Layer Thickness Research Articles

How is the posterior ocular segment affected in cesarean section and normal vaginal delivery?

To evaluate the effects of normal vaginal delivery (NVD) and cesarean section (CS) on the retina, optic disc, and choroid in healthy pregnant women by using optical coherence tomography (OCT). This prospectively designed study included 60 healthy pregnant women, of whom 30 underwent NVD and 30 underwent CS. Ophthalmological examinations and OCT scans were performed on all pregnant women during the third trimester and the first postpartum week. The measurements were compared between the two visits within each group. Central retinal thickness, ganglion cell layer and inner plexiform layer (GCL + IPL) thickness, peripapillary retinal nerve fiber layer thickness, and optic disc morphology were determined using OCT scans. Central, nasal, and temporal choroidal thicknesses were manually measured using HD-line OCT. Choroidal vascular parameters were calculated from HD-line OCT scans by using a special image processing module. The ratio of the luminal choroidal area to the total choroidal area was determined as the choroidal vascular index (CVI). In the NVD group, the thinning in the mean and inferior pRNLF, the decrease in the rim area, and the increase in the mean cup/disc and cup volume at the first postpartum week were found to be statistically significant (P < 0.05). In the same group, the CVI was calculated as 0.69 ± 0.02 in the third trimester and 0.66 ± 0.03 in the first postpartum week (P = 0.001). In the CS group, except for the increase in the GCL + IPL thickness, no significant difference was detected in the measurements of the retina, optic disc, and choroid (P < 0.001 and P > 0.05). This is the first study to evaluate the effect of the delivery method on the retina, choroid, and optic disc. In NVD, changes in the choroidal vascular structure and optic disc morphology can be observed in the early postpartum period, which may be attributed to hormonal effects.

Seismic performance and calculation method for plastic hinge length of RC pier reinforced with UHPC

Piers are highly vulnerable load-bearing components, and their seismic performance determines the integral seismic resistance of bridges to a certain degree. They play crucial roles in evacuation during earthquakes and post-earthquake rescue. The manner in which piers meet the seismic performance requirements after reinforcement has become a popular research topic. In this study, ultra-high-performance concrete (UHPC) and HTRB600E high-tensile reinforcements were used to expand the cross section of a cast-in-place square pier with severe bending damage. The earthquake-resistant behaviour indicators of the pier were compared and analysed by conducting pseudo-static tests on a reinforced concrete pier before and after reinforcement. These indicators included the hysteretic curve, skeleton curve, energy dissipation curve, rigidity degradation, residual displacement, and pier body curvature. Based on the results of the seismic reinforcement quasi-static tests, a finite element model (FEM) of the bridge pier was constructed using the ABAQUS software, and the accuracy of the FEM was averaged. The impact of the reinforcement layer height, thickness, longitudinal strength and axial compression ratio on the equivalent plastic-hinge length of the reinforced pier was analysed, and the formula for the equivalent plastic-hinge length of the reinforced pier was obtained based on multiple linear regression fitting. The analysis results demonstrated that the broadened section method, utilising UHPC and high-tensile reinforcement, significantly enhanced the flexural capacity, energy dissipation, and first rigidity of the bridge pier. The earthquake-resistant behaviour of pier was effectively restored and improved, and the seismic reinforcement effect was significant. The equivalent plastic hinge length of the pier after reinforcement is proportional to the height of the reinforcement layer, the thickness of the reinforcement layer, the strength of the longitudinal reinforcement, and inversely proportional to the axial compression ratio.

Facile synthesis of Fe3O4 photothermal nanoparticles coated with poly-3,4-dihydroxybenzaldehyde for improved photothermal therapy of cancer cells

