Department of Mechanical Engineering

The vast capabilities of autonomous underwater vehicles (AUVs)—such as in assisting scientific research, conducting military tasks, and repairing oil pipelines—are limited by high operating costs and the relative inaccessibility of power in the open ocean. Wave powered AUV charging stations may address these issues. With projected increases in usage of AUVs globally in the next five years, AUV charging stations can enable less expensive and longer AUV missions. This paper summarizes the design process and investigates the feasibility of a wave powered, mobile AUV charging station, including the choice of a wave energy converter and AUV docking station as well as the ability to integrate the charging station with an autonomous surface vehicle. The charging station proposed in this paper meets many different commercial, scientific, and defense needs, including continuous power availability, data transmission capabilities, and mobility. It will be positioned as a hub for AUV operations, enabling missions to run autonomously with no support ship. The potential market for this design is very promising, with an estimated $1.64 million market size just for AUV technologies by 2025.

Computed Axial Lithography (CAL) represents a significant advancement in the emerging field of Volumetric Additive Manufacturing (VAM). CAL addresses key limitations of traditional photopolymer additive manufacturing technologies, by eliminating the need for layering and support structures. Unlike conventional methods, CAL prints components by illuminating all points within a desired geometry simultaneously, using tomographic reconstruction to form the object in a single step. This unique approach eliminates the relative motion between the object and the precursor material, enabling faster printing speeds and reducing the waste associated with support structures. However, CAL parts require post-processing steps before they can be utilized. CAL's core attributes make it particularly suited for In-Space Manufacturing (ISM), due to its fast fabrication times, wide breadth of materials it can use, and minimized footprint. CAL has been successfully demonstrated in microgravity during parabolic flight experiments. However to fully validate and understand CAL's behaviour in microgravity, all manufacturing and post-processing steps must be integrated. In June 2024, we conducted SpaceCAL Mission 3, testing this entire workflow on a suborbital flight aboard Virgin Galactic's SpaceShipTwo. During ∼140 s of microgravity, the system autonomously manufactured and post-processed four parts using PEGDA700 resin. Post-flight analysis showed that 2/4 parts were recognisable, while others were distorted due to bubble formation from residual water droplets, off-axis optical aberrations, and non-uniform solvent rinsing. Despite these limitations, this study represents the first integrated CAL workflow in space, providing an initial experimental demonstration and analysis for closed-loop in-space manufacturing.

Understanding and improving the performance and longevity of lithium-ion batteries critically depends on insight into the dynamic processes occurring at buried electrode-electrolyte interfaces. However, direct, depth-resolved, and operando diagnosis of these interfaces remains a longstanding challenge due to their inaccessibility beneath bulk materials, the limitations of conventional surface- and bulk-sensitive characterization tools, and the difficulty of maintaining realistic cell environments during measurement. These challenges have made it nearly impossible to uniquely resolve important interfacial properties such as charge transfer resistance, SEI (solid electrolyte interphase) resistance, and solvation entropy at the individual electrode interfaces within a working cell, information that is essential for mechanistic insight and accelerated battery design. Here, we report the development of multiharmonic electro-thermal spectroscopy (METS), an operando technique that enables depth-resolved measurement of solvation entropy, interfacial transport resistance, charge-transfer resistance, and SEI resistance at individual electrode-electrolyte interfaces within practical lithium-ion batteries. By leveraging frequency-dependent, thermal-wave sensing and interface-specific modeling, METS uniquely attributes interfacial properties to specific electrodes, as validated by comparison with traditional electrochemical impedance spectroscopy (EIS). The ability to spatially and temporally resolve interfacial processes in real time provides new diagnostic capabilities that are crucial for mechanistic studies of battery degradation and for the rapid development of next-generation energy storage systems.

