Open Access Publications

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Open access publications by faculty, postdocs, and graduate students in the Department of Mechanical Engineering.

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Enhancing cathode composites with conductive alignment synergy for solid-state batteries
(Science Advances, 2025-01-03) Cao, Zhang; Yao, Xinxin; Park, Soyeon; Deng, Kaiyue; Zhang, Chunyan; Chen, Lei; Fu, Kelvin
Enhancing transport and chemomechanical properties in cathode composites is crucial for the performance of solid-state batteries. Our study introduces the filler-aligned structured thick (FAST) electrode, which notably improves mechanical strength and ionic/electronic conductivity in solid composite cathodes. The FAST electrode incorporates vertically aligned nanoconducting carbon nanotubes within an ion-conducting polymer electrolyte, creating a low-tortuosity electron/ion transport path while strengthening the electrode’s structure. This design not only mitigates recrystallization of the polymer electrolyte but also establishes a densified local electric field distribution and accelerates the migration of lithium ions. The FAST electrode showcases outstanding electrochemical performance with lithium iron phosphate as the active material, achieving a high capacity of 148.2 milliampere hours per gram at 0.2 C over 100 cycles with substantial material loading (49.3 milligrams per square centimeter). This innovative electrode design marks a remarkable stride in addressing the challenges of solid-state lithium metal batteries.
Transforming CO2 into advanced 3D printed carbon nanocomposites
(Nature Communications, 2024-12-04) Crandall, Bradie S.; Naughton, Matthew; Park, Soyeon; Yu, Jia; Zhang, Chunyan; Mahtabian, Shima; Wang, Kaiying; Liang, Xinhua; Fu, Kelvin; Jiao, Feng
The conversion of CO2 emissions into valuable 3D printed carbon-based materials offers a transformative strategy for climate mitigation and resource utilization. Here, we 3D print carbon nanocomposites from CO2 using an integrated system that electrochemically converts CO2 into CO, followed by a thermocatalytic process that synthesizes carbon nanotubes (CNTs) which are then 3D printed into high-density carbon nanocomposites. A 200 cm2 electrolyzer stack is integrated with a thermochemical reactor for more than 45 h of operation, cumulatively synthesizing 37 grams of CNTs from CO2. A techno-economic analysis indicates a 90% cost reduction in CNT production on an industrial scale compared to current benchmarks, underscoring the commercial viability of the system. A 3D printing process is developed that achieves a high nanocomposite CNT concentration (38 wt%) while enhancing composite structural attributes via CNT alignment. With the rapidly rising demand for carbon nanocomposites, this CO2-to-nanocomposite process can make a substantial impact on global carbon emission reduction efforts.
Visualizing fiber end geometry effects on stress distribution in composites using mechanophores
(Soft Matter, 2024-11-14) Haque, Nazmul; Chang, Hao Chun; Chang, Chia-Chih; Davis, Chelsea S.
Localized stress concentrations at fiber ends in short fiber-reinforced polymer composites (SFRCs) significantly affect their mechanical properties. Our research targets these stress concentrations by embedding nitro-spiropyran (SPN) mechanophores into the polymer matrix. SPN mechanophores change color under mechanical stress, allowing us to visualize and quantify stress distributions at the fiber ends. We utilize glass fibers as the reinforcing material and employ confocal fluorescence microscopy to detect color changes in the SPN mechanophores, providing real-time insights into the stress distribution. By combining this mechanophore-based stress sensing with finite element analysis (FEA), we evaluate localized stresses that develop during a single fiber pull-out test near different fiber end geometries—flat, cone, round, and sharp. This method precisely quantifies stress distributions for each fiber end geometry. The mechanophore activation intensity varies with fiber end geometry and pull-out displacement. Our results indicate that round fiber ends exhibit more gradual stress transfer into the matrix, promoting effective stress distribution. Also, different fiber end geometries lead to distinct failure mechanisms. These findings demonstrate that fiber end geometry plays a crucial role in stress distribution management, critical for optimizing composite design and enhancing the reliability of SFRCs in practical applications. By integrating mechanophores for real-time stress visualization, we can accurately map quantified stress distributions that arise during loading and identify failure mechanisms in polymer composites, offering a comprehensive approach to enhancing their durability and performance.