Given the significant rise in the number of individuals diagnosed with cancer, the management of cancer therapy has become a prominent concern in society and a formidable task in human health care. Photothermal therapy has garnered significant interest in cancer treatment because of its exceptional efficacy and minimal invasiveness. Thus, current research mainly focuses on developing biocompatible materials with excellent photothermal properties. Therefore, we synthesized Fe3O4 nanoparticles coated with poly-3,4-dihydroxybenzaldehyde (Fe3O4@PDBA) where 3,4-dihydroxybenzaldehyde was covalently polymerized onto the surface of Fe3O4. The induction of PDBA leads to a dramatical improvement in the photothermal properties of Fe3O4. Besides, the thickness of the PDBA shell layer is also a key factor in the photothermal performance and various physicochemical properties of Fe3O4@PDBA and the photothermal performance of Fe3O4@PDBA increases with increasing thickness of the PDBA shell. Additional structural characterization of the products, DFT calculations of the UV-Vis absorption spectra and the HOMO-LUMO gap under the simple model of the polymer, and product identification by the use of H1NMR, MS, and other techniques were performed. Through multiple characterizations, the reaction solution color and UV-Vis absorption spectra were essentially consistent with the computed findings. The calculations confirm that the polymerization process of PDBA is progressively red-shifted and the absorption is gradually enhanced in the NIR region. Fe3O4@PDBA exhibited strong cytotoxicity against cancer cells (Hela, 98.0%) in vitro photothermal treatment. Hence, Fe3O4@PDBA exhibits superior photothermal characteristics, targeting, biocompatibility (99.0%), and degradability, which brings about significant potential for photothermal cancer therapy.

Retinal Damage and Visual Network Reconfiguration Defines Visual Function Recovery in Optic Neuritis.

Recovery of vision after acute optic neuritis (AON) is critical to improving the quality of life of people with demyelinating diseases. The objective of the study was to prospectively assess the changes in visual acuity, retinal layer thickness, and cortical visual network in patients with AON to identify the predictors of permanent visual disability. We studied a prospective cohort of 88 consecutive patients with AON with 6-month follow-up using high and low-contrast (2.5%) visual acuity, color vision, retinal thickness from optical coherence tomography, latencies and amplitudes of multifocal visual evoked potentials, mean deviation of visual fields, and diffusion-based structural (n = 53) and functional (n = 19) brain MRI to analyze the cortical visual network. The primary outcome was 2.5% low-contrast vision, and data were analyzed with mixed-effects and multivariate regression models. We found that after 6 months, low-contrast vision and quality of vision remained moderately impaired. The thickness of the ganglion cell layer at baseline was a predictor of low-contrast vision 6 months later (ß = 0.49 [CI 0.11-0.88], p = 0.012). The structural cortical visual network at baseline predicted low-contrast vision, the best predictors being the betweenness of the right parahippocampal cortex (ß = -036 [CI -0.66 to 0.06], p = 0.021), the node strength of the right V3 (ß = 1.72 [CI 0.29-3.15], p = 0.02), and the clustering coefficient of the left intraparietal sulcus (ß = 57.8 [CI 12.3-103.4], p = 0.015). The functional cortical visual network at baseline also predicted low-contrast vision, the best predictors being the betweenness of the left ventral occipital cortex (ß = 8.6 [CI: 4.03-13.3], p = 0.009), the node strength of the right intraparietal sulcus (ß = -2.79 [CI: -5.1-0.4], p = 0.03), and the clustering coefficient of the left superior parietal lobule (ß = 501.5 [CI 50.8-952.2], p = 0.03). The assessment of the visual pathway at baseline predicts permanent vision disability after AON, indicating that damage is produced early after disease onset and that it can be used for defining vision impairment and guiding therapy.

Interface characteristics and fracture mechanism of laser-arc hybrid welded Al-Ti dissimilar butt-joint through beam oscillation

Two laser oscillating patterns including circle and inscribed double-circle were adopted for the laser-arc hybrid welding of Al-Ti dissimilar butt-joint, and compared with the none-oscillating hybrid welding. The results showed that a two-layer intermetallic compounds (IMCs) including Al3Ti and Al2Ti was formed at the Al-Ti interface without laser oscillation, and the thickness (τ) of IMCs layer reached up to 5.56 μm. The IMCs layer was transferred to a single-layer Al2Ti with decreased the τ to 1.18 μm by the optimized inscribed double-circle oscillating hybrid welding. The optimized laser oscillation benefited to form local turbulences inside the molten pool, which optimized the composition of interface IMCs layer and effectively reduced its thickness. Due to the combined improvements, the ultimate tensile strength of Al-Ti dissimilar butt-joint was increased by 18% from 182.6 to 215 MPa. The corresponding tensile fracture of welded joint changed from the two-layer IMCs layer to the base metal. Because no orientation relationship between them along the Al3Ti/ Al2Ti was formed, the tensile crack preferentially propagated between the Al3Ti and Al2Ti IMCs at the interface, resulting in the poor tensile properties.

