Pressure-Sensitive Microvalves Made from Polymer Brushes

1994 ◽  
Vol 360 ◽  
Author(s):  
E.M. Sevick ◽  
D.R.M. Williams
Keyword(s):  
Polymer Brushes ◽  
Critical Pressure ◽  
Feedback Mechanism ◽  
Polymer Chains ◽  
Narrow Slit ◽  
Solvent Quality ◽  
Pressure Sensitive ◽  
Wide Range ◽  
Valve Assembly ◽  
Valve Operation

AbstractWe describe a novel microvalve, constructed from polymer chains end-grafted onto opposing surfaces of a narrow slit. The assembly of polymer chains acts as both sensor and valve for microflow control and bypasses the need to construct an external feedback mechanism. This microflow control results from densely grafted chains which repel one another and stretch away from the surface, forming a brush which acts as an elastic and impenetrable layer. The height of a sheared brush increases or decreases depending upon solvent quality, i.e the layer can show a negative Poission's ratio. The discharge through the brushlined conduit is a non-linear function of pressure enabling different modes of valve operation. For brushes which extend moderately into the inter-slit region the valve assembly maintains constant discharge over a wide range of pressure. For brushes which extend far into the inter-slit region the valve assembly cuts off flow above a critical pressure, limiting the maximum discharge.

Shear Forces between Tethered Polymer Chains as a Function of Compression, Sliding Velocity, and Solvent Quality

2003 ◽  
Vol 36 (2) ◽  
pp. 389-398 ◽  
Author(s):  
Phillip A. Schorr ◽  
Thomas C. B. Kwan ◽  
S. Michael Kilbey ◽  
Eric S. G. Shaqfeh ◽  
Matthew Tirrell
Keyword(s):  
Polymer Chains ◽  
Sliding Velocity ◽  
Shear Forces ◽  
Solvent Quality ◽  
Tethered Polymer Chains

scholarly journals Synthesis of photoreactive solvent-free acrylic pressure-sensitive adhesives in the recovered system

2007 ◽  
Vol 9 (2) ◽  
pp. 5-9 ◽  
Author(s):  
Roland Milker ◽  
Zbigniew Czech ◽  
Marta Wesołowska
Keyword(s):  
Organic Solvent ◽  
Solvent Free ◽  
The Novel ◽  
Pressure Sensitive Adhesive ◽  
Adhesive Film ◽  
Pressure Sensitive Adhesives ◽  
Pressure Sensitive ◽  
Wide Range ◽  
Protective Films ◽  
New Type

Synthesis of photoreactive solvent-free acrylic pressure-sensitive adhesives in the recovered system The present paper discloses a novel photoreactive solvent-free acrylic pressure-sensitive adhesive (PSA) systems, especially suitable for the so much adhesive film applications as the double-sided, single-sided or carrier-free technical tapes, self-adhesive labels, protective films, marking and sign films and wide range of medical products. The novel photoreactive solvent-free pressure-sensitive adhesives contain no volatile organic compounds (residue monomers or organic solvent) and comply with the environment and legislation. The synthesis of this new type of acrylic PSA is conducted in common practice by solvent polymerisation. After the organic solvent are removed, there remains a non-volatile, solvent-free highly viscous material, which can be processed on a hot-melt coating machine at the temperatures of about 100 to 140°C.

scholarly journals Self-restoring polymer brushes under tribological stress and the biomedical applications

MRS Advances ◽  
2016 ◽  
Vol 1 (27) ◽  
pp. 1971-1976
Author(s):  
Troels Røn ◽  
Irakli Javakhishvili ◽  
Søren Hvilsted ◽  
Katja Jankova ◽  
Seunghwan Lee
Keyword(s):  
Polymer Brushes ◽  
Diblock Copolymers ◽  
Polymer Chains ◽  
Aqueous Environment ◽  
Pdms Film ◽  
Pdms Surface ◽  
Tribological Application ◽  
Optimal Functions ◽  
Amphiphilic Diblock Copolymers

ABSTRACTFor biological and mechanical systems involving moving parts, surface slipperiness is often a critical attribute for their optimal functions. Surface grafting with hydrophilic polymers is a powerful means to render materials slippery in aqueous environment. In “inverted grafting-to approach”, the hydrophilic polymer chains of amphiphilic diblock copolymers dispersed within a poly(dimethylsiloxane) (PDMS) network are selectively segregated upon exposure to aqueous solution. This allows formation of extremely stable brush-like polymer layers. Tribological application of inverted grafting-to approach was successfully demonstrated with PDMS-block-poly(acrylic acid) (PDMS-b-PAA) dispersed within thin PDMS films on PDMS blocks by showing friction coefficients (µ) of ca 10-2 to 10-3, depending on the load, pH and buffer salinity in the absence of other external re-supply of PAA chains. Further manipulations of the thin PDMS film incorporating PDMS-b-PAA to optimize the tribological properties are presented. Lastly, first trials to employ PAA-grafted PDMS surface to generate in-vitro mucosae model are also presented and discussed.

