm thicknesses. Radiomics signatures of intratumor, peritumor, and habitat were developed using the features extracted from intraoperative CT data. The performance of these signatures was primarily evaluated using the area under the receiver operating characteristics curve (AUC) via the DeLong test, calibration curves through the Hosmer-Lemeshow test, and decision curve analysis.ResultsA total of 412 out of 515 metastases (80%) achieved complete response. Four clinical variables (cancer antigen 19–9, simultaneous systemic treatment, site of lung metastases, and electrode type) were utilized to construct the clinical model. The Habitat signature was combined with the Peri-5 signature, which achieved a higher AUC than the Peri-10 signature in the test set (0.825 vs. 0.816). The Habitat+Peri-5 signature notably surpassed the clinical and intratumor radiomics signatures (AUC: 0.870 in the test set; both, p < 0.05), displaying improved calibration and clinical practicality.ConclusionsThe habitat-based radiomics signature can offer precise predictions and valuable assistance to physicians in developing personalized treatment strategies.

Processing characteristics and ablation mechanism of CMC-SiCf/SiC by rotational thirteen-beam coupling nanosecond laser

Silicon carbide fiber reinforced silicon carbide ceramic matrix composite (CMC SiCf/SiC) has the advantages of high temperature resistance, corrosion resistance, high strength, low density, and oxidation resistance. It is a high-performance advanced material in aerospace, energy and other fields. However, due to its high hardness, brittleness and anisotropy of fiber structure, the research on application-oriented high-quality processing technology has become a hot issue. In this paper, a new process of rotational thirteen-beam coupling nanosecond laser processing of CMC-SiCf/SiC was studied. The rotational thirteen-beam coupling ablation experiments were carried out on CMC-SiCf/SiC workpiece. A laser beam is divided into thirteen beams and rotated around the beam center by using a beam splitter element. The morphology, structure and composition of ablation holes at different speeds were observed and analyzed by laser confocal microscope, scanning electron microscope, and X-ray energy dispersive spectrometer. It is found that the characteristics of rotational beam coupling have a significant effect on the laser ablation morphologies. The results show that the ablation region of CMC-SiCf/SiC is elliptical due to the fast heat transfer of fibers. The energy density distribution of the waist section of the Gaussian like beam after beam coupling is similar to the “W" shape, and the central energy is lower than the surrounding energy, and the ablation holes also show a similar “W" shape. With the increase of rotational speed, the hole depth first decreased and then increased, the hole diameter and roundness first increased and then decreased, and the hole section was “W" shaped. The ablation area can be divided into five parts: the white granular SiO2 solid coverage area, the recast layer, the lower recast layer, the molten layer, and the heat affected zone. The rotational characteristics will make the reaction intensity of the whole ablation area more uniform in the circumferential direction. The formation mechanism and element distribution of each part were explored. The research work in this paper will provide a new technical way for the high-performance application of CMC-SiCf/SiC.

Radiation and heat transport in divergent shock–bubble interactions

Shock–bubble interactions (SBIs) are important across a wide range of physical systems. In inertial confinement fusion, interactions between laser-driven shocks and micro-voids in both ablators and foam targets generate instabilities that are a major obstacle in achieving ignition. Experiments imaging the collapse of such voids at high energy densities (HED) are constrained by spatial and temporal resolution, making simulations a vital tool in understanding these systems. In this study, we benchmark several radiation and thermal transport models in the xRAGE hydrodynamic code against experimental images of a collapsing mesoscale void during the passage of a 300 GPa shock. We also quantitatively examine the role of transport physics in the evolution of the SBI. This allows us to understand the dynamics of the interaction at timescales shorter than experimental imaging framerates. We find that all radiation models examined reproduce empirical shock velocities within experimental error. Radiation transport is found to reduce shock pressures by providing an additional energy pathway in the ablation region, but this effect is small (∼1% of total shock pressure). Employing a flux-limited Spitzer model for heat conduction, we find that flux limiters between 0.03 and 0.10 produce agreement with experimental velocities, suggesting that the system is well-within the Spitzer regime. Higher heat conduction is found to lower temperatures in the ablated plasma and to prevent secondary shocks at the ablation front, resulting in weaker primary shocks. Finally, we confirm that the SBI-driven instabilities observed in the HED regime are baroclinically driven, as in the low energy case.

Arcing Stabilization Effect and Ablation Characteristics for C–Cu Electrodes at Low Air Pressure

Arc ablation is a widespread problem in electrical contact systems. The fault of the system caused by arc ablation significantly restricts its lifespan. Facing the development goal of electrified aircraft and low vacuum high-speed railways, the problem of arc ablation at low air pressure cannot be ignored. In this paper, an experimental platform for arcing and ablation at low air pressure is built. The influence of low air pressure on the characteristics of arc ablation is explored. The results show that the stability of the arc column at low air pressure varies significantly. Under the condition of different air pressures, the traces and morphology in the ablation region of the electrode differ significantly. These are caused by Rayleigh-Taylor instability between the arc and air, and by the motion of the arc root which is driven by the arc column. Importantly, the low-pressure stabilization effect for the arc is found. The corresponding relationship between electrode ablation traces, surface morphology, and air pressure is revealed. The action mechanism of air pressure on the arcing process and ablation characteristics of the electrode are clarified. This research provides theoretical support for restraining arc ablation and prolonging the lifespan of the electrical contact system.

Nonlinear imaging-based bubble cloud size estimates compared with histotripsy treatment zone: An in vitro study

Volterra filtering combined with subharmonic imaging was previously reported to enhance the visualization of the histotripsy bubble cloud. In this study, we compared the bubble cloud size obtained by imaging to the histotripsy ablation region using receiver operating characteristic (ROC) analysis. Histotripsy was performed in a red blood cell (RBC)-doped agarose phantom using a 1 MHz transducer. Ultrasound imaging data was acquired using a C5-2V probe and chirp-coded excitation (bandwidth: 2–5 MHz). These ultrasound acquisitions were then processed by subharmonic (SH) matched filtering alone, SH with quadratic Volterra filtering, and SH with cubic Volterra filtering. The therapy pulse and imaging sequence were interleaved (N = 100 frames), and a video camera was used to visualize the damaged region. A mean bubble cloud image was generated across all treatment sequences and co-registered with the camera image. A ROC curve was formed using binary classification of the mean bubble cloud versus the ablation zone, and the area under the ROC curve was determined. Filtering by quadratic and cubic Volterra filters reduced artifacts significantly [over 20 and 30 dB contrast-to-tissue enhancement (p &amp;lt; 0.01), respectively], along with achieving a high area under the ROC curve (0.97). These findings highlight the potential of Volterra filtering for histotripsy guidance.

A novel strategy for preparation of ZrB2–SiC self-transpiration cooling coating by dilution effect of high speed laser cladding

An ablation resistant coating with self-transpiration cooling effect was prepared on the surface of aluminum alloy by dilution effect of high speed laser cladding. The coatings mainly contain ablation resistant phases ZrB2 and SiC, and low-melting phases Al and Al3.21Si0.47. The ablation property of coatings was investigated at different heat fluxes (35.39, 70.77, 106.16, 141.54) MW⸱m−2. The mass ablation rate increased gradually, and the morphology of ablation region changed significantly with the increased heat flux. The self-transpiration cooling effect of coatings was studied by phase, morphology, and element distribution of ablation region. The self-transpiration cooling effect weakened the oxidation behavior of ZrB2 and SiC at heat fluxes of 35.39 and 70.77 MW⸱m−2 and protected the coating from being exhausted when the heat fluxes were 106.16 and 141.54 MW⸱m−2.