Exploring retinal vessel density alterations in prolactinoma patients: Insights from OCTA imaging.

To investigate microvascular changes in the macular and peripapillary area in prolactinoma patients by using optical coherence tomography angiography (OCTA). A retrospective study. This study included 40 patients with treatment-naive prolactinoma and 42 healthy controls. Participants underwent comprehensive ophthalmic examinations, visual field testing, and optical coherence tomography (OCT) assessments, including retinal nerve fiber layer (RNFL) thickness, macular, and peripapillary region OCTA by using the Topcon DRI OCT Triton Swept Source-OCT system. The OCTA results were evaluated between groups and then correlated with PRL levels. The differences in best-corrected visual acuities were statistically significant among the groups. The RNFL thickness in the superior and nasal quadrants was significantly lower in the prolactinoma group. The prolactinoma group showed significant reductions in macular vessel density (VD) across all layers than the control group, except in the deep retinal capillary plexus temporal quadrants. The radial peripapillary capillary (RPC) temporal VD in the prolactinoma group was significantly lower. In patients with optic neuropathy, correlations were observed between the RPC temporal and RNFL temporal sectors (r = 0.650, P = 0.03), and between the RPC inferior and RNFL inferior sectors (r = -0.612, P = 0.045). Between PRL levels and OCTA parameters, negative correlations were observed (RPC inferior: r = -0.452, P = 0.003; DCP superior: r = -0.379, P = 0.016). Our study revealed reduced VD in the macula and RPC temporal regions in patients with treatment-naive prolactinoma. OCTA holds significant importance in detecting potential retinopathies and vasculopathies. Future research should focus on examining pre- and post-treatment changes in treatment-naive patients without ON to better understand the impact of prolactinoma.

Optimizing laser parameters and exploring building direction dependence of corrosion behavior in NiTi alloys fabricated by laser powder bed fusion

The microstructure and materials performance of Laser Powder Bed Fusion-fabricated (LPBFed) NiTi shape memory alloys (SMAs) varies depending on the laser parameters and building directions. This study initially optimized the laser processing parameters (laser power and scanning speed) for LPBFed NiTi SMAs to enhance their printing quality and mechanical properties. We determined that with fixed hatch spacing of 80 μm and layer thickness of 30 μm, the laser power of 105 W, and scanning speed of 600 mm/s produced the best results. Subsequently, the corrosion behavior of LPBFed NiTi SMAs built in three different building directions (0°, 45°, 90°) was investigated in 0.9 wt.% NaCl solution at 37 °C. The electrochemical data revealed that the corrosion current density (Icorr) decreased with increasing building direction angle (Icorr-90° <Icorr-45° <Icorr-0°). The corrosion resistance followed the order of 0° sample ˂ 45° sample ˂ 90° sample. These findings were attributed to the difference in the grain size and boundary density. Higher boundary densities enhanced the electron activity capacity and the element diffusion rates, facilitating the rapid formation of a protective film and thus improving the corrosion resistance. This new insight into the anisotropy of corrosion behavior relative to building directions can inform the design of NiTi-SMA products and improve their reliability in tissue engineering applications.

Characterization of thin oxide layers formed by Ti-Nb Alloy anodization

Ti-Nb alloys are gaining more prominence in the industrial and scientific environment due to their high biocompatibility, mechanical strength/weight ratio, and exceptional corrosion resistance compared to other metallic materials. Metals exhibiting this passivation characteristic are known as metal valves and may exhibit semiconductive or insulating oxides. Controlling the growth of distinct thickness layer films is possible through tunning anodization conditions. In this work, a Ti-Nb binary system is anodized, and the grown oxide layer is comprehensively characterized using ellipsometry based on its optical properties and thickness at different applied potentials. Confocal Microscopy assessed their surface roughness, and SEM/EDS probed the surface material's elemental composition. CF-LIBS successfully confirmed the 70/30 composition of the Ti-Nb alloy. Raman spectra have detected the presence of amorphous TiO2 and Nb2O5 at potentials higher than 80V, 100V, and 120V. Finally, a linear dependence of the oxide thickness with the applied potential was observed.

