environmentally-controlled-microtensile-testing-mechanically-adaptive

Environmentally-controlled Microtensile Testing of Mechanically-adaptive Polymer Nanocomposites for <em>ex vivo</em> Characterization

Implantable microdevices are gaining significant attention for several biomedical applications1-4. Such devices have been made from a range of materials, ...

Louis Stokes Cleveland Department of Veterans Affairs Medical Center

Case Western Reserve University

Nanoelectromechanical systems: Nanodevice motion at microwave frequencies.

The physiology of glomerular permselectivity remains mechanistically obscure, despite its importance in human disease. Although electrical contributions to glomerular permselectivity have long been considered important, two recent reports demonstrated enhanced glomerular permeability to anionic versus neutral polysaccharides. The interpretation of these observations is complicated by confounding of the effects of chemical modification on charge with effects on size and shape. In this report, neutral and anionic Ficoll are characterized by size-exclusion chromatography with online light scattering and viscometry and filtration through a highly defined anionic filtration membrane. Neutral and carboxymethylated Ficoll are nearly identical in size and conformation, yet carboxymethylated Ficoll is retained by an anionic membrane in excess of neutral Ficoll. This suggests that comparisons between clearances of neutral and carboxymethylated Ficoll may be a sensitive probe of electrostatic interactions independent of size and conformation.

Molecular conformation and filtration properties of anionic Ficoll.

The role electrical charge plays in determining glomerular permeability to macromolecules remains unclear. If the glomerular basement membrane (GBM) has any significant role in permselectivity, physical principles would suggest a negatively charged GBM would reject similarly charged more than neutral species. However, recent in vivo studies with negative and neutral glomerular probes showed the opposite. Whether this observation is due to unique characteristics of the probes used or is a general physiological phenomenon remains to be seen. The goal of this study was to use the basement membrane deposited by Madin-Darby canine kidney epithelial cells as a simple model of a biologically derived, negatively charged filter to evaluate size- and charge-based sieving properties. Fluorescein isothiocyanate-labeled carboxymethylated Ficoll 400 (FITC-CM Ficoll 400) and amino-4-methyl-coumarin-labeled Ficoll 400 (AMC Ficoll 400) were used as negatively charged and neutral tracer molecules, respectively, during pressure-driven filtration. Streaming potential measurement indicated the presence of fixed, negative charge in the basal lamina. The sieving coefficient for neutral Ficoll 400 decreased by âˆ¼0.0013 for each 1-â„« increment in solute radius, compared with a decrease of 0.0023 per â„« for the anionic Ficoll 400. In this system, molecular charge played a significant role in determining the sieving characteristics of the membrane, pointing to solute charge as a potential contributor to GBM permselectivity.

Basal lamina secreted by MDCK cells has size- and charge-selective properties.

Surface charge characterization is important in the design and testing of coatings and membranes for biological and industrial applications, but commercial zeta potential meters are expensive and difficult to adapt to a variety of membrane designs. We combined inexpensive off-the-shelf components, a test mount fabricated with a conventional rapid prototyping system, and software written using a no-cost integrated development environment to implement a low-cost, automated streaming potential meter. Software written in Visual C# managed a USB data acquisition and control pod to regulate the transmembrane pressure while simultaneously reading transmembrane voltages from a digital multimeter with 0.1-nV precision. The streaming potential was measured through a commercially available polyethersulfone membrane with repeatable results for transmembrane pressures between -15 and 15 kPa. The transmembrane voltages for each set of six pressures were linear, with R (2) values greater than 0.9995. The zeta potentials calculated from the measured streaming potentials are in agreement with previous results for the same commercial membrane previously reported in the literature. The material cost for the system is less than $4000.

A low-cost automated streaming potential measurement system.

Poly-dimethylsiloxane (PDMS) is a highly attractive polymer to encapsulate implantable micro-electromechanical systems (MEMS) due to its biocompatibility, simplicity in processing, and low Young's Modulus. However, conventional deposition processes introduce defects that prevent the use of PDMS as a long term packaging material. In order to address these issues, we have developed a novel roller-casting process for depositing PDMS. This paper presents the findings of a study to simultaneously investigate the adhesion properties and moisture barrier characteristics of roller-cast, multilayered PDMS encapsulants subjected to testing in saline at 85Â°C.

Adhesion and Moisture Barrier Characteristics of Roller-Cast Polydimethylsiloxane Encapsulants for Implantable Microsystems.

Crystal defects can confine isolated electronic spins and are promising candidates for solid-state quantum information. Alongside research focusing on nitrogen-vacancy centres in diamond, an alternative strategy seeks to identify new spin systems with an expanded set of technological capabilities, a materials-driven approach that could ultimately lead to 'designer' spins with tailored properties. Here we show that the 4H, 6H and 3C polytypes of SiC all host coherent and optically addressable defect spin states, including states in all three with room-temperature quantum coherence. The prevalence of this spin coherence shows that crystal polymorphism can be a degree of freedom for engineering spin qubits. Long spin coherence times allow us to use double electron-electron resonance to measure magnetic dipole interactions between spin ensembles in inequivalent lattice sites of the same crystal. Together with the distinct optical and spin transition energies of such inequivalent states, these interactions provide a route to dipole-coupled networks of separately addressable spins.

Article	Year
Nanoelectromechanical systems: Nanodevice motion at microwave frequencies. Nature\| PubMed ID: 12556880	2003
Molecular conformation and filtration properties of anionic Ficoll. American journal of physiology. Renal physiology\| PubMed ID: 20668097	2010
Basal lamina secreted by MDCK cells has size- and charge-selective properties. American journal of physiology. Renal physiology\| PubMed ID: 20980405	2011
A low-cost automated streaming potential measurement system. Journal of laboratory automation\| PubMed ID: 22357558	2012
Adhesion and Moisture Barrier Characteristics of Roller-Cast Polydimethylsiloxane Encapsulants for Implantable Microsystems. Proceedings of IEEE Sensors / IEEE International Conference on Sensors ; sponsored by the IEEE Sensor Council. IEEE International Conference on Sensors\| PubMed ID: 23418410	2012
Polytype control of spin qubits in silicon carbide. Nature communications\| PubMed ID: 23652007	2013

Christian A. Zorman

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