Thomas Roussel | University of Louisville (original) (raw)

Papers by Thomas Roussel

Respiratory Training (RT) is an essential aspect of rehabilitation for patients with compromised ... more Respiratory Training (RT) is an essential aspect of rehabilitation for patients with compromised respiratory function including individuals with spinal cord injury (SCI) above T5. In this population, respiratory and cardiovascular problems are the main cause of morbidity and mortality. With the help of RT, patients are able to regain a percentage of their prior lung and cardiovascular capacity and capabilities. However, current RT devices are based on manually adjusted air pressure threshold or resistance; they do not have a data collection option; and they do not provide biofeedback during training session. BreathForce RT technology eliminates the need for the patient to be in a clinical setting during data recording and provides monitoring of the functional changes over the course of training. BreathForce is a portable RT system with an integrated pressure sensor, system actuated proportional control valve, and touchscreen interface that allows the patient to undergo therapy at their convenience according to the individually developed training protocol. However, the first prototype required manual adjustment of the pressure threshold valves. This study investigated the use of a program actuated ball valve driven by a servo motor. 3D printed gears with a 5:3 ratio, with the larger gear on the ball valve, were mounted onto the ball valve and servo. This configuration proportionally controls the amount of air flowing through the device depending on the patient’s desired level of inspiratory and expiratory loads. Through preliminary data obtained from one test subject, the proportional valve demonstrated the ability to automatically change the resistance which in turn altered the amount of breathing work. Overall, BreathForce is an inexpensive, effective, and innovative alternative to existing RT devices which will allow patients suffering from respiratory-cardiovascular deficits to perform controlled therapy at home.

Passive, one-way valves, also known as check valves, while common at the macro scale, are an esse... more Passive, one-way valves, also known as check valves, while common at the macro scale, are an essential microfluidic feature that facilitates flow rectification. These structures are commonly used in micropump configurations to control flow. Check valves have numerous applications within microfluidics with the large majority being fabricated by replica molding. There has been a shift towards 3D printing microfluidics to reduce the time and cost associated with developing prototypes. Only a handful of studies have developed microvalves using stereolithography (SLA). However, fused deposition modeling (FDM) printers are more widely available and cost effective compared to SLA. This study focused on analyzing the range of valve thicknesses necessary to promote forward flow using commonly available FDM filaments. An arbitrary Lagrangian-Eulerian model, a form of fluid-structure interaction (FSI), was set-up in COMSOL Multiphysics 4.2a. Five 3D printer filament materials were compared in simulations of valve deformation over a 0.75 second transient period using the material properties of PDMS as a baseline. The maximum valve deflection for ABS, nylon, PETG, PLA, and TPU was 3.34, 3.08, 3.37, 3.00, and 6.45 mu\mumu m, respectively. The simulation resulted in a maximum valve deformation of 6.65 mu\mumu m for PDMS. As expected, materials with a Young’s modulus close to PDMS allows valve structures to actuate with adequate forward flow.

The purpose of this effort has been to develop a selfcontained, transportable capillary electroph... more The purpose of this effort has been to develop a selfcontained, transportable capillary electrophoresis (CE) with electrochemical (EC) detection analysis system, which contains all electrodes "on-chip" and employs specially made, miniaturized CE and EC supporting electronics. A novel fabrication process that produced recessed platinum electrodes was developed to form the CE/EC device from two patterned ultra-flat glass substrates. The electrodes in the bottom substrate were formed by a self-aligned etch and deposition technique using a photholithographic lift-off process. The top substrate was etched to form the microchannels (20 µm deep x 50 µm wide [avg]) and thermally bonded to the bottom substrate. The CE/EC experiments were performed using 0.02M phosphate buffer (pH 6) and a buffer/analyte solution (2.2 mM dopamine, 2.3 mM catechol) with an applied voltage of 250V, which was delivered by a custom electronics unit interfaced to a laptop computer equipped with data acquisition software. Detection limits (S/N = 3) were found to be 4.3 µM for dopamine and 4.4 µM for catechol. A linear response was observed up to 2200 µM and 2300 µM for dopamine and catechol, respectively. Overall, the analytical performance of our CE/EC device is comparable to previously reported hybrid lab-on-a-chip devices with external CE and/or EC electrodes.