Surface protection and functional modification of aircraft-certified aluminum alloys are essential for corrosion resistance, durability, and long-term airworthiness. At the same time, increasingly restrictive environmental regulations motivate the development of alternatives to legacy wet-chemical surface treatments. This study presents an integrated assessment of ultrafast femtosecond laser surface texturing as a surface functionalization approach for Aluminum 6061 alloys within an aerospace manufacturing and sustainability context. Ultrashort-pulse laser processing enables controlled micro- and nano-scale surface topographical modification with limited thermal impact, allowing adjustment of wettability and surface functionality while preserving bulk material integrity. As a dry and contactless process, femtosecond laser treatment eliminates the use of hazardous chemicals, reduces consumable inputs, and generates minimal secondary waste. A streamlined cradle-to-gate life cycle assessment conducted in accordance with ISO 14040/14044 indicates a lower global-warming potential per functional unit compared with conventional surface treatments, including anodization, plasma-assisted coatings, and organic coating systems. Complementary qualitative analyses addressing environmental health and safety, supply-chain risk, and ESG alignment indicate potential advantages related to occupational safety, regulatory compliance, waste management, and end-of-life recyclability. The investigation is performed on planar Aluminum 6061 reference surfaces with a treated area of 25 mm2, providing a controlled laboratory-scale basis for analyzing process behavior, functional surface modification, and associated environmental metrics. Within this defined scope, the results support further evaluation of femtosecond laser surface texturing as a surface engineering option for future aerospace manufacturing.

BACKGROUND: Sex-based disparities remain a major challenge in musculoskeletal medicine. Women and men experience different anterior cruciate ligament (ACL) injury rates and severity, but the causes remain unclear. We hypothesized that cellular differences in human progenitor cells contribute to the higher ACL tear risk observed in females. METHODS: ACL samples were collected from 4 male and 5 female patients undergoing ACL reconstruction surgery. Live cells were collected through flow cytometry and sent for single-cell RNA sequencing. Significantly greater expression in either sex relative to the other was defined as a >25% increase in expression level (log 2 fold change > 0.32) and p < 0.05). Subpopulation characterization was performed with immunofluorescence on tissue sections. RESULTS: We discovered sex-based differences in all of the native cell types within the ACL. In particular, fibroblast progenitor-like (TPPP3+) cells from female patients expressed genes associated with dysregulation and degradation of collagen more highly than progenitor cells from male patients. CONCLUSIONS: These results highlight a ligament progenitor population with a sex-dependent gene expression profile. This work suggests that sex-based differences in stem cell populations may drive differential injury rates and outcomes between male and female patients with musculoskeletal injuries. CLINICAL RELEVANCE: The differential gene expression among TPPP3+ progenitor-like cells provides a possible target population for studying ligamentous injury and regeneration. Differential expression of collagen and extracellular matrix-related genes provides evidence of specific genes that could be therapeutically targeted to strengthen the ACL and reduce the risk of rupture, particularly in female athletes.

Vortex induced vibration (VIV) experienced during flow past a cylinder can reduce equipment performance and in some cases lead to failure. Previous studies have shown that the shift in shedding frequency and vibration amplitude under the influence of gas injection at the upper subcritical range can produce a premature shift to supercritical flow (and the drag crisis). To date, the influence of the gas distribution along the cylinder span has not yet been investigated. Time-resolved particle image velocimetry (TR-PIV), proper orthogonal decomposition (POD) and spectral proper orthogonal decomposition (SPOD) of the wake structures, as well as bubble image velocimetry (BIV) are used to assess the flow topology changes under the influence of spanwise uniform and spanwise discontinuous gas injection. We demonstrate that for gas injected along the span of the cylinder, a premature shift to supercritical flow occurs even at volumetric qualities of 0.034%, which is lower than has been previously shown in literature. For gas injected along the central 1.3 D of the channel (30% of the channel width), a local transition to supercritical flow occurs at the channel centerline; however, the wake recovers to that of subcritical flow by 3.6 D downstream, as mixing occurs with the predominantly single-phase flow to either side of the bubble injection. This downstream transition in the shedding frequency resembles that of single-phase dual step cylinders, which to the author’s knowledge has not yet been shown to occur under two-phase conditions. At two-phase supercritical flow, for R e D = 360,000, we demonstrate a significant shift in near-wake gas motion and vortex shedding frequency, with gas motion driven by vortex interaction in the separated shear layer.

