Minimal Thermal Effects Research Articles

Pre- and post-surface treatments using electron beam technology for load-related application of thermochemical and PVD hard coatings on soft substrate materials

With their specific layer features and properties, surface treatments such as thermochemical treatment (nitriding, boriding) and hard coating cover a broad field of application in the wear and corrosion protection of steels. Limitations exist, however, when applying these surface treatments to softer materials, such as cast irons and aluminum alloys in terms of both their treatability and load-bearing capacity.This contribution deals with investigations into duplex surface treatments, where a pre- and post-electron beam (EB) surface treatment (e.g., hardening, remelting, alloying etc.) was combined with one of the above-mentioned treatments. Among other characteristics, the thermal EB surface treatments were characterized by high heating and cooling rates that facilitated the generation of a variety of non-equilibrium microstructures, which exhibited increased hardness and had minimal thermal effects on the surrounding base material. Furthermore, the layer thicknesses were one or two orders of magnitude higher than those generated by thermochemical treatment or hard coating.Based on the comprehensive results and using cast irons and Al alloys as examples, the study demonstrates the extent to which duplex treatments can overcome the aforementioned limitations, and how the tribological and/or corrosive load behavior is affected. The property profiles achieved after duplex surface treatment were strongly dependent on the inherent microstructural and chemical processes. These complex processes were influenced by a range of factors, such as the thermal stability of the EB surface layer generated in the first process step, the respective temperature and time period of the secondary process, etc.Hardness measurements, scratch tests, unlubricated pin-on-disc wear tests using different normal loads and potentiodynamic corrosion tests were realized to facilitate characterization of the different load behaviors of the single- and duplex-treated layers.

Formation and homogenisation of Sn[sbnd]Cu interconnects by self-propagated exothermic reactive bonding

We produced SnCu interconnects by self-propagated exothermic reactions using AlNi NanoFoil at ambient conditions, through the instantaneous localised heat across the interfaces between Sn electroplated Cu substrates. This technique presents a great potential for electronics integration with minimal thermal effects to the components. However, the metastable phases resulted from the non-equilibrium interfacial reactions and solidification were inevitable under a highly transient regime due to a drastic heating/cooling (over 107 K/s). In this study, Finite Element Analysis was performed to predict the temperature profiles across bonding interfaces, which were subsequently correlated with the formation and homogenisation of the bonded structures during the bonding and post-bonding ageing process. It has been revealed that, for nano-sized metastable phases, their formation, morphologies and distribution were primarily attributed to the convective mass transportation, liquid-solid inter-diffusion, and directional non-equilibrium solidification of Sn in molten zone of the bonding interfaces. The non-equilibrium phases initially formed in the SnCu interconnects can be homogenised towards the equilibrium status by accelerated ageing. This was achieved through the coalescing and subsequent growth of the original nano-sized metastable phases, as a result of the solid-diffusion of Cu and Ag atoms at intergranular boundary regions of Sn grains, AlNi NanoFoil/Sn. and Cu/Sn interfaces.

A Review of Low-Intensity Pulsed Ultrasound for Therapeutic Applications.

Ultrasound therapy has a long history of novel applications in medicine. Compared to high-intensity ultrasound used for tissue heating, low-intensity ultrasound has drawn increasing attention recently due to its ability to induce therapeutic changes without biologically significant temperature increase. Low-intensity pulsed ultrasound (LIPUS) is a specific type of ultrasound that delivers at a low intensity and outputs in the mode of pulsed waves. It has minimal thermal effects while maintaining the transmission of acoustic energy to the target tissue, which is able to provide noninvasive physical stimulation for therapeutic applications. LIPUS has been demonstrated to accelerate the healing of fresh fracture, nonunion and delayed union in both animal and clinical studies. The effectiveness of LIPUS for the applications of soft-tissue regeneration and inhibiting inflammatory responses has also been investigated experimentally. Additionally, research has shown that LIPUS is a promising modality for neuromodulation. The purpose of this review is to provide an overview of the recent developments of LIPUS for therapeutic applications, based on the papers that report positive effects, and to present the findings on the understanding of its mechanism. Current available LIPUS devices are also briefly described in this paper.

