Minimal Thermal Effects Research Articles

Optimizing Flexible Microelectrode Designs for Enhanced Efficacy in Electrical Stimulation Therapy.

To investigate the impact of electrode structure on Electrical Stimulation Therapy (EST) for chronic wound healing, this study designed three variants of flexible microelectrodes (FMs) with Ag-Cu coverings (ACCs), each exhibiting distinct geometrical configurations: hexagonal, cross-shaped, and serpentine. These were integrated with PPY/PDA/PANI (3/6) (full name: polypyrrole/polydopamine/polyaniline 3/6). Hydrogel dressing comprehensive animal studies, coupled with detailed electrical and mechanical modeling and simulations, were conducted to assess their performance. Results indicated that the serpentine-shaped FM outperformed its counterparts in terms of flexibility and safety, exhibiting minimal thermal effects and a reduced risk of burns. Notably, FMs with metal coverings under 3% demonstrated promising potential for optoelectronic self-powering capabilities. Additionally, simulation data highlighted the significant influence of hydrogel non-uniformity on the distribution of electrical properties across the skin surface, providing critical insights for optimizing EST protocols when employing hydrogel dressings.

In Vitro Assay Development to Study Pulse Field Ablation Outcome Using Solanum Tuberosum.

Exposing cells to intense and brief electric field pulses can modulate cell permeability, a phenomenon termed electroporation. When applied in medical treatments of diseases like cancer and cardiac arrhythmias, depending on level of cellular destruction, it is also referred to as irreversible electroporation (IRE) or Pulsed Field Ablation (PFA). For ablation device testing, several pulse parameters need to be characterized in a comprehensive manner to assess lesion boundary and efficacy. Overly aggressive voltages and application numbers increase animal burden. The potato tuber is a widely used initial model for the early testing of electroporation. The aim of this study is to characterize and refine bench testing for the ablation outcomes of PFA in this simplistic vegetal model. For in vitro assays, several pulse parameters like voltage, duration, and frequency were modulated to study effects not only on 2D ablation area but also 3D depth and volume. As PFA is a relatively new technology with minimal thermal effects, we also measured temperature changes before, during, and after ablation. Data from experiments were supplemented with in silico modeling to examine E-field distribution. We have estimated the irreversible electroporation threshold in Solanum Tuberosum to be at 240 V/cm. This bench testing platform can screen several pulse recipes at early stages of PFA device development in a rapid and high-throughput manner before proceeding to laborious trials for IRE medical devices.

VARIPULSE: A step-by-step guide to pulmonary vein isolation.

The VARIPULSE™ variable-loop circular catheter (VLCC) is a bidirectional, multielectrode catheter that can perform electrophysiological mapping and deliver pulsed field energy through the TRUPULSE™ Generator for the treatment of atrial fibrillation. This ablation system, including the CARTO 3™ three-dimensional electroanatomical mapping system, represents a fully integrated system. Pulsed field ablation (PFA) is a novel, primarily cardiac tissue-selective ablation technology with a minimal thermal effect, potentially eliminating the collateral tissue damage associated with radiofrequency ablation or cryoablation. Integration of a mapping system may lead to shorter fluoroscopy times and improve the usability of the system, allowing tracking of energy density and placement to confirm no areas around the vein are left untreated. This step-by-step review covers patient selection, mapping, the step-by-step ablation workflow, details on catheter repositioning and ensuring contact, considerations for ablation of specific anatomical variations, and discussion of ablation without fluoroscopy based on our initial clinical experience. The VLCC is part of the fully integrated PFA system designed for pulmonary vein isolation, using mapping to guide catheter placement and lesion set creation. The current workflow, which is based on our initial clinical experience, may be further refined as the PFA system is used in real-world settings.

