Search NASA⌕ Search

SEARCH · Search NASA

Results for “MEMBRANE FORCE”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

Uncooled tunneling infrared sensor

An uncooled infrared tunneling sensor in which the only moving part is a diaphragm which is deflected into contact with a micromachined silicon tip electrode prepared by a novel lithographic process. Similarly prepared deflection electrodes employ electrostatic force to control the deflection of a silicon nitride, flat diaphragm membrane. The diaphragm exhibits a high resonant frequency which reduces the sensor's sensitivity to vibration. A high bandwidth feedback circuit controls the tunneling current by adjusting the deflection voltage to maintain a constant deflection of the membrane. The resulting infrared sensor can be miniaturized to pixel dimensions smaller than 100 .mu.m. An alternative embodiment is implemented using a corrugated membrane to permit large deflection without complicated clamping and high deflection voltages. The alternative embodiment also employs a pinhole aperture in a membrane to accommodate environmental temperature variation and a sealed chamber to eliminate environmental contamination of the tunneling electrodes and undesireable accoustic coupling to the sensor.

Kenny, Thomas W.↗
NASA NTRS1998

Launch Conditions Might Affect the Formation of Blood Vessel in the Quail Chorioallantoic Membrane

AS 2 part of the first joint USA-Russian MIR/Shuttle program, fertilized quail eggs were flown on the MIR 18 mission. Post-flight examination indicated impaired survival of both the embryos in space and also of control embryos exposed to vibrational and g-forces simulating the conditions experienced during the launch of Progress 227. We hypothesized that excess mechanical forces and/or other conditions during the launch might cause abnormal development of the blood supply in the chorioallantoic membrane (CAM) leading to the impaired survival of the embryos. The CAM, a highly vascularized extraembryonic organ, provides for the oxygen exchange across the egg shell and is thus pivotal for proper embryonic development. To test our hypothesis, we compared angiogenesis In CAMS of eggs which were either exposed to the vibration and g-force profile simulating the conditions at launch of Progress 227 (synchronous controls), or kept under routine conditions in a laboratory Incubator (laboratory controls). At various time points during Incubation, the eggs were fixed in paraformaldehyde for subsequent dissection. At the time of dissection, the CAM was carefully lifted from the egg shell and examined as whole mounts by bright-field and fluorescent microscopy. The development or the vasculature (angiogenesis) was assessed from the density of blood vessels per viewing field and evaluated by computer aided image analysis. We observed a significant decrease In blood-vessel density in the synchronous controls versus "normal" laboratory controls beginning from day 10 of Incubation. The decrease in vascular density was restricted to the smallest vessels only, suggesting that conditions during the launch and/or during the subsequent Incubation of the eggs may affect the normal progress of angiogenesis in the CAM. Abnormal angiogenesis In the CAM might contribute to the impaired survival of the embryos observed in synchronous controls as well as in space.

Henry, M. K.↗
NASA NTRS2005

SOLAR SAIL PROPULSION SENSITIVITY TO MEMBRANE SHAPE AND OPTICAL PROPERTIES USING THE SOLAR VECTORING EVALUATION TOOL (SVET)

Solar sail propulsive performance is dependent on sail membrane optical properties and on sail membrane shape. Assumptions of an ideal sail (flat, perfect reflector) can result in errors which can affect spacecraft control, trajectory analyses, and overall evaluation of solar sail performance. A MATLAB(R) program has been developed to generate sail shape point cloud files for two square-architecture solar sail designs. Simple parabolic profiles are assumed for sail shape under solar pressure loading. These files are then input into the Solar Vectoring Evaluation Tool (SVET) software to determine the propulsive force vector, center of pressure, and moments about the sail body axes as a function of sail shape and optical properties. Also, the impact of the center-line angle, due to non-perfect optical properties, is addressed since this constrains sail force vector cone angle and is often overlooked when assuming ideal-reflector membranes. Preliminary sensitivity analysis using these tools aids in determining the key geometric and optical parameters that drive solar sail propulsive performance.

Ewing, Anthony↗
NASA NTRS1979

Relationship between proton motive force and potassium ion transport in Halobacterium halobium envelope vesicles

The permeability of Halobacterium halobium vesicle membranes to potassium ions was investigated, and possible mechanisms for the regulation of the gradient of protons by the transmembrane movement of these ions were studied. The lack of a potassium ion diffusion potential in the absence of valinomycin, light-induced electrical potentials in excess of the chemical potential difference for potassium ions, and direct measurements of potassium ion influx during illumination show that the membranes are relatively impermeable to these ions. As a result of sodium ion extrusion during illumination, chlorine ions and water must be lost and the vesicles collapse. The light-induced collapse of vesicles is diminished only if the influx of potassium ions is increased.

