Mechanical and Aerospace Engineering

Metallic materials under high stress often exhibit deformation localization, manifesting as slip banding. Over seven decades ago, Frank and Read introduced the well-known model of dislocation multiplication at a source, explaining slip band formation. Here, we reveal two distinct types of slip bands (confined and extended) in compressed CrCoNi alloys through multi-scale testing and modeling from microscopic to atomic scales. The confined slip band, characterized by a thin glide zone, arises from the conventional process of repetitive full dislocation emissions at Frank-Read source. Contrary to the classical model, the extended band stems from slip-induced deactivation of dislocation sources, followed by consequent generation of new sources on adjacent planes, leading to rapid band thickening. Our findings provide insights into atomic-scale collective dislocation motion and microscopic deformation instability in advanced structural materials.

As an emerging technology, polymer electrolyte fuel cells (PEFCs) powered by clean hydrogen can be a great source of renewable power generation with flexible utilization because of high gravimetric energy density of hydrogen. To be used in real-life applications, PEFCs need to maintain their performance for long-term use under a wide range of conditions. Therefore, it's important to understand the degradation of the PEFC under protocols that are closely related to the catalyst lifetime. Alloying Pt with transitional metal improves catalyst activity. It is also crucial to understand Pt alloys degradation mechanisms to improve their durability. To study durability of Pt alloys, accelerated stress tests (ASTs) are performed on Pt−Co catalyst supported on two types of carbon. Two different AST protocols were being studied: Membrane Electrolyte Assembly (MEA) AST based on the protocol introduced by the Million Mile Fuel Cell Truck consortium in 2023 and Catalyst AST, adopted from the U.S. Department of Energy (DoE).

Centrifugal microfluidic platforms are highly regarded for their potential in multiplexing and automation, as well as their wide range of applications, especially in separating blood plasma and manipulating two-phase flows. However, the need to use stroboscopes or high-speed cameras for monitoring these tasks hinders the extensive use of these platforms in research and commercial settings. In this study, we introduce an innovative and cost-effective strategy for using an array of light-dependent resistors (LDRs) as optical sensors in microfluidic devices, particularly centrifugal platforms. While LDRs are attractive for their potential use as photodetectors, their bulky size frequently restricts their ability to provide high-resolution detection in microfluidic systems. Here, we use specific waveguides to direct light beams from narrow apertures onto the surface of LDRs. We integrated these LDRs into electrified Lab-on-a-Disc (eLOD) devices, with wireless connectivity to smartphones and laptops. This enables many applications, such as droplet/particle counting and velocity measurement, concentration analysis, fluidic interface detection in multiphase flows, real-time monitoring of sample volume on centrifugal platforms, and detection of blood plasma separation as an alternative to costly stroboscope devices, microscopes, and high-speed imaging. We used numerical simulations to evaluate various fluids and scenarios, which include rotation speeds of up to 50 rad/s and a range of droplet sizes. For the testbed, we used the developed eLOD device to analyze red blood cell (RBC) deformability and improve the automated detection of sickle cell anemia by monitoring differences in RBC deformability during centrifugation using the sensors signals. In addition to sickle cell anemia, this device has the potential to facilitate low-cost automated detection of other medical conditions characterized by altered RBC deformability, such as thalassemia, malaria, and diabetes.

Polycarbonate polyurethane (PCU) resins are widely used in biomedical applications due to their excellent mechanical properties, biocompatibility, and resistance to degradation. The performance of these materials in implantable devices depends on factors such as hardness, molecular weight, and their interactions with cells and tissues. Understanding the relationship between material properties and biological outcomes is essential for optimizing their use in medical devices. In this study, three PCU resins were selected for evaluation as potential polymer implant materials: Chronoflex (CF) 65D, and two Carbothane (CB) samples 95A with different molecular weights. Dynamic mechanical analysis (DMA) revealed that the storage modulus was primarily influenced by the hard domain content, with greater elasticity observed at higher frequencies and lower temperatures. Tensile hysteresis behavior at room temperature was strongly correlated with hardness, with lower hardness samples demonstrating improved strain recovery. Cytotoxicity testing indicated cell viability above 70% for both CF and CB films. Normal Human Lung Fibroblasts (NHLF) grown on CF films exhibited a more homogeneous distribution across the surface, adopting an elongated morphology that conformed closely to the underlying topography. In contrast, cells on CB films tend to aggregate, forming clustered structures. This study demonstrates that the mechanical and biological performance of PCU resins is closely linked to their hardness, molecular weight, and structural composition. The results highlight that a morphology with a higher proportion of hard domains produces a more uniform and favorable environment for cell adhesion and organization.