Characteristics of Solidification Cracking for Ni-P Coated Cu-Al5052 Single-Mode Fiber Laser Welds

This study fundamentally examines the characteristics of solidification cracking in Cu-Al5052 single-mode fiber laser welding by utilizing uncoated and Ni-P coated Cu plates for the high durability busbar welding of pouch-type lithium-ion battery packs. Weld solidification cracking was confirmed regardless of Ni-P coating for both weld materials. However, there were differences in the regions of crack occurrence. Unlike the uncoated Cu-Al5052 welds where cracks occurred randomly within the fusion zone, for the Ni-P coated Cu-Al5052 welds, solidification cracks were concentrated near the faying surface of the upper and lower materials, particularly near the fusion line. The effect of the Ni and P components on the solidification cracking susceptibility, i.e., the welding solidification temperature range, was considered. Diffusion-controlled Scheil’s solidification calculations revealed that the mushy zone range enlarged with the use of a Ni coating layer. It was confirmed that an extremely wide mushy zone range of 1060 K was calculated at the solidification cracking region. Furthermore, P was also identified as an element that expands the solidification temperature range based on the Cu-P binary system. Consequently, during the laser welding of Cu-Al5052 dissimilar materials, the behavior of solidification cracking in the welds is influenced by the composition of the coating material and the incorporated composition within the weld fusion zone. Hence, it is necessary to select the optimal coating material and layer thickness considering weld solidification cracking susceptibility.

Geoelectrical resistivity mapping for sustainable groundwater management in Umuahia South: Insights from vertical electrical sounding

The study of geoelectrical resistivity provides critical insights into subsurface characteristics and aquifer dynamics, particularly in regions with varying geological formations. This research investigates the geoelectrical properties of the aquifer system in Umuahia South, highlighting its significance for sustainable groundwater management. The primary aim of this study is to characterize the geoelectrical layers, assess aquifer thickness and resistivity, and evaluate the implications for groundwater resource management. Vertical Electrical Sounding (VES) was conducted across ten locations to measure the resistivity and thickness of subsurface layers. The data collected were analyzed to identify distinct geoelectrical layers, their respective resistivity values, and thicknesses. The study reveals significant variations in aquifer properties across the region, with VES 1 showcasing the largest thickness of 69.2 m and VES 9 the smallest at 5.2 m. Aquifer thickness decreases from the Benin Formation toward the Ameki and Ogwashi-Asaba Formations. Hydraulic conductivity ranges from 0.207 to 0.954 m/day, indicating varying groundwater flow potential, while transmissivity values vary from 4.965 to 30.441 m²/day, with 60% of aquifers classified as intermediate. Groundwater Potential Index (GWPI) highlights approximately 70% of the area as high potential, underscoring the need for targeted management strategies to optimize water resource extraction and sustainability. The variability in resistivity and thickness across the study area suggests significant subsurface heterogeneity. High resistivity values indicate favorable conditions for groundwater flow, particularly in areas like VES 6. Conversely, lower resistivity in locations such as VES 9 indicates potential challenges for groundwater storage. This study provides vital information on the aquifer system in Umuahia South, emphasizing the need for targeted groundwater management strategies based on the geoelectrical characteristics identified. The research contributes to a deeper understanding of the aquifer dynamics in the region and offers a framework for sustainable groundwater resource management, highlighting the importance of geoelectrical assessments.

