Liquid Environment Research Articles

Soliton solutions of nonlinear stochastic Fitz-Hugh Nagumo equation

This study deals with the stochastic Fitz-Hugh Nagumo (FHN) equation and its multiple soliton solutions. The underlying model has numerous applications in neuroscience that express the pulse behavior of neurons. In general, different kinds of noise affect neurons, e.g., oscillations in the opening and closing of ion stations within cell membranes and the fluctuations of the different conductivities in the system. This fluctuation creates a sequence of stochastic excitation. Various applications are branching Brownian motion process, flame propagation, nuclear reactor theory, autocatalytic chemical reaction, mobility in neurons, population growth in the open environment, and liquid environment. So, need of the hour to consider the FHN equation under the impact of noise. The ϕ6\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\phi ^6$$\\end{document}-model expansion method is used to extract the analytical solutions that give a dynamic attitude of the transmission for the nerve impulses of a nervous system. The different constraint conditions for the existence of these solutions are also discussed. The solutions of this model are represented in hyperbolic, trigonometric, and rational forms. The 2 and 3-dimensional behavior of these solutions are depicted by choosing the different values of parameters. The impact of noise on the physical system is analyzed and its real-world applications are discussed. The spikes in the solutions are controlled through the Borel function. These important results will open a new horizon of research for the young researchers.

Unveiling the roles of initial phase constituents and phase metastability in hydrogen embrittlement of TRIP‐assisted VCrCoFeNi medium‐entropy alloys

Medium-entropy alloys (MEAs) that exhibit transformation-induced plasticity (TRIP) from face-centered cubic (FCC) to body-centered cubic (BCC) are considered promising for liquid hydrogen environments due to their remarkable cryogenic strength. Nonetheless, studies on hydrogen embrittlement (HE) in BCC-TRIP MEAs have not been conducted, although the TRIP effect and consequent BCC martensite usually deteriorate HE susceptibility. In these alloys, initial as-quenched martensite alters hydrogen diffusion and trap behavior, and deformation-induced martensitic transformation (DIMT) provides preferred crack propagation sites, which critically affects HE susceptibility. Therefore, this study aims to investigate the HE behavior of BCC-TRIP MEAs by designing four V10Cr10Co30Fe50–xNix (x = 0, 1, 2, and 3 at%) MEAs, adjusting both the initial phase constituent and phase metastability. A decreased Ni content leads to a reduced fraction and mechanical stability of FCC, which in turn increases HE susceptibility, as determined through electrochemical hydrogen pre-charging and slow-strain rate tests The permeation test and thermal desorption analysis reveal that the hydrogen diffusivity and content are affected by initial BCC fraction, interconnectivity of BCC, and refined FCC. As these initial phase constituents differ between the alloys with FCC- and BCC- dominant initial phase, microstructural factors affecting HE are unveiled discretely among these alloy groups by correlation of hydrogen-induced crack behavior with hydrogen diffusion and trap behavior. In alloys with an FCC-dominant initial phase, the initial BCC fraction and DIMT initiation rate emerge as critical factors, rather than the extent of DIMT. For BCC-dominant alloys, the primary contributor is an increase in the initial BCC fraction, rather than the extent or rate of DIMT. The unraveled roles of microstructural factors provide insights into designing HE-resistant BCC-TRIP MEAs.

Optical, Structural, and Morphological Characterization of Titanium Oxide (TiO2) Nanoparticles from Laser Ablation in Deionized Water

