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Abstract The cosmetic-tattoo industry is evolving every year and the microstructures of the equipment have the great potential for semi-permanent makeup applications. Present paper explores the materials and microparticles of semi-permanent makeup tattoo needles. The surface of the five-round-shader tattoo needle used in semi-permanent makeup process was examined by scanning electron microscopy, and its elemental composition was analyzed by energy-dispersive X-ray spectroscopy. The comparison of five-round-shader needles have undergone thorough observation: original five-round-shader needle and distorted five-round-shader needle. The diameter of the sharp and rounded needle tip was measured at approximately 6.80 μm, while the deformed needle tip was approximately 16 μm thick, about 2.5 times thicker than the rounded needle tip. Many rosette-shaped lead (Pb) particles and irregular clusters adhere to the welded areas and closely adjacent needle shaft surfaces. The lead particles have a diameter ranging from 4 μm to 5 μm and exhibit a grid-like structure with a consistent thickness of plate-like shape. The distorted structure of Pb in rosette-shaped formations is shown to have originated from the grinding and polishing processes during needle manufacturing. To produce sterilized tattoo needles, high-quality tattoo needle inspection processes are necessary to remove any unhygienic substances adhering to the needle surface.

Abstract Glass vials are the most widely used primary containers for the packaging of parenteral products due to their optical clarity, general inertness, and hermetic properties, but under certain circumstances, they can pose safety concerns. Most of these issues are related to the potential formation of glass particulates through delamination or precipitation, resulting from the chemical interaction between the drug product and the inner surface of the glass vial. Hence, it is imperative for pharmaceutical companies to conduct product-vial compatibility studies to determine the appropriate packaging/container closure system. To support this development activity, scientists need to develop analytical methods to detect subvisible glass particulates in parenteral products, along with the appropriate positive controls, to facilitate detection and identification. This paper outlines the utilization of coaxial/episcopic and oblique illumination microscopy, combined with spectroscopic techniques, to detect thin glass particulates generated from a modified procedure. It also showcases the importance of angle-dependent lighting in visualizing positive control samples containing thin glass particulates. The analytical microscopy techniques discussed in this paper can assist scientists in selecting suitable container closure systems for developing parenteral products.

Abstract Oxide-supported metal catalysts are essential components in industrial processes for catalytic conversion. However, the performance of these catalysts is often compromised in high temperature reaction environments due to sintering effects. Currently, a number of studies are underway with the objective of improving the metal support interaction (MSI) effect in order to enhance sintering resistance by surface modification of the oxide support, including the formation of inhomogeneous defects on the oxide support, the addition of a rare earth element, the use of different facets, encapsulation, and other techniques. The recent developments in in situ gas phase transmission electron microscopy (TEM) have enabled direct observation of the sintering process of NPs in real time. This capability further allows to verify the efficacy of the methods used to tailor the support surface and contributes effectively to improving sintering resistance. Here, we review a few selected studies on how in situ gas phase TEM has been used to prevent the sintering of catalyst NPs on oxide supports.

There is an increasing need for compact low-cost NMR apparatus that can be used on the laboratory bench and in the field. There are four main usage variants of usage: (a) time-domain apparatus, particularly for physical measurements; (b) frequency-domain apparatus, particularly for chemical analysis, (c) NMR Cryoporometry apparatus for measuring pore-size distributions; and (d) MRI apparatus for imaging. For all of these, variable temperature capability may be vital. We have developed compact low-cost apparatus targeted at these applications. We discuss a hand-held NMR Spectrometer, and three different holdable NMR magnets, with sufficiently large internal bores for the Lab-Tools compact Peltier thermo-electric cooled variable-temperature probes. Currently, the NMR Spectrometer is very suitable for (a) NMR time-domain relaxation and (c) NMR Cryoporometry. With a suitable high-homogeneity magnet, it is also appropriate for simple use (b), spectral analysis, or, with a suitable gradient set, (d) MRI. Together, the NMR Spectrometer, one of the NMR variable-temperature probes, and any of these NMR magnets make excellent NMR Cryoporometers, as demonstrated by this paper and previously published research. Equally, they make versatile general-purpose variable-temperature NMR systems for materials science.

This study presents the design and simulation of an RF MEMS variable capacitor with a high tuning ratio and high linearity factor of capacitance–voltage response. An electrostatic torsion actuator with planar and non-planar structures is presented to obtain the high tuning ratio by avoiding the occurrence of pull-in point. In the proposed design, the capacitor plate is connected to the electrostatic actuators by using the s-shaped beam. The proposed design shows a 138% tuning ratio with the planar structure of the actuator and 167% tuning ratio by implementing the non-planar structure. A linearity factor of 99% is attained by adjusting the rates at which the capacitor plate rises as the actuation voltage increases and the rate at which the capacitance decreases as the plate rises. Parametric optimization of the design is performed by utilizing the finite element method (FEM) analysis and high-frequency structural simulator (HFSS) analysis to obtain an optimized high-tuning ratio RF MEMS varactor at low actuation voltage. S-parameters of the design are presented on HFSS, with a 50 ohm coplanar waveguide (CPW) serving as the transmission line. The proposed RF MEMS varactor can be utilized in tunable RF devices.

Recent advancements in 3D-bioprinting technology have sparked a growing interest in its application for brain repair, encompassing tissue regeneration, drug delivery, and disease modeling. This literature review examines studies conducted over the past five years to assess the current state of research in this field. Common bioprinting methods and key parameters influencing their selection are explored, alongside an analysis of the diverse types of bioink utilized and their associated parameters. The extrusion-based 3D-bioprinting method emerged as the most widely studied and popular topic, followed by inkjet-based and laser-based bioprinting and stereolithography. Regarding bioinks, fibrin-based and collagen-based bioinks are predominantly utilized. Furthermore, this review elucidates how 3D bioprinting holds promise for neural tissue repair, regeneration, and drug screening, detailing the steps involved and various approaches employed. Neurovascular 3D printing and bioscaffold 3D printing stand out as the top two preferred methods for brain repair. The recent studies’ shortcomings and potential solutions to address them are also examined and discussed. Overall, by synthesizing recent findings, this review provides valuable insights into the potential of 3D bioprinting for advancing brain repairment strategies.

Abstract The sliding filament theory and the cross-bridge model have been fundamental in understanding muscle contraction. While the cross-bridge model explains the interaction between a single myosin head and actin filament, the native myosin molecule consists of two heads. This review explores the possibility and mechanism of two-headed binding in myosin II to the actin. Recent studies using electron tomography and resonance energy transfer have provided evidence in support of the occurrence of two-headed binding. The flexibility of the regulatory light chain (RLC) appears to play a significant role in enabling this binding mode. However, high-resolution structures of the RLCs in the two-headed bound state have not yet been reported. Resolving these structures, possibly through sub-tomogram averaging or single-particle analysis, would provide definitive proof of the conformational flexibility of RLCs and their role in facilitating two-headed binding. Further investigations are also required to address questions such as the predominance of two-headed versus single-headed binding and the influence of the state of each of the heads on the other. An understanding of the mechanism of two-headed binding is crucial for developing a comprehensive model of the cross-bridge cycle of the native myosin molecule.