Pulmonary and cardiovascular dysfunction are consistently reported as the leading causes of morbi... more Pulmonary and cardiovascular dysfunction are consistently reported as the leading causes of morbidity and mortality among the 1,275,000 people who are living with chronic spinal cord injury (SCI) in the United States. Respiratory-cardiovascular complications from neurological disorders (primarily COPD and sleep apnea) are currently the number one cause of death and disability in the US and, in 2020, are projected to be ranked first worldwide in terms of burden of disease. The main goal of this project is to develop an inspiratory-expiratory training device for use in the rehabilitation of patients with respiratory motor and cardiovascular deficits that incorporates existing technologies and promotes successful training methodologies performed at the clinic and at home. An embedded microprocessor was to convert pressure from a physiological range sensor into appropriate units and guide the user through a therapy session, while saving the data for later use by the clinician. Rechargeable batteries were used to allow for portability. A bi-directional breathing apparatus to accompany the microprocessor was developed using FDA approved, off-the-shelf parts. v Table of Contents

Asaio Journal, Dec 9, 2020

Supplemental Digital Content is available in the text. Pediatric heart failure (HF) patients have... more Supplemental Digital Content is available in the text. Pediatric heart failure (HF) patients have been a historically underserved population for mechanical circulatory support (MCS) therapy. To address this clinical need, we are developing a low cost, universal magnetically levitated extracorporeal system with interchangeable pump heads for pediatric support. Two impeller and pump designs (pump V1 and V2) for the pediatric pump were developed using dimensional analysis techniques and classic pump theory based on defined performance criteria (generated flow, pressure, and impeller diameter). The designs were virtually constructed using computer-aided design (CAD) software and 3D flow and pressure features were analyzed using computational fluid dynamics (CFD) analysis. Simulated pump designs (V1, V2) were operated at higher rotational speeds (~5,000 revolutions per minute [RPM]) than initially estimated (4,255 RPM) to achieve the desired operational point (3.5 L/min flow at 150 mm Hg). Pump V2 outperformed V1 by generating approximately 30% higher pressures at all simulated rotational speeds and at 5% lower priming volume. Simulated hydrodynamic performance (achieved flow and pressure, hydraulic efficiency) of our pediatric pump design, featuring reduced impeller size and priming volume, compares favorably to current commercially available MCS devices.

Through parabolic and suborbital research flights, fluid mechanics, biological systems and other ... more Through parabolic and suborbital research flights, fluid mechanics, biological systems and other experimental topics can be investigated in reduced gravity. When testing under such extreme conditions, a secondary containment is needed in order to keep experimental and potentially hazardous material from floating freely through the aircraft; this stimulated the need for a flight research glovebox. The initial version of the research glovebox was adapted from a neonatal intensive-care incubator which was used on 18 parabolic flights. With the advent of research during suborbital flight opportunities, the glovebox needed to be redesigned to become a more compact and capable containment chamber. To meet this objective, a smaller, lighter glovebox was designed and constructed. By using aluminum and transparent polycarbonate, the weight of the glovebox was reduced to only 35 lbs. Based on current guidelines for experimental suborbital flights, this allows for 65 lbs. of experimental equipment. Mimicking the original glovebox, two side doors that fold down were implemented. These would allow for placing the experiment in the glovebox, proper fastening and easy removal of the experiment. During experimentation, arm access through ports with surgical gown sleeves allow for sample manipulation without the risk of experimental particulates leaving the glovebox, while allowing for up to three investigators to work inside the glovebox at once. Using a stand and mounting board, the experiment can be held at a comfortable height, provides feet restraints for investigators, and allows for attachment to the aircraft for parabolic and suborbital flights. This set-up has been implemented when testing a new surgical fluid-management system, leak-free surgical trocars, and rehydration of red blood cells for transfusion therapy during spaceflight. This glovebox will be able to provide an effective secondary containment for reduced gravity test conditions, as well as other extreme environment test conditions. (Supported by NASA-80NSSC18K1664 and NASA-NNX16AC59G)