Development of craquelure patterns in paintings on canvas

Canvas paintings are layered structures composed of canvas support sized with animal glue, a preparatory layer of the ground, and paint and varnish layers on the top. Preventing or limiting humidity-induced stresses in these structures requires an understanding of the relevant processes and risks. A three-dimensional model of a canvas painting was used to analyse stresses and crack development in the two-layer structure comprised of a glue-sized canvas on a wooden stretcher with a layer of stiff chalk-glue ground representing a pictorial layer in historic canvas paintings. The model was subjected to a large relative humidity fall which induced shrinkage of the glue-sized canvas. The modelling revealed that when a stretcher with flexible wooden bars is considered, high tensile stresses arise in the ground layer at the corners of the painting, and cracks are formed in these areas in the direction perpendicular to the painting’s diagonal. Ratios of critical distances between cracks to the ground layer thickness for which stresses in the midpoints between the cracks dropped to below the level inducing fracture in the material were estimated for various magnitudes of the relative humidity drop and thicknesses of the ground layer. Increasing ground layer thickness limits the hygric response of the sized canvas and makes the paintings less vulnerable to humidity variations. The ratio of stress along the diagonal calculated for painting with one crack to the solution without cracks was described by the double Lorentz function. A simple procedure of calculating stress variations along the diagonal—using the function—on a sequential addition of cracks was developed. Cracks in central parts of canvas painting were found to be induced by permanent cumulative drying shrinkage of the oil-based paints and grounds due to the evolution of the molecular composition of the oil binder. The outcome of the modelling indicated that the risk of cracking of the pictorial layers in canvas paintings due to drops in ambient relative humidity was small.

Optimization of MBE-grown GaSb buffer on GaAs substrates for infrared detectors

The aim of this work was to improve the quality of the GaSb buffer layers on GaAs substrates using the molecular beam epitaxy (MBE) technology. The high quality of the GaSb buffer layers is one of the most important elements enabling the synthesis of good quality of type II superlattices (T2SL) structures for infrared applications. The main challenges in this regard are: compensation of the difference in lattice constants between GaAs and GaSb and obtaining the highest achievable surface quality of the final GaSb layer. In the literature, many authors describe different techniques to obtain the best quality of a GaSb buffer layer. In this work, we present the results of HRXRD, AFM, TOF-SIMS, SEM, and Nomarski optical microscope measurements obtained for 2 μm thick GaSb buffer layers. The GaSb layers are made according to different techniques and these results are compared with a GaSb buffer construction technique according to our own technology. During the processes, we also obtained an unintentional structure of one of the buffer layers, which allowed us to obtain very good results in terms of surface structure and crystallographic quality where FWHM in ωRC scan was equal to 138 arcsec and RMS 0.20 nm proving that there is still a lot of work to be done in this area.

Multiple high-Q resonances from mirror-coupled dielectric arrays

This paper reports how high-Q resonances can be created at multiple designated wavelengths in a low-index-contrast dielectric nanoparticle array coupled with a metal mirror. A rectangular array of TiO2 nanoparticles over a silver film (separated by a SiO2 spacer layer) can support collective resonances of magnetic and electric dipoles with their wavelengths determined mainly by the lattice spacings of the rectangular lattice. These resonances can be modulated by the spacer layer thickness to form accidental bound states in the continuum. Furthermore, resonances related to the periodicity along the diagonal of the rectangular unit cell can be produced by perturbing the lattice through modifying the dimensions of adjacent nanoparticles in the unit cell. Our result expands the potential of lattice resonances in low-index-contrast dielectric lattices, making them promising for applications in compact multi-wavelength and unidirectional light-emitting devices.

Digital Light Process 3D Printing of Magnetically Aligned Liquid Crystalline Elastomer Free-forms.

Liquid crystalline elastomers (LCEs) are anisotropic soft materials capable of large dimensional changes when subjected to a stimulus. The magnitude and directionality of the stimuli-induced thermomechanical response is associated with the alignment of the LCE. Recent reports detail the preparation of LCEs by additive manufacturing (AM) techniques, predominately using direct ink write printing. Another AM technique, digital light process (DLP) 3D printing, has generated significant interest as it affords LCE free-forms with high fidelity and resolution. However, one challenge of printing LCEs using vat polymerization methods such as DLP is enforcing alignment. Here, we document the preparation of aligned, main-chain LCEs via DLP 3D printing using a 100 mT magnetic field. Systematic examination isolates the contribution of magnetic field strength, alignment time, and build layer thickness on the degree of orientation in 3D printed LCEs. Informed by this fundamental understanding, DLP is used to print complex LCE free-forms with through-thickness variation in both spatial orientations. The hierarchical variation in spatial orientation within LCE free-forms is used to produce objects that exhibit mechanical instabilities upon heating. DLP printing of aligned LCEs opens new opportunities to fabricate stimuli-responsive materials in form factors optimized for functional use in soft robotics and energy absorption.