Femtosecond laser precision machining of carbon film based on aramid paper substrate

Carbon film has many applications in flexible electronic devices (FED) due to its low cost and high conductivity. However, it is difficult to remove carbon film from the substrate without damaging it. This research explores the use of femtosecond laser, which has minimal thermal effect and non-contact processing, for carbon film ablation. The main objectives are to determine the ablation threshold of carbon film and aramid paper, to optimize the laser ablation parameters and scanning path, and to analyze the ablation mechanism and quality. The results show that the optimal laser fluence is between 0.22 J/cm2 and 1.45 J/cm2, and the optimal scanning method is grid scanning method. The laser ablation achieves a removal depth of 9.4 μm and a minimum Sa of 3.0 μm. Raman spectroscopy confirms the complete removal of carbon film and the transformation of graphite to amorphous carbon. The ablation process is mainly governed by combustion and evaporation. A resistance strain gauge is fabricated using laser ablation to demonstrate its potential in carbon film FED manufacturing.

Knittable Electrochemical Yarn Muscle for Morphing Textiles.

Morphing textiles, crafted using electrochemical artificial muscle yarns, boast features such as adaptive structural flexibility, programmable control, low operating voltage, and minimal thermal effect. However, the progression of these textiles is still impeded by the challenges in the continuous production of these yarn muscles and the necessity for proper structure designs that bypass operation in extensive electrolyte environments. Herein, a meters-long sheath-core structured carbon nanotube (CNT)/nylon composite yarn muscle is continuously prepared. The nylon core not only reduces the consumption of CNTs but also amplifies the surface area for interaction between the CNT yarn and the electrolyte, leading to an enhanced effective actuation volume. When driven electrochemically, the CNT@nylon yarn muscle demonstrates a maximum contractile stroke of 26.4%, a maximum contractile rate of 15.8% s-1, and a maximum power density of 0.37 W g-1, surpassing pure CNT yarn muscles by 1.59, 1.82, and 5.5 times, respectively. By knitting the electrochemical CNT@nylon artificial muscle yarns into a soft fabric that serves as both a soft scaffold and an electrolyte container, we achieved a morphing textile is achieved. This textile can perform programmable multiple motion modes in air such as contraction and sectional bending.

Laser punching of soft magnetic Fe-based amorphous ribbons

Soft-magnetic Fe-based amorphous materials are indispensable in electronic components. However, traditional processing methods (mechanical punching or wire cutting) degrade the amorphous structure, introduce stress, and are inefficient. To overcome these limitations, we introduce a precision processing technique for the Fe-based amorphous ribbons, namely laser punching. We compare two laser types: the picosecond pulse ultraviolet (PS-UV) laser, representing “cold” lasers, and the continuous-wave infrared (CW-IR) laser, epitomizing “hot” lasers. Our results demonstrate that the PS-UV laser can produce intricate geometries with minimal thermal or stress-induced effects. In contrast, the CW-IR laser induces nano-crystallization and crinkling due to heavy thermal effect. As an example, we successfully craft an amorphous motor stator using the PS-UV laser-processed ribbons, which exhibits considerably reduced iron losses compared to that fabricated with CW-IR laser. The reduction in iron loss and enhanced efficiency underscores the potential of PS-UV laser punching as a promising method for manufacturing amorphous motors.

Precise patterning of carbon films on polyethylene terephthalate polymer substrates using femtosecond lasers

A carbon film on a polyethylene terephthalate (PET) substrate is a novel type of flexible laminated material with unique mechanical and electrical properties, making it suitable for the fabrication of various flexible electronic components. However, due to its micron-level thickness, conventional mechanical processing methods are incapable of precisely removing the carbon film without damaging the substrate. Femtosecond laser processing is an advanced technique for achieving precise etching of thin-film materials due to its non-contact, high-precision, and minimal thermal effects. Therefore, we use femtosecond lasers to achieve precision etching of carbon resistive films on PET substrates to minimize substrate damage. In this study, a series of orthogonal and single-factor experiments were conducted to optimize the laser processing parameters. Various measurement and characterization methods, including X-ray photoelectron spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, Raman spectroscopy, ultraviolet–visible spectroscopy, and confocal microscopy, were employed to analyze the removal of the carbon layer, changes in light transmittance, surface quality, and chemical composition of the processed substrate. Furthermore, the mechanisms of carbon film removal and PET substrate damage are explained.