Nanoscale oxides grown in c-silicon, implanted with low-energy (2 keV) H+ ions and fluences ranging from 1013 cm−2 to 1015 cm−2 by RF plasma immersion implantation (PII), have been investigated. The oxidation of the implanted Si layers proceeded in dry O2 at temperatures of 700 °C, 750 °C and 800 °C. The optical characterization of the formed Si/SiOx structures was conducted by electroreflectance (ER) and spectroscopic ellipsometric (SE) measurements. From the ER and SE spectra analysis, the characteristic energy bands of direct electron transitions in Si are elaborated. The stress in dependence on hydrogenation conditions is considered and related to the energy shifts of the Si interband transitions around 3.4 eV. Silicon oxides, grown on PII Si at a low H+ fluence, have a non-stoichiometric nature, as revealed by IR-SE spectra analysis, while with an increasing H+ fluence in the PII Si substrates and/or the subsequent oxidation temperature the stoichiometric Si-O4 units in the oxides become predominant. The development of surface morphology is studied by atomic force microscopy (AFM) imaging. Oxidation of the H+-implanted Si surface region flattens out the surface pits created on the Si surface by H+ implants. Based on the evaluation of the texture index and mean fractal dimension, the isotropic and self-similar character of the studied surfaces is emphasized.

The manufacturing and characterization of nanographite films on substrates form the foundation for advances in materials science. Conductive graphite films are challenging products, as isolating graphite oxide is often necessary. In this study, nanographite suspensions containing non-oxidized graphite flakes were used to fabricate novel thin and ultrathin films via blade coating on industry-standard substrates. Films as thin as 346 nm were successfully fabricated. Moreover, it was possible to induce the orientation of the graphite nanoflakes via blade coating. This orientation led to electrical anisotropy; thus, the electrical behavior of the films in each orthogonal direction differed. After adjusting the coating parameters and the concentration of the nanographite flakes, the electrical conductivity ranged from 0.04 S/cm to 0.33 S/cm. In addition, with such adjustments, the transparency of the films in the visible range varied from 20% to 75%. By establishing a methodology for the tuning of both electrical and optical properties via adjustments in the nanographite suspension and coating parameters, we can fabricate resistant, conductive, and transparent films satisfying certain requirements. The results presented here can be extrapolated to enhance applications, especially for photonics and solar cells, in fields that require electrical conductive materials with high levels of transparency.

This study investigates the influence of microstructure patterns on the hydrophobic properties of surfaces of 3D-printed objects generated using photopolymer resin. Various arrangements and designs of microstructures on the surface of 3D-printed objects were examined. Leveraging the superior resolution of stereolithography printers (SLA) over fused deposition modeling, intricate microfeature designs were well-implemented. The experiments involved a range of structures on the surface of the 3D-printed objects, including precisely defined arrays of microcylinders, microchannels, and other complex designs generated by parametric equations. The hydrophobicity of the 3D-printed objects was assessed through the water droplet test, revealing a spectrum of results ranging from hydrophobic to weakly hydrophobic, and to hydrophilic surfaces. Light microscopy was employed to characterize the surface morphological properties of the 3D-printed objects, which were then correlated with the measured contact angles. It was discovered that the 3D-printed objects with microstructures formed using parametric functions exhibited patterns with irregularities and fluctuations along all directions or axes, resulting in a higher degree of hydrophobicity compared to structured matrices with pillared arrays. However, some surfaces created with parametric functions resulted in an anisotropic system where the material properties varied along one direction, while the other direction exhibited a flat, planar surface. These anisotropic systems were found to be less hydrophobic according to the water droplet test.

Understanding the spatial distribution (SD) of unicellular organisms is crucial for comprehending population dynamics and adaptive strategies at the microbial scale. These behaviors include the formation of ordered structures through intercellular interactions and the broader implications for ecosystem interactions. In this study, the spatial distribution of the motile unicellular alga Chlamydomonas reinhardtii was investigated, with a focus on high-density conditions approximated by an area fraction of φ = 10%. Cell counting was carried out by image analysis, which applies the quasi-two-dimensional observation technique developed in our previous studies to analyze cell interactions in microspaces with thicknesses of 80 µm and 200 µm using both variance-to-mean ratio (VMR) and Eberhardt statistics (ES). The study reveals that experimental results, when evaluated using both VMR and ES, confirmed a similar trend and a density-dependent transition in cellular interaction. This transition ranges from swarming at lower densities to dispersal at higher densities, with a critical boundary observed at approximately φ = 8%. The findings suggest that cell behavior in dense populations shifts due to limited space and resources, offering a new perspective on the adaptive strategies of cells. These insights could enhance understanding of the mechanisms governing cell behavior in crowded environments.

This work delves into the preparation of ATO thin films and their characterization, fabrication, and calibration of a NO2 gas sensor, as well as the development of the packaged sensor. ATO thin films were prepared by e-beam evaporation using green synthesized ATO nanomaterials on different substrates and annealed at 500 and 600 °C for one hour. The structural and morphological properties of the developed thin films were studied using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) techniques. An orthorhombic SnO2 crystal structure was recognized through XRD analysis. The granular-shaped nanoparticles were revealed through SEM and TEM images. The films annealed at 600 °C exhibited improved crystallinity. ATO films prepared on normal 5 µm interdigitated electrodes (IDEs) and annealed at 600 °C exhibited a response of 10.31 ± 0.25 with an optimum temperature of 200 °C for a 4.8 ppm NO2 gas concentration. The packaged NO2 gas sensor developed using IDEs with a microheater demonstrated an improved response of 16.20 ± 0.25 for 4.8 ppm of NO2 gas.

We report the fabrication and characterisation of near-IR reflecting films and coatings based on shear-assembled crystalline ensembles of polymer composite microspheres, also known as “polymer opals”. Extension of the emulsion polymerisation techniques for synthesis of tractable larger core-interlayer-shell (CIS) particles, of up to half a micron diameter, facilitates the engineering and processing of thin-film synthetic opals, with a tunable photonic stopband spanning an extended spectral range of λ ≈ 700–1600 nm. Samples exhibit strong “scattering cone” interactions, with considerable angular dependence and angle tuning possible, as measured with a goniometric technique. These intense optical resonances in the near-IR, particularly within the important region around λ ~ 800 nm, combined with an appreciable translucency within the visible light spectrum, is indicative of the potential applications in coatings technologies and solar cells.