Mechanical Deformation Behavior of Polymer Blend Thin Films
(Macromolecular Rapid Communications, 2024-12-31) Pokhrel, Geeta; Jo, Hyungyung; Christ, Nicholas M.; Son, Hyeyoung; Howarter, John A.; Davis, Chelsea S.
Examining the mechanical properties of polymer thin films is crucial for high-performance applications such as displays, coatings, sensors, and thermal management. It is important to design thin film microstructures that excel in high-demand situations without compromising mechanical integrity. Here, a polymer blend of polystyrene (PS) and polyisoprene (PI) is used as a model to explore microscale deformation behavior under uniaxial mechanical testing. Six thin film compositions ranging from pure PS to a 4.5:5.5 ratio of PS to PI are fabricated. The thin films are deformed under compression, tension, and cyclic loadings, while monitoring the behavior utilizing a micromechanical stage and optical microscopy. To calculate the plane strain modulus, a strain-induced elastic buckling instability technique is employed. The results show that as the PI concentration increases, the plane strain modulus of the films decreases while the fracture strain increases. For the 4.5:5.5 ratio of PS to PI with a continuous rubbery PI phase, the thin films show major recoverable mechanical performance. This behavior is attributed to the mechanical strength of glassy PS combined with the strain energy absorption capability of rubbery PI, enabling elastic recovery. These fundamental observations provide valuable insights for designing mechanically resilient thin films for coatings and flexible devices.
Mechanical evaluation of mandibular fractures stabilized with absorbable implants or intraoral splints in cats
(Frontiers in Veterinary Science, 2025-01-07) Castejon-Gonzalez, Ana C.; Friday, Chet S.; Hast, Michael W.; Reiter, Alexander M.
Introduction: The goal of this cadaver study in cats was to compare the mechanical properties of intact mandibles (C) with mandibles whose simulated fracture was located between the third and fourth premolar teeth and repaired with four possible treatments: (1) Stout multiple loop interdental wiring plus bis-acryl composite intraoral splint (S); (2) modified Risdon interdental wiring plus bis-acryl composite intraoral splint (R); (3) ultrasound-aided absorbable fixation plate (P); and (4) ultrasound-aided absorbable fixation mesh (M). Materials and methods: Thirty feline mandibles were randomly assigned to the control and treatment groups. Mandibles were loaded by cantilever bending on the canine tooth, first in non-destructive cyclic loading followed by destructive ramp-to-failure loading. Results: Cyclic loading showed no differences between the treatment groups in angular deflection (a measure of sample flexion under non-destructive loads); however, the R group had significantly higher angular deflection than the C group. In destructive testing, no differences in mechanical properties were found between the treatment groups; however, all treatment groups demonstrated significantly lower maximum bending moment, bending stiffness, energy to failure, and maximum force when compared to the control group. The main mode of failure of the intraoral splint groups (S and R) was fracture of the bis-acryl composite (50%), and the main mode of failure of the absorbable fixation groups (P and M) was fracture of the pins (91.7%). Discussion: Intraoral splint and absorbable fixation methods have low strength and stiffness. The four treatments tested provided similar stabilization of mandibular fractures located between the third and fourth premolar teeth.