Laser-assisted synthesis of two-dimensional transition metal dichalcogenides: a mini review.

The atomically thin two-dimensional (2D) transition metal dichalcogenides (TMDCs) have attracted the researcher's interest in the field of flexible electronics due to their high mobility, tunable bandgaps, and mechanical flexibility. As an emerging technique, laser-assisted direct writing has been used for the synthesis of TMDCs due to its extremely high preparation accuracy, rich light-matter interaction mechanism, dynamic properties, fast preparation speed, and minimal thermal effects. Currently, this technology has been focused on the synthesis of 2D graphene, while there are few literatures that summarize the progress in direct laser writing technology in the synthesis of 2D TMDCs. Therefore, in this mini-review, the synthetic strategies of applying laser to the fabrication of 2D TMDCs have been briefly summarized and discussed, which are divided into top-down and bottom-up methods. The detailed fabrication steps, main characteristics, and mechanism of both methods are discussed. Finally, prospects and further opportunities in the booming field of laser-assisted synthesis of 2D TMDCs are addressed.

Design and Fabrication of a Flexible Opto-Electric Biointerface for Multimodal Optical Fluorescence and Electrical Recording

Optical fluorescence and electrical monitoring of cell activity are two powerful approaches to study organ functions. Simultaneous recording of optical and electrical data types will provide complementary information from and take advantage of each approach. However, devices that can concurrently record optical signals from the same cell population underneath the microelectrodes have not been widely explored and remain a grand technical challenge. This work presents an innovative flexible opto-electric device that monolithically integrates transparent gold nanogrid microelectrodes directly above microscale light-emitting diodes, photodetectors, and optical filters to achieve co-localized crosstalk-free optical fluorescence and electrical recording. The optimized gold nanogrid microelectrodes show an excellent optical transparency (>81%) and a low normalized 1 kHz electrochemical impedance (6.3 Ω cm2). The optical recording subsystem offers high wavelength selectivity (>1,300) and linearity (R2 > 0.99) for exciting and capturing green fluorescence from various fluorescent reporters in measurement ranges relevant for in vivo applications with minimal thermal effects. The opto-electric device exhibits remarkable durability under soaking for 40 days and repetitive mechanical bending for 5000 cycles. The work may provide a versatile approach for constructing mechanically compliant biointerfaces containing crosstalk-free optical and electrical modalities with widespread application potentials in basic and clinical research.

Femtosecond Laser-Induced Nano-Joining of Volatile Tellurium Nanotube Memristor.

Nanowire/nanotube memristor devices provide great potential for random-access high-density resistance storage. However, fabricating high-quality and stable memristors is still challenging. This paper reports multileveled resistance states of tellurium (Te) nanotube based on the clean-room free femtosecond laser nano-joining method. The temperature for the entire fabrication process was maintained below 190 °C. A femtosecond laser joining technique was used to form nanowire memristor units with enhanced properties. Femtosecond (fs) laser-irradiated silver-tellurium nanotube-silver structures resulted in plasmonic-enhanced optical joining with minimal local thermal effects. This produced a junction between the Te nanotube and the silver film substrate with enhanced electrical contacts. Noticeable changes in memristor behavior were observed after fs laser irradiation. Capacitor-coupled multilevel memristor behavior was observed. Compared to previous metal oxide nanowire-based memristors, the reported Te nanotube memristor system displayed a nearly two-order stronger current response. The research displays that the multileveled resistance state is rewritable with a negative bias.