Endometriosis is a chronic gynecological disorder marked by the growth of endometrial-like tissue outside the uterus, often resulting in pain and infertility and affecting overall quality of life. Despite its prevalence, diagnostic delays persist due to reliance on invasive laparoscopy and the lack of sensitive, specific, non-invasive biomarkers. Current molecular and imaging tools have improved detection but remain limited, underscoring the need for new diagnostic strategies. This review introduces a mechanobiological perspective, exploring how cellular biophysical properties such as cell stiffness, deformability, and contractility can potentially serve as functional biomarkers for endometriosis. We examine lesion subtypes, menstrual cycle dynamics, and key biological processes such as decidualization, epithelial-mesenchymal transition (EMT), and stromal remodeling through a mechanical lens. Parallels are drawn between endometriosis and cancer to underscore the diagnostic potential of tissue and cell mechanics. We specifically highlight menstrual effluent as a promising non-invasive, cell-rich sample uniquely suited for mechanical profiling. Together, these insights suggest that viewing endometriosis with a mechanical lens may accelerate diagnostic innovation and uncover new mechanisms driving disease development and progression.

Achieving rapid and adaptive locomotion in soft robots is essential for navigating complex environments and enabling diverse real-world functions. Here, we present a jellyfish-inspired magnetic soft robot (J-MSR) capable of ultrafast swimming and seamless multimodal motion transitions in liquid environments. By employing an asymmetric trapezoidal magnetic field waveform for actuation, the J-MSR capitalizes on spatial and temporal asymmetries during its swimming cycle, mimicking the natural propulsion mechanism of jellyfish. Through magnetic-fluid-solid multiphysical field coupling analysis and magnetic field waveform optimization, the J-MSR achieves a remarkable swimming speed of 14.85 body lengths per second, demonstrating notably enhanced propulsion performance compared with previously reported jellyfish-inspired robots. Unlike traditional designs relying on auxiliary buoyancy structures, the J-MSR demonstrates versatile multimodal motions under natural negative buoyancy conditions, including large-angle multidirectional swimming (0° to 122°), slit traversal, and rolling. Meanwhile, its exceptional locomotion capabilities facilitate the integration of functional devices, enabling it to perform diverse tasks such as emitting light to mimic fluorescent jellyfish, capturing objects, injecting microneedles, and conducting gastroscopy. These capabilities highlight the J-MSR's substantial potential as a versatile platform for biomedical applications in confined and unstructured environments.

A comprehensive mechanics theory was developed to analyze multiscale contact and friction behavior of elastic-plastic fractal surfaces coated with a boundary film. This approach accounts for the size-dependent behavior of asperity microcontacts that arise from the inherent roughness of fractal topographies. To capture the fundamental mechanisms governing interfacial friction, representative single-asperity models were formulated to describe both elastic and plastic deformation modes at the microscale. These models were then systematically extended across the entire asperity population, enabling an accurate representation of contact interactions over a broad range of length scales. In the elastic regime, frictional resistance is primarily attributed to shearing of the boundary film between opposing asperities. Conversely, in the plastic regime, asperities indent and plow through the softer counterface material, while the boundary film remains attached to the deformed surface contributing additional resistance through interfacial shear. The total frictional force is obtained by integrating the contributions from both elastic and plastic microcontacts, which are weighted according to the asperity-size distribution that characterizes the fractal contact interface. The developed theoretical framework provides a rigorous and scalable model for predicting the frictional behavior of rough contact interfaces covered by a strongly adhered boundary film and yields fundamental insight into the interplay between surface topography, prevalent deformation mode at the asperity scale, and boundary film shear resistance, which is especially relevant for the design and analysis of engineered surfaces in contact-mode mechanical systems.

Quantum sensing with nitrogen-vacancy centers in diamond has emerged as a powerful tool for measuring diverse physical parameters, yet the versatility of these measurement approaches is often limited by the achievable layout and dimensionality of bulk-crystal platforms. Here, we demonstrate a versatile approach to creating designer quantum sensors by surface-functionalizing multiphoton lithography microstructures with NV-containing nanodiamonds. We showcase this capability by fabricating a 150 μm × 150 μm × 150 μm triply periodic minimal surface gyroid structure with millions of attached nanodiamonds. We demonstrate a means to volumetrically image these structures using a refractive index matching confocal imaging technique and extract ODMR spectra from 1.86 μm × 1.86 μm areas of highly concentrated nanodiamonds across a cross-section of the gyroid. Furthermore, the high density of sensing elements enables ensemble temperature measurements with a sensitivity of 0.548 ± 0.084 K/√Hz at 5 mW excitation power. This approach to creating quantum-enabled microarchitectures opens new possibilities for multimodal sensing in complex three-dimensional environments.