Polymethylmethacrylate Piece Research Articles

In vitro analysis of factors affecting the continuous hemodiafiltration clearance of teicoplanin.

In the treatment of sepsis, continuous hemodiafiltration (CHDF) and the administration of antibiotics such as teicoplanin (TEIC) are frequently performed in parallel. We aimed to clarify the factors influencing the CHDF clearance (CLCHDF ) of TEIC using a polymethylmethacrylate (PMMA) membrane or a polyacrylonitrile and sodium methallyl sulfonate copolymer membrane coated with polyethylenimine (AN69ST). We also investigated whether the adsorption of TEIC onto the hemofilters inhibits the adsorption of interleukin (IL)-6 onto the membranes. TEIC, human serum albumin (HSA), and IL-6 were incubated with pieces of hemofilter membranes and adsorption rates were calculated. The CLCHDF , diafiltration rate, and adsorption rate of TEIC were calculated using an in vitro CHDF circuit model. The adsorption rates of TEIC onto the pieces of PMMA and AN69ST membranes ranged from 15.0% to 100% and from -10% to 5%, respectively. The adsorption rate of IL-6 was similar with or without TEIC. The CLCHDF and adsorption rate of TEIC under PMMA-CHDF depended on HSA, but not on effluent flow rate (Qe). The CLCHDF under AN69ST-CHDF depended on HSA and Qe. The observed CLCHDF under AN69ST-CHDF was similar to the predicted value (the product of Qe and the plasma unbound fraction). The observed CLCHDF under PMMA-CHDF was 2.0-7.8 times greater than the predicted value. Adsorption mainly contributes to the CLCHDF of TEIC using PMMA membranes, whereas diafiltration mainly contributes to the CLCHDF of TEIC using AN69ST membranes. TEIC adsorption might not affect the adsorption of IL-6 onto PMMA membrane.

Dendrite-joining of air-gap-separated PMMA substrates using ultrashort laser pulses

We demonstrate joining polymethyl methacrylate (PMMA) substrates by a dendrite pattern of a quenched melt using ultrashort laser pulses. Laser pulses from a 250-fs fiber laser at a repetition rate of 1 MHz were focused at the interface of the two PMMA substrates with an air gap of approximately 14 μm and direct laser joining was accomplished between two pieces of PMMA. Melted PMMA from the laser-irradiated region spread within a gap between the substrates and dendrite morphology of the melt spread outside the direct laser irradiated area of square spiral contour and increased the joining strength. The joint strength was 11 MPa for tensile and 21 MPa for the shear stress. Ultrashort laser pulses are useful to directly join PMMA substrates using localized melting and resolidification with a gap between the substrates.

Laser micromachined wax-covered plastic paper as both sputter deposition shadow masks and deep-ultraviolet patterning masks for polymethylmethacrylate-based microfluidic systems

We report a technically innovative method of fabricating masks for both deep-ultraviolet (UV) patterning and metal sputtering on polymethylmethacrylate (PMMA) for microfluidic systems. We used a CO 2 laser system to cut the required patterns on wax-covered plastic paper; the laser-patterned wax paper will either work