scholarly journals Mapping calcium dynamics in a developing tubular structure

2020 ◽  
Author(s):  
Jorgen Hoyer ◽  
Morsal Saba ◽  
Daniel Dondorp ◽  
Kushal Kolar ◽  
Riccardo Esposito ◽  
...  
Keyword(s):  
Cell Types ◽  
Feedback Mechanism ◽  
Adult Brain ◽  
Actin Dynamics ◽  
Cytoskeletal Network ◽  
Notochord Cell ◽  
Wide Range ◽  
Store Operated Calcium Entry ◽  
And Function ◽  
Cell Intercalation

AbstractCalcium is a ubiquitous and versatile second messenger that plays a central role in the development and function of a wide range of cell types, tissues and organs. Despite significant recent progress in the understanding of calcium (Ca2+) signalling in organs such as the developing and adult brain, we have relatively little knowledge of the contribution of Ca2+ to the development of tubes, structures widely present in multicellular organisms. Here we image Ca2+ dynamics in the developing notochord of Ciona intestinalis. We show that notochord cells exhibit distinct Ca2+ dynamics during specific morphogenetic events such as cell intercalation, cell elongation and tubulogenesis. We used an optogenetically controlled Ca2+ actuator to show that sequestration of Ca2+ results in defective notochord cell intercalation, and pharmacological inhibition to reveal that stretch-activated ion channels (SACs), inositol triphosphate receptor (IP3R) signalling, Store Operated Calcium Entry (SOCE), Sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) and gap junctions are required for regulating notochord Ca2+ activity during tubulogenesis. Cytoskeletal rearrangements drive the cell shape changes that accompany tubulogenesis. In line with this, we show that Ca2+ signalling modulates reorganization of the cytoskeletal network across the morphogenetic events leading up to and during tubulogenesis of the notochord. We additionally demonstrate that perturbation of the actin cytoskeleton drastically remodels Ca2+ dynamics, suggesting a feedback mechanism between actin dynamics and Ca2+ signalling during notochord development. This work provides a framework to quantitatively define how Ca2+ signalling regulates tubulogenesis using the notochord as model organ, a defining structure of all chordates.

scholarly journals Effect of Structure of Polymers Grafted from Graphene Oxide on the Compatibility of Particles with a Silicone-Based Environment and the Stimuli-Responsive Capabilities of Their Composites

Nanomaterials ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 591 ◽  
Author(s):  
Monika Zygo ◽  
Miroslav Mrlik ◽  
Marketa Ilcikova ◽  
Martina Hrabalikova ◽  
Josef Osicka ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Graphene Oxide ◽  
Radical Polymerization ◽  
Polymer Brushes ◽  
Silicone Oil ◽  
Polymer Chains ◽  
Butyl Methacrylate ◽  
Raman Shift ◽  
Stimuli Responsive ◽  
Grafted Polymer

This study reports the utilization of controlled radical polymerization as a tool for controlling the stimuli-responsive capabilities of graphene oxide (GO) based hybrid systems. Various polymer brushes with controlled molecular weight and narrow molecular weight distribution were grafted from the GO surface by surface-initiated atom transfer radical polymerization (SI-ATRP). The modification of GO with poly(n-butyl methacrylate) (PBMA), poly(glycidyl methacrylate) (PGMA), poly(trimethylsilyloxyethyl methacrylate) (PHEMATMS) and poly(methyl methacrylate) (PMMA) was confirmed by thermogravimetric analysis (TGA) coupled with online Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Various grafting densities of GO-based materials were investigated, and conductivity was elucidated using a four-point probe method. Raman shift and XPS were used to confirm the reduction of surface properties of the GO particles during SI-ATRP. The contact angle measurements indicated the changes in the compatibility of GOs with silicone oil, depending on the structure of the grafted polymer chains. The compatibility of the GOs with poly(dimethylsiloxane) was also investigated using steady shear rheology. The tunability of the electrorheological, as well as the photo-actuation capability, was investigated. It was shown that in addition to the modification of conductivity, the dipole moment of the pendant groups of the grafted polymer chains also plays an important role in the electrorheological (ER) performance. The compatibility of the particles with the polymer matrix, and thus proper particles dispersibility, is the most important factor for the photo-actuation efficiency. The plasticizing effect of the GO-polymer hybrid filler also has a crucial impact on the matrix stiffness and thus the ability to reversibly respond to the external light stimulation.