Application of laser heating and its effects on bonding strengths for varied copper wire purity levels

Gold as the medium of interconnection is rapidly being replaced by copper as a means of creating connectivity in integrated circuit packaging. However, the use of copper wire is known to pose many threats in integrated circuit packaging, especially for devices with very thin die structures. The process of wire bonding which involves the formation of free air ball can be risky to the quality of integrated circuit packaging. The impact of hard copper free air ball onto the bonding surfaces may damage the bond pad and the silicon die. These challenges require innovative solutions that are able to be applied to integrated circuit packaging with minimal thermal and mechanical effect on the device. Through recent research, it is apparent that the laser processing technology can provide viable innovative solutions to electronic packaging. This research paper investigates the application of laser heating on copper wire bonding technology and its effects on bonding strength for three copper wire purity types, 99.9% purity (3 N), 99.99% purity (4 N), and 99.999% purity (5 N) copper wires. Wire bonding was performed on bond pads consisting of NiPdAu metallization under 16 different temperature conditions. Results of this study showed that different copper purity levels exhibit different bonding strengths with the application of laser heating. It is shown in this research that significantly higher as-bonded ball shear strengths were obtained when laser heating was applied at all three copper wire purity types. The results of this study can be helpful for integrated circuit packaging with copper wire bonding on thin die structures. Copper wires with lower purity levels are shown as a viable option by further improving the wire bonding quality with the application of laser heating without the need to use excessive bonding temperature, higher bonding force, and excessive ultrasonic energy.Gold as the medium of interconnection is rapidly being replaced by copper as a means of creating connectivity in integrated circuit packaging. However, the use of copper wire is known to pose many threats in integrated circuit packaging, especially for devices with very thin die structures. The process of wire bonding which involves the formation of free air ball can be risky to the quality of integrated circuit packaging. The impact of hard copper free air ball onto the bonding surfaces may damage the bond pad and the silicon die. These challenges require innovative solutions that are able to be applied to integrated circuit packaging with minimal thermal and mechanical effect on the device. Through recent research, it is apparent that the laser processing technology can provide viable innovative solutions to electronic packaging. This research paper investigates the application of laser heating on copper wire bonding technology and its effects on bonding strength for three copper wire purity types, 99.9...

Electron beam welding of copper‐niobium microcomposites for pulsed power applications

AbstractThe main objective of this work is to explore the possibility of applying electron beams to connect copper‐niobium conductors. Electron beam welding of copper–niobium microcomposite wires was investigated. The evaluation of welded joint properties was carried out according to the same methodology applied to contact electrical connections. The major electrical and mechanical properties of welded joints were established. The microscopic examination of the joint cross‐section showed that welded joints of copper‐niobium conductors have minimal thermal effects on the structure of the conductor and on the propagation of welding defects thanks to the welding in a vacuum. According to the non‐destructive radiographic test, the joint structure does not have welding defects. The difference in electrical resistances of the conductor and welded joint was below 20 %. The welded joint can withstand the maximum load, which is equal to 31.25 % of the load‐bearing capacity of microcomposite conductor.

Influence of Stoichiometry on the Thrust and Heat Deposition of On‐Chip Nanothermites

AbstractCurrently, there is very little systematic work quantifying the thrust or heat applied to an electronic circuit or other substrate by a deposited layer of energetic material. A better understanding of the interactions between nanoscale energetic materials and electronic systems, as a function of stoichiometry, is needed. For this purpose, formulations of nAl‐CuO and nAl‐Bi2O3 nanothermites were prepared at different equivalence ratios and selectively deposited onto electronic circuit analogues (silicon wafers) and the amounts of thrust production and heat deposition were measured. Both nanothermite systems produced maximum thrust near stoichiometric ratios, accompanied by a shock wave, with minimal thermal effects due to large gas production, which ejects the hot products of the substrates. Conversely, more fuel‐rich mixtures led to significantly decreased thrust while increasing heat deposition due to the lower gas production, which allowed more heat to diffuse to the substrates. This shows that the energetic material response can be tuned between thrust or heat deposition by just varying the equivalence ratio. The conductive heat transfer within the silicon substrates from the nAl‐CuO system increased more than the nAl‐Bi2O3 system at fuel rich conditions due to its higher heat of combustion.