Cardiovascular Engineering and Technology, 2021

Despite the availability of first-generation extracorporeal mechanical circulatory support (MCS) ... more Despite the availability of first-generation extracorporeal mechanical circulatory support (MCS) systems that are widely used throughout the world, there is a need for the next generation of smaller, more portable devices (designed without cables and a minimal number of connectors) that can be used in all in-hospital and transport settings to support patients in heart failure. Moreover, a system that can be universally used for all indications for use including cardiopulmonary bypass (CPB), uni-or biventricular support (VAD), extracorporeal membrane oxygenation (ECMO) and respiratory assist that is suitable for use for adult, neonate, and pediatric patients is desirable. Providing a single, well designed, universal technology could reduce the incidence of human errors by limiting the need for training of hospital staff on a single system for a variety of indications throughout the hospital rather than having to train on multiple complex systems. The objective of this manuscript is to describe preliminary research to develop the first prototype pump for use as a ventricular assist device for pediatric patients with the Inspired Universal MCS technology. The Inspired VAD Universal System is an innovative extracorporeal blood pumping

The Journal of the Acoustical Society of America, 2020

Acoustofluidic devices are in development for high-precision cell manipulation and molecular load... more Acoustofluidic devices are in development for high-precision cell manipulation and molecular loading applications. In this study, experimental results were compared with computational modeling to characterize the ultrasound pressures within acoustofluidic channels. Acoustofluidic devices were fabricated by integrating PZT transducers into PDMS chips. Viability of Jurkat T cells was measured with MTT assays after acoustofluidic treatment at different ultrasound frequencies between 4.970 and 5.030 MHz. A computational model was implemented using a layered resonator approach to characterize the acoustic pressure profiles within the fluidic channels. The computational results revealed distinct frequencies at which the ultrasound pressures within the channels increased by several orders of magnitude due to constructive interference. Experimental results indicated a significant frequency-dependent difference in cell viability after acoustofluidic treatment (ANOVA p-value = 0.02, n = 10/co...

Recent contamination events have emphasized the need for widespread heavy metal monitoring over e... more Recent contamination events have emphasized the need for widespread heavy metal monitoring over extended periods of time. The customary and laborious random "grab sampling" for later analysis at central laboratories does not adequately satisfy this need. Our group is developing an electroanalytical approach that allows highly sensitive, calibration-less measurements to quantify heavy metals in microliter volumes. This approach offers promise for economical, miniaturized, remotely-deployable sensor networks. This study reports the application of microfabricated gold microelectrode arrays within a thin-layer cell and demonstrates sufficient sensitivity to detect sub-5-ppb arsenic concentrations in a microfluidic sample volume (< 5 µL).