In this research, we focus on the synthesis of titanium oxide (TiO2) nanoparticles using the Nd:Utilization of YAG laser pulse ablation technique in liquid environments, with pulse energies from 100 to 500 millijoules. The process employs a Nd:YAG laser operating at a frequency of 6 Hz and a wavelength of 1064 nm. (The TiO2 nanoparticles synthesized in this study could be used in different high-temperature environments, as they are characterized by favorable physical, chemical, and mechanical properties). The synthesized product was further treated by calcination for four hours at temperatures higher than 600°C which promoted crystalline structure in the lattice. Comprehensive analyses were carried out to determine the nanoparticles' features. Optical features were studied through UV-visible spectroscopy to examine the absorption spectrum and band gap. The detailed examination of the crystal and surface structures was done using X-ray diffraction and field emission scanning electron microscopy (FE-SEM), in order to obtain insight into the structural integrity and the morphology of the titanium oxide nanoparticles. The study provides a deeper insight into TiO2 nano particle production and their characteristics, thereby emphasizing their suitability for advanced material applications.

Development of a superconducting undulator cryostat based on the thermosiphon effect

As a specific device for light production, undulators have been researched and developed since the third generation of synchrotron photon sources. Nowadays, superconducting undulators become a research hotspot. However, the cryostat, which is used to create a liquid helium temperature environment, often causes the failure of the superconducting undulator. In this paper, a cryostat for a superconducting undulator is designed and investigated. First, a new refrigeration distribution is proposed that can provide more excess cooling capacity at 4.2 K temperature. For the cooling of the superconducting magnet, a liquid helium circulation loop based on the thermosiphon effect is designed, which has no pump or any other moving parts. Next, based on high-temperature superconducting technology, six binary current leads are used to decrease the heat load. The beam chamber is cooled below 20 K to reduce possible effect on the magnet. In addition, for the tubes that connect the 4.2 K helium tank to the room temperature component, the thermoacoustic oscillation is studied. In the experiment, the superconducting magnet could be cooled and maintained at 4.2 K depending on the thermosiphon loop. No helium was discharged when the magnet went through a quench which generated large heat in a short time. There was no liquid helium consumption and the excess cooling capacity reached 2.2 W. The maximum magnet current is as high as 470 A. This study can provide a valuable reference for the development of superconducting undulator cryostats.

Analysis of Transient Thermoacoustic Characteristics and Performance in Carbon Nanotube Sponge Underwater Transducers.

Recent advancements in marine technology have highlighted the urgent need for enhanced underwater acoustic applications, from sonar detection to communication and noise cancellation, driving the pursuit of innovative transducer technologies. In this paper, a new underwater thermoacoustic (TA) transducer made from carbon nanotube (CNT) sponge is designed to achieve wide bandwidth, high energy conversion efficiency, simple structure, good transient response, and stable sound response, utilizing the TA effect through electro-thermal modulation. The transducer has potential application in underwater acoustic communication. An electro-thermal-acoustic coupled simulation for the open model, sandwich model, and encapsulated model is presented to analyze the transient behaviors of CNT sponge TA transducers in liquid environments. The effects of key design parameters on the acoustic performances of both systems are revealed. The results demonstrate that a short pulse excitation with a low duty cycle could greatly improve the heat dissipation of the encapsulated transducer, especially when the thermoacoustic response time becomes comparable to thermal relaxation time.

An AlScN Piezoelectric Micromechanical Ultrasonic Transducer-Based Power-Harvesting Device for Wireless Power Transmission.

Ultrasonic wireless power transfer technology (UWPT) represents a key technology employed for energizing implantable medical devices (IMDs). In recent years, aluminum nitride (AlN) has gained significant attention due to its biocompatibility and compatibility with complementary metal-oxide-semiconductor (CMOS) technology. In the meantime, the integration of scandium-doped aluminum nitride (Al90.4%Sc9.6%N) is an effective solution to address the sensitivity limitations of AlN material for both receiving and transmission capabilities. This study focuses on developing a miniaturized UWPT receiver device based on AlScN piezoelectric micro-electromechanical transducers (PMUTs). The proposed receiver features a PMUT array of 2.8 × 2.8 mm2 comprising 13 × 13 square elements. An acoustic matching gel is applied to address acoustic impedance mismatch when operating in liquid environments. Experimental evaluations in deionized water demonstrated that the power transfer efficiency (PTE) is up to 2.33%. The back-end signal processing circuitry includes voltage-doubling rectification, energy storage, and voltage regulation conversion sections, which effectively transform the generated AC signal into a stable 3.3 V DC voltage output and successfully light a commercial LED. This research extends the scope of wireless charging applications and paves the way for further device miniaturization by integrating all system components into a single chip in future implementations.