Clinical applications of low-intensity pulsed ultrasound and its potential role in urology.

Low-intensity pulsed ultrasound (LIPUS) is a form of ultrasound that delivered at a much lower intensity (<3 W/cm2) than traditional ultrasound energy and output in the mode of pulse wave, and it is typically used for therapeutic purpose in rehabilitation medicine. LIPUS has minimal thermal effects due to its low intensity and pulsed output mode, and its non-thermal effects which is normally claimed to induce therapeutic changes in tissues attract most researchers’ attentions. LIPUS have been demonstrated to have a rage of biological effects on tissues, including promoting bone-fracture healing, accelerating soft-tissue regeneration, inhibiting inflammatory responses and so on. Recent studies showed that biological effects of LIPUS in healing morbid body tissues may be mainly associated with the upregulation of cell proliferation through activation of integrin receptors and Rho/ROCK/Src/ERK signaling pathway, and with promoting multilineage differentiation of mesenchyme stem/progenitor cell lines through ROCK-Cot/Tpl2-MEK-ERK signaling pathway. Hopefully, LIPUS may become an effective clinical procedure for the treatment of urological diseases, such as chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS), erectile dysfunction (ED), and stress urinary incontinence (SUI) in the field of urology. It still needs an intense effort for basic-science and clinical investigators to explore the biomedical applications of ultrasound.

Ablation characteristics of quantum square pulse mode dental erbium laser.

Erbium lasers are by now an accepted tool for performing ablative medical procedures, especially when minimal invasiveness is desired. Ideally, a minimally invasive laser cutting procedure should be fast and precise, and with minimal pain and thermal side effects. All these characteristics are significantly influenced by laser pulse duration, albeit not in the same manner. For example, high cutting efficacy and low heat deposition are characteristics of short pulses, while vibrations and ejected debris screening are less pronounced at longer pulse durations. We report on a study of ablation characteristics on dental enamel and cementum, of a chopped-pulse Er:YAG [quantum square pulse (QSP)] mode, which was designed to reduce debris screening during an ablation process. It is shown that in comparison to other studied standard Er:YAG and Er,Cr:YSGG laser pulse duration modes, the QSP mode exhibits the highest ablation drilling efficacy with lowest heat deposition and reduced vibrations, demonstrating that debris screening has a considerable influence on the ablation process. By measuring single-pulse ablation depths, we also show that tissue desiccation during the consecutive delivery of laser pulses leads to a significant reduction of the intrinsic ablation efficacy that cannot be fully restored under clinical settings by rehydrating the tooth using an external water spray.

Multi-criteria optimization in CO2 laser ablation of multimode polymer waveguides

High interconnection density associated with current electronics products poses certain challenges in designing circuit boards. Methods, including laser-assisted microvia drilling and surface mount technologies for example, are being used to minimize the impacts of the problems. However, the bottleneck is significantly pronounced at bit data rates above 10Gbit/s where losses, especially those due to crosstalk, become high. One solution is optical interconnections (OI) based on polymer waveguides. Laser ablation of the optical waveguides is viewed as a very compatible technique with ultraviolet laser sources, such as excimer and UV Nd:YAG lasers, being used due to their photochemical nature and minimal thermal effect when they interact with optical materials. In this paper, the authors demonstrate the application of grey relational analysis to determine the optimized processing parameters concerning fabrication of multimode optical polymer waveguides by using infra-red 10.6µm CO2 laser micromachining to etch acrylate-based photopolymer (Truemode™). CO2 laser micromachining offers a low cost and high speed fabrication route needed for high volume productions as the wavelength of CO2 lasers can couple well with a variety of polymer substrates. Based on the highest grey relational grade, the optimized processing parameters are determined at laser power of 3W and scanning speed of 100mm/s.