Feasibility of a No-Implant Approach to Interatrial Shunts: Preclinical and Early Clinical Studies

BackgroundHeart failure with preserved ejection fraction represents a major unmet clinical need with limited treatment options. Recent device therapies under investigation have focused on decompression of the left atrium through an implantable interatrial shunt. Although these devices have shown favorable safety and efficacy signals, an implant is required to maintain shunt patency, which may increase the patient risk profile and complicate subsequent interventions requiring transseptal access. MethodsThe Alleviant System is a no-implant approach to creating an interatrial shunt using radiofrequency energy to securely capture, excise, and extract a precise disk of tissue from the interatrial septum. Acute preclinical studies in healthy swine (n = 5) demonstrated the feasibility of the Alleviant System to repeatably create a 7 mm interatrial orifice with minimal collateral thermal effect and minimal platelet and fibrin deposition observed histologically. ResultsChronic animal studies (n = 9) were carried out to 30- and 60-day time points and exhibited sustained shunt patency with histology demonstrating completely healed margins, endothelialization, and no trauma to adjacent atrial tissue. Preliminary clinical safety and feasibility were validated in a first-in-human study in patients with heart failure with preserved ejection fraction (n = 15). All patients demonstrated shunt patency by transesophageal echocardiographic imaging at 1, 3, and 6 months, as well as cardiac computed tomography imaging at 6-month follow-up timepoints. ConclusionsCombined, these data support the safety and feasibility of a novel no-implant approach to creating an interatrial shunt using the Alleviant System. Continued follow-up and subsequent clinical studies are currently ongoing.

Ultrafast pulsed laser stealth dicing of 4H-SiC wafer: Structure evolution and defect generation

Ultrafast pulsed laser for wafer processing has been promising in the semiconductor industry due to its high precision and low thermal effect. The microstructure and defect during the stealth dicing process is critical to controlling the desired quality of the wafer. The structural evolution and defect formation mechanisms during stealth dicing of 4H-SiC with femtosecond and picosecond lasers were investigated. In order to understand the ultrafast pulsed laser interaction with 4H-SiC wafer, we studied the laser intensity dependence of the nonlinear refractive index, the propagation of laser beam focusing in 4H-SiC, the laser absorption, electron concentration evolution and energy deposition. The effect of two significant processing factors was discussed, including laser fluence and laser scribing times. The propagation paths and energy deposition of femtosecond and picosecond lasers in the internal processing of 4H-SiC were calculated by finite element method. The evolution of electrons temperature, lattice temperature and free electron concentration in the material during laser processing was analyzed. Femtosecond laser stealth dicing had higher processing accuracy due to minimal thermal effects. The defect induced by femtosecond laser was dominated by nanovoids and micro-cracks. The defect structure was affected by laser processing parameters such as scanning passes and laser power density. Multi-focusing of ultrafast pulsed lasers in transparent materials was generally considered to be a dynamic balance of nonlinear self-focusing and plasma defocusing. Picosecond laser processing resulted a higher processing efficiency under the same laser energy density comparing with femtosecond laser processing. However, defects during picosecond laser dicing were dominated by thermal ablation, which impaired the processing accuracy.

Optically Controlled TiO2-Embedded Supercapacitors: The Effects of Colloidal Size, Light Wavelength, and Intensity on the Cells' Performance.

Optically controlled supercapacitors (S-C) could be of interest to the sensor community, as well as set the stage for novel optoelectronic charging devices. Here, structures constructed of two parallel transparent current collectors (indium-tin-oxide, ITO films on glass substrates) were considered. Active-carbon (A-C) films were used as electrodes. Two sets of electrodes were used: as-is electrodes that were used as the reference and electrodes that were embedded with submicron- or micron-sized titanium oxide (TiO2) colloids. While immersed in a 1 M Na2SO4, the electrodes exhibited minimal thermal effects (<3 °C) throughout the course of experiments). The optically induced capacitance increase for TiO2-embedded S-C was large of the order of 30%, whereas S-C without the TiO2 colloids exhibited minimal optically related effects (<3%). Spectrally, the blue spectral band had a relatively larger impact on the light-induced effects. A lingering polarization effect that increased the cell capacitance in the dark after prolonged light exposure is noted; that effect occurred without an indication of a chemical reaction.

