Search Results (173)

The covalent cross-linking of caseins by the enzyme transglutaminase (Tgase) stabilizes the structure of casein micelles. In our study, the effects of a pretreatment of skim milk (SM) by Tgase on milk protein fractionation by microfiltration were tested. Tgase was found to induce amount-dependent modifications of all milk proteins in SM and a reduction in deposit resistance for laboratory dead-end filtrations of up to 20%. This improvement in process performance could partially be confirmed in pilot-scale cross-flow filtrations of Tgase-pretreated SM and micellar casein solutions (MCC). These comparative trials with untreated retentates under a variation of ΔpTM (0.5–2 bar) at 10 and 50° revealed distinct differences in deposit behavior and achieved the reduction in deposit resistance in a range of 0–20%. The possibility of pre-fouling with enzymatically pretreated MCC prior to SM filtration was also investigated. Under different pre-fouling conditions, practical modes of retentate change, and pre-foulant compositions, a switch to untreated SM consistently resulted in an immediate and major increase in deposit resistance by 50–150%. This was partially related to the change in the ionic environment and the protein fraction. Nevertheless, our results underline the potential of Tgase pretreatment and pre-fouling approaches to alter filtration performance for different applications. Full article

Background and Objectives: To evaluate the mRNA vaccine platform for blood-stage Plasmodium parasites, we completed a proof-of-concept study using the P. yoelii mouse model of malaria and two mRNA-based vaccines. Both encoded PyMSP1₁₉ fused to PyMSP8 (PyMSP1/8). One was designed for secretion of the encoded protein (PyMSP1/8-sec); the other encoded membrane-bound antigen (PyMSP1/8-mem). Methods: Secretion of PyMSP1/8-sec and membrane localization of PyMSP1/8-mem were verified in mRNA-transfected cells. As recombinant PyMSP1/8 (rPyMSP1/8) is known to protect mice against lethal P. yoelii 17XL infection, we first compared immunogenicity and efficacy of the PyMSP1/8-sec mRNA vaccine versus the recombinant formulation in outbred mice. Animals were immunized three times followed by challenge with a lethal dose of P. yoelii 17XL-parasitized RBCs (pRBCs). Similar immunization and challenge experiments were conducted to compare PyMSP1/8-sec versus PyMSP1/8-mem mRNA vaccines. Results: Immunogenicity of the PyMSP1/8-sec mRNA vaccine was superior to the recombinant formulation, inducing higher antibody titers against both vaccine components. Following challenge with P. yoelii 17XL pRBCs, all PyMSP1/8-sec-immunized animals survived, with 50% of these showing no detectible pRBCs in circulation (<0.01%). In addition, mean peak parasitemia in PyMSP1/8-sec mRNA-immunized mice was significantly lower than that in the rPyMSP1/8 vaccine group. Both PyMSP1/8-sec and PyMSP1/8-mem were protective against P. yoelii 17XL challenge, with PyMSP1/8-mem immunization providing a significantly higher level of protection than PyMSP1/8-sec immunization considering the number of animals with no detectable pRBCs in circulation and the mean peak parasitemia in animals with detectable parasitemia. Conclusions: mRNA vaccines were highly immunogenic and potently protective against blood-stage malaria, outperforming a similar recombinant-based vaccine. The membrane-bound antigen was more effective at inducing protective antibody responses, highlighting the need to consider antigen localization for mRNA vaccine design. Full article

The high cost of platinum (Pt) catalysts impedes the widespread commercialization of proton exchange membrane fuel cells (PEMFCs). Reducing Pt loading will increase local oxygen transport resistance ($R_{\mathrm{Pt}}^{{\mathrm{O}}_2}$) and decrease performance. Due to the oxygen transport resistance, the reactants in the cathode catalyst layer (CCL) are not evenly distributed. The gradient structure can cooperate with the unevenly distributed reactants in CL to enhance the Pt utilization. In this work, a one-dimensional gradient CCL model considering $R_{\mathrm{Pt}}^{{\mathrm{O}}_2}$ is established, and the optimal gradient structure is optimized by combining the artificial neural network (ANN) model and the genetic algorithm (GA). The optimal structure parameters of non-gradient CCL are l_CL equal to 8.86 μm, r_C equal to 36.82 nm, and I/C equal to 0.48, with the objective of maximum current density (I_max); l_CL equal to 4.24 μm, r_C equal to 36.60 nm, and I/C equal to 0.76, with the objective of maximum power density (P_max). For the gradient CCL, the best gradient distribution enables Pt loading to increase from the membrane (MEM) side to the gas diffusion layer (GDL) side and the ionomer volume fraction to decrease from the MEM side to the GDL side. Full article