This study introduces a novel approach for analyzing thin film interference spectra by employing a micro-spectrometer equipped with a spectral chip. Focusing on zinc oxide (ZnO) thin films prepared via the sol–gel method, this research aims to explore the films’ physical properties through spectral analysis. After obtaining the interference spectrum of the ZnO thin films, the peak positions within the spectrum were cataloged. Mathematical simulation was used to adjust the refractive index and thickness of the films to match the simulated interference peak positions with the observed peak positions. The thickness of the prepared ZnO film was estimated to be 4.9 μm and its refractive index at 80 °C was estimated to be 1.96. In addition, the measurement system was used to detect environmental changes, including temperature changes and gas exposure. It was observed that the optical characteristics of ZnO films exhibit marked variations with temperature shifts, enabling the establishment of a temperature calibration curve based on spectral feature displacement. In addition, experiments using a variety of gases showed that NO2 and gaseous isopropanol significantly affect the interference spectrum of ZnO, with the peak of the interference spectrum shifted by 2.3 nm and 5.2 nm, respectively, after injection of the two gases. This indicates that interferometric spectroscopy can serve as an effective tool for ZnO monitoring, capable of selectively detecting specific gases.

Considering that the plasmonic properties of metallic nanoparticles (NPs) are strongly influenced by their dielectric environment, comprehension and manipulation of this interplay are crucial for the design and optimization of functional plasmonic systems. In this study, the plasmonic behavior of silver nanoparticles encapsulated in diverse copolymer dielectric environments was investigated, focusing on the analysis of the emerging localized surface plasmon resonances (LSPRs) through both experimental and theoretical approaches. Specifically, two series of nanostructured silver ultrathin films were deposited via magnetron sputtering on heated Corning Glass substrates at 330 °C and 420 °C, respectively, resulting in the formation of self-assembled NPs of various sizes and distributions. Subsequently, three different polymeric layers were spin-coated on top of the silver NPs. Optical and structural characterization were carried out by means of UV–Vis spectroscopy and atomic force microscopy, respectively. Rigorous Coupled Wave Analysis (RCWA) was employed to study the LSPRs theoretically. The polymeric environment consistently induced a red shift as well as various alterations in the LSPR amplitude, suggesting the potential tunability of the system.

This study presents an innovative lateral flow microfluidic paper-based analytical device (μPAD) designed for conducting quantitative paper-based enzyme-linked immunosorbent assays (p-ELISA), seamlessly executing conventional ELISA steps in a paper-based format. The p-ELISA device utilizes a passive fluidic circuit with functional elements such as a multi-bi-material cantilever (B-MaC) assembly, delay channels, and a buffer zone, all enclosed within housing for autonomous, sequential loading of critical reagents onto the detection zone. This novel approach not only demonstrates a rapid assay completion time of under 30 min, but also boasts reduced reagent requirements, minimal equipment needs, and broad applicability across clinical diagnostics and environmental surveillance. Through detailed descriptions of the design, materials, and fabrication methods for the multi-directional flow assay (MDFA), this manuscript highlights the device’s potential for complex biochemical analyses in a user-friendly and versatile format. Analytical performance evaluation, including a limit of detection (LOD) of 8.4 pM for Rabbit IgG, benchmarks the device’s efficacy compared to existing p-ELISA methodologies. This pioneering work lays the groundwork for future advancements in autonomous diagnostics, aiming to enhance global health outcomes through accessible and reliable testing solutions.

The aim of this study is to predict the distribution of temperature at various positions on silver-coated firefighter protective clothing when subjected to external radiant heat flux. This will be helpful in the determination of thermal protective performance. Firefighter clothing consists of three layers, i.e., the outer shell, moisture barrier and thermal liner. The outer shell is the exposed surface, which was coated with silver particles through a physical vapor deposition process called magnetron sputtering. Afterwards, these uncoated and silver-coated samples were exposed to radiant heat transmission equipment at 10 kW/m2 as per the ISO 6942 standard. Silver-coated samples displayed better thermal protective performance as the rate of temperature rise in silver-coated samples slowed. Later, a numerical approach was employed, contemplating the impact of metallic coating on the exterior shell. The finite difference method was utilized for solving partial differential equations and the implicit method was employed to discretize the partial differential equations. The numerical model displayed a good prediction of the distribution of temperature at different nodes with respect to time. The comparison of time vs. temperature graphs at different nodes for uncoated and silver-coated samples acquired from numerical solutions showed similar patterns, as witnessed in the experimental results.

Micro-electromechanical systems (MEMS) have the potential to provide low-power phase shifting in silicon photonics, but techniques for designing low-loss devices are necessary for adoption of the technology. Based on coupled mode theory (CMT), we derive analytical expressions relating the loss and, in particular, the phase-dependent loss, to the geometry of the MEMS phase shifters. The analytical model explains the loss mechanisms of MEMS phase shifters and enables simple optimization procedures. Based on that insight, we propose phase shifter geometries that minimize coupling power out of the waveguide. Minimization of the loss is based on mode orthogonality of a waveguide and phase shifter modes. We numerically model such geometries for a silicon nitride MEMS phase shifter over a silicon nitride waveguide, predicting less than −1.08 dB loss over a 2π range and −0.026 dB loss when optimized for a π range. We demonstrate this design framework with a custom silicon nitride process and achieve −0.48 dB insertion loss and less than 0.05 dB transmission variation over a π phase shift. Our work demonstrates the strength of the coupled mode approach for the design and optimization of MEMS phase shifters.

Abstract Plant cells are uniquely characterized by exhibiting cell walls, pigments, and phenolic compounds, which can impede microscopic observations by absorbing and scattering light. The concept of clearing was first proposed in the late nineteenth century to address this issue, aiming to render plant specimens transparent using chloral hydrate. Clearing techniques involve chemical procedures that render biological specimens transparent, enabling deep imaging without physical sectioning. Drawing inspiration from clearing techniques for animal specimens, various protocols have been adapted for plant research. These procedures include (i) hydrophobic methods (e.g., Visikol™), (ii) hydrophilic methods (ScaleP and ClearSee), and (iii) hydrogel-based methods (PEA-CLARITY). Initially, clearing techniques for plants were mainly utilized for deep imaging of seeds and leaves of herbaceous plants such as Arabidopsis thaliana and rice. Utilizing cell wall-specific fluorescent dyes for plants and fungi, researchers have documented the post-penetration behavior of plant pathogenic fungi within hosts. State-of-the-art plant clearing techniques, coupled with microbe-specific labeling and high-throughput imaging methods, offer the potential to advance the in planta characterization of plant microbiomes.