Transient uniaxial orientation of flexible polymer chains in a wide range of elongation rates

Polymer ◽  
2005 ◽  
Vol 46 (11) ◽  
pp. 3927-3935 ◽  
Author(s):  
Andreas Schoene ◽  
Andrzej Ziabicki ◽  
Leszek Jarecki
Keyword(s):  
Polymer Chains ◽  
Flexible Polymer ◽  
Uniaxial Orientation ◽  
Wide Range

Polymer Brushes as Pressure-Sensitive Automated Microvalves

1994 ◽  
Vol 27 (19) ◽  
pp. 5285-5290 ◽  
Author(s):  
E. M. Sevick ◽  
D. R. M. Williams
Keyword(s):  
Polymer Brushes ◽  
Pressure Sensitive

The Effect of Nanoclay on the Rheological Properties of Polylactic Acid/Polyhydroxybutyrate-Valerate Blends

2015 ◽  
Author(s):  
Haibin Zhao ◽  
Xiangfang Peng
Keyword(s):  
Injection Molding ◽  
Polylactic Acid ◽  
Strong Interaction ◽  
Rheological Behavior ◽  
Full Range ◽  
Complex Viscosity ◽  
Polymer Chains ◽  
Wide Range ◽  
Strong Shear ◽  
Microcellular Injection Molding

In this article, the effects of nanoclay (CN) on the rheological behavior of polylactic acid (PLA)/polyhydroxybutyrate–valerate (PHBV) blends was investigated. The rheological behavior of PLA/PHBV blends showed a Newtonian plateau that converted to strong shear thinning behavior over the full range of frequency by the incorporation of nanoclay. The results indicate that the storage modulus and complex viscosity of PLA/PHBV blends were sensitive to nanofillers. An obvious pseudo-solid-like behavior over a wide range of frequency in PLA/PHBV/CN nanocomposites showed that the strong interaction between the PLA/PHBV blend and the nanoclay restricted the relaxation process of the polymer chains. Therefore, the PLA/PHBV/CN nanocomposites possess a higher modulus and greater melt strength, which are desirable for creating an improved foamed structure when manufactured via microcellular injection molding.

Nanopatterned polymer brushes: conformation, fabrication and applications

Nanoscale ◽  
2016 ◽  
Vol 8 (2) ◽  
pp. 680-700 ◽  
Author(s):  
Qian Yu ◽  
Linnea K. Ista ◽  
Renpeng Gu ◽  
Stefan Zauscher ◽  
Gabriel P. López
Keyword(s):  
Polymer Brushes ◽  
Wide Range

Nanopatterned polymer brushes provide versatile platforms for investigation of nanoscale phenomena at biointerfaces and for a wide range of applications in biotechnology and electronics.

Dynamics of Polystyrene in Confining Geometry: Transition from Dilute to Semidilute

1992 ◽  
Vol 290 ◽  
Author(s):  
Iwao Teraoka ◽  
Kenneth H. Langley ◽  
Frank E. Karasz
Keyword(s):  
Diffusion Coefficient ◽  
Light Scattering ◽  
Apparent Diffusion Coefficient ◽  
Chemical Potential ◽  
Polymer Concentration ◽  
Polymer Chains ◽  
Molecular Weights ◽  
Highly Nonlinear ◽  
Wide Range ◽  
Apparent Diffusion

AbstractDynamics of polystyrene molecules inside controlled pore glasses, a typical confining geometry, was studied by dynamic light scattering over a wide range of concentrations of polystyrene in solutions in equilibrium with the porous glasses. Index-matching of the solvent to the silica glasses effectively facilitates the acquisition of information on the dynamics of polymer chains inside the pore without compromising that information by multiple light scattering. When the concentration outside the pore is much smaller than the overlap concentration v*, the apparent diffusion coefficient Dporc of polymers within the pore shows little dependence on concentration. As the outside concentration increases and approaches v*, Dporc rapidly increases. This tendency is more pronounced for polystyrene samples that have higher molecular weights and are predicted to have a lower concentration inside the pore. With further increases of concentration beyond v*, Dporc approaches the apparent diffusion coefficient outside the pore. Moreover, Dporc becomes almost the same for the three different molecular weights of polystyrene fractions studied and depends primarily on the weight concentration of the solute outside the pore. These features are typical of a semidilute solution regime for flexible polymers. The rapid increase in Dporc, is ascribed to a drastic increase of the polymer concentration inside the pore, which results from an equilibration of the chemical potential of the polymer molecule between the interior of the pore and the exterior. Thus, a rapid increase in the osmotic pressure outside the pore drives the polymers into pore channels even at the expense of reduced entropy. We present a quantitative analysis of this highly nonlinear partitioning of polymer molecules.

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