Model-Driven Manufacturing of High-Energy-Density Batteries: A Review
(Batteries & Supercaps, 2024-10-09) Maksimovna Vakhrusheva, Daria; Xu, Jun
Graphical Abstract This review offers a comprehensive review of recent advancements in model-driven manufacturing approaches for high-energy-density batteries. It highlights the integration of computational models with experimental manufacturing processes to optimize battery performance, reliability, and cost-effectiveness. Additionally, the review addresses the challenges associated with scaling up these model-driven approaches, focusing on critical issues such as model validation, parameter sensitivity, and the incorporation of artificial intelligence. Graphical Abstract available at: https://doi.org/10.1002/batt.202400539 Abstract The rapid advancement in energy storage technologies, particularly high-energy density batteries, is pivotal for diverse applications ranging from portable electronics to electric vehicles and grid storage. This review paper provides a comprehensive analysis of the recent progress in model-driven manufacturing approaches for high-energy-density batteries, highlighting the integration of computational models and simulations with experimental manufacturing processes to optimize performance, reliability, safety, and cost-effectiveness. We systematically examine various modeling techniques, including electrochemical, thermal, and mechanical models, and their roles in elucidating the complex interplay of materials, design, and manufacturing parameters. The review also discusses the challenges and opportunities in scaling up these model-driven approaches, addressing key issues such as model validation, parameter sensitivity, and the integration of machine learning and artificial intelligence for predictive modeling, process optimization, and quality assurance. By synthesizing current research findings and industry practices, this paper aims to outline a roadmap for future developments in model-driven manufacturing of high-energy density batteries, emphasizing the need for interdisciplinary collaboration and innovation to meet the increasing demands for energy storage solutions.
Visualizing separation at composite interfaces via spirolactam mechanophores
(RSC Mechanochemistry, 2024-10-17) Gohl, Jared A.; Roberts, Tyler J.; Freund, Anna C.; Haque, Nazmul; Rueschhoff, Lisa M.; Baldwin, Luke A.; Davis, Chelsea S.
The failure of interfaces between polymers and inorganic substrates often leads to deteriorated performance, as is the case for polymer matrix composites. Interfacial mechanophores (iMPs) have the potential to fluorescently measure interfacial failures. Spirolactam-based mechanophores are of interest due to their readily available synthetic precursors and compatibility with epoxy matrices. In this work, spirolactam is covalently bound at the interface of silica surfaces and epoxy, chosen due to the industrial relevance of glass fiber composites. The iMPs are mechanically activated through uniaxial tension applied to the composite while the resulting fluorescent response is observed in situ with a confocal microscope. Due to their real time sensing capabilities, iMPs are a promising technique to measure interfacial failures in composite materials more easily than with traditional optical microscopy techniques.
Trace inequalities and kinematic metrics
(Robotica, 2024-09-12) Wu, Yuwei; Chirikjian, Gregory S.
Kinematics remains one of the cornerstones of robotics, and over the decade, Robotica has been one of the venues in which groundbreaking work in kinematics has always been welcome. A number of works in the kinematics community have addressed metrics for rigid-body motions in multiple different venues. An essential feature of any distance metric is the triangle inequality. Here, relationships between the triangle inequality for kinematic metrics and so-called trace inequalities are established. In particular, we show that the Golden-Thompson inequality (a particular trace inequality from the field of statistical mechanics) which holds for Hermitian matrices remarkably also holds for restricted classes of real skew-symmetric matrices. We then show that this is related to the triangle inequality for SO(3) and SO(4) metrics.
Roles and interplay of reinforcement-based and error-based processes during reaching and gait in neurotypical adults and individuals with Parkinson’s disease
(PLoS Computational Biology, 2024-10-14) Roth, Adam M.; Buggeln, John H.; Hoh, Joanna E.; Wood, Jonathan M.; Sullivan, Seth R.; Ngo, Truc T.; Calalo, Jan A.; Lokesh, Rakshith; Morton, Susanne M.; Grill, Stephen; Jeka, John J.; Carter, Michael J.; Cashaback, Joshua G. A.
