Abstract The development of lightweight, soft robotic pediatric exosuits offers a novel approach to enhancing motor function. Crucially, the efficiency and ultimate adoption of such devices depend on their safe yet useful functionality. This requires a thorough assessment of the forces generated by the actuators of the exosuit. We assessed the assistive forces of fabric-based pneumatic actuators designed for upper-extremity motion support in a pediatric robotic exosuit. Experiments used infant-sized upper-body test rigs to collect data on forces exerted on different body segments by two shoulder and two elbow actuator variants across multiple anchoring configurations. The selection of actuators (1-cell and 2-cell shoulder, and square and circular elbow) was informed by earlier work in terms of their reachable workspaces and ability to support smooth end-effector motion paths. Results confirmed that all tested actuator variants generated forces no greater than 32 N, remaining below the minimum threshold of force exertion for the infant body, a range deduced by the literature to be between 43 N and 184 N. The results also revealed that the 1-cell shoulder and circular elbow actuator variants can strike a balance between force exertion and efficiency by providing appropriate mechanical output while exerting smaller amounts of force than other actuator variants. This effort contributes to identifying force limits for the infant population, offers guidance on suitable actuator selection, and outlines a design framework for pediatric wearable robotic exosuits.
Abstract Biomechanical factors play a crucial role in glaucoma development, the world-leading cause of irreversible blindness. Although age is known to affect the tissues? biomechanical properties, early-onset menopause has recently been associated with the risk of developing glaucoma, and the effects of aging relative to early-onset menopause on eye?s biomechanical factors remain underexplored. This work?s goals were to study the effects of aging and early-onset menopause on intraocular pressure (IOP), aqueous humor outflow facility, and ocular compliance. Female Brown Norway rats underwent Sham or surgical menopause (ovariectomy; OVX) at 3-4 months of age and were split into young (5-6 months) or middle-aged groups (9-10 months). We monitored IOP until the established aging time points and performed ex vivo biomechanical measurements via the iPerfusion system. IOP was higher for the middle-aged Sham and OVX animals by 25% and 35%, respectively (p<0.001), when compared to their respective initial IOPs. Furthermore, middle-aged OVX animals had a 11% higher IOP compared to Sham animals (p=0.005), and a 20% lower outflow facility (p=0.031). Ocular compliance decreased with age in the Sham (24.9%, p=0.011) and OVX (24.5%, p=0.005) cohorts and by 24.1% independent of cohort (p=0.0001). Elucidating the effects of age and early-onset menopause on biomechanical factors that contribute to glaucoma pathology is necessary to help move the field forward and preserve the eyesight of millions of patients.
Abstract Emerging evidence suggests that cells can retain information about previous mechanical environments and subsequently exhibit altered phenotypes even after the original mechanical stimulus is removed. This phenomenon is known as cellular mechanical memory that occurs in three phases: memory acquisition, storage, and recall. The literature supports a model in which mechanical experiences become encoded through interconnected cytoskeletal, nuclear, metabolic, and epigenetic mechanisms. Mechanical memory is increasingly recognized as a central regulator of cell fate and tissue remodeling, as well as a fundamental principle in development, aging, fibrosis, cancer, and regenerative medicine. We here give a concise overview of the historical origins and defining features of mechanical memory, discuss the emergence of mechanical memory in aqueous humor outflow dysfunction in glaucoma, summarize key unanswered questions, and close with a discussion of the clinical relevance of targeting mechanical memory for therapeutic purposes.
Abstract Aortic valve disease initiates on the fibrosa (aorta-facing) side of the valve leaflets, whereas the ventricularis side is disease-protected. Spatially predictable disease correlates with side-specific hemodynamics and gene expression: fibrosa-side valvular endothelial cells (VECs) experience low magnitude, oscillatory shear stress and have lower expression of pathological inhibitors, whereas ventricularis VECs experience higher magnitude shear stress and have a more protective phenotype. Among the protective genes higher expressed on the ventricular side, C-type natriuretic peptide (CNP) stands out as an endogenous inhibitor of fibrotic differentiation of aortic valve interstitial cells and valvular disease in vivo. However, shear stress regulation of CNP in aortic valves has not been characterized. To this end, porcine VECs were subjected to prescribed shear stresses in vitro. Steady, high magnitude shear stress and ventricular side-specific shear stress waveforms upregulated CNP gene (NPPC) expression in a KLF2-dependent manner. NPPC was upregulated by shear stress in VECs isolated from both the fibrosa and ventricularis sides, but with greater sensitivity in fibrosa-side cells. Notably, while KLF2 expression was upregulated with shear stress in both male and female VECs, NPPC was upregulated only in male VECs. Side- and sex-specific CNP expression patterns observed in vitro were also observed in immunohistochemically-stained human aortic valves. This work positions CNP as a biomechanically regulated factor in aortic valve homeostasis and pathogenesis, and provides insights into the factors regulating sex differences in valvular disease.
Abstract The advancements in vehicle safety have mainly focused on front-seat occupants. With an increasing focus on autonomous mobility, there is a considerable need to improve occupant protection in rear-seats. This study presents a computational investigation to evaluate the safety performance of modern vehicle rear seats. Full-body injury risks were calculated for mid-sized male occupants seated in the rear seat during frontal crashes, employing the Global Human Body Models Consortium (GHBMC) 50th male (M50-O) human body model (HBM). Four modern vehicle rear-seat models, including both conventional and advanced restraint systems, were evaluated under New Car Assessment Program (NCAP) crash pulse (ΔV of 56 kph). Injury risks for the human body regions were analyzed, with particular attention to the risk of submarining, where the pelvis slips beneath the lap belt during high-speed crashes. The predictions of FE simulations showed agreement against post-mortem human surrogate (PMHS) test data in terms of occupant kinematics and injury predictions. While some kinematic differences were observed between the GHBMC model and PMHS data, particularly in vertical excursions, the HBM successfully captured the submarining response across different seat designs. This indicates that the GHBMC model provides a tool for assessing rear-seat injury risks. The overall risk of serious injury ranged from ~60% to nearly certain, highlighting a significant room for improvement in rear-seat safety. Advanced restraint systems and steeper seat pan angles showed to have potential to reduce injury risks, though other factors play a role as well.