validate this procedure as a viable methodology for the construction of 3-D microchannels. Figure... more validate this procedure as a viable methodology for the construction of 3-D microchannels. Figure 1. Stylus-draw method of creating PMMA fibers. FABRICATION Initially, fibers were drawn from reservoirs of solvated poly-methyl methacrylate (PMMA) (MicroChem) using a tungsten stylus (tip radius = 20 nm) to create a filament of solution between the two reservoirs (Fig. 1). As the solvent (chlorobenzene) evaporates, surface tension forces cause the filament to thin, resulting in the formation of a cylindrical polymer fiber with a nearly uniform cross-section Precise positioning of the fibers was accomplished by controlling the stylus with a programmable, custom-made ultra-high-precision micromilling machine (MMM) (Dover Instruments, Inc.) [3]. An alternative, direct-write, method of fiber drawing was also developed. This new technique involved loading a glass capillary (1-mm I.D.) with solvated PMMA and utilizing it to both deposit the reservoirs and draw the fibers, eliminating the need for the low-precision, manual reservoir deposition in the method previously described (Fig. 2). Manipulation of the direct-write capillary process was also controlled with the MMM, enabling nanoscale positioning resolution. Channels were fabricated by coating the PMMA fibers with a layer of borosilicate glass (BSG) followed by Parylene®. BSG was deposited via RF sputtering (Technics 4604) to a thickness of 25 nm to establish a hydrophilic interior channel wall. A 10 µm Parylene® layer (SCS Parylene Deposition System 2010) was included to provide structural reinforcement for the fragile BSG thin wall. 500 µm-diameter holes were drilled into the coated and dried PMMA reservoirs to provide access to the PMMA and completed channels. The entire platform was submerged in acetone

... Willard, et al., &amp;amp;amp;amp;amp;amp;amp;amp;quot;Instrumental Methods of Analys... more ... Willard, et al., &amp;amp;amp;amp;amp;amp;amp;amp;quot;Instrumental Methods of Analysis,&amp;amp;amp;amp;amp;amp;amp;amp;quot; SeventhEd, 1988, p. 701. [2] A. Woolley, K. Lao, A, Glazer, and R. Mathies, &amp;amp;amp;amp;amp;amp;amp;amp;quot;Capillary Electrophoresis Chips with Integrated Electrochemical Detection,&amp;amp;amp;amp;amp;amp;amp;amp;quot; AnaL Chem., 1998, 70, 684-688. [3] 0. Klett, F. Bjorefors, and L. Nyholm, &amp;amp;amp;amp;amp;amp;amp;amp;quot; ...

We report the development of a simple microfluidic device, which uses a carbon nanotube (CNT) mem... more We report the development of a simple microfluidic device, which uses a carbon nanotube (CNT) membrane (CNTM) to separate two proteins based on their molecular weights (MW). The device was fabricated by traditional microfabrication techniques and chemical vapor deposition (CVD). Protein A (MW= 42 kDa) and Aprotinin (MW= 6.5 kDa) were flowed through the CNTM in separate identical electrophoresis runs. The larger protein was observed to accumulate ahead of the CNTMs, whereas in the case of the smaller protein, no accumulation was observed, indicating that the buildup was due to the larger size of the higher MW protein.

Analytica Chimica Acta, Nov 1, 2013

Remote unattended sensor networks are increasingly sought after to monitor the drinking water dis... more Remote unattended sensor networks are increasingly sought after to monitor the drinking water distribution grid, industrial wastewater effluents, and even rivers and lakes. One of the biggest challenges for application of such sensors is the issue of in-field device calibration. With this challenge in mind, we report here the use of anodic stripping coulometry (ASC) as the basis of a calibration-free micro-fabricated electrochemical sensor (CF-MES) for heavy metal determinations. The sensor platform consisted of a photo-lithographically patterned gold working electrode on SiO2 substrate, which was housed within a custom stopped-flow thin-layer cell, with a total volume of 2-4 μL. The behavior of this platform was characterized by fluorescent particle microscopy and electrochemical studies utilizing Fe(CN)6(3-/4-) as a model analyte. The average charge obtained for oxidation of 500 μM ferrocyanide after 60s over a 10 month period was 176 μC, corresponding to a volume of 3.65 μL (RSD = 2.4%). The response of the platform to copper concentrations ranging from 50 to 7500 ppb was evaluated, and the ASC results showed a linear dependence of charge on copper concentrations with excellent reproducibility (RSD ≤ 2.5%) and accuracy for most concentrations (≤ 5-10% error). The platform was also used to determine copper and mercury mixtures, where the total metallic content was measurable with excellent reproducibility (RSD ≤ 4%) and accuracy (≤ 6% error).