A multi-criteria decision analysis of implanted biomedical device antenna: electro-thermal simulation, design, and data analysis

In this article, three elemental (dipole, loop, and meander) designs of an implanted biomedical device (IBD) antenna are studied to provide an enhanced understanding of fundamental (material and geometry) factors which would contribute to the regulation of a steady vital sign, with minimal effect on the surrounding tissue during monitoring and treatment. Dipole and Loop antennas are known to offer similar advantages in that they are both balanced antennas, while the Meander antenna is likely to offer better radiation resistance. The investigation was carried out through the design of experiments and finite element modeling of the temperature field due to the AC level applied (10 or 100mA), under the geometry of each given antenna type and three material options (Titanium, Cobalt Chromium, and Macor). Finally, a multi-criteria decision-making process is applied to select the optimal design under maximum field temperature, thermal conductivity, electrical conductivity, density, and specific heat attributes. The findings suggested that the Meander design made of Titanium would allow for a maximized overall performance with minimal thermal and radiation effects.

Low-Intensity Pulsed Ultrasound Stimulation for Bone Fractures Healing: A Review.

Low‐intensity pulsed ultrasound (LIPUS) is a developing technology, which has been proven to improve fracture healing process with minimal thermal effects. This noninvasive treatment accelerates bone formation through various molecular, biological, and biomechanical interactions with tissues and cells. Although LIPUS treatment has shown beneficial effects on different bone fracture locations, only very few studies have examined its effects on deeper bones. This study provides an overview on therapeutic ultrasound for fractured bones, possible mechanisms of action, clinical evidences, current limitations, and its future prospects.

Er:YAG laser promotes proliferation and wound healing capacity of human periodontal ligament fibroblasts through Galectin-7 induction

Among various dental lasers, the erbium-doped yttrium-aluminum-garnet (Er:YAG) laser has great potential for periodontal treatment including soft and hard tissue ablation with minimal thermal side effects under suitable energy densities and it has multiple effects on tissues for wound-healing benefits. In the present study, we sought to reveal the molecular mechanism underlying the impact of Er:YAG laser on PDL fibroblasts. Cells were irradiated by a Er:YAG laser with various energy densities (3.6-6.3J/cm2). MTT assay was used for cell proliferation, and the transwell system was employed for migration and invasion abilities. The wound healing capacity was evaluated by a scratch assay. After confirming these effects, qRT-PCR and western blotting analysis was applied to identify the differentially galectin-7 expression in the irradiated cells. Knockdown experiments were conducted to reveal the functional role of galectin-7 in the modulation of Er:YAG laser-mediated effects. 4.2J/cm2 was the lowest energy density to induce the optimal cell proliferation, migration and invasion abilities. In the group of upregulated genes, galectin-7 was selected for further examination and its elevation after Er:YAG laser treatment was validated by RT-PCR and Western blot. We demonstrated that silence of galectin-7 abrogated the effects of Er:YAG laser on cell proliferation, migration ad invasion, suggesting the Er:YAG laser promoted these effects through induction of galectin-7. These findings indicated that Er:YAG laser may accelerate the regeneration process in periodontal tissues through enhancement of their proliferative and mobile activities. Additionally, the significance of galectin-7 in the Er:YAG laser-elicited benefits was demonstrated.

Low-Temperature Bonding of Cu Through Self-Propagating Reaction Under Various Temperatures and Pressures

Abstract Low temperature soldering has been realized to create a strong metallurgical interconnection between Cu using the self-propagating exothermic reaction by Al–Ni NanoFoil. This technique presents a great potential for electronics integration with a significantly reduced processing temperature (at least 150 °C lower than traditional techniques) and minimal thermal effects to the components. In this study, finite element analysis was performed to predict the temperature profiles across bonding interfaces, which were subsequently correlated with the formation and quality of the bonded structures. It has been revealed that, for nonequilibrium nanosized phases and defects, their formation and distribution were primarily attributed to the solid–liquid interdiffusion and rapid solidification, under the highly transient regime due to a drastic heating/cooling (105–107 °C/s). The preheating and pressure applied to the bonding structure were clearly beneficial to improve the quality of bonding. This was achieved by the thinned solder thickness and the correspondingly improved temperature profiles that enable a sufficient wetting, filling, and interfacial reactions. Through the comparative analysis of the numerical predictions and the experimental results, the solder layers must completely melt across their thickness and have a total heat over 30 K ms on the Cu to ensure robust interconnections with a shear strength of approximately 37 ± 3 MPa and dense continuous bonding interfaces.