The advancement of both porous materials and nanomaterials has brought about porous nanomaterials. These new materials present advantages both due to their porosity and nano-size: small size apt for micro/nano device integration or in vivo transport, large surface area for guest/target molecule adsorption and interaction, porous channels providing accessibility to active/surface sites, and exposed reactive surface/active sites induced by uncoordinated bonds. These properties prove useful for the development of different porous composition types (metal oxides, silica, zeolites, amorphous oxides, nanoarrays, precious metals, non-precious metals, MOFs, carbon nanostructures, MXenes, and others) through different synthetic procedures—templating, colloidal synthesis, hydrothermal approach, sol-gel route, self-assembly, dealloying, galvanostatic replacement, and so—for different applications, such as catalysis (water-splitting, etc.), biosensing, energy storage (batteries, supercapacitors), actuators, SERS, and bio applications. Here, these are presented according to different material types showing the evolution of the structure design and development towards the formation of hierarchical porous structures, emphasizing that the formation of porous nanostructures came about out of the desire and need to form hierarchical porous nanostructures. Common trends observed across these different composition types include similar (aforementioned) applications and the use of porous nanomaterials as templates/precursors to create novel ones. Towards the end, a discussion on the link between technological advancements and the development of porous nanomaterials paves the way to present future perspectives on these nanomaterials and their hierarchical porous architectures. Together with a summary, these are given in the conclusion.

Magnetic micro and nano sensors can be used in a broad variety of applications, e.g., for navigation, automotives, smartphones and also for health monitoring. Based on physical effects such as the well-known magnetic induction, the Hall effect, tunnel magnetoresistance and giant magnetoresistance, they can be used to measure positions, flow, pressure and other physical properties. In biomedicine and healthcare, these miniaturized sensors can be either integrated into garments and other wearables, be directed through the body by passive capsules or active micro-robots or be implanted, which usually necessitates bio-functionalization and avoiding cell-toxic materials. This review describes the physical effects that can be applied in these sensors and discusses the most recent micro and nano sensors developed for healthcare applications.

Additive manufacturing (AM) is an advanced manufacturing method that produces objects by sequential layering. Material extrusion AM (MEAM) with continuous-fibre reinforcement is becoming more widely used in naval structures, which are exposed to the marine environment. However, the water diffusion process and the effect of water ageing on the mechanical performance of AM materials are not yet well understood because of their complex internal structure, caused by defects generated during manufacturing. Current research on diffusion is mostly based on experimental methods for conventionally manufactured materials without considering AM-induced defects. The objective of this study is to explore how the defects inherent to MEAM affect water diffusion in a composite material by the capillary effect. Results from a numerical study of capillary flow in MEAM polymer are applied as a boundary condition in the subsequent finite-element analysis. The study illustrates that flow in the capillary reaches the steady state quicker compared to the saturation time in the matrix, predicted by Fick’s diffusion equation. It is demonstrated that the capillary effect can significantly affect the water diffusion in MEAM parts and reduce the saturation time to one-third compared to the case without accounting for this effect.

This study evaluated the potential of gelatin methacryloyl (GelMA) for single-cell screening compared to polyethylene glycol diacrylate (PEGDA). GelMA photopolymerized at 1000–2000 mJ/cm2 produced consistent patterns and supported HeLa cell viability. GelMA (5%w/v) facilitated better cell collection within 2 days due to its shape retention. GelMA demonstrated biocompatibility with HeLa cells exhibiting exponential proliferation and biodegradation over 5 days. The average cell displacement over 2 days was 16 µm. Two targeted cell recovery strategies using trypsin were developed: one for adherent cells encapsulated at 800 mJ/cm2, and another for floating cells encapsulated at 800 mJ/cm2, enabling the selective removal of unwanted cells. These findings suggest GelMA as a promising biomaterial for single-cell screening applications, offering advantages over PEGDA in cell encapsulation and targeted recovery.

Abstract In this study, we investigate the effectiveness of noise reduction in electron holography, based on the wavelet hidden Markov model (WHMM), which allows the reasonable separation of weak signals from noise. Electron holography observations from a Nd2Fe14B thin foil showed that the noise reduction method suppressed artificial phase discontinuities generated by phase retrieval. From the peak signal-to-noise ratio, it was seen that the impact of denoising was significant for observations with a narrow spacing of interference fringes, which is a key parameter for the spatial resolution of electron holography. These results provide essential information for improving the precision of electron holography studies.

This study describes the synthesis and characterization of the lead-free organic ferroelectric perovskite N-methyl-N’-diazabicyclo [2.2.2]octonium)-ammonium trichloride (MDABCO-NH4Cl3). The electrospinning technique was employed to obtain nanofibers embedded with this perovskite in a PVC polymer for hybrid fiber production. The dielectric, piezoelectric, and pyroelectric properties of these fibers were carefully examined. Based on measurements of the dielectric permittivity temperature and frequency dependence, together with the pyroelectric results, a transition from a high temperature paraelectric to a ferroelectric phase that persisted at room temperature was found to occur at 438 K. The measured pyroelectric coefficient yielded values as high as 290 μC K−1 m−2, which is in between the values reported for MDABCO-NH4I3 and the semiorganic ferroelectric triglycine sulfate (TGS). The hybrid nanofibers exhibited good morphological characteristics and demonstrated very good piezoelectric properties. Specifically, a piezoelectric coefficient of 42 pC/N was obtained when applying a periodical force of 3 N and a piezoelectric voltage coefficient of geff = 0.65 V mN−1. The performance of these fibers is on par with that of materials discussed in the existing literature for the fabrication of nano energy-harvesting generators. Importantly, the perovskite nanocrystals within the fibers are protected from degradation by the surrounding polymer, making them a promising environmentally friendly platform for flexible mechanical energy harvesting.

The present study attempted for the first time an investigation on the effect of deep cryogenic treatment in liquid nitrogen (LN) on magnesium–cerium oxide (Mg/2wt.%CeO2) composites containing equal amounts of different length scales (micron and nanosize) cerium oxide (CeO2) particles. The disintegrated melt deposition method was used to synthesize Mg-2CeO2 micro- and nanocomposites, followed by hot extrusion as the secondary processing. Further liquid nitrogen treatment was performed at a cryogenic temperature of −196 °C. The combined effects of cryogenic treatment and reinforcement length scale on physical, mechanical, and thermal behaviors were studied. The results indicate that LN-treated micro- and nanocomposite samples exhibit, in common, a reduction in porosity, similar grain size, and a limited effect on the original texture of the matrix. However, microhardness, 0.2% Compressive Yield Strength (CYS), failure strain, and energy absorbed increased for both micro- and nanocomposite samples. Overall, results clearly indicate the capability of deep cryogenic treatment with LN to positively diversify the properties of both micro- and nanocomposite samples.