Hearing loss is a widespread and disabling condition with no current cure, underscoring the urgent need for new therapeutic approaches for treatment and prevention. A recent mitochondrial therapy approach by introducing exogenous mitochondria to the cells has shown promising results in mitigating mitochondria-related disorders. Despite the essential role of mitochondria in hearing, this novel strategy has not yet been tested for the treatment of hearing loss. More importantly, whether cochlear cells take up exogenous mitochondria and its consequence on cell bioenergetics has never been tested before. Here, we showed that exogenous mitochondria from HEI-OC1 auditory cells internalize into a new set of HEI-OC1 cells through co-incubation in a dose-dependent manner without inducing toxicity. We observed that auditory cells that received exogenous mitochondria exhibited increased bioenergetics compared to the controls that received none. Furthermore, we found that mitochondrial transplantation protects cells from oxidative stress and H2O2-induced apoptosis, while partially restoring bioenergetics diminished by H2O2 exposure. These findings support initial evidence for the feasibility and potential advantages of mitochondrial therapy in auditory cells. If successful in animal models and ultimately in humans, this novel therapy offers prominent potential for the treatment of sensorineural hearing loss.

This paper presents the design methodology for integrating a hydrogen solid oxide fuel cell/gas turbine (SOFC/GT) propulsion system into a blended-wing–body (BWB) aircraft and tube-and-wing (T&W) configurations for 365 and 162 passengers. The design methodology utilizes aircraft sizing and modeling tools that encompass aerodynamic properties, structural design, and powertrain integration. The proposed hydrogen BWB and T&W aircraft are compared against conventional models like the B777-300ER and B737-800. Key results indicate significant reductions in fuel consumption and emissions. For instance, the hydrogen BWB aircraft, on average, exhibits a 56% reduction in Megajoule of fuel energy consumption per passenger-kilometer compared to conventional aircraft. The analysis highlights the environmental benefits, with [Formula: see text] equivalent emissions per passenger-kilometer being significantly lower for hydrogen-powered models. The total takeoff weight per passenger for the hydrogen BWB-365 is 714 kg, compared to 916 kg for the conventional B777-300ER. Hydrogen aircraft configurations, on average, also show a 21% increase and 99.48% decrease in [Formula: see text] and [Formula: see text] emissions. Moreover, hydrogen BWB configurations exhibit reduced emissions compared to hydrogen T&W despite higher takeoff weights. This study underscores the potential of hydrogen SOFC/GT systems and BWB configurations to enhance efficiency and reduce the environmental impacts for future aircraft.

Microelectromechanical systems (MEMSs) and nanoelectromechanical systems (NEMSs) are revolutionary technologies that merge mechanical and electronic components on microscopic and nanoscopic scales [...].

Today’s commercial aviation industry centers on the tube-and-wing aircraft configuration with underwing-mounted engines, possibly nearing convergence on optimal performance capabilities with acceptable community noise. A potentially feasible breakthrough for obtaining lower noise levels for commercial aviation is the blended-wing–body (BWB), which presents unique noise-reducing characteristics such as engine shielding and simplified high-lift devices. The significance of characteristics unique to BWBs on overall aircraft noise is assessed through a study of a BWB aircraft design representative of the JetZero vehicle. This paper presents a methodology capable of modeling the aircraft’s propulsion system and corresponding performance capabilities necessary to assess the vehicle noise sources and overall community noise impact. Analysis of Part 36 certification noise levels indicates that the vehicle’smarginto Stage 5 standards is 35.8 effective perceived noise level (in EPNdB), and an additional 2.0 EPNdB is achievable with a decreased maximum takeoff thrust engine variant. Community noise impacts of departure and arrival procedures are studied through comparison of single-event noise contours. Significant contour area reductions were observed when compared to conventional tube-and-wing aircraft of similar weight and range class. Further departure and approach noise reductions were modeled through additional full-flight procedure variations.