Lanyi, J. K.↗
DOE OSTI2023

Surface Functional Groups Affect Iron (Hydr)oxide Heterogeneous Nucleation: Implications for Membrane Scaling

Because of its favorable thermodynamics and fast kinetics, heterogeneous solid nucleation on membranes triggers early-stage mineral scaling. Iron (hydr)oxide, a typical membrane scale, initially forms as nanoparticles that interact with surface functional groups on membranes, but these nanoscale phenomena are difficult to observe in real time. In this study, we utilized in situ grazing incidence small angle X-ray scattering and ex situ atomic force microscopy to examine the heterogeneous nucleation of iron (hydr)oxide on surface functional groups commonly used in membranes, including hydroxyl (OH), carboxyl (COOH), and fluoro (F) groups. We found that, compared to nucleation on hydrophilic OH- and COOH-surfaces, the high hydrophobicity of an F-modified surface significantly reduced the extents of both heterogeneously and homogeneously formed iron (hydr)oxide nucleation. Moreover, on the OH-surface, the high functional group density of 0.76 nmol/cm 2 caused faster heterogeneous nucleation than that on a COOH-surface, with a density of 0.28 ± 0.04 nmol/cm 2 . The F-surface also had the highest heterogeneous nucleation energy barrier (26 ± 0.6 kJ/mol), followed by COOH- (23 ±0.8 kJ/mol) and OH- (20 ± 0.9 kJ/mol) surfaces. The kinetic and thermodynamic information provided here will help us better predict the rates and extents of early-stage scaling of iron (hydr)oxide nanoparticles in membrane processes. Finally, this work provides both kinetic and thermodynamic information about iron (hydr)oxide nucleation controlled by membrane-related functional groups (OH, COOH, and F).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2008

Embossed Teflon AF Laminate Membrane Microfluidic Diaphragm Valves

A microfluidic system has been designed to survive spaceflight and to function autonomously on the Martian surface. It manipulates microscopic quantities of liquid water and performs chemical analyses on these samples to assay for the presence of molecules associated with past or present living processes. This technology lies at the core of the Urey Instrument, which is scheduled for inclusion on the Pasteur Payload of the ESA ExoMars rover mission in 2013. Fabrication processes have been developed to make the microfabricated Teflon-AF microfluidic diaphragm pumps capable of surviving extreme temperature excursions before and after exposure to liquid water. Two glass wafers are etched with features and a continuous Teflon membrane is sandwiched between them (see figure). Single valves are constructed using this geometry. The microfabricated devices are then post processed by heating the assembled device while applying pneumatic pressure to force the Teflon diaphragm against the valve seat while it is softened. After cooling the device, the embossed membrane retains this new shape. This solves previous problems with bubble introduction into the fluid flow where deformations of the membrane at the valve seat occurred during device bonding at elevated temperatures (100-150 C). The use of laminated membranes containing commercial Teflon AF 2400 sheet sandwiched between spun Teflon AF 1600 layers performed best, and were less gas permeable than Teflon AF 1600 membranes on their own. Spinning Teflon AF 1600 solution (6 percent in FLOURINERT(Registered TradeMark) FC40 solvent, 3M Company) at 500 rpm for 1.5 seconds, followed by 1,000 rpm for 3 seconds onto Borofloat glass wafers, results in a 10-micron-thick film of extremely smooth Teflon AF. This spinning process is repeated several times on flat, blank, glass wafers in order to gradually build a thick, smooth membrane. After running this process at least five times, the wafer and Teflon coating are heated under vacuum at 220 C for one hour in order to drive off any residual solvent present in the composite film. After this, a second blank, glass wafer is brought down from above and the stack is held under vacuum at 3 atm mechanical pressure for ten 10 hours.

Willis, Peter↗
NASA NTRS2004

Method for determining the three-dimensional structure of a protein

Microcapsules prepared by encapsulating an aqueous solution of a protein, drug or other bioactive substance inside a semi-permeable membrane by are disclosed. The microcapsules are formed by interfacial coacervation under conditions where the shear forces are limited to 0-100 dynes/cm.sup.2 at the interface. By placing the microcapsules in a high osmotic dewatering solution, the protein solution is gradually made saturated and then supersaturated, and the controlled nucleation and crystallization of the protein is achieved. The crystal-filled microcapsules prepared by this method can be conveniently harvested and stored while keeping the encapsulated crystals in essentially pristine condition due to the rugged, protective membrane. Because the membrane components themselves are x-ray transparent, large crystal-containing microcapsules can be individually selected, mounted in x-ray capillary tubes and subjected to high energy x-ray diffraction studies to determine the 3-D structure of the protein molecules. Certain embodiments of the microcapsules of the invention have composite polymeric outer membranes which are somewhat elastic, water insoluble, permeable only to water, salts, and low molecular weight molecules and are structurally stable in fluid shear forces typically encountered in the human vascular system.