Detection of In Vivo-like Cells by a Biosensor Chip Based on Metamaterials in Terahertz Regime.

Early diagnosis of diseases, especially cancer, is critical for effective treatment. The unique properties of terahertz technology have attracted attention in this field. However, current terahertz bio-detection methods face challenges due to differences between the test environment and the actual in vivo conditions. In this study, a novel method is proposed for detecting in vivo-like cells using a biosensor chip composed of metamaterials and a cavity. The cavity has a thickness of ~50 μm. The structure can protect cells from damage and provides a liquid environment like an in vivo state. Through simulation analysis, the metamaterials sensor exhibits a theoretical sensitivity of 0.287 THz/RIU (Refractive Index Unit) with a 50 μm thick analyte. The detection method is experimentally validated using the apoptosis of glioma cells and various cell types. The biosensor investigates the apoptosis of glioma cells under the impact of temozolomide, and the trend of the results was consistent with the Cell Counting Kit-8 method. Furthermore, at a concentration of ~5200 cells/cm2, the experimental results demonstrate that the sensor can distinguish between neurons and glioma cells with a resonance frequency difference of approximately 30 GHz. This research has significant potential for detecting glioma cells and offers an alternative approach to in vivo-like cell detection.

Dimensional and Structural Instability of Electrospun Polylactic Acid Membranes in Liquid Environments: Role of Water, Ethanol, and Temperature

Electrospun nanofibres of polylactic acid (PLA) are suggested for a variety of uses, including scaffolds for tissue engineering, components of drug delivery devices, sustainable packaging materials and membranes for liquid filtration/purification. For all these applications, it is critical to consider the stability of the PLA electrospun materials once in operation. Exposure to certain liquids and temperatures can modify their dimensions, shape, surface topography and mechanical response and compromise their performance. In this study, electrospun PLA mats were exposed to water and ethanol solutions, at different temperatures and for defined time periods, and changes in their properties were analysed. It was found that the impact of water on area shrinkage and fibre arrangement strongly depended on temperature, particularly if the treatment was performed at the glass transition temperature of PLA. Ethanol, instead, induced significant alterations in the size, morphology, and elastic modulus of the electrospun mats, even at room temperature and determined the formation of crimped structures. This work provides insights into the conditions that can critically affect the properties of PLA electrospun fibres and, hence, impact on their usage.

Sub-bandgap photo-response of black silicon fabricated by femtosecond laser irradiation under water

Here we propose a method to fabricate black Si without the need for any chalcogenide doping, accomplished by femtosecond (fs) laser irradiation in a liquid environment, aiming to fabricate the infrared detector and investigating their optoelectronic performance. Multi-scale laser-induced periodical surface structures (LIPSSs), containing micron sized grooves decorated with low spatial frequency ripples on the surface, can be clearly observed by SEM and 3D confocal microscope. The generated black Si demonstrates superior absorption capabilities across a broad wavelength range of 200-2500 nm, achieving an average absorptance of up to 71%. This represents a notable enhancement in comparison to untreated Si, which exhibits an average absorption rate of no more than 20% across the entire detectable spectrum. A metal-semiconductor-metal (MSM) type photodetector was fabricated based on this black Si, demonstrating remarkable optoelectronic properties, specifically, it attains a responsivity of 50.2 mA/W@10 V and an external quantum efficiency (EQE) of 4.02% at a wavelength of 1550 nm, significantly outperforming the unprocessed Si by more than five orders of magnitude. The great enhancement in infrared absorption as well as the optoelectronic performance can be ascribed to the synergistic effect of the multi-scale LIPSSs and the generated intermediate energy levels. On one hand, the multi-scale structures contribute to an anti-reflection and light trapping property; on the other hand, the defects levels generated through fs laser ablation process under water may narrow the band gap of the Si. The results therefore underscore the remarkable potential of black Si processed by fs laser under water for the application of photodetection, especially in the near-infrared band.