Radiofrequency transoral microsurgical procedures in benign and malignant laryngeal and hypopharyngeal lesions (institutional experiences).

Besides cold-steel and laser instruments, the use of radiofrequency (RF) devices in transoral microsurgery is getting increasing popularity mainly due to its minimal thermal effect on the collateral soft tissue. Authors summarize their surgical technique, results, and experience gained with RF applied during laryngeal interventions at the Department of Otorhinolaryngology, Head and Neck Surgery at Medical School, University of Pécs. Transoral microsurgery using radiofrequency was carried out in 23 cases in total between 1 January 2011 and 1 March 2013. Fourteen histopathologically different benign lesions and 9 malignant planocellular carcinomas of the larynx were removed using different Micro-Larynx RF Probes powered by Surgitron Dual 4.0 MHz Frequency RF (Ellman International, Oceanside, NY, USA) device. No major bleeding event occurred during or after the procedures and neither laryngeal oedema nor significant postoperative pain was recorded. Authors also reviewed the international literature in this topic while detailing some of their most interesting cases.

Boiling histotripsy: A noninvasive method for mechanical tissue disintegration

Boiling histotripsy is an experimental noninvasive focused ultrasound therapy that applies shocked ms-length pulses to achieve mechanical disintegration of a targeted tissue. Localized delivery of high-amplitude shocks causes rapid heating, resulting in boiling of the tissue. The interaction of incident shocks with the boiling bubble results in tissue disruption and liquefaction without significant thermal injury. Simulations are utilized to design and characterize therapy sources, predicting focal waveforms, shock amplitudes, and boiling times. Transducers have been developed to generate focal shock amplitudes &amp;gt;70 MPa and achieve rapid boiling at depth in tissue. Therapy systems including ultrasound-guided single-element sources and clinical MRI-guided phased arrays have been successfully used to create ex vivo and in vivo lesions at ultrasound frequencies in the 1–3 MHz range. Histological and biochemical analyses show mechanical disruption of tissue architecture with minimal thermal effect, similar to cavitation-based histotripsy. Atomization as observed with acoustic fountains has been proposed as an underlying mechanism of tissue disintegration. This promising technology is being explored for several applications in tissue ablation, as well as new areas such as tissue engineering and biomarker detection. [Work supported by NIH 2T32DK007779-11A1, R01EB007643-05, 1K01EB015745, and NSBRI through NASA NCC 9-58.]

THERMAL ANALYSIS AND EXPERIMENTS OF LASER–TISSUE INTERACTIONS: A REVIEW

Studying the interaction of ultra-short pulse lasers with biological tissues and the corresponding mathematical modeling of possible thermal damage is of fundamental importance to the understanding of laser-tissue interaction for advancing surgical application of lasers. The objective of this paper is to review the existing techniques for thermal analysis of laser-tissue interaction. Different laser-tissue interaction mechanisms are discussed and the existing techniques for characterization of extent of damage are presented. A novel approach of using a focused laser beam from an ultra-short pulse laser source to ablate the subcutaneous tumors with minimal thermal effects is introduced. The extent of laser-induced damage is studied by determining the spatiotemporal expression patterns of Heat Shock Proteins. Keywords: Thermal ablation, Heat Shock Proteins, tumor removal, short-pulse laser, laser-tissue interaction, plasma mediated ablation, HSP70, HSP47, ablation modeling.

