Steven W Day

Rochester Institute of Technology | RIT · Department of Biomedical Engineering

Non-invasive monitoring of pulmonary health may be useful for tracking several conditions such as COVID-19 recovery and the progression of pulmonary edema. Some proposed methods use impedance-based technologies to non-invasively measure the thorax impedance as a function of respiration but face challenges that limit the feasibility, accuracy, and p...

Microfluidic devices promise to overcome the limitations of conventional hemodialysis and oxygenation technologies by incorporating novel membranes with ultra-high permeability into portable devices with low blood volume. However, the characteristically small dimensions of these devices contribute to both non-physiologic shear that could damage blo...

The majority of bearingless permanent magnet slice motors (BPMSMs) used in commercially available rotary blood pumps use a two-phase configuration, but it is unclear as to whether or not a comparable three-phase configuration would offer a better performance. This study compares the performance of two-phase and three-phase BPMSM configurations. Ini...

Plastic debris is a growing threat in freshwater ecosystems and transport models predict that many plastics will sink to the benthos. Among the most common plastics found in the Laurentian Great Lakes sediments are polyethylene terephthalate (especially fibers; PET), polyvinylchloride (particles; PVC), and styrene-butadiene rubber resulting from ti...

To address the unmet clinical need for pediatric circulatory support, we are developing an operationally versatile, hybrid, continuous-flow, total artificial heart (“Dragon Heart”). This device integrates a magnetically levitated axial and centrifugal blood pump. Here, we utilized a validated axial flow pump, and we focused on the development of th...

Microfluidic devices promise to overcome the limitations of conventional hemodialysis and oxygenation technologies by incorporating novel membranes with ultrahigh permeability into portable devices with low blood volume. However, the characteristically small dimensions of these devices contribute to both non-physiologic shear that could damage bloo...

In-home physiological monitoring devices enable the monitoring of vital health parameters and can facilitate health recovery. The current state of the art is inclined towards non-invasive technologies such as wearable mobile devices and patch-based sensors. In this chapter, we provide an overview of progress made in the field of dry electrodes for...

Throughout evolution, organisms repeatedly developed elastic elements to power explosive body motions, overcoming ubiquitous limits on the power capacity of fast-contracting muscles. Seahorses evolved such a latch-mediated spring-actuated (LaMSA) mechanism; however, it is unclear how this mechanism powers the two complementary functions necessary f...

The emergence of wearable and remote sensing devices in e-health has revolutionized personalized healthcare monitoring, but the field of dermatology has yet to witness significant progress in this area. The diagnosis and monitoring of atopic dermatitis (AD), a common skin disease causing inflammation and rashes, depend on in-person assessment, lead...

Background: The purpose of this research is to address ongoing device shortfalls for pediatric patients by developing a novel pediatric hybrid total artificial heart (TAH). The valveless magnetically-levitated MCS device (Dragon Heart) has only two moving parts, integrates an axial and centrifugal blood pump into a single device, and will occupy a...

Dry electrodes offer an accessible continuous acquisition of biopotential signals as part of current in-home monitoring systems but often face challenges of high-contact impedance that results in poor signal quality. The performance of dry electrodes could be affected by electrode material and skin hydration. Herein, we investigate these dependenci...

Non-invasive monitoring of pulmonary health could revolutionize the care of health conditions ranging from COVID19 to asthma to heart failure, but current technologies face challenges that limit their feasibility and adoption. Here, we introduce a novel approach to monitor respiration by measuring changes in impedance from the back of the thigh. Th...

Aligned collagen I (COL1) fibers guide tumor cell motility, influence endothelial cell morphology, control stem cell differentiation, and are a hallmark of cardiac and musculoskeletal tissues. To study cell response to aligned microenvironments in vitro, several protocols have been developed to generate COL1 matrices with defined fiber alignment, i...

Microfluidic tissue barrier models have emerged to address the lack of physiological fluid flow in conventional “open‐well” Transwell‐like devices. However, microfluidic techniques have not achieved widespread usage in bioscience laboratories because they are not fully compatible with traditional experimental protocols. To advance barrier tissue re...

