Donna M. Meyer

Titin Isoforms, Extracellular Matrix, and Global Chamber Remodeling in Experimental Dilated CardiomyopathyCLINICAL PERSPECTIVE

Background—Altered titin isoforms may modify cardiac function in heart failure (HF), but the nature of isoform switches and associated functional implications are not well defined. Limited studies have reported an increased compliant isoform (N2BA) expression in human systolic HF. Titin may also modulate stretch-regulated responses such as myocardial natriuretic peptide production. Methods and Results—We characterized titin isoform expression and extracellular matrix in all 4 cardiac chambers and the left ventricular (LV) epicardium and endocardium in normal dogs (n=6) and those with HF (n=6) due to tachypacing and characterized functional implications at the LV myofiber and chamber level. Recognizing the potential for uncoupling of the extracellular matrix and cardiomyocyte in tachypacing, myocardial natriuretic peptide production, a molecular marker of stretch-regulated responses, was also assessed. All chambers were dilated in HF, but the extracellular matrix was not increased. HF dogs had markedly lower N2BA in the atria and right ventricle. In failing LVs, N2BA was decreased only in the epicardium, where myofiber passive stiffness was increased. However, LV chamber mechanics were driven by the marked LV dilatation, with no increase in LV diastolic stiffness. Natriuretic peptide concentrations increased markedly in the endocardium in relation to increases in LV wall stress. Conclusions—Tachypacing HF is characterized by decreases in compliant titin isoform expression in the atria, right ventricle, and LV epicardium. However, LV chamber mechanics are principally determined by geometric and extracellular matrix changes rather than titin-based myofiber stiffness in this model. Stretch-regulated myocardial responses (natriuretic peptide production) appeared intact, suggesting that the mechanotransduction role of titin was not impaired in HF.

A Streaming Flow Based Lab-on-Chip Platform Technology

Numerous studies on microfluidics diagnostic devices have been published in the last decade. Although the first generation of Lab-on-chip (LOC) devices was functional in 1999, some of the promises of microfluidics (integration of all functions on a chip and the commercialization of truly handheld microfluidic instruments) have yet to be fulfilled. The major challenges of LOC technology include costeffective pumping, function integration, multiple detection, and system miniaturization. In this paper, we propose a novel and simple streaming-based LOC technology that may have potential to directly address these challenges. The phenomenon of the flow streaming is found in zero-mean velocity oscillating flows in a wide range of channel geometries. Although there is no net flow (zero-mean velocity) across the channel, a discrepancy in velocity profiles between the forward flow and backward flow causes fluid particles near the walls to drift toward one end, while fluid particles near the centerline drift to the other end. We hypothesize that the unique characteristics of flow streaming could be used: 1) to transport, mix and separate particles/molecules/bacterium/cells entrained in flows; 2) to perform multi-channel/generation micro-array sample distributions; and 3) to achieve function integrations and biomarker detections. Mechanisms of using flow streaming to achieve the various LOC functions are described. Preliminary results are presented to demonstrate the potential of this technology for LOC applications.

Frictional Behavior and Topography of Porous Polyurethane on Copper and Silicon Dioxide Articulating Contacts

Frictional behavior and topographical changes of material surfaces with applications in the microelectronics industry were experimentally observed. This work was performed to unveil trends in tribological characteristics of porous polyurethane material separately against copper and silicon dioxide materials typically found in integrated circuit (IC) polishing manufacturing processes. A linear reciprocating tribometer was utilized to translate the loaded contact of the polymer and contacting materials in the presence of a colloidal silica slurry. Contact forces were monitored throughout the experiments while surface topography of contacting surfaces was quantified using profilometry. Trials of polishing experiments were performed through a range of normal pressures and velocities to identify trends of interest, which are important in polishing. Coefficients of friction (COFs) between the polymer and contacting materials showed a decreasing trend with increasing polishing time and distance traveled. The copper and polymer material contacts were found to have a lower COF than that for the silicon dioxide and polymer contacts. Surface roughness of the polymer showed a general decreasing trend with increasing polishing time. This trend indicates a potential correlation between polymer surface roughness and the COF between the polymer and contacting materials. Evolution of the surface roughness of the materials differed depending on the direction along which topography was measured. An uncertainty analysis of the quantified parameters was conducted to provide knowledge in the confidence of the experimental results. Tribological behavior of the porous polyurethane and copper and silicon dioxide contacts is gathered from this experimental work for more complete characterization of the material.

Experimental Investigation on Geometric Effect on Micro Fluidic Diodicity

The Micro pump is an essential component in a Micro Total Analysis System (μTAS). A feasible and reliable design of the micro pump is a key for the development of the μTAS. The Valve-less Rectification Micro Pump (VRMP) has many advantages, such as: non-moving parts, independent of fluids and channels properties, reliable, and easy to fabricate. Fluid diodicity is an essential parameter of the VRMP design. In this study, we investigate the fluid diodicity (the ratio of forward to reverse flow’s pressure drop) of micro rectifying geometries for more effective design of VRMPs. An experimental apparatus is designed and constructed. In our preliminary experiments, we measured diodicities of four different rectifying geometries, including bifurcation, heart shape, semi-circle and triangle. Experimental results demonstrate that rectifying geometries can take different designs that differ from the conventional diffuser-nozzle and Tesla’s designs; therefore, there is an opportunity to enhance the performances of VRMP by choosing the application-specific rectifying geometries.Copyright

Polyethylene Wear Debris From Hip Simulator Fluid Captured and Separated Using Bio-Ferrography