Morrison, Dennis R.↗
NASA NTRS2002

Microencapsulated Bioactive Agents and Method of Making

Microcapsules prepared by encapsulating an aqueous solution of a protein, drug or other bioactive substance inside a semi-permeable membrane by are disclosed. The microcapsules are formed by interfacial coacervation under conditions where the shear forces are limited to 0- 100 dynes per sq cm at the interface. By placing the microcapsules in a high osmotic watering solution, the protein solution is gradually made saturated and then supersaturated, and the controlled nucleation and crystallization of the protein is achieved. The crystal-filled microcapsules prepared by this method can be conveniently harvested and stored while keeping the encapsulated crystals in essentially pristine condition due to the rugged, protective membrane. Because the membrane components themselves are x-ray transparent, large crystal-containing microcapsules can be individually selected. mounted in x-ray capillary tubes and subjected to high energy x-ray diffraction studies to determine the 3-D structure of the protein molecules. Certain embodiments of the microcapsules of the invention have composite polymeric outer membranes which are somewhat elastic, water insoluble, permeable only to water, salts, and low molecular weight molecules and are structurally stable in fluid shear forces typically encountered in the human vascular system.

Dennis R Morrison↗
NASA NTRS2004

X-Ray Crystallography Reagent

Microcapsules prepared by encapsulating an aqueous solution of a protein, drug or other bioactive substance inside a semi-permeable membrane by are disclosed. The microcapsules are formed by interfacial coacervation under conditions where the shear forces are limited to 0-100 dynes per square centimeter at the interface. By placing the microcapsules in a high osmotic dewatering solution. the protein solution is gradually made saturated and then supersaturated. and the controlled nucleation and crystallization of the protein is achieved. The crystal-filled microcapsules prepared by this method can be conveniently harvested and stored while keeping the encapsulated crystals in essentially pristine condition due to the rugged. protective membrane. Because the membrane components themselves are x-ray transparent, large crystal-containing microcapsules can be individually selected, mounted in x-ray capillary tubes and subjected to high energy x-ray diffraction studies to determine the 3-D smucture of the protein molecules. Certain embodiments of the microcapsules of the invention have composite polymeric outer membranes which are somewhat elastic, water insoluble, permeable only to water, salts, and low molecular weight molecules and are structurally stable in fluid shear forces typically encountered in the human vascular system.

Dennis R Morrison↗
NASA NTRS1994

A Study of Parameters Affecting Fibroblast Morphology in Response to an Applied Mechanical Force

A precisely controlled stretch/relaxation regimen (20% elongation at 6.6 cycles/min) was applied to normal human fetal, neonatal and aged dermal fibroblasts cultured on flexible membranes. Culture conditions included poly (NH2) or collagen type I coated substrate membranes; control cultures were grown on the same pliable material in the absence of applied stretch. Direct observation and immunofluorescence analyses revealed a progressive change in cell body orientation limited to the stretched dermal fibroblast cultures. Monolayers gradually (over 4 days) acquired a symmetric, radial distribution equivalent to the biaxial array of the applied force. At high seeding density, alignment was inhibited in the fetal cell cultures. This cell strain required collagen type I coating for optimal attachment to the flexible membrane, preferring growth in three-dimensional cell 'balls' on the poly(NH2) coated substrate. Neonatal cells also required the collagen type I coating, but both neonatal and aged dermal fibroblasts aligned efficiently at all seeding densities examined. The randomly oriented neonatal cells on the unstretched control membranes spontaneously detached at confluence, as a single cell sheet. Their aligned counterparts did not detach until the applied stretch stimulus was removed. Low concentrations of cytochalasin D (62.5 ng/ml) disrupted the stretch-related alignment response. Rhodamine phalloidin staining visualized fewer actin stress fibers in stretched, aligned cells than in controls. Both intercellular interactions and cytoskeletal integrity mediate the response to mechanical strain. Normal rabbit corneal stroma fibroblasts (NRC) were also analyzed, and failed to orient under these conditions. This cell type may require a different regimen, or a longer time period, to demonstrate alignment behavior. Supported by NASA Space Biology RTOP 199-40-22 and the NASA-ARC Director's Discretionary Fund.