Clinically-available blood pumps and total artificial hearts for pediatric patients continue to lag well behind those developed for adults. We are developing a hybrid, continuous-flow, magnetically levitated, pediatric total artificial heart (TAH). The hybrid TAH design integrates both an axial and centrifugal blood pump within a single, compact ho...

Randomly oriented type I collagen (COL1) fibers in the extracellular matrix are reorganized by biophysical forces into aligned domains extending several millimeters and with varying degrees of fiber alignment. These aligned fibers can transmit traction forces, guide tumor cell migration, facilitate angiogenesis, and influence tissue morphogenesis....

Background: Mechanical circulatory support (MCS) devices, such as ventricular assist devices (VADs) and total artificial hearts (TAHs), have become a vital therapeutic option in the treatment of end-stage heart failure for adult patients. Such therapeutic options continue to be limited for pediatric patients. Clinicians initially adapted or scaled...

Microfluidic approaches to study tissue barriers have emerged to address the lack of fluid flow in conventional "open-well" Transwell™-like devices. However, microfluidic techniques have not achieved widespread usage in bioscience laboratories because they are not fully compatible with conventional tried-and-true experimental protocols. To advance...

Advances in the integration of wearable devices in our daily life have led to the development of new electrode designs for biopotential monitoring. Historically, the development and testing of wearable electrodes for the acquisition of biopotential signals has been empirical, relying on experiments on human volunteers. However, the lack of explicit...

Randomly oriented type I collagen (COL1) fibers in the extracellular matrix (ECM) in vivo are reorganized by biophysical forces into aligned domains extending several millimeters and with varying degrees of fiber alignment. These aligned fibers can transmit traction forces, guide tumor cell migration, facilitate angiogenesis, and influence tissue m...

Introduction Blood contacting medical devices, including rotary blood pumps, can cause shear-induced blood damage that may lead to adverse effects in patients. Due in part to an inadequate understanding of how cell-scale fluid mechanics impact red blood cell membrane deformation and damage, there is currently not a uniformly accepted engineering mo...

Introduction Blood contacting medical devices, including rotary blood pumps, can cause shear-induced blood damage that may lead to adverse effects in patients. Due in part to an inadequate understanding of how cell-scale fluid mechanics impact red blood cell membrane deformation and damage, there is currently not a uniformly accepted engineering mo...

Cardiac related diseases are a common health risk for adults. Consequently, therapies such as heart transplants and medication exist to treat these ailments. Heart transplants remain the gold standard for treating severe heart failure, however, left ventricular assistive devices, a cardiac blood pump, are gaining popularity and not just as a bridge...

Ubiquitous constraints derived from the muscle's structure limit the power capacity of fast contracting muscles. Correspondingly, organisms evolved elastic elements that store energy which, when released, can be used to rapidly accelerate appendages. Such latch-mediated spring actuation (LaMSA) systems comprise of a single elastic element and are u...

Microfluidic devices may overcome the limitations of conventional hemodialysis and oxygenation technology to improve patient outcomes. Namely, the small form of this technology and parallel development of highly permeable membranes may facilitate the development of portable, low-volume, and efficient alternatives to conventional membrane-based equi...

Spatial Visualization (SV) refers to the ability to mentally manipulate two-dimensional and three-dimensional objects. This skill has been shown to impact student retention and success in many STEM disciplines. For example, it is used in organic chemistry to visualize chiral molecules or in physics to visualize free body diagrams from many perspect...

Purpose A credible computational fluid dynamics (CFD) model can play a meaningful role in evaluating the safety and performance of medical devices. A key step towards establishing model credibility is to first validate CFD models with benchmark experimental datasets to minimize model-form errors before applying the credibility assessment process to...

This paper studies the acoustic signals of left ventricular assist devices (LVADs) as it relates to machine health. Current LVAD condition monitoring requires examination from trained medical professionals, and is both inefficient and roughly-prognostic. To better quantify a patient's condition, the diagnostic method must be robust, non-invasive, a...