Acoustic focusing of particle flow in microfluidics has been shown to be an efficient tool for particle separation for various chemical and biomedical applications. The mechanism behind the method is the selective effect of the acoustic radiation force on distinct particles. In this way, they can be selectively focused and separated. The technique can also be applied under stationary conditions, i.e., in the absence of fluid flows. In this study, the manipulation of self-propelled particles, such as Janus particles, in an acoustofluidic setup was investigated. In experiments with self-propelled Janus particles and passive beads, we explored the interplay between self-propulsion and the acoustic radiation force. Our results demonstrated unusual and potentially useful effects such as selective trapping, escape, and assisted escape in binary mixtures of active and passive particles. We also analyzed various aspects related to the behavior of Janus particles in acoustic traps in the presence and absence of flows.

Surface modification of the Ti6Al4V alloy (ASTM grade 5), with the fabrication of vertically oriented TiO2 nanotubes, has been receiving increasing attention both as a way to provide advanced bioactive features and the ability to act as reservoirs for a localized, controlled drug release. In this work, TiO2 nanotubes were grown on the surface of a Ti6Al4V alloy through electrochemical anodization. An ethylene glycol-based electrolyte containing 0.5 wt.% NH4F and 2.5% (v/v) H2O was used. Post-anodizing heat treatments at 500 °C in air atmosphere were performed to achieve a crystalline oxide layer with a higher mechanical stability. Following these treatments, Zn or Cu nanoparticles were incorporated into the nanotubular structures through electrodeposition processes. Then, the antimicrobial performance of the obtained surfaces was assessed against Staphylococcus epidermidis, a Gram-positive bacterium common in implant-related infections. Lastly, the cytotoxicity of the produced surface was evaluated against MC3T3-E1 mouse pre-osteoblast cells. In general, Cu-doped TiO2 nanotubes presented an almost total antimicrobial action, while Zn doped samples had a lower, but still significant antibacterial effect. However, a highly cytotoxic effect against MC3T3-E1 cells was observed on all anodized samples due to the release of vanadium from the alloy. In spite of this, the surface modification reported in this work can be a valid solution for existing commercially available orthopedic implants, considering that similar solutions were already studied in in vivo assays.

Nanotechnology has played a pioneering role in advancing medical applications, aiming to enhance healthcare through innovation and collaboration. Nanomedicine can be seen expanding into many fields from cancer therapies, cosmetics, tissue regeneration, biosensing, and infectious diseases, and now, it is seen venturing into the realm of research geared toward autism spectrum disorder (ASD). ASD is a neurodevelopmental disorder characterized by restrictive, monotonous activities or fixed interests as well as difficulties with social communication. As of now, there are no validated quantitative metrics for diagnosing autism, nor is there a drug that is specifically designed to treat the condition. As identifiers of ASD have improved, the diagnosis of individuals who meet established criteria have dramatically increased over the years. Although there is still no recognized nanomedicine treatment specifically intended for ASD, research is looking into how nanotechnology might be used in a number of ASD-related areas. This comprehensive review examines prior research efforts aimed at preventing, treating, and diagnosing individuals with ASD. It particularly focuses on the significance of prenatal care and investigates advancements in drug delivery methods through the blood–brain barrier concerning ASD treatment and management.

Thin metal layers such as silver (Ag) are being utilized for various optical and plasmonic applications as well as for electrical purposes, e.g., as transparent electrodes in display devices or solar cells. This paper focuses on optical MEMS applications such as the Fabry–Pérot interferometer (FPI). Within such filters, reflector materials such as distributed Bragg reflectors (DBRs) or subwavelength gratings (SWGs) have been widely used so far, whereas metallic thin films (MTFs) were limited in application due to their comparatively higher absorption. In this paper, thin sputtered Ag layers with thicknesses of 20, 40 and 60 nm on glass substrates have been investigated, and it is shown that the absorption is very low in the visible spectral range (VIS) and increases only in near-infrared (NIR) with increasing wavelength. Thus, we consider Ag-thin layers to be an interesting reflector material at least for the VIS range, which can be easily fabricated and integrated. However, Ag is not inert and stable when exposed to the atmosphere. Hence, it needs a passivation material. For this purpose, AlN has been chosen in this contribution, which can be deposited by sputtering as well. In this contribution, we have chosen thin AlN layers for this purpose, which can also be deposited by sputtering. Thus, various AlN/Ag/AlN-reflector stacks were created and patterned by lift-off technology preferably. The fabricated reflectors were characterized with respect to adhesion, stress, cohesion, homogeneity, and most importantly, their optical properties. It was found that the thickness of the AlN can be used to adjust the reflectance–transmittance ratio in the VIS range, and influences the adsorption in the NIR range as well. Based on the measured values of the reflectors with 40 nm Ag, an exemplary transmission filter characteristics has been predicted for a wavelength range from 400 to 800 nm. Both the maximum transmittance and the full width at half maximum (FWHM) can be tuned by variation of the AlN thickness from 20 to 60 nm.

The Eugénio de Almeida Foundation’s Casa de Fresco is a historical monument of valuable historic–artistic significance, which currently reveals an assortment of biofilms due to the proliferation of microorganisms in the stone and rocaille elements. The biodeterioration in this area was studied as part of the Conservation and Restoration Project. We effectively characterized the local microbial community using modern high-throughput DNA analysis. Our results suggested the existence of a variety of lichens or lichenized fungi, including genera such as Variospora, Verrucaria, Circinaria, and Caloplaca. Furthermore, we detected several prokaryote microorganisms related to the identification of these lichens. To properly deal with this microbiological issue and avoid fungal recolonization, we evaluated available commercial antimicrobial treatments.

Due to their unique properties, porous silicon nanostructures have garnered much attention in photonics. For example, these structures can exhibit photoluminescence and are highly efficient in trapping light, making them ideal for applications such as biosensors, optical communication, and solar cells. The production of electromagnetic forces by light is a well-established concept, and the mechanism behind it is well-understood. In the past, we have used these forces to induce mechanical oscillations in a photonic structure based on porous silicon. Usually, to detect the oscillations, a high-precision vibrometer is utilized. However, we report a novel approach to visualizing photonic structure oscillations here. The traditional method of using a vibrometer as an indirect measurement tool has been replaced by one that involves directly observing the changes using a camera, digital movement amplification, a theoretical approximation, and FDTE simulations. This original technique provides researchers with a less expensive means of studying photonic structure movements. This proposal could be extended to other microscopic movements or for dynamical interferometric fringe analysis.