Grymes, Rosalind A.↗
DOE OSTI2020

Electrical and Elastic Properties of Individual Single-Layer Nb 4 C 3 T x MXene Flakes

2D carbides and nitrides (MXenes) are widely recognized for their exceptional promise for numerous applications. However, physical property measurements of their individual monolayers remain very limited despite their importance for revealing the intrinsic physical properties of MXenes. The first mechanical and electrical measurements of individual single-layer flakes of Nb 4 C 3 T x MXene, which are prepared via an improved synthetic method are reported. Characterization of field-effect transistor devices based on individual single-layer Nb 4 C 3 T x flakes shows an electrical conductivity of 1024 ± 165 S cm -1 , which is two orders of magnitude higher than the previously reported values for bulk Nb 4 C 3 T x assemblies, and an electron mobility of 0.41 ± 0.27 cm 2 V -1 s -1 . Atomic force microscopy nanoindentation measurements of monolayer Nb 4 C 3 T x membranes yield an effective Young's modulus of 386 ± 13 GPa, assuming a membrane thickness of 1.26 nm. This is the highest value reported for nanoindentation measurements of solution-processable 2D materials, revealing the potential of Nb 4 C 3 T x as a primary component for various mechanical applications. In conclusion, the agreement between the mechanical properties of 2D Nb 4 C 3 T x MXene and cubic NbC suggests that the extensive experimental data on bulk carbides could be useful for identifying new MXenes with improved functional characteristics.

36 MATERIALS SCIENCE↗
NASA NTRS1992

Wall to membrane linkers, stretch activated channels, and the detection of tension, voltage, temperature, auxin, and pH

Introduction. The higher plant is a heterogeneous, mechanically prestressed structure continually subject to shifting forces. When a cell grows in a plant at gravitropic equilibrium, it must create localized maxima of shear in walls of neighboring cells. Such mechanical stress and strain are likely detected in a variety of ways. However, tension-sensitive ion channels are of particular interest because it appears that they are elaborately evolved for sensory function. We hypothesize that 1) the patchy patterns of high shear are focused via wall-to-membrane linkers onto the plasma membrane, where 2) they are translated by mechanosensory cation channels into corresponding patterns of high cytosolic Ca2+, which 3) initiate local enhancement of wall expansion. Further, we hypothesize that the local promotion of enhancement is achieved at least in part by local intensification of auxin transport across the plasma membrane. By implication, when an organ is asymmetrically pressed, rubbed, or bent or when it is displaced in the gravitational field, the net asymmetry of shear stress occurring across the organ would lead to asymmetric redistribution of auxin and corrective asymmetric growth. We shall describe a representative mechanosensitive Ca(2+) -selective cation channel (MCaC) with susceptibilities to xenobiotics implicating it as a force transducer in thigmo- and gravitropism. Then, we shall consider whether a putative wall-to-membrane linker (WML) could be a key feature of the molecular architecture permitting the stress distributed in the wall system to be focused on the channels.

NASA Discipline Number 40-50↗
NASA NTRS1993

Permeable membrane experiment

The purpose of the Permeable Membrane Experiment is to gather flight data on three areas of membrane performance that are influenced by the presence of gravity. These areas are: (1) Liquid/gas phase separation, (2) gas bubble interference with diffusion through porous membranes and (3) wetting characteristics of hydrophilic membrane surfaces. These data are important in understaning the behavior of membrane/liquid/gas interfaces where surface tension forces predominate. The data will be compared with 1-g data already obtained and with predicted micrograviity behavior. The data will be used to develop designs for phase separation and plant nutrient delivery systems and will be available to the life support community for use in developing technologies which employ membranes. A conceptual design has been developed to conduct three membrane experiments, in sequence, aboard a single Complex Autonomous Payload (CAP) carrier to be carried in the Shuttle Orbiter payload bay. One experiment is conducted for each of the three membrane performance areas under study. These experiments are discussed in this paper.

Slavin, Thomas J.↗
NASA NTRS1997

A novel culture morphology resulting from applied mechanical strain

To demonstrate that cells both perceive and respond to external force, a strain/relaxation regimen was applied to normal human fetal and aged dermal fibroblasts cultured as monolayers on flexible membranes. The precisely controlled protocol of stretch (20% elongation of the culture membrane) at 6.67 cycles/min caused a progressive change in the monolayers, such that the original randomly distributed pattern of cells became a symmetric, radial distribution as the cell bodies aligned parallel to the applied force. High cell density interfered with the success of re-alignment in the fetal cell cultures observed, which may reflect a preference in this cell strain for cell-cell over cell-matrix contacts. The chronologically aged cells observed did not demonstrate this feature, aligning efficiently at all seeding densities examined. The role of microfilaments in force perception and transmission was investigated through the addition of cytochalasin D in graded doses. Both intercellular interactions and cytoskeletal integrity mediate the morphological response to mechanical strain.