CO2 laser micromachining of optical waveguides for interconnection on circuit boards

The introduction of microvia and surface mount technologies into the manufacturing process for printed circuit boards (PCBs) has significantly improved the interconnection density. However, as the speed of signals for data communication on the board approaches and begins to exceed 10Gb/s, the loss and crosstalk of copper interconnections increase. To resolve these problems, optical interconnections (OI) have been suggested as a viable solution. Literature reports have proved the photochemical nature of excimer laser ablation with its minimal thermal effect, and other ultra-violet lasers are also being investigated for the fabrication of polymer waveguides by laser ablation. In this paper, the authors demonstrate the fabrication of multimode optical polymer waveguides by using infra-red 10.6μm CO2 laser micromachining to etch acrylate-based photopolymer (Truemode™). CO2 lasers offer a low cost and high speed fabrication route as CO2 lasers can be used to cut through various engineering materials including polymers and metals. The paper characterises the relationship between the laser ablation power, the fabrication speed and the resulting effect on the waveguide optical insertion loss for the first time.

Er:YAG LASER APPLICATION IN ORTHODONTIC PRACTICE. A case report

Introduction: Er:YAG lasers generate wave length of 2940 nm which coincides with the absorptions spectrum of water. For these reasons it is possible to work with Er:YAG lasers both on soft and hard tissues with minimal thermal effects. Lasers due to their wide-spectrum of biological action and high therapeutic effectiveness are used long ago in certain specialties like oral surgery and cariesology. In orthodontic lasers are poorly known and are not routine tool despite their beneficial application abilities. Aim: The presented case report discusses alternative surgical approach for laser-assisted uncovering of ectopically impacted canines for orthodontic reasons. Conclusions: Er:YAG laser is a revolutionary technology providing alternatives for orthodontists in solving different problems in their everyday practice. It is effective and comfortable tool to reduce treatment time and to promote excellent clinical results.To patients is offered method of choice with comfort guarantee, less pain sensations and accelerated healing process

A fibre-optic UV system for H 2SO 4 production in aerosol chambers causing minimal thermal effects

A novel fibre-optic UV illumination system for sulphuric acid (H 2SO 4) production has been developed. The illumination system described in this paper provides sufficient ultraviolet light (UV) power while causing practically no thermal effect on the aerosol chamber (temperature variation <0.005 °C at full UV illumination). A similar thermal stability has not been achieved in other comparable experimental set-ups so far. The spectrum provided by the fibre-optic UV system corresponds to the UVB region, illuminates the chamber in a reasonably uniform way and is comparable to the ground level actinic flux. The UV system has been installed for the Cosmics Leaving OUtdoor Droplets (CLOUD) chamber experiments at CERN. Precise, easily-adjustable and reproducible concentrations of H 2SO 4 were generated by adjusting the UV light intensity. This paper gives an overview on the design of this new system as well as insights on its performance and application.

DIAMOND SHAPED OPTICAL FIBER DELIVERY SYSTEM

Optical fibers are generally used with a flat cut end. The adaptation of a coaxial exit of a refrigerated gas near the distal tip of the optical fiber cools the tissue where the laser beam is applied and reduces the injury of thermal effects on biological tissue. We have changed the flat end geometry of the fiber's end to a pyramidal end shape (named: Diamond tip). In this project we have evaluated the new shape of the fiber's end using laboratory tests and in real conditions. We have examined the emission pattern in the air and in water as well as its performance in surgery. With the new shape better results were obtained: higher power density, more utilizations of the same fiber (after sterilization) resulting in economical savings. The diamond tip is characterized by greater mechanical resistance then conical tip delivery systems. The greater resistance of the Diamond tip prevents optical fiber breakage during surgery. The delivered system can be reshaped by a trained hospital physician and reused. Our experience shows that delivery systems intended by the producer to one use only can be converted, by reshaping their tips, to highly performing delivery systems, which can be reused many times. In addition less power was needed, with less tissue penetration. The thermal effect was minimized and higher mechanical resistance was achieved, which allowed reusing the fiber more than six times. The special structure of the faces of the optical fiber diamond tip eased its sliding. The Diamond tip is superior to other fiber end tips by having minimal thermal effects, higher mechanical resistance and by being reused many times.