Drug carriers hold significant promise for precision medicine but face persistent challenges in balancing high encapsulation efficiency with structural preservation during active loading. In this study, we present a microelectromechanical system (MEMS)-driven platform that can generate gigahertz (GHz)-frequency acoustic streaming (1.55 GHz) to enable nondestructive, power-tunable drug encapsulation in lipid vesicles. Utilizing DSPE-PEG-modified bilayers with hydrodynamic shear forces, our method achieves transient membrane permeability that preserves membrane integrity while permitting controlled doxorubicin (DOX) influx. We developed the GHz acoustic MEMS platform and applied it to systematically investigate two drug loading strategies: (1) loading DOX into giant unilamellar vesicles (GUVs, >10 μm in diameter) prior to extrusion into small unilamellar vesicles (SUVs, 100 nm) versus (2) direct acoustic loading into pre-formed SUVs. The GUV-first approach demonstrated better performance, achieving 60.04% ± 1.55% encapsulation efficiency (EE%) at 250 mW acoustic power—a 5.93% enhancement over direct SUV loading (54.11% ± 0.72%). Structural analysis via TEM confirmed intact SUV morphology post-loading, while power-dependent EE% analysis showed a linear trend. This work bridges gaps in nanocarrier engineering by optimizing drug loading strategies, aiming to offer a potential drug carrier platform for drug delivery in biomedical treatment in future. Full article

Background/Objectives: Acute otitis media is a common pediatric infection caused primarily by nontypeable Haemophilus influenzae. With rising antibiotic resistance, vaccines are essential for combating this public health issue. Although the PD-1/PD-L1 pathway has been extensively studied for its role in tumor immunity, its impact on mucosal immunity, particularly in vaccine responses, is unclear. Methods: BALB/c mice were intranasally immunized with nontypeable H. influenzae outer membrane protein and treated with anti-PD-L1 antibodies. Immune responses were evaluated in middle ear mucosa (MEM), the cervical lymph node, and the spleen using an enzyme-linked immunosorbent assay, an enzyme-linked immunospot assay, and flow cytometry. The effects on CD4⁺ T cells, T follicular helper (Tfh) cells, and B-cell differentiation were analyzed. Results: Anti-PD-L1 antibody treatment increased CD3⁺CD4⁺CD185⁺ (CXCR5⁺) Tfh cells in MEM, which play a crucial role in supporting B-cell activation and antibody production. This correlated with a significant increase in IgA- and IgG-producing cells in MEM, which enhanced local bacterial clearance. Although B-cell activation and differentiation into plasmablasts were observed in MEM, no significant changes were noted in the cervical lymph node and spleen, suggesting a localized enhancement of mucosal immunity. Conclusions: Anti-PD-L1 antibodies promoted Tfh cell expansion and B-cell differentiation in MEM, leading to enhanced antibody production and improved bacterial clearance. These findings suggest that PD-L1 blockade can potentiate mucosal vaccine-induced immunity by strengthening local humoral responses. This supports its potential application in developing intranasal vaccines for acute otitis media. Full article

The pull-in and pull-out voltages are important characteristics of Capacitive Micromachined Ultrasound Transducers (CMUTs), marking the transition between conventional and collapse operation regimes. These voltages are commonly determined using capacitance–voltage (C-V) sweeps. By modeling the operating conditions of an LCR meter in COMSOL Multiphysics^®, we demonstrate that the measured capacitance comprises both static and dynamic capacitances, with the dynamic capacitance causing the appearance of a peak in the effective C-V curve. Furthermore, Laser Doppler Vibrometer (LDV) measurements and electromechanical simulations indicate the occurrence of collapse–snapback phenomena during the C-V sweeps. This study, through advanced simulations and experimental analyses, demonstrates that the transient membrane behavior significantly affects the apparent capacitance–voltage characteristics of electrostatically actuated Micro-Electromechanical Systems (MEMS). Full article