IFMBE proceedings, 2010

... AgCl) The TFMEAs were characterized via Cyclic Voltam-metry (CV) and AC-impedance. CV measure... more ... AgCl) The TFMEAs were characterized via Cyclic Voltam-metry (CV) and AC-impedance. CV measurements were performed using a BAS CV-50W electrochemical analyzer (Bioanalytical Systems, West Lafayette, IN). The AC ...

OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information), Aug 2, 2011

The purpose of this study was to compare experimental electrokinetic plug flow velocities to comp... more The purpose of this study was to compare experimental electrokinetic plug flow velocities to computational flow models of microfabricated capillaries. Electroosmotic flow studies of dichlorofluorescein and electrophoretic separation of dopamine and catechol in a microfabricated capillary electrophoresis (CE) system were performed both experimentally and computationally. A “balanced cross design” consisting of a bent 2 cm long injection channel and a straight 2 cm long separation channel was used. The geometry of the capillary was 65 μm wide and 20 μm deep. For the fluorescein study, separation voltages ranging between 0.25 kV and 1 kV were applied, while voltages ranging from 100 V to 550 V were used in the separation studies. Laser Induced Fluorescent (LIF) images were obtained for flow visualization and qualitative analysis in the electroosmotic flow studies, while electrochemical potentials were acquired using “on-chip” electrodes interfaced to a custom-designed power supply and electrochemical detection (ECD) circuit. Finite element models of the experimental device were generated and flows were simulated using commercially available software. For the electroosmotic flow studies, the computational results were found to be within ± 11% of the experimentally obtained values. Similarly, the results of the computational separations of catechol and dopamine predicted plug velocities that were within ± 7.6% of the experimentally determined values.

Journal of Applied Microbiology, Mar 1, 2022

Aims: This study assessed the use of high-energy, visible light on the survival rates of three ba... more Aims: This study assessed the use of high-energy, visible light on the survival rates of three bacteria commonly found in middle ear infections (i.e. otitis media; Streptococcus pneumoniae, Moraxella catarrhalis and Haemophilus influenzae). Method and Results: Bacteria were cultured and then subjected to a single, 4-h treatment of 405 nm wavelength light at two different intensities. All three bacteria species were susceptible to the light at clinically significant rates (>99.9% reduction). Bacteria were susceptible to the high-energy visible (HEV) light in a dose-dependent manner (lower survival rates with increased intensity and duration of exposure). Conclusions: The results suggest that HEV light may provide a non-surgical, nonpharmaceutical approach to the therapeutic treatment of otitis media. Significance an Impact of the Study: Given the growing concerns surrounding antibiotic resistance, this study demonstrates a rapid, alternative method for effective inactivation of bacterial pathogens partly responsible for instances of otitis media.

Surface Laplacian (SL) electrograms have been found to be superior to unipolar electrograms in de... more Surface Laplacian (SL) electrograms have been found to be superior to unipolar electrograms in detecting local activation by providing local activation time, activation block and wavefront initiation information. Traditional electrode configurations do not provide adequate spatial resolution or signal-to-noise ratios (SNRs) to measure SLs accurately in vivo. The purpose of this work is to develop a customized thin-film microelectrode array (TFMEA) with a custom multichannel signal conditioning microchip (SCM) that significantly improves the SNRs to make high-quality SL measurements feasible. In vitro and in vivo testing and characterization results clearly demonstrate the ability of the TFMEA-SCM system to obtain detailed SL measurements.

Asaio Journal, Dec 9, 2020

Cardiovascular Engineering and Technology, 2021

The Journal of the Acoustical Society of America, 2020

Analytica Chimica Acta, Nov 1, 2013

IFMBE proceedings, 2010

OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information), Aug 2, 2011

Journal of Applied Microbiology, Mar 1, 2022