From a game of darts to neurorehabilitation, the ability to explore and fine tune our movements is critical for success. Past work has shown that exploratory motor behaviour in response to reinforcement (reward) feedback is closely linked with the basal ganglia, while movement corrections in response to error feedback is commonly attributed to the cerebellum. While our past work has shown these processes are dissociable during adaptation, it is unknown how they uniquely impact exploratory behaviour. Moreover, converging neuroanatomical evidence shows direct and indirect connections between the basal ganglia and cerebellum, suggesting that there is an interaction between reinforcement-based and error-based neural processes. Here we examine the unique roles and interaction between reinforcement-based and error-based processes on sensorimotor exploration in a neurotypical population. We also recruited individuals with Parkinson’s disease to gain mechanistic insight into the role of the basal ganglia and associated reinforcement pathways in sensorimotor exploration. Across three reaching experiments, participants were given either reinforcement feedback, error feedback, or simultaneously both reinforcement & error feedback during a sensorimotor task that encouraged exploration. Our reaching results, a re-analysis of a previous gait experiment, and our model suggests that in isolation, reinforcement-based and error-based processes respectively boost and suppress exploration. When acting in concert, we found that reinforcement-based and error-based processes interact by mutually opposing one another. Finally, we found that those with Parkinson’s disease had decreased exploration when receiving reinforcement feedback, supporting the notion that compromised reinforcement-based processes reduces the ability to explore new motor actions. Understanding the unique and interacting roles of reinforcement-based and error-based processes may help to inform neurorehabilitation paradigms where it is important to discover new and successful motor actions. Author summary Reinforcement-based and error-based processes play a pivotal role in regulating our movements. Converging neuroanatomical evidence show interconnected reinforcement-based and error-based neural circuits. Yet is unclear how reinforcement-based and error-based processes interact to influence sensorimotor behavior. In our past work we showed that reinforcement-based and error-based processes are dissociable. Building on this work, here we show that these process can also interact to influence trial-by-trial sensorimotor behaviour.
Activity and Selectivity in the Electrochemical Reduction of CO2 at CuSnx Electrocatalysts Using a Zero-Gap Membrane Electrode Assembly
(Journal of The Electrochemical Society, 2024-08-28) Dauda, Monsuru; Hendershot, John; Bello, Mustapha; Park, Junghyun; Orduz, Alvaro Loaiza; Kizilkaya, Orhan; Sprunger, Phillip; Engler, Anthony; Yao, Koffi; Plaisance, Craig; Flake, John
In this study Cu, Sn, and bimetallic CuSnx nanoparticles were synthesized and evaluated as electrocatalysts for CO2 reduction using zero gap membrane electrode assemblies. Results show bimetallic electrocatalysts with Sn contents above 10% yield formate as a primary product with Faradaic Efficiencies near 70% at 350 mA cm−2. Cu-Snx electrocatalysts with less than 10% Sn yield CO at current densities below 350 mA cm−2 and relatively lower cell potentials. When the low-Sn content bimetallic electrocatalysts were evaluated in alkaline anolytes at 350 mA cm−2, ethanol was recorded as the primary product (FE = 48.5% at Ecell ≥ 3.0 V). We propose enhanced C2 activity and selectivity originate from Cu dimers adjacent to Sn atoms for bimetallic electrocatalyst with low-Sn content. The C2 active sites are lost when the surface Sn content exceeds 25%–38%.
AerialVL: A Dataset, Baseline and Algorithm Framework for Aerial-Based Visual Localization With Reference Map
(IEEE Robotics and Automation Letters, 2024-08-09) He, Mengfan; Chen, Chao; Liu, Jiacheng; Li, Chunyu; Lyu, Xu; Huang, Guoquan
Visual localization plays an essential role in the autonomous flight of Unmanned Aerial Vehicles (UAVs) especially for the Global Navigation Satellite System (GNSS) denied environments. Existing aerial-based visual localization methods mainly focus on eliminating image variance between database map and captured frames. However, these is a lack of public dataset and baseline for method comparisons, which impedes the development of aerial-based visual localization. To address this issue, we construct AerialVL, a large-scale dataset, which is collected using UAV flying at different altitudes, along various routes, and during diverse time periods. AerialVL consists of 11 image sequences covering approximately 70 km of trajectory and includes a reference satellite image database corresponding to the flight area. Leveraging AerialVL, we perform thorough evaluations on various mainstream solutions designed for aerial-based visual localization for the first time. This evaluation encompasses visual place recognition, visual alignment localization and visual odometry, serving as comparison baselines. Furthermore, we present a general aerial-based visual localization framework, which unifies various methods and integrates them into a modular architecture. We note that across all flight trajectories, the proposed framework achieves higher localization accuracy and robustness against the existing methods.