Imaging biomacromolecules in action with liquid-phase electron microscopy

Imaging biomacromolecules in action in a liquid environment poses a challenge to single-molecule experiments. Liquid-phase electron microscopy (LP-EM) has demonstrated its unique ability to reveal previously unseen transient dynamics and intermediate states of delicate biomacromolecular systems (protein, DNA/RNA) with deep-learning methods and careful evaluation of electron beam effects.

Development status of the in-situ measurement system for ortho-to-parahydrogen fractions for the ESS cryogenic moderator system

The Cryogenic Moderator System (CMS) is equipped with a catalyst to convert hydrogen from the ortho state to the para state in order to keep desirably high parahydrogen fractions of 99.5%. An in-situ measurement system for the ortho and para fractions of liquid hydrogen (OPMS) by means of a Raman spectroscopy with an accuracy of 0.1% is being developed to detect any undesirable shift towards a high orthohydrogen fraction caused by neutron scattering driven para-to-ortho back conversion. We have demonstrated that our developed sapphire window, through which the laser and backscattered photon travel, has endured the required pressure and thermal cycles in a liquid hydrogen environment. Meanwhile, a Raman optics system has been developed using normal hydrogen. Eventually, we have succeeded in detecting the parahydrogen peak at J = 4, which is our primary goal, because the peak ratio of parahydrogen at 1245 cm−1 to ortho hydrogen at 587 cm−1 corresponds to 0.5%. It can be expected that it would achieve our requirement for liquid hydrogen with higher density.

Etching of quartz crystals in liquid phase environment: A review

Quartz crystals are the most widely used material in resonant sensors, owing to their excellent piezoelectric and mechanical properties. With the development of portable and wearable devices, higher processing efficiency and geometrical precision are required. Wet etching has been proven to be the most efficient etching method for large-scale production of quartz devices, and many wet etching approaches have been developed over the years. However, until now, there has been no systematic review of quartz crystal etching in liquid phase environments. Therefore, this article provides a comprehensive review of the development of wet etching processes and the achievements of the latest research in this field, covering conventional wet etching, additive etching, laser-induced backside wet etching, electrochemical etching, and electrochemical discharge machining. For each technique, a brief overview of its characteristics is provided, associated problems are described, and possible solutions are discussed. This review should provide an essential reference and guidance for the future development of processing strategies for the manufacture of quartz crystal devices.

193 nm immersion photodetector with an ultra-high EQE of 83.7%

With the development of chip to high-density integration, the requirement of lithography precision is higher and higher. In this process, controlling the power of the lithography exposure light source is very important to improve the quality of the chip. However, most detectors are unable to conduct light detection in liquid environments, especially in the aspects of real-time detection and calibration of light power in immersion deep ultraviolet lithography. In this paper, the AlN film epitaxial on n-SiC substrate by MOCVD is used as the photoelectrode, based on which an immersion detector with a quick response to 193 nm vacuum ultraviolet (VUV) light is fabricated. Impressively, under 0 V bias, the detector achieves a high responsiveness (130 mA/W) and an EQE up to 83.7% under an excitation with lower light power (45 nW), illustrating its ability to perform highly efficient detection of light signals and underwater imaging in weak-light environment. In addition, the detector also has the shortest detection wavelength when compared with the immersion photodetectors reported so far. At the same time, the simulated immersion lithography monitoring experiment shows that the detector has good real-time monitoring ability. In a word, this work provides a novel method for detecting underwater light power and can work as reference for realizing the real-time monitoring of immersive lithography light sources in future applications.