Surface Mechanical Property Prediction and Process Optimization of 18CrNiMo7-6 Carburized Steel Stator Guide Based on Radial Basis Function Neural Network and NSGA-II Algorithm

The carburizing process is a key technology that affects the mechanical properties of the surface of the hydraulic motor stator guide rail, and the related process parameters have an important influence on surface hardness, the thickness of the carburized layer, and the deformation of the guide rail. However, at present, the relationship between the carburizing process parameters and the surface mechanical properties of the target is not clear. This paper proposes a “hardness prediction and process parameter optimization” method. Firstly, a finite element model is established, with carburizing time, temperature, and carbon potential as the three input factors; the optimal Latin hypercubic experimental design and sensitivity analysis are applied. Secondly, surface hardness, carburized layer thickness, and deformation are taken as the output values, and an RBF neural network is used to construct the prediction model. The results show that the RBF neural network can be accurately used for the prediction of surface hardness, the thickness of the carburized layer, and deformation, and for the optimization of process parameters. The optimized parameters of surface hardness and the thickness of the carburized layer were increased by 4.2% and 5.1%, respectively, and the deformation amount was reduced to 0.31 mm, achieving the goal of optimal design.

Influence of Density of 3D Printing Using the Fdm Method on Productivity and Mechanical Properties of ABS

The economic and technical advantages of 3D printing make it a possible replacement for conventional production processes, especially for complex products and small batches. It is important to point out that technological parameters of 3D printing, such as layer thickness, print density, print speed, melting temperature, and table temperature, have a significant impact on the mechanical properties and productivity of parts obtained by 3D printing. Because of all the above, there is a great interest in research in this area. The paper presents the results of testing the tensile strength of the ABS polymer, in which two parameters were varied: the thickness of the print layer (0.39 mm) and the print density of 60–100% in steps of 10% each. The samples were obtained on a ZORTRAX M200+ 3D printer using fused filament deposition (FDM) technology. The selected thickness of the printing layer is relatively large, and with it, parts with lower accuracy and high surface roughness are obtained, although at the same time high productivity is achieved, which can satisfy some requirements. The obtained tensile strength values show that increasing the print density leads to an increase in its value, with a deviation in the sample with a print density of 100%, whereas the tensile strength values are comparable to the values obtained by other authors.

Numerical Modeling and Experimental Validation of Icing Phenomena on the External Surface of a U-Bend Tube

The regasification of liquefied natural gas (LNG) is a crucial process that involves certain challenges created by the low temperature of LNG and the risk of ice formation on the external surfaces of the tubes of heat exchangers, which can hinder heat transfer and increase flow resistance. This study presents a numerical model for ice formation on the external surface of the U-bend tube of shell-and-tube heat exchangers. The numerical model has been further enhanced by applying a custom user-defined function. The numerical results were validated using experimental data and demonstrated excellent predictive capability, particularly for the surface temperature of the tubes and the thickness of the ice layer. Hence, this model can reliably capture the overall behavior of the ice formation on the external surfaces of the tubes of shell-and-tube heat exchangers. By highlighting the importance of maintaining stable heat transfer conditions to prevent freezing, this study offers valuable insights that can guide the optimization of heat exchanger designs for LNG regasification.

An Innovative Fuel Design for HTGRs: Evaluating a 10-Hour High-Temperature Oxidation of the SiC Fuel Matrix During Air Ingress Accident Conditions