The Variable Stiffness Treadmill 2: Development and Validation of a Unique Tool to Investigate Locomotion on Compliant Terrains
(Journal of Mechanisms and Robotics, 2025-09-03) Chambers, Vaughn; Hobbs, Bradley; Gaither, William; Thé, Zachary; Zhou, Anthony; Karakasis, Chrysostomos; Artemiadis, Panagiotis
Understanding legged locomotion in various environments is valuable for many fields, including robotics, biomechanics, rehabilitation, and motor control. Specifically, investi- gating legged locomotion in compliant terrains has recently been gaining interest for the robust control of legged robots over natural environments. At the same time, the importance of ground compliance has also been highlighted in poststroke gait rehabilitation. Currently, there are not many ways to investigate walking surfaces of varying stiffness. This article introduces the variable stiffness treadmill (VST) 2, an improvement of the first version of the VST, which was the first treadmill able to vary belt stiffness. In contrast to the VST 1, the device presented in this paper (VST 2) can reduce the stiffness of both belts independently, by generating vertical deflection instead of angular, while increasing the walking surface area from 0.20 m 2 to 0.74 m 2 . In addition, both treadmill belts are now driven independently, while high-spatial-resolution force sensors under each belt allow for measurement of ground reaction forces and center of pressure. Through validation experiments, the VST 2 displays high accuracy and precision. The VST 2 has a stiffness range of 13 kN/m to 1.5 MN/m, error of less than 1%, and standard deviations of less than 2.2 kN/m, demonstrating its ability to simulate low-stiffness environments reliably. The VST 2 constitutes a drastic improvement of the VST platform, a one-of-its-kind system that can improve our understanding of human and robotic gait while creating new avenues of research on biped locomotion, athletic training, and rehabilitation of gait after injury or disease.
Thermal conductance of interfaces between titanium nitride and group IV semiconductors at high temperatures
(Applied Physics Letters, 2024-07-22) Khan, Samreen; Shi, Xinping; Feser, Joseph; Wilson, Richard
Measuring the temperature dependence of material properties is a standard method for better understanding the microscopic origins for that property. Surprisingly, only a few experimental studies of thermal boundary conductance at high temperatures exist. This lack of high temperature data makes it difficult to evaluate competing theories for how inelastic processes contribute to thermal conductance. To address this, we report time domain thermoreflectance measurements of the thermal boundary conductance for TiN on diamond, silicon-carbide, silicon, and germanium between 120 and 1000 K. In all systems, the interface conductance increases monotonically without stagnating at higher temperatures. For TiN/SiC interfaces, ranges from 330 to 1000 MW/m2-K, with a room temperature conductance of 750 MW/m2-K. The interface conductance for TiN/diamond ranges from 140 to 950 MW/m2-K. Notably, for all four interfacial systems, the conductance continues to increase with temperature even after all phonon modes in the vibrationally soft material are thermally excited. This observation suggests that inelastic processes are significant contributors to the thermal conductance in all four interfacial systems, regardless of whether the materials forming the interface are vibrationally similar or dissimilar. Our study fills a notable gap in the literature for how interfacial conductance evolves at high temperatures and tests burgeoning theories for the role of inelastic processes in interfacial thermal transport.
Preliminary Evidence That Design Fluency Is Related to Dual-Task Treadmill Gait Variability in Healthy Adults
(NeuroSci, 2024-09-12) Higginson, Christopher I.; Bifano, Morgan K.; Seymour, Kelly M.; Orr, Rachel L.; DeGoede, Kurt M.; Higginson, Jill S.
Evidence supporting a link between gait and cognition is accumulating. However, the relation between executive functioning and spatiotemporal gait parameters has received little attention. This is surprising since these gait variables are related to falls. The goal of this preliminary study was to determine whether performance on measures of inhibition, reasoning, and fluency is related to variability in stride length and step width during dual-task treadmill walking in a sample of healthy adults. Nineteen healthy adults averaging 40 years of age were evaluated. Results indicated that processing speed was reduced, t(18) = 6.31, p = 0.0001, step width increased, t(18) = −8.00, p = 0.0001, and stride length decreased, t(18) = 3.06, p = 0.007, while dual tasking, but variability in gait parameters did not significantly change, consistent with a gait/posture-first approach. As hypothesized, better performance on a visual design fluency task which assesses cognitive flexibility was associated with less dual-task stride length variability, rs(17) = −0.43, p = 0.034, and step width variability, r = −0.56, p = 0.006. The results extend previous findings with older adults walking over ground and additionally suggest that cognitive flexibility may be important for gait maintenance while dual tasking.