Perpendicular magnetic anisotropy at transition metal/oxide interfaces plays a significant role in technological applications such as magnetic storage and spintronics. In this study, we investigate the effects of thermal annealing and Pt ultrathin interlayers on the magnetic anisotropy in Ni/NiO multilayers. Ni/NiO/Pt multilayers were fabricated via radiofrequency magnetron sputtering and natural oxidation. The static magnetic properties of the samples were studied using temperature-dependent SQUID magnetometry. We focus on a sample with a Nickel thickness of 6.7 nm in each multilayer period. This multilayer in Ni/NiO form showed the maximum enhancement of perpendicular magnetic anisotropy after mild thermal annealing in past work. In this work, we study the effects of ultrathin Pt interlayers on the magnetic properties of such a Ni/NiO multilayer before and after annealing. We have observed a further increase in perpendicular magnetic anisotropy, and we study the temperature-dependent magnetic properties of this system, which combines the favorable magnetic properties of Ni/Pt and Ni/NiO multilayers.

Abstract Due to the unique properties of the silk fibroin (SF) made from silkworm, SF-based hydrogels have recently received significant attention for various biomedical applications. However, research on the SF-based hydrogels isolated from spider silks has been rtricted due to the limited collection and preparation of naïve silk materials. Therefore, this study focused on the microstructural characteristics of hydrogel scaffolds derived from two types of woven silk glands: the major ampullate gland (MAG) and the tubuliform gland (TG), in the orb-web spider Trichonephila clavate. We compared these spider glands with those of the silk fibroin (SF) hydrogel scaffold extracted from the cocoon of the insect silkworm Bombyx mori. Our FESEM analysis revealed that the SF hydrogel has high porosity, translucency, and a loose upper structure, with attached SF fibers providing stability. The MAG hydrogel displayed even higher porosity, as well as elongated fibrous structures, and improved mechanical properties: while the TG hydrogel showed increased porosity, ridge-like or wall-like structures, and stable biocapacity formed by physical crosslinking. Due to their powerful and versatile microstructural characteristics, the MAG and TG hydrogels can become tailored substrates, very effective for tissue engineering and regenerative medicine applications.

Abstract There has been an increase in the demand for purified protein as a result of recent developments in the structural biology of myosin 2. Although promising, current practices in myosin purification are usually time-consuming and cumbersome. The reported increased actin to myosin ratio in smooth muscles adds to the complexity of the purification process. Present study outlines a streamlined approach to isolate smooth muscle myosin 2 molecules from actomyosin suspension of chicken gizzard tissues. The procedure entails treating actomyosin for a brief period with actin-binding peptide phalloidin, followed by co-sedimentation and short column size exclusion chromatography. Typical myosin molecule with heavy and light chains and approximately 95% purity was examined using gel electrophoresis. Negative staining electron microscopy and image processing showed intact 10S myosin 2 molecules, proving that phalloidin is effective at eliminating majority of actin in the form of F-actin without dramatic alteration in the structure of myosin. The entire purification discussed here can be completed in a few hours, and further analysis can be done the same day. Thus, by offering quick and fresh supplies of native myosin molecules suited for structural research, specially cryo-electron microscopy, this innovative approach can be adapted to get around the drawbacks of time-intensive myosin purifying processes.

This work presents the development of novel gypsum board composites for advanced thermal energy storage (TES) and electromagnetic interference (EMI) shielding applications. Activated carbon (AC) derived from spent coffee with a high surface area (SBET = 1372 m2/g) was used as a shape stabilizer, while the commercial paraffin, RT18HC, was used as organic encapsulant phase change material (PCM). The AC showed a remarkable encapsulation efficiency as a shape stabilizer for PCM, with ~120.9 wt% (RT18HC), while the melting enthalpy (ΔHm) of the shape-stabilized PCM was 117.3 J/g. The performance of this PCM/carbon nanocomposite as a thermal energy storage material was examined by incorporating it into building components, such as gypsum wallboards. The microstructure of these advanced panels, their density, and their dispersion of additives were examined using X-ray microtomography. Their thermal-regulated performance was measured through a self-designed room model with a similar homemade environmental chamber that was able to create a uniform temperature environment, surrounding the test room during heating and cooling. The measurements showed that the advanced panels reduce temperature fluctuations and the indoor temperature of the room model, in comparison with normal gypsum panels, by a range of 2–5%. The investigated gypsum board composite samples showed efficient electromagnetic shielding performance in a frequency range of 3.5–7.0 GHz, reaching an EMI value of ~12.5 dB, which is adequate and required for commercial applications, when filled with PCMs.

Metal–organic frame (MOF) materials may have the advantages of a regular pore structure, large porosity, and large specific surface area, which could provide better catalytic activity, but they have some disadvantages in electrocatalysis. In contrast, carbon nanofibers (CNFs) prepared by electrospinning methods have good conductivity and stability. Therefore, this research aimed to generate MOF/CNFs composite materials to improve the electrochemical properties of MOF materials and apply them to the field of electrochemical sensing. This experiment was based on the preparation of straight unidirectional CNFs by an electrospinning method at 2000 RPM. The original method of preparing zeolitic imidazolate frameworks (ZIF-8) was improved and ZIF-8 was uniformly dispersed on the surface of CNFs to form a ZIF-8/CNF composite with a fiber diameter of about 0.10 to 0.35 µm. The specific surface area of the CNFs was about 42.28 m2/g, while that of the ZIF-8/CNF composite was about 999.82 m2/g. The specific surface area of the ZIF-8/CNF composite was significantly larger than that of CNFs. The GCE/ZIF-8/CNF electrode had an excellent electrochemical reaction, with an oxidation peak at about 216 μA, which proved that the ZIF-8/CNF composite material would have good catalytic activity and excellent electrochemical properties for the detection of nitrofurazone compared to other modified electrodes.

A miniaturized electrochemical sensor was developed for the remote detection of chemical warfare agent (CWA) simulants. To facilitate drone-based remote sensing, this present study focuses on advancing the miniaturized and compact electrochemical sensor for monitoring two CWA simulants, diisopropyl fluorophosphate (DFP) and O,S-diethylmethylphosphonothioate (O,S-DEMPT). The differential pulse voltammetry (DPV) signal was processed, and the DPV signature features were extracted on the basis of the redox properties associated with the absence and the presence of DFP and O,S-DEMPT. Upon the addition of 0.10 equivalence of DFP or O,S-DEMPT, a shift in potential (E) of ~0.13 V was recorded. The limit of detection (LOD) was calculated to be 0.25 µM (0.046 ppm) and 0.10 µM (0.017 ppm) for DFP and O,S-DEMPT, respectively. These results were validated using a portable Palmsens Emstat HR potentiostat, which corroborated the results obtained using a lab benchtop potentiostat. Additionally, Boolean logic (“AND” operation) was implemented for future drone technology deployment. This advancement enables the fabrication of a networked device capable of autonomously executing tasks without constant oversight.