Characterization of Buried Interfaces of Silicone Materials in Situ to Understand Their Fouling-Release, Antifouling, and Adhesion Properties.

Poly(dimethylsiloxane) (PDMS) has numerous excellent properties and is extensively used as the main component of many silicone products in a variety of research fields and practical applications such as biomedical materials, aviation, construction, electronic devices, and automobiles. Interfacial structures of PDMS and other components in silicone systems are important for such research and applications. It is difficult to probe interfacial molecular structures of buried solid-liquid and solid-solid interfaces of silicone materials due to the lack of appropriate analytical tools. In this feature article, we presented our research on elucidating the molecular structures of PDMS as well as other additives in silicone samples at buried interfaces in situ at the molecular level using a nonlinear optical spectroscopic technique, sum frequency generation (SFG) vibrational spectroscopy. SFG was applied to study various PDMS surfaces in liquid environments to understand their fouling-release and antifouling activities. SFG has also been used to study buried solid-solid interfaces between silicone adhesives and polymers, elucidating the molecular adhesion mechanisms. Our SFG studies provide important knowledge on interfacial structure-function relationships of silicone materials, helping the design and development of silicone materials with improved properties through optimization of silicone interfacial structures.

Ecological packaging: Creating sustainable solutions with all-natural biodegradable cellulose materials

Plastics, accumulating globally as microplastics in living organisms, significantly contribute to environmental issues. Current materials like polylactic acid and commercial paper face limitations due to inadequate heat and water resistance, resulting in various practical inconveniences. This study reports a high-strength, water-resistant, recyclable, and naturally degradable pure cellulose food packaging material, which is crafted from bacterial cellulose (BC) and ethyl cellulose (EC) by a straightforward filtration and scratch coating process. The use of the EC ethanol solution eliminates the need for additional binders. Remarkably, the EC-BC pure cellulose material exhibits excellent mechanical properties (tensile strength of 195.3 ± 23.2 MPa), a stability in liquid environments (136.9 ± 24.2 MPa mechanical strength after 30 minutes of immersion in water), recyclability, natural degradability, cost-effectiveness, and non-toxicity. These attributes position binder-free hybrid designs, based on cellulose structures, as a promising solution to address environmental challenges arising from the extensive use of single-use plastics.

Optimization and Artifacts of Photothermal Excitation of Microresonators

AbstractThe excitation of microresonators using focused intensity modulated light, known as photothermal excitation, is gaining significant attention due to its capacity to accurately excite microresonators without distortions, even in liquid environments, which is driving key advancements in atomic force microscopy and related technologies. Despite progress in the development of coatings, the conversion of light into mechanical movement remains largely inefficient, limiting resonator movements to tens of nanometers even when milliwatts of optical power are used. Moreover, how photothermal efficiency depends on the relative position of a microresonator along the propagation axis of the photothermal beam remains poorly studied, hampering the understanding of the conversion of light into mechanical motion. Here, photothermal measurements are performed in air and water using cantilever microresonators and a custom‐built picobalance, to determine how photothermal efficiency changes along the propagation beam axis. It is identified that far out‐of‐band laser emission can lead to visual misidentification of the beam waist, resulting in a drop of photothermal efficiency of up to one order of magnitude. The measurements also unveil that the beam waist is not always the position of highest photothermal efficiency, and can reduce the efficiency up to 20% for silicon cantilevers with trapezoidal cross section.

Laser-induced plasma micromachining on surfaces parallel to the incident laser in different solutions

Laser-induced plasma micromachining (LIPMM) is an advanced technology that utilizes the plasma generated from laser breakdown to remove material, thereby facilitating the fabrication of microstructures. This paper explores the use of LIPMM on 304 stainless steel surfaces parallel to the laser beam in different solutions, focusing on the impact of the liquid environment on the machining process. It presents a theoretical analysis of the material removal mechanisms unique to this orientation and experimentally investigates how water, a salt solution, and ethanol affect plasma shockwave characteristics. Notably, the plasma shockwave in the salt solution demonstrates the most significant peak pressure and energy, enhancing the micromachining efficiency. These findings suggest that varying the liquid environment can significantly influence LIPMM's effectiveness, offering potential improvements in precision and control. This study broadens the understanding of LIPMM applications, especially in orientations not commonly explored, and opens new possibilities for advanced micromachining techniques in various industrial applications.