Ultrasound (US) elastography, or elasticity imaging, is an adjunct imaging technique that utilizes sequential US images of soft tissues to measure the tissue motion and infer or quantify the underlying biomechanical characteristics. For abdominal aortic aneurysms (AAA), biomechanical properties such as changes in the tissue's elastic modulus and es...

Computational models are useful for understanding respiratory physiology. Crucial to such models are the boundary conditions specifying the flow conditions at truncated airway branches (terminal flow rates). However, most studies make assumptions about these values, which are difficult to obtain in vivo. We developed a computational fluid dynamics...

Transabdominal ultrasound elasticity imaging could improve the assessment of rupture risk for abdominal aortic aneurysms by providing information on the mechanical properties and stress or strain states of vessel walls. We implemented a non-rigid image registration method to visualize the pressure-normalized strain within vascular tissues and adapt...

There is increasing evidence for successful management of end-stage heart failure with continuous-flow left ventricular assist device (CF-LVAD) technology. However, passive flow adjustment at fixed CF-LVAD speed is susceptible to flow balancing issues as well as adverse hemodynamic effects relating to the diminished arterial pulse pressure and flow...

Computational fluid dynamics (CFD) is increasingly being used to develop blood-contacting medical devices. However, the lack of standardized methods for validating CFD simulations and blood damage predictions limits its use in the safety evaluation of devices. Through an FDA initiative, two benchmark models of typical device flow geometries (nozzle...

Microbubble-based contrast agents are commonly used in ultrasound imaging to help differentiate the blood pool from the endocardial wall. It is essential to use an agent which produces high image intensity relative to the surrounding tissue, commonly referred to contrast effect. When exposed to ultrasound waves, microbubbles produce an intense back...

Suction feeding is pervasive among aquatic vertebrates, and our understanding of the functional morphology and biomechanics of suction feeding has recently been advanced by combining experimental and modeling approaches. Key advances include the visualization of the patterns of flow in front of the mouth of a feeding fish, the measurement of pressu...

Pressure wave velocity (PWV) is commonly used as a clinical marker of vascular elasticity. Recent studies have increased clinical interest in also analyzing the impact of heart rate, blood pressure, and left ventricular ejection time on PWV. In this article we focus on the development of a theoretical one-dimensional model and validation via direct...

The U.S. Food and Drug Administration recently hosted an interlaboratory study to assess the suitability and methodology of computational fluid dynamics (CFD) for demonstrating medical device safety in regulatory submissions. The benchmark study was performed in a generic medical device consisting of a 0.012 m diameter cylindrical nozzle with a sud...

Advancements in technology have led to the ability to tag virtually any cell with magnetic particles so long as the surface protein is known. In theory, these tagged cells may then be identified, imaged, or manipulated by magnetic force. In vitro separation using a magnetized stent and magnetically tagged cells was demonstrated by [1]. The motivati...

Experimental modeling of arteriovenous hemodialysis fistula (AVF) hemodynamics is challenging. Mathematical modeling struggles to accurately represent the capillary bed and venous circulation. In vivo animal models are expensive and labor intensive. We hypothesized that an in vitro, physiologic model of the extremity arteriovenous circulation with...

Ventricular assist devices emerged as a widely used modality for treatment of end-stage heart failure; however, despite significant advances, external energy supply remains a problem contributing to significant patient morbidity and potential mortality. One potential solution is using the nuclear radioisotope Plutonium-238 as a power source. Given...

While computational fluid dynamics (CFD) is commonly used for medical device development, its usefulness for demonstrating device safety has not been proven. Reliable standardized methods for this specialized need are lacking and are inhibiting the use of computational methods in the regulatory review of medical devices. To meet this need, particip...

Introduction: Arterial compliance is a marker for cardiac burden in atherosclerotic disease, with the pressure Pulse Wave Velocity (PWV) correlated to compliance. Current clinical practice employs pulsed wave Doppler to measure Flow Wave Velocity (FWV) as a surrogate of PWV. We hypothesized that PWV and FWV are not directly related and are affected...

OBJECTIVES: Contrast angiography can diagnose arterial occlusive disease but cannot provide hemodynamic data. Past work has attempted to calculate angiographic blood flow but clinical use has been limited by measurement error of >10%. Our hypothesis was that blood flow could be calculated from a contrast angiogram with <10% error through the applic...