NASA Discipline Cell Biology↗
DOE OSTI2023

Co-Assembly of Carbon Nanotube Porins into Biomimetic Peptoid Membranes

Robust and cost-effective membrane-based separations are essential to solving many global crises, such as the lack of clean water. Even though the current polymer-based membranes are widely used for separations, their performance and precision can be enhanced by using a biomimetic membrane architecture that consists of highly permeable and selective channels embedded in a universal membrane matrix. Researchers have shown that artificial water and ion channels, such as carbon nanotube porins (CNTPs), embedded in lipid membranes can deliver strong separation performance. However, their applications are limited by the relative fragility and low stability of the lipid matrix. In this work, we demonstrate that CNTPs can co-assemble into two-dimension (2D) peptoid membrane nanosheets, opening up a way to produce highly programmable synthetic membranes with superior crystallinity and robustness. A combination of molecular dynamics (MD) simulations, Raman spectroscopy, X-ray diffraction (XRD), and atomic force microscopy (AFM) measurements to verify the co-assembly of CNTP and peptoids are used and show that it does not disrupt peptoid monomer packing within the membrane. In conclusion, these results provide a new option for designing affordable artificial membranes and highly robust nanoporous solids.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Ion Transport in Charged Membranes: Linking Electric-Field-Driven Mechanisms to Pore Size via Perturbation Analysis

Ion-exchange membranes are a critical component in electrochemical systems. Nevertheless, the understanding and modeling of ion transport within these porous structures have been limited by particular complexity reductions, either ignoring the dimensionality of their porous network architecture or imposing geometric assumptions (i.e., overlapping double layers). Before addressing this morphology-transport gap, a framework that relates the driving forces of transport to the geometry of a single pore is required. In this work, our modeling domain consists of a two-dimensional single pore with charged walls, connecting two identical electrolyte reservoirs. Using the Poisson-Nernst-Planck equations and regular perturbation theory, we decouple the electric fields and analyze the driving forces of ion transport, specifically electromigration and induced electroosmosis within the pore. These processes are described as analytical functions of the interaction aspect ratio, ?, defined as the ratio of the pore radius to the Debye length. Using this parameter, our study (i) describes the interplay between electromigrative and electroosmotic mechanisms that set ionic conductivity, (ii) identifies a dimensionless group of intrinsic electrolyte properties that indicates the predominant driving force, and (iii) provides a qualitative, confinement-dependent perspective on selectivity in ion-conducting membranes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Mechanistic study of pH effect on organic solvent nanofiltration using carboxylated covalent organic framework as a modeling and experimental platform

Covalent organic framework (COF) membranes for organic solvent nanofiltration (OSN) have attracted growing interest due to their high stability, well-defined pore size, and controllable pore functionality. In aqueous nanofiltration processes, solution pH has a significant effect on membrane permeability, selectivity, and fouling. However, our understanding of pH effects on OSN processes is still limited. In this work, we present experimental and reactive force field molecular dynamics (ReaxFF MD) simulation results on the effect of pH on OSN using a well-characterized carboxylated COF (C-COF) membrane. Filtration experimental and modeling results both demonstrate that pH changes can affect solvent permeance and solute rejection dramatically. Specifically, methanol permeance decreases with the increase of NaOH and HCl concentration, respectively. When Alcian Blue dye was used as the solute in methanol, the selectivity increased from 23% to 98% when changing the feed pH from 2.2 to 10.1, respectively. While ReaxFF MD results show that C-COF solvated pore size is only marginally affected by the pH of solution, methanol diffusion is affected by the size of methanol-solvated Na + and Cl - ions, which increase with increasing Na + and Cl - concentrations. Solution pH change also affected solute solvation layer thicknesses and C-COF pore charges, contributing to the significant AB dye selectivity increase with pH increase. To summarize, we have shown that dramatic changes in C-COF selectivity are not anomalous in OSN, but are instead controllable by varying feed solution pH to modify solvated solute radii and surface charge.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1983

Prediction of impact force and duration during low velocity impact on circular composite laminates

Two simple and improved models--energy-balance and spring-mass--were developed to calculate impact force and duration during low velocity impact of circular composite plates. Both models include the contact deformation of the plate and the impactor as well as bending, transverse shear, and membrane deformations of the plate. The plate was transversely isotropic graphite/epoxy composite laminate and the impactor was a steel sphere. Calculated impact forces from the two analyses agreed with each other. The analyses were verified by comparing the results with reported test data.

Shivakumar, K. N.↗