This paper describes an experimental method, Bio-Ferrography, to separate ultra high molecular weight polyethylene (UHMWPE) wear debris, generated in hip simulators, from bovine serum lubricating fluid. A total of 54 experiments were performed in which an enzyme digestion “cocktail” was developed and used to clean the bovine serum samples of extraneous sugars, proteins and lipids that interfere with the UHMWPE particle separation. Erbium chloride was used to marginally magnetize particles in the fluid prior to passing through the ferrographic device. The particles were captured and separated from the fluid by traversing the treated serum across a magnetic gap of a bio-ferrograph. Morphology of the captured and separated wear debris was compared with particles from samples of fluid filtered through a paper sieve arrangement with pores of 0.05 micrometers in diameter. The UHMWPE wear debris collected using the described experimental method, were found to be between 0.1 and 20 micrometers in diameter with spherical and pill-shaped particles. The filtered UHMWPE particles were also in the same size range as the debris separated using bio-ferrography, 0.1 to 20 micrometers. To show that the experimental method captured UHMWPE particles, the spectra of the chemical composition of UHMWPE from an acetabular cup insert of a hip implant and of UHMWPE particles separated using Bio-Ferrography were compared and found to be the same. To further demonstrate that polyethylene could be captured and separated through the experimental method, manufactured polyethylene microspheres in the diameter range of 3 to 45 micrometers, were captured and separated using the bio-ferrographic process.Copyright

PDMS Flow Cell for Monitoring Bacterial Adhesion Capacity of Escherichia coli O157:H7 in Beverages

Aims: To develop and standardize a polydimethylsiloxane (PDMS) flow cells for monitoring bacterial adhesion capacity of biofilm formation by Escherichia coli O157:H7 in Beverages industry. Study Design: PDMS chip was fabricated in house and placed in a metal chamber. The bioFerrograph generated different flow rates of bacterial cell suspension in the PDMS cells. Methodology: PDMS flow cells were used to monitor bacteria adhesion capacity of E. coli O157:H7 inoculated into some beverages. The Effect of fluid flow rate and temperature on bacteria adhesion capacity was studied in order to standardize the system. Buffer system of adhesion was modified by varying the concentrations of PBS, Saline concentrations and PH value. The impact of elapsing time and initial number of bacterial cells were investigated. Fluorescence imaging of biofilm formation was also captured. Results: Bacterial adhesion capacity reached the maximum at 0.1 ml/min and then dramatically dropped down when fluid flow rate increases. Maximized adhesion capacity occurred with a buffer Original Research Article Abolmaaty and Meyer; JABB, 15(4): 1-12, 2017; Article no.JABB.37682 2 system of 0.01M Phosphate buffer, 1.0% NaCl, pH 7.5 at 30°C. A complete linear relationship (R ; 0.9956 0.9815) occurred between adhesion capacity of E. coli O157:H7 cells and elapsing time of food beverage. This linear relationship would help to predict and study biofilm formation in fluid and beverage industry. Maximum adhesion capacity occurred with beverages at the following order: skim milk followed by apple juice and then grape juice. Conclusion: PDMS flow cell enables non-destructive, in situ investigation of bacteria adhesion capacity as an initial step for biofilm formation in real time under a wide range of flow rates, nutrient conditions, fluid temperature, and elapsing times. It is inexpensive, simple, disposable, easy-to-use, and can accurately mimic the dynamic flow conditions in beverage industry.

Optical Method for Microfluidic Detection of Bacteria in Water

Fluorescence scanner was used to detect and quantify K12 bacteria in water to a detection limit of 3800 CFU/mL by correlating quantum dot fluorescence signal intensity to number of bacteria obtained by plate count.

A Valve-Less Rectification Minipump Based on Dynamic Rectifying Geometries

The advantages of valve-less rectification micro pumps include having no moving parts, low cost, reliable, having the ability to pump particles-laden fluids and live cells, being compatible with a wide range of micro channel materials and working fluids. Most valve-less rectification micro pumps are based on passive rectifying geometries such as a nozzle/diffuser, Tesla (Valvular Conduit), and Bifurcation geometries. In this study, we present a new valve-less rectification minipump based on a dynamic rectifying geometry. The present work includes design, fabrication, and testing of the pump. The experimental results are presented in terms of flow rates and maximum back pressures.Copyright

The Effect of Material Properties on the Efficiency of Valve-Less Rectification Micropumps

High efficiency valve-less rectification micropumps are essential in developing effective microfluidic systems. Many parameters have been reported in the literature to have an effect on the efficiency of valve-less rectification micropumps. These parameters are related to the dynamics of fluid flow (such as Reynolds number), rectifying geometries, or actuators (such as actuator frequency). In this work, we studied the effect of the material properties on the efficiency of valve-less rectification micropumps. Two valve-less rectification micropumps based on the same rectifying geometry, bifurcation, are fabricated using two different materials, Polydimethylsiloxane (PDMS) and SU-8 photoresist. The pumps are tested and results are compared. Experimental results suggest that the material properties have an apparent effect on the pumping performance of valve less rectification micropumps. The results are presented in terms of flow rates and maximum back pressures.Copyright

A Multifunctional Microfluidic Device Based on Bifurcation Geometry

Developing multifunctional devices are essential to realize more efficient Microsystems. With miniaturization processes taking place in many different applications, the rooms for single function microfluidic devices are limited. In this study, we introduce a multifunctional micro fluidic device based on bifurcation geometry which is capable of performing pumping and mixing at the same time. Optical lithography is used to fabricate the designed microfluidic device. The microfluidic device is tested at low actuator frequencies, and ethanol is employed as a working fluid. The operational principles are based on rectifying the oscillatory flows by using bifurcation structures for flow rectification. The results prove the feasibility of the novel design, and results are presented in terms of flow rates and maximum back pressures.Copyright