Application of low intensity pulsed ultrasound in treating urinary system diseases

Low-intensity pulsed ultrasound (LIPUS) is a form of ultrasound that delivered at a much lower intensity (<3 W/cm2) than traditional ultrasound and output in the mode of pulse wave, it is typically used for therapeutic purpose in rehabilitation medicine. It 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 effect in tissues attracting much attentions. LIPUS have been demonstrated to have a rage of biological effects on tissues, including accelerating soft-tissue regeneration, promoting bone-fracture healing, inhibiting inflammatory responses, etc. 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). It still needs an intense effort for basic and clinical investigators to explore the biomedical applications of microenergy medicine. Key words: Urologic diseases; Ultrasonic therapy; Review

Thermal Assessment of Ex Vivo Laser Ablation of Cortical Bone.

As a potential osteotomy tool, laser ablation is expected to provide rapid machining of bone, while generating minimal thermal damage (carbonization) and physical attributes within the machined region conducive to healing. As these characteristics vary with laser parameters and modes of laser operation, the clinical trials and in vivo studies render it difficult to explore these aspects for optimization of the laser machining parameters. In light of this, the current work explores various thermal and microstructural aspects of laser-ablated cortical bone in ex vivo study to understand the fundamentals of laser-bone interaction using computational modeling. The study employs the Yb-fiber Nd:YAG laser (λ = 1064 nm) in the continuous wave mode to machine the femur section of bovine bone by a three-dimensional machining approach. The examination involved thermal analysis using differential scanning calorimetry and thermogravimetry, phase analysis using X-ray diffractometry, qualitative analysis using X-ray photoelectron spectroscopy, and microstructural and semiquantitative analysis using scanning electron microscopy equipped with energy-dispersive spectrometry. The mechanism of efficient bone ablation using the Nd:YAG laser was evaluated using the computational thermokinetics outcome. The use of high laser fluence (10.61 J/mm2) was observed to be efficient to reduce the residual amorphous carbon in the heat-affected zone while achieving removal of the desired volume of the bone material at a rapid rate. Minimal thermal effects were predicted through computational simulation and were validated with the experimental outcome. In addition, this work reveals the in situ formation of a scaffold-like structure in the laser-machined region which can be conducive during healing.

Formation and homogenization of Si interconnects by non-equilibrium self-propagating exothermic reaction

Si chips have been interconnected by the self-propagating exothermic reactions using Al–Ni NanoFoil and Au80Sn20 solder layers. The instantaneous localized heat across the entire solder presents great potential for the integration of MEMS and optoelectronic components requiring minimal thermal effects. However, the extremely rapid heating and cooling (105−7 °C/s) in the reaction can cause non-equilibrium interfacial reactions and metastable solidification in the transient bonding region. Segregations and metastable phases different from equilibrium ones are inevitably formed in the Si interconnects. In this study, numerical predictions on the temperature profile of the bonding process and the microstructural characterizations by in-situ TEM/SEM were carried out to reveal the formation and homogenization of the reactive bonded structures. The convective mass transportation, directional solidification and inverse segregation due to the great perpendicular temperature gradient in the mushy reacting zone are confirmed to cause the formation of nano-sized metastable phases. Significant segregation of high-temperature phases (Au-enriched phases) was observed, likely due to the convective flow and the inverse segregation induced by volume contraction. These non-equilibrium phases can be homogenized towards the equilibrium status in subsequently accelerated aging, which was supported by the evident inter-diffusion, intermixing and subsequent growth.