In Situ Formation of Suspended Graphene Windows for Lab‐Based XPS in Liquid and Gas Environments

Environmental cells sealed with photoelectron‐transparent graphene windows are promising for extending X‐ray photoelectron spectroscopy (XPS) to liquid and high‐pressure gas environments for in situ and operando studies. However, the reliable production of graphene windows that are sufficiently leak‐tight for extended measurements remains a challenge. Here we demonstrate a PDMS/Au(100 nm)‐supported transfer method that reliably produces suspended graphene on perforated silicon nitride membranes without significant contamination. A yield of ~95% is achieved based on single‐layer graphene covering >98% of the holes in the silicon nitride membrane. Even higher coverages are achieved for stacked bilayer graphene, allowing wet etching (aqueous KI/I2) of the Au support to be observed in a conventional lab‐based XPS system, thereby demonstrating the in situ formation of leak‐tight, suspended graphene windows. Furthermore, these windows allow gas‐phase measurements at close to atmospheric pressure, showing future promise for XPS under higher‐pressure gas environments in conventional lab‐based systems.

Co-N-C axially coordination regulated H2O2 selectivity via water medicated recombination of solute •OH: A new route

The cobalt, earth abundant transition metal, embedded in nitrogen doped carbon material as single atom site (Co-N-C) has been manifested as promising electrochemical oxygen reduction reaction (ORR) catalyst, however the unsatisfying production selectivity has hampered its widespread applications. Herein, the H2O2 selectivity of Co-N-C catalyst has been tailored with Co axial functional groups. Thermodynamically, the selectivity is regulated due to the fine-tuning of the adsorption of the key reaction intermediates (ΔG*OOH), and five functional groups, including −O, –OH, –CN, −CH3 and −SO3, endow the Co-N-C catalyst with superior H2O2 selectivity. Importantly, we unravel a new water medicated recombination of solute •OH reaction pathway for H2O2 production, which was the result of dissociation of *HOOH in explicit water environment. That is, two •OH species reaction in the liquid environment which originated from the creaking of *OOH intermediates due to the weakened O-O bond by the interaction with surrounding water. This study provides foundational understanding for the ORR catalytic mechanism at the electrochemical interface and opens up new avenues for rational design of targeted high efficiency electrocatalysts.

Responsiveness of Charged Double Network Hydrogels to Ionic Environment

AbstractCharged double network (DN) hydrogels are widely studied for their desirable mechanical strength and tunable properties. In this work, the influence of polymer concentration on microstructure and properties of agarose/polyacrylic acid DN hydrogels is studied. Agarose, the first network, is a brittle biopolymer, while polyacrylic acid (PAAc) is a weak polyelectrolyte. The microstructure, visualized in liquid environment, displays an agarose scaffold coated and interconnected by PAAc, deviating from the common assumption of an entangled double network. Importantly, the charging of PAAc in the hydrogel is regulated not only by the pH and weak polyelectrolyte effects, but also by the restricted swelling of the double network, and hence, it is an inherent regulation mechanism of charged hydrogels. The interactions between the hydrogel and the ionic environment induce microstructural changes and charging of the double network, impacting surface properties such as topography, stiffness, and adhesion, which are spatially resolved by liquid‐environment atomic force microscopy. The responsiveness of the DN hydrogels significantly depends on both polymer concentrations and ion concentrations. These findings provide insights into the responsive behavior of double network hydrogels and reveal universal mechanisms for charged hydrogels, which can guide the future development of functional soft materials.