Membrane proteins constitute essential biomolecules attached to or integrated into cellular and organelle membranes, playing diverse roles in cellular processes. Their precise localization is crucial for understanding their functions. Existing protein subcellular localization predictors are predominantly trained on globular proteins; their performance diminishes for membrane proteins, explicitly via deep learning models. To address this challenge, the proposed study segregates membrane proteins into three distinct locations, including the plasma membrane, internal membrane, and membrane of the organelle, using deep learning algorithms including recurrent neural networks (RNN) and Long Short-Term Memory (LSTM). A redundancy-curtailed dataset of 3000 proteins from the MemLoci approach is selected for the investigation, along with incorporating pseudo amino acid composition (PseAAC). PseAAC is an exemplary technique for extracting protein information hidden in the amino acid sequences. After extensive testing, the results show that the accuracy for LSTM and RNN is 83.4% and 80.5%, respectively. The results show that the LSTM model outperforms the RNN and is most commonly employed in proteomics. Full article

In order to meet the better performance requirements of pressure detection, a microelectromechanical system (MEMS) piezoresistive pressure sensor utilizing an array-type aluminum–silicon hybrid structure with high sensitivity and low temperature drift is designed, fabricated, and characterized. Each element of the 3 × 3 sensor array has one stress-sensitive aluminum–silicon hybrid structure on the strain membrane for measuring pressure and another temperature-dependent structure outside the strain membrane for measuring temperature and temperature drift compensation. Finite-element numerical simulation has been adopted to verify that the array-type pressure sensor has an enhanced piezoresistive effect and high sensitivity, and then this sensor is fabricated based on the standard MEMS process. In order to further reduce the temperature drift, a thermodynamic control system whose heating feedback temperature is measured by the temperature-dependent structure is adopted to keep the working temperature of the sensor constant by using the PID algorithm. The experiment test results show that the average sensitivity of the proposed sensor after temperature compensation reaches 0.25 mV/ (V kPa) in the range of 0–370 kPa, the average nonlinear error is about 1.7%, and the thermal sensitivity drift coefficient (TCS) is reduced to 0.0152%FS/°C when the ambient temperature ranges from −20 °C to 50 °C. The research results may provide a useful reference for the development of a high-performance MEMS array-type pressure sensor. Full article

In this paper, different concepts of reconfigurable RF-MEMS attenuators for beamforming applications are proposed and critically assessed. Capitalizing on the previous part of this work, the 1-bit attenuation modules featuring series and shunt resistors and low-voltage membranes (7–9 V) are employed to develop a 3-bit attenuator for fine-tuning attenuations (<−10 dB) in the 24.25–27.5 GHz range. More substantial attenuation levels are investigated using fabricated samples of coplanar waveguide (CPW) sections equipped with Pi-shaped resistors aiming at attenuations of −15, −30, and −45 dB. The remarkable electrical features of such configurations, showing flat attenuation curves and limited return losses, and the investigation of a switched-line attenuator design based on them led to the final proposed concept of a low-voltage 24-state attenuator. Such a simulated device combines the Pi-shaped resistors for substantial attenuations with the 3-bit design for fine-tuning operations, showing a maximum attenuation level of nearly −50 dB while maintaining steadily flat attenuation levels and limited return losses (<−11 dB) along the frequency band of interest. Full article

In this work, a closed loop control system is developed to optically localize and track micro-robots with high precision. These micro-robots (i.e., micro-conveyors) are in motion simultaneously across a smart surface.The developed method’s primary objectives are to optimize their trajectories, avoid collisions between them, and control their position with micrometric resolution. This article presents and characterizes the tracking of a single micro-conveyor, and the method works similarly when multiple micro-robots move over the surface. Our tracking method starts with a scanning phase, where a 2D steering mirror, placed above the smart surface, reflects a laser beam toward the conveying surface seeking for the target. Localization occurs when this light beam reaches the micro-conveyor. By adding a retro-reflective element, that reflects the light in the same direction of the the incident light, onto the surface of the micro-conveyor, the light will be reflected towards a photodetector. Depending on the feedback from the photodetector, the steering mirror rotates to track the trajectory of the micro-conveyor. The tip-tilt angular values of the steering mirror allows the micro-conveyor position to be obtained via calibrated localization system. The aim of this work is to regulate the micro-conveyor, within a closed-loop control system, to reduce the positional error between the actual and desired position. The actual position value is measured in real-time application using our developed optical sensor. Results for tracking in the x-and y-axis have validated the proposed method, with an average tracking error less than 30 µm within a range 150 mm × 150 mm. Full article