Preventing severe corrosion incidents caused by air ingress accidents in high-temperature gas-cooled reactors (HTGRs) while improving heat removal efficiency from the core is of paramount importance. To enhance both safety and efficiency, a sleeveless silicon carbide (SiC)-matrix fuel compact has been proposed. This study evaluates the 10-hour oxidation of reaction-sintered SiC (RS-SiC)-matrix fuel compact under the conditions of an air ingress accident within the temperature range of 1000 to 1400 °C. The oxidation tests were conducted in a stagnant air environment without flow. As a result, it is demonstrated that RS-SiC exhibits exceptional resistance to air oxidation up to 1400 °C, as shown by the thermogravimetric analysis (TGA), with minimal mass loss due to the oxidation of free carbon. Scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM–EDX) analysis reveals that the morphology and thickness of the SiO2 layer formed on the RS-SiC surface vary with temperature. At 1400 °C, uniform oxide layer thickness ranging from 1.59 to 4.10 μm and localized nodule-like oxide formations of approximately 10 μm are observed. In contrast, at 1000–1200 °C, thinner oxide layers are identified, indicating that oxide growth accelerates at higher temperatures. The oxidation rates measured provide insights into the mechanisms of oxide growth.

Scalable enzymatic lactate sensor for continuous monitoring in interstitial fluid

Abstract Elevated lactate levels have been shown to be an indicator of poor outcome in cardiovascular patients [1]. Moreover, continuous monitoring of lactate may be more clinically valuable than the absolute value of lactate for risk stratification [2]. A promising approach involves the implementation of a lactate monitoring system inspired by advanced continuous glucose monitoring [3] to provide real-time measurements of lactate in interstitial fluid (ISF) based on miniaturized lactate sensors with submillimeter dimensions. The proposed amperometric lactate sensor employs Pt electrodes (WE = 0.785 mm²) on which the enzyme lactate oxidase is immobilized to selectively detect lactate. The sensing mechanism, shown in Fig. 1a, is based on the conversion of lactate to hydrogen peroxide, which then undergoes oxidation at the electrode surface, generating a current proportional to the concentration of lactate. Amperometric measurements are performed with an applied potential of 0.5 V, a sample volume of 2 µL and a flow rate of 1 µL/min, respecting real-life conditions. The response of the sensor towards lactate is shown in Fig. 1c, demonstrating excellent reversibility, long-term stability over 8 hours and negligible cross sensitivity to glucose (G), ascorbic acid (AA) and uric acid (UA). In addition, the sensor linear range can be extended by 10x by incorporating an outer Nafion layer, acting as a diffusion-limiter. As shown in Fig. 1d, by adjusting the thickness of Nafion layer, the linear range increases up to 20 mM lactate, as per ICU specifications. The physiological challenges associated with ISF extraction prompted us to develop a minimally invasive, submillimeter-sized sensor for direct placement inside the body. To address the most critical step of miniaturization, we have successfully fabricated a three-electrode platform on a Si ribbon measuring 300x1500 µm² and a thickness of 100 µm (Fig. 2a). The sensor is also drastically scaled down, with smallest design having a total sensing area of 200x500 µm² (WE = 0.026 mm², Fig. 2b). Its response to lactate is displayed in Fig. 2c, confirming a reliable functionality. Fig. 2d presents the calibration curves obtained from sensors with different sizes, indicating that the reduction in size does not affect the sensitivity. The developed lactate sensor demonstrates excellent performance: high sensitivity, excellent reversibility, and high stability. In addition, the linear range of the sensor is tunable by integrating an outer Nafion membrane. Finally, we demonstrate the successful fabrication and characterization of submillimeter-sized sensors, opening up their potential for minimally invasive in-vivo measurements.Working principle and characterizationCharacterization miniaturized sensors

Exploring the impact on contact adhesion layer properties in numerical simulations.

This paper presents a comprehensive investigation into the impact of key parameters on contact adhesion layer properties using numerical simulations, addressing fundamental questions in contact mechanics. Aiming to explore interfacial penetration and contact pressure dynamics between a wavy punch and an adhesive-coated body, the study focuses on the influence of adhesive layer thickness, elasticity modulus, and punch geometry on mechanical behavior. The study includes the application of Green's function to address deficiencies in existing models, revealing how contact stiffness, influenced by the flexibility relationship between the coating and substrate, affects the size of the contact area. Finally, conclusions are drawn that adjusting coating factors can induce full contact conditions. Quantitative analysis shows a 2.23-fold increase in load-bearing capacity with a 2 mm increase in adhesive layer thickness, and a 23-fold increase with a toughness ratio rise from 0.1 to 5. These findings are recommended for optimizing adhesive layer properties, contributing to advancements in materials science and innovation.