Dynamics of Intra-Cell Thermal Front Propagation in Lithium-Ion Battery Safety Issues
(Advanced Energy Materials, 2024-08-09) Jia, Yikai; Zhao, Peng; Finegan, Donal P.; Xu, Jun
Thermal runaway (TR), a critical failure mode in lithium-ion batteries (LIBs), poses significant safety risks and hinders wider application of LIBs. TR typically begins at a localized heat source and spreads across the cell. Understanding thermal front propagation (TFP) characteristics, such as front and velocity, is crucial for assessing energy release and temperature distribution for battery hazardous estimation. Recent studies assume that TR within cells propagates at a near-constant velocity, based on the reaction kinetics and thermal properties. Here, an intra-battery TR model is further proposed and it indicates that TFP velocity stabilizes when the front is distanced from the heat source. Theoretical estimates for propagation velocity and front are developed and validated through numerical simulations and experimental tests from the NREL Battery Failure Databank. The energy release rate during TFP and the impact of preheating based on a point heat source are explored. This work clarifies the long-standing clouds of the thermal font propagation behaviors within the single cell, highlights the power and beauty of mathematics modeling to describe the complicated thermal behaviors, and provides important guidelines for thermal hazardous understanding for next-generation batteries.
Universal Carbonizable Filaments for 3D Printing
(Advanced Functional Materials, 2024-06-23) Park, Soyeon; Shi, Baohui; Islam, Md Mohaiminul; He, Jinlong; Sung, Dae Han; Zhang, Chunyan; Cao, Zhang; Shang, Yuanyuan; Liu, Ling; Fu, Kelvin
Carbon additive manufacturing emerges as a powerful technique for crafting tunable 3D carbon architectures, employing multiscale arrangement and topological design for mechanical and functional applications. However, the potential of 3D carbon fabrication is constrained when utilizing state-of-the-art feedstock and manufacturing routes. To address these limitations, a 3D carbon fabrication strategy is developed named carbonizable filament technology (CAFIT). In CAFIT, the evolution of high-loaded carbon composite filaments broadens the capabilities of straightforward 3D printing technology by ensuring structural stability for subsequent post-carbonization to achieve scalable and engineered 3D carbon structures. This strategy has strengths regarding 1) simplicity, 2) applicability to a variety of carbon materials, and 3) creating nearly replicated 3D carbon structures with multiscale features. The fundamental mechanisms governing the processability of the universal filament and structural change of carbon particles throughout the process using carbon nanotubes as an example are explored. Moreover, through simulation and demonstration, the adaptability of CAFIT is illustrated by utilizing a wide range of carbon materials, including low-dimensional nano/micro carbons (carbon blacks, carbon nanotubes, and graphenes), as well as carbon fibers, to fabricate 3D architected carbon structures.
Biomimetic Proteoglycans Strengthen the Pericellular Matrix of Normal and Osteoarthritic Human Cartilage
(ACS Biomaterials Science & Engineering, 2024-08-12) Kahle, Elizabeth R.; Fallahi, Hooman; Bergstrom, Annika R.; Li, Anita; Trouillot, Colette E.; Mulcahey, Mary K.; Lu, X. Lucas; Han, Lin; Marcolongo, Michele S.
In osteoarthritis (OA), degradation of cartilage pericellular matrix (PCM), the proteoglycan-rich immediate cell microniche, is a leading event of disease initiation. This study demonstrated that biomimetic proteoglycans (BPGs) can diffuse into human cartilage from both normal and osteoarthritic donors and are preferentially localized within the PCM. Applying immunofluorescence (IF)-guided AFM nanomechanical mapping, we show that this localization of BPGs increases the PCM micromodulus of both normal and OA specimens. These results illustrate the capability of BPGs to integrate with degenerative tissues and support the translational potential of BPGs for treating human OA and other diseases associated with proteoglycan degradation.