On radiation-induced fluidization (quasi-melting) of silicate glasses

AbstractThe effect of intensive electron radiation on viscous flow in silicate glasses is analysed and shown that it can result in a many orders of magnitude decrease of viscosity and stepwise decrease of activation energy of flow. Fluidisation or quasi-melting of glasses on intensive electron irradiation is caused by bond breaking via the radiation-chemical reaction ≡Si-O-Si≡ + e− Si-O + Si + (e−)′ which weakens the silicate glass network and leads tofive-fold coordination of oxygens around the silicon. An explicit equation of viscosity wasobtained for irradiated glasses as well as an equation for glass transition temperature. Theassessments of temperature increase by electron radiation show that radiation-inducedfluidisation of glasses can occur at minimal thermal effects. Radiation-induced fluidisation ofglasses can result in nanoscale patterning effects caused by surface tension forces. Changes inthe viscous flow behaviour are also important in conditions of long-term irradiation for glassesused in nuclear installations as well as for nuclear waste glasses.

Enhanced microwave processing of oil-water emulsions confined within ceramic and ceramic/metallic or composite plates

A detailed theoretical analysis has been carried out on enhanced microwave heating of one-dimensional emulsion samples confined within ceramic and ceramic/metallic or composite plates. A preliminary study has been carried out via average power vs emulsion thickness diagram to estimate microwave power absorption within emulsion samples (o/w and w/o) for various plate assemblies. Two maxima in average power or resonances ( R 1 and R 2 modes) have been considered corresponding to specific emulsion thicknesses for efficient processing of samples. It is observed that, microwave power absorption is enhanced for both o/w and w/o emulsions in presence of metallic (single/composite) plates during both R 1 and R 2 modes. However, efficient heating strategies are characterized by ‘large heating rates’ with ‘minimal thermal runaway effects’ within the sample. Therefore, based on a number of case studies for detailed distributions of power and temperature, suitable heating strategies have been recommended for various compositions of o/w and w/o emulsion samples.

Lasers in the Preservation of Cultural Heritage

To date, it has been proven that modern laser technologymay well serve the future of our past, the preservation and revelation of cultural heritage. This field is now coming to an era of maturity both in terms of the level of understanding of the fundamental aspects involved and the practical diagnostics and restoration applications, which have been demonstrated. The workshop on “Lasers in the Preservation of Cultural Heritage,” held in June 27-28, 2006 in St. Petersburg, Russia, was organized in the framework of the Laser Optics Conference, attracting contributions which reflect the state of the art and the potential for future developments. The workshop took place in the premises of the State Heritage Museum and included presentations of fundamentals and test case studies, some of which are described in this special issue of laser chemistry. In particular, laser-based spectroscopic techniques of noninvasive character, such as laser-induced fluorescence (LIF) and raman spectroscopy are now capable of providing in situ and remote analytical information of organic materials. Novel aspects of laser-induced breakdown spectroscopy (LIBS) for the elemental analysis of the original materials or pollutants of artifacts by using ultra-fast lasers (fs-LIBS) were also presented, together with a range of test case applications. Besides the established use of lasers emitting pulses of nanosecond duration for cleaning applications, femtosecond lasers also present interesting new possibilities for demanding conservation cases (e.g., for cleaning of polychromes and sensitive materials like those used in modern paintings). It is the extremely high spatial resolution of the ablation processes and the minimal thermal and photochemical effects which may be achieved by using femtosecond lasers that leads to the success of these applications. Finally, interferometric techniques for the detection and evaluation of defects and the structural status of artifacts appear to come to age. Along these lines, optical coherence tomography (OCT) was reported to be a promising technique for exciting new applications.

Ablation of hard bone tissue with pulsed CO2 lasers

Abstract Results of systematic measurements of the ablation parameters for hard bone tissue by application of different CO 2 lasers with wavelength of 9.6 and 10.6 μm, pulse durations from 40 ns up to 225 μs and diverse focusing conditions are described. Influence of thermal diffusion, absorption in ablation debris and other physical processes on the ablation characteristics and preconditions for effective ablation with minimal thermal side effects are discussed. The main features of the mobile system for laser osteotomy and first results with this system are presented.