Calorimetry is a powerful method for characterising materials. The heat of a reaction can be directly measured with good accuracy. The established method usually requires large amounts of materials, which is a major drawback when studying thin film reactions. A MEMS microhotplate-based microcalorimeter is developed in this study; it allows us to investigate thin film reactions by using a very small amount of materials. The temperature scale is calibrated by a well-known heat method of melting of two metal films. Energy calibration is also solved, and thus real information can be extracted for various solid-phase thin film reactions. In order to study reactions taking place close to room temperature, a cooled sample holder is developed, and the measurements can be started well below 0 °C. Full article

This study presents a new design for a MEMS electrostatic speaker array with out-of-plane piston-like diaphragm displacement using a simplified silicon-on-insulator microfabrication process. The device comprises an array of parallel actuating membranes with small circular mechanically open but acoustically sealed apertures that enable controlled etching of the buried oxide to be released directly from the front side, but retain a high acoustic impedance acting as a flat membrane. This approach simplifies the microfabrication process, requiring only two lithography masks and increasing process tolerances. Preliminary experimental measurements validate the concept and demonstrate the electromechanical and acoustic performance compared with theoretical models. Full article

Solid-state nanopores have become a prominent tool in the field of single-molecule detection. Conventional solid-state nanopores are thick, which affects the spatial resolution of the detection results. Graphene is the thinnest 2D material and has the highest spatial detection resolution. In this study, a graphene membrane chip was fabricated by combining a MEMS process with a 2D material wet transfer process. Raman spectroscopy was used to assess the quality of graphene after the transfer. The mechanism behind the influence of the processing dose and residence time of the helium ion beam on the processed pore size was investigated. Subsequently, graphene nanopores with diameters less than 10 nm were fabricated via helium ion microscopy. DNA was detected using a 5.8 nm graphene nanopore chip, and the appearance of double-peak signals on the surface of 20 mer DNA was successfully detected. These results serve as a valuable reference for nanopore fabrication using 2D material for DNA analysis. Full article

In order to realize the measurement of three-axis acceleration, pressure, and magnetic field, monolithic integrated three-axis acceleration/pressure/magnetic field sensors are proposed in this paper. The proposed sensors were constructed with an acceleration sensor consisting of four L-shaped double beams, two masses, middle double-beams, and twelve piezoresistors, a pressure sensor made of a square silicon membrane, and four piezoresistors, as well as a magnetic field sensor composed of five Hall elements. COMSOL software and TCAD-Atlas software were used to simulate characteristics of integrated sensors, and analyze the working principles of the sensors in measuring acceleration, pressure, and magnetic field. The integrated sensors were fabricated by using micro-electro-mechanical systems (MEMS) technology and packaged by using inner lead bonding technology. When applying a working voltage of 5 V at room temperature, it is possible for the proposed sensors to achieve the acceleration sensitivities of 3.58 mV/g, 2.68 mV/g, and 9.45 mV/g along the x-axis, y-axis, and z-axis (through an amplifying circuit), and the sensitivities towards pressure and magnetic field are 0.28 mV/kPa and 22.44 mV/T, respectively. It is shown that the proposed sensors can measure three-axis acceleration, pressure, and magnetic field. Full article

In this paper, a MEMS piezoresistive ultrathin silicon membrane-based strain sensor is presented. The sensor’s ability to capture an acoustic emission signal is demonstrated using a Hsu–Nielsen source, and shows comparable frequency content to a commercial piezoceramic ultrasonic transducer. To the authors’ knowledge, this makes the developed sensor the first known piezoresistive strain sensor which is capable of recording low-energy acoustic emissions. The improvements to the nondestructive evaluation and structural health monitoring arise from the sensor’s low minimum detectable strain and wide-frequency bandwidth, which are generated from the improved fabrication process that permits crystalline semiconductor membranes and advanced polymers to be co-processed, thus enabling a dual-use application of both acoustic emission and static strain sensing. The sensor’s ability to document quasi-static bending is also demonstrated and compared with an ultrasonic transducer, which provides no significant response. This dual-use application is proposed to effectively combine the uses of both strain and ultrasonic transducer sensor types within one sensor, making it a novel and useful method for nondestructive evaluations. The potential benefits include an enhanced sensitivity, a reduced sensor size, a lower cost, and a reduced instrumentation complexity. Full article