The emergence of a robust lithium gallium oxide surface layer on gallium-doped LiNiO2 cathodes enables extended cycling stability
(Materials Advances, 2024-08-01) Mishra, Mritunjay; Yao, Koffi P. C.
LiNiO2 is a promising cobalt-free cathode for lithium-ion batteries due to its high theoretical capacity and low cost. Although intensely studied, the occurrence of several phase transformations and particle pulverization causing capacity fading in cobalt-free LiNiO2 have yet to be effectively resolved. Herein, a sol–gel synthesis process is utilized for gallium (Ga) doping of LiNiO2 at 2% (solution-doping) and 5% (excess-doping) molar ratios. Transmission electron microscopy and X-ray diffraction Rietveld refinement reveal the opportune formation of an α-LiGaO2 shell at 5% doping beyond the solubility limit of 2%. Alongside solution-doping at the Ni and Li crystallographic sites, the emergence of this α-LiGaO2, isostructural and lattice-matched to the R[3 with combining macron]m LiNiO2, is shown to improve capacity retention by a factor of 2.45 after 100 cycles at C/3. Particles with the LiGaO2 shell experience significantly less pulverization during extended cycling. In contrast, the solution-doped LiNiO2 with 2% Ga experiences extensive particle fracturing similar to the baseline undoped LiNiO2. In turn, no significant electrochemical performance difference is found between the solution-doped and baseline LiNiO2. The evidence garnered suggests that a surface gallium oxide phase achievable with excess Ga is key to enabling extended cycling using Ga doping.
Programmable acoustic modular microrobots
(Journal of Micro and Bio Robotics, 2024-08-03) Cherukumilli, Subrahmanyam; Kirmizitas, Fatma Ceren; Rivas, David P.; Sokolich, Max; Karakan, M. Cagatay; White, Alice E.; Das, Sambeeta
The field of microrobotics has emerged as a promising area of research with significant applications in biomedicine, both in vitro and in vivo, such as targeted cargo delivery, microsurgery, and cellular manipulation. Microrobots actuated with multiple modalities have the potential for greater adaptability, robustness, and capability to perform various tasks. Modular units that can reconfigure into various shapes, create structures that may be difficult to fabricate as one whole unit, and be assembled on-site, could provide more versatility by assembly and disassembly of units on demand. Such multi-modal modular microrobots have the potential to address challenging applications. Here, we present a biocompatible cylindrical microrobot with a dome-shaped cavity. The microrobot is actuated by both magnetic and acoustic fields and forms modular microstructures of various shapes. We demonstrate the use of these microrobots for cellular manipulation by creating patterns on a surface.
Adaptive Functional Electrical Stimulation Delivers Stimulation Amplitudes Based on Real-Time Gait Biomechanics
(Journal of Medical Devices, 2024-05-21) Donlin, Margo C.; Higginson, Jill S.
Functional electrical stimulation (FES) is often used in poststroke gait rehabilitation to decrease foot drop and increase forward propulsion. However, not all stroke survivors experience clinically meaningful improvements in gait function following training with FES. The purpose of this work was to develop and validate a novel adaptive FES (AFES) system to improve dorsiflexor (DF) and plantarflexor (PF) stimulation timing and iteratively adjust the stimulation amplitude at each stride based on measured gait biomechanics. Stimulation timing was determined by a series of bilateral footswitches. Stimulation amplitude was calculated based on measured dorsiflexion angle and peak propulsive force, where increased foot drop and decreased paretic propulsion resulted in increased stimulation amplitudes. Ten individuals with chronic poststroke hemiparesis walked on an adaptive treadmill with adaptive FES for three 2-min trials. Stimulation was delivered at the correct time to the dorsiflexor muscles during 95% of strides while stimulation was delivered to the plantarflexor muscles at the correct time during 84% of strides. Stimulation amplitudes were correctly calculated and delivered for all except two strides out of nearly 3000. The adaptive FES system responds to real-time gait biomechanics as intended, and further individualization to subject-specific impairments and rehabilitation goals may lead to improved rehabilitation outcomes.

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