In order to improve the performance of a magnetically levitated (maglev) axial flow blood pump, three-dimensional (3-D) finite element analysis (FEA) was used to optimize the design of a hybrid magnetic bearing (HMB). Radial, axial, and current stiffness of multiple design variations of the HMB were calculated using a 3-D FEA package and verified b...

Particle image velocimetry (PIV) has been used in regulatory submissions to the FDA for pre-clinical and post-market evaluations of flow fields in medical devices, such as artificial heart valves, blood pumps, and stents. The velocity and shear fields obtained from the PIV experiments are also used to validate computational fluid dynamics (CFD) dat...

This study is part of a FDA-sponsored project to evaluate the use and limitations of computational fluid dynamics (CFD) in assessing blood flow parameters related to medical device safety. In an interlaboratory study, fluid velocities and pressures were measured in a nozzle model to provide experimental validation for a companion round-robin CFD st...

This article introduces a unique miniaturization process of a magnetically levitated axial flow blood pump from a functional prototype to a pump suitable for animal trials. Through COMSOL three-dimensional finite element analysis and experimental verification, the hybrid magnetic bearings of the pump have been miniaturized, the axial spacing betwee...

This paper introduces the development of hybrid magnetic bearings (HMBs) for a maglev axial flow blood pump. The design criteria for the radial, axial and current stiffness of the HMB are proposed and the HMB is accordingly designed through theoretical calculation, 3-Dimensional Finite Element Analysis (3-D FEA) and experimental verification. Based...

Particulates that deposit in the acinus region of the lung have the potential to migrate through the alveolar wall and into the blood stream. However, the fluid mechanics governing particle transport to the alveolar wall are not well understood. Many physiological conditions are suspected to influence particle deposition including morphometry of th...

A novel transaortic ventricular cannula, known as the ‘double barrel’ cannula (DBC), is designed to minimize the invasiveness of Ventricular Assist Device (VAD) implantation by combining the inlet and outlet cannulae into a single dual lumen cannula. Both flows will pass through a single opening in the apex of the Left Ventricle with the outflow th...

Magnetic bearings are becoming increasingly popular in ventricular assist devices. In most cases, blood fills a portion of the gap between the magnetic actuators and rotor. Understanding the effects of the operating fluid on magnetic suspension is necessary, particularly when the device geometry features a relatively large gap (typically defined as...

Implantable rotary blood pumps are very effective at supporting patients with heart failure. New designs demonstrate distinct advantages over their predecessor diaphragm type pumps and have generated vast interest in the medical devices community, as demonstrated by hundreds of technical publications and newer commercially available devices. In add...

When suction-feeding vertebrates expand their buccal cavity to draw water into their mouth, they also exert a hydrodynamic force on their prey. This force is key to strike success, directly countering forces exerted by escaping or clinging prey. While the ability to produce high flow accelerations in front of the mouth is central to the predator's...

During ontogeny, animals undergo changes in size and shape that result in shifts in performance, behavior and resource use. These ontogenetic changes provide an opportunity to test hypotheses about how the growth of structures affects biological functions. In the present study, we ask how ontogenetic changes in skull biomechanics affect the ability...

The ability to protrude the jaws during prey capture is a hallmark of teleost fishes, widely recognized as one of the most significant innovations in their diverse and mechanically complex skull. An elaborated jaw protrusion mechanism has independently evolved multiple times in bony fishes, and is a conspicuous feature in several of their most spec...

Hemolysis is the break up of red blood cells, and is a condition that is of concern during the design process of blood contacting prostheses. In turbulent flows, hemolysis has been most often correlated to Reynolds shear stress. Mini-scale turbulent jets have been used for hemolysis experiments because they allow for explicit control of shear. Quan...

Blood clotting, or thrombosis, is an interesting biological application for computational fluid dynamics. Existing numerical thrombosis models have previously been shown to be effective for low shear rates and simple geometries. For these models to be used in biomedical applications such as the design of rotary blood pumps, however, they must first...