Photochromism refers to a reversible colour change induced by the irradiation of photochromic materials with ultraviolet (UV) or visible light that reverts to the original colour after the light source is removed. This effect arises from chemical transformations between two isomers with different absorption spectra, involving processes like proton transfer, chemical-bond formation, and isomerisation. These photochromic inks, appearing as crystalline powders with micro-sized particles, require dissolution in a suitable matrix to achieve the colour change. Photochromic inks are used in security, as functional coatings for paper and packaging, in the fabric industry, and in other ways. This study examines the influence of varying concentrations of micro-sized photochromic pigments and different ink-coating thicknesses on the photochromic effect on sustainable paperboard substrates. Artificial ageing was performed to assess the photochromic response and lightfastness in relation to pigment concentration, ink-coating thickness, and the influence of the paperboard substrates. The results of this research could contribute to enhancing knowledge on employing photochromic inks for diverse packaging applications.

Abstract The neuroprotective effects of umbelliferone (UMB) were visualized in three-dimensional (3D) images on vesicle density changes of organotypic hippocampal slice tissues (OHSCs) induced by scopolamine by high voltage electron microscopy. Observations revealed that the number of vesicles decreased in OHSCs induced by scopolamine, and UMB was found to inhibit scopolamine-induced reduction in vesicles, resulting in an increase in vesicle count. These 3D models provide valuable insight for understanding the increase of synapse vesicles in hippocampal tissues treated with UMB.

The structure and phenomena arising from charge transfer in cold field emission mode in a single closed carbon nanotube (CNT) under cold field emission conditions are studied. Inhomogeneities of the structure of CNT in the form of two types of superlattices are found by studying microphotographs obtained by AFM, SEM, and TEM. The features of charge transfer in a quasi-one-dimensional carbon nanotube emitter with a small gap between the anode and cathode are studied under conditions of low-voltage field emission. It is established that the I-V characteristics reveal voltage thresholds and resonant peaks, which are associated with the opening of conduction channels in the region of van Hove singularities. In the region of peaks in the I-V characteristics, the emission current exceeds the one calculated using the Fowler–Nordheim (F-N) function by one to three orders of magnitude. The I-V characteristic is not that the curve straightens in F-N coordinates. It is found that the peaks in the I-V characteristics have distinct regions of negative differential conductivity.

Micromechanical switches are of significant interest for advanced radio frequency and microwave systems, but their practical implementation is limited by low reliability. Electrodes of a microscopic size develop weak contact force that leads to high and unstable contact resistance. The force is typically increased by using a sophisticated switch design with extended lateral dimensions, although a simple and compact cantilever is more preferable. The paper describes for the first time a comprehensive approach to enhance the force of an electrostatically actuated switch. The strategy is applied to a miniature device based on a 50 µm long cantilever. The contact force is increased from 10 to 112 µN, making the switch strong enough to achieve low and stable contact resistance. The restoring force is also enhanced in order to ensure reliable de-actuation. The growth of forces is accompanied by a reduction in the pull-in voltage. Connecting several cantilevers in parallel and manipulating the number and position of contact bumps additionally improves the force and mechanical stability of the switch. An optimal design contains a triple cantilever with two bumps. It provides 50% higher force per contact compared to the single-cantilever switch at the same pull-in voltage and keeps the advantages of a miniature device. The proposed design strategy may be used for building reliable MEMS switches.

This research article provides a comprehensive investigation into the optoelectronic characteristics of three distinct types of cadmium sulfide (CdS) thin films, namely: (a) conventionally prepared CdS thin films using chemical bath deposition (CBD-CdS), (b) CdS thin films produced via chemical bath deposition with the inclusion of zinc (CBD-Cd(1−x)ZnxS, x = 0.3), and (c) CdS thin films synthesized using a seed-assisted approach, treated with ethylenediaminetetraacetic acid (EDTA), and incorporating zinc (ED/CBD + EDTA-Cd(1−x)ZnxS). The investigation reveals that the crystallite size of these thin films decreases upon the addition of EDTA to the reaction solution, leading to an increase in the inter-planar spacing and dislocation density. Furthermore, a blue shift in the transmittance edge of the ED/CBD + EDTA-Cd(1−x)ZnxS samples compared to CBD-CdS implies modifications in the band gaps of the deposited films. The incorporation of Zn2+ into the reaction solution results in an increased band gap value of up to 2.42 eV. This suggests that Cd(1−x)ZnxS thin films permit more efficient photon transmission compared to conventional CdS. Among the three types of films studied, ED/CBD + EDTA-Cd(1−x)ZnxS exhibits the highest optical band gap of 2.50 eV. This increase in the optical band gap is attributed to the smaller crystallite size and the splitting of the tail levels from the band structure. Additionally, the increment in the optical band gap leads to reduced light absorption at longer wavelengths, thereby enhancing the electrical properties. Notably, ED/CBD + EDTA-Cd(1−x)ZnxS thin films demonstrate improved photovoltaic performance in a photoelectrochemical (PEC) cell, characterized by enhanced open-circuit voltage (363 mV, VOC), short-circuit current (35.35 μA, ISC), and flat-band voltage (−692 mV, Vfb). These improvements are attributed to the better adhesion of CdS to the fluorine-doped tin oxide (FTO) substrate and improved inter-particle connectivity.

The functionalization of copolyfluorenes containing dicyanophenanthrene units by closo-decaborate anion is described. Target copolyfluorenes were analyzed using SEM, UV-vis, luminescence, NMR, and Fourier-transform infrared (FTIR) spectroscopy. The effect of complexation with the closo-decaborate anion on the photophysical properties was studied both experimentally and theoretically. The PL data indicate an efficient charge transfer from fluorene to the dicyanophenanthrene units coordinated to the closo-decaborate. The coordination of closo-decaborate clusters to the nitrile groups of copolyfluorenes provides an important route to new materials for sensors and light-emitting devices while, at the same time, serving as a platform for further study of the nature of boron clusters.

In this work, we aimed to analyze the impact of extracts prepared from dried Lavandula angustifolia (lavender) flowers and leaves on the synthesis of silver nanoparticles (AgNPs) (wherein the shape and size of AgNPs and the efficiency of the process were analyzed) and to prove the possibility of transferring the AgNPs’ properties into a polymer matrix. An ex situ method was used to incorporate AgNPs and prepare polymer matrix composite (PVP-AgNPs) films (via casting) and fibers (via electrospinning). We used UV-vis absorption spectrophotometry, Fourier Transform Infrared Spectroscopy (FTIR), Transmission Electron Microscopy (TEM), and Scanning Electron Microscopy (SEM) to analyze and characterize the AgNPs and prepared composites. The results of FTIR analysis confirmed the presence of phytochemicals that can reduce silver ions from Ag+ to Ag0 in both extracts. The presence of spherical nanoparticles was confirmed via TEM regardless of the type of extract used. However, leaf extract caused the formation of AgNPs with a narrower size interval (an average size of 20 nm), and with higher efficiency, compared to the nanoparticles prepared using the flower extract. The nanoparticles prepared using the leaf extract were then incorporated into the polymer matrix, and thin polymer composite films and fibers were successfully prepared. The anti-biofilm activity of AgNPs colloids and prepared polymer nanocomposites against green algae Chlorella kessleri was studied. The anti-biofilm properties of the AgNPs were proved, along with the efficient transfer of their toxic properties into nontoxic polymer.

In this research article we report the potentials of chitin-based silver nanoparticles (chitin AgNPs) derived from Indian mimic goatfish (Mulloidichthys ayliffe) scales as an effective food preservation agent. The study comprehensively presents the multifaceted attributes of chitin AgNPs, including their synthesis, characterization, and antimicrobial properties. Chitin yield from M. ayliffe scales and three-spot swimming crab (P. sanguinolentus) exoskeleton was determined, with the insoluble content quantified. FTIR analysis unveiled distinct absorption peaks for chitin, and scanning electron microscopy revealed the ultrastructure of chitin from both the sources. Using UV–visible spectroscopy, the biosynthesis of AgNPs was accomplished and characterized, with the color shift of the solution serving as proof of a successful synthesis. UV–vis spectra provided insights into nanoparticle size and shape. SEM micrographs exhibited spherical particle morphology, while FTIR spectra indicated amino group interactions contributing to AgNP stabilization. The antimicrobial potential of chitin AgNPs was assessed against the food pathogen, Vibrio spp. Chitin films displayed significant antimicrobial activity, particularly AgNP-synthesized chitin from M. ayliffe scales, demonstrated the highest Vibrio spp. inhibition activity. Furthermore, chitin AgNPs were incorporated into the common chili, Capsicum annuum and the tomato, Solanum lycopersicum to extend their shelf life at room temperature. This study reveals the efficacy of chitin AgNPs from M. ayliffe scales as potent agents for food preservation, offering insights into their physical, mechanical, and antimicrobial attributes. The application of chitin AgNPs to perishable food items highlights their potential in enhancing shelf life and quality, opening innovative avenues for sustainable food preservation.

The present study focuses on the synthesis of the natural product 4-methyl-umbelliferone (4-MU, hymecromone), the preparation, characterization, and biological activity evaluation of 4-MU inclusion complexes with β-cyclodextrin (β-CD), as well as their incorporation into pharmaceutical tablets. The inclusion complexes (ICs) were characterized using DLS, SEM, TGA as well as FT-IR, UV-vis, and NMR spectroscopies. The release profile of 4-MU from the β-CD-4-MU ICs was studied in three different pH: 1.2 (aqueous hydrochloric acid), 7.4, and 6.8 (phosphate-buffered solutions), to simulate the stomach, physiological, and intestine pH, respectively. The ICs were incorporated in pharmaceutical tablets which were prepared by direct compression and were characterized for their mechanical properties. The optimal composition of 4-MU as the active pharmaceutical ingredient (API) and excipients was determined using design of experiment (DoE), and the dissolution studies were performed at pH 1.2 at 37 ± 0.5 °C. The sustained release profile of the pharmaceutical tablets showed a delayed burst release effect at 20 min (20% drug release) compared to that of the ICs at the same time interval (70%). The results indicated that the kinetic model describing the release profile of 4-MU from the ICs and tablets is the Higuchi model, while the release mechanism is swelling and diffusion, as was indicated by the Korsmeyer–Peppas kinetic model. The optimization analysis revealed that the optimum composition contains x1 = 150.95 mg of β-CD-4-MU ICs, x2 = 82.65 mg of microcrystalline cellulose, and x3 = 12.40 mg of calcium phosphate.

Abstract The purple spaghetti-eel Moringua raitaborua lives on the sandy or muddy bottoms of estuaries, which are subject to rapid and wide changes in salinity, pH, and osmoregulatory and hypoxic conditions due to the influx of organic materials from sources of freshwater. The species has adapted to hypoxic environments by developing a thicker epidermis with stratified polygonal cells, club cells, two types of mucous cells (goblet and, oval cells), stratified cuboidal cells and dermis with abundant blood capillaries. Among them, histological modification of thinner dorsal, lateral, and ventral body skin to include abundant capillaries and well-developed dermal vascularization may provide cutaneous respiration, permitting survival in brackish waters with low levels of oxygen and variable environmental parameters.

This work presents a dynamic modeling approach for analyzing the behavior of a bi-material cantilever actuator structure, consisting of a strip of filter paper bonded to a strip of tape. The actuator’s response is induced by a mismatch strain generated upon wetting, leading to the bending of the cantilever. The study delves into a comprehensive exploration of the dynamic deflection characteristics of the bilayer structure. It untangles the intricate connections among the saturation, modulus, hygro-expansion strain, and deflection, while uniquely addressing the challenges stemming from fluid–structure coupling. To solve the coupled fluid–solid differential equations, a combined numerical method is employed. This involves the application of the Highly Simplified Marker and Cell (HSMAC) technique for fluid flow analysis and the Finite Difference Method (FDM) for response deflection computation. In terms of the capillary flow model, the Computational Fluid Dynamics (CFD) simulations closely align with the classical Washburn relationship, depicting the wetted front’s evolution over time. Furthermore, the numerical findings demonstrate that heightened saturation levels trigger an increase in hygro-expansion strain, consequently leading to a rapid rise in response deflection until a static equilibrium is achieved. This phenomenon underscores the pivotal interplay among saturation, hygro-expansion strain, and deflection within the system. Additionally, the actuator’s response sensitivity to material characteristics is highlighted. As the mismatch strain evolving from paper hygro-expansion diminishes, a corresponding reduction in the axial strain causes a decrease in response deflection. The dynamic parameter demonstrates that the deflection response of the bilayer actuator diminishes as dynamic pressure decreases, reaching a minimal level beyond which further changes are negligible. This intricate correlation underscores the device’s responsiveness to specific material traits, offering prospects for precise behavior tuning. The dependence of paper modulus on saturation levels is revealed to significantly influence bilayer actuator deflection. With higher saturation content, the modulus decreases, resulting in amplified deflection. Finally, strong concordance is observed among the present fluidically coupled model, the static model, and empirical data—a testament to the accuracy of the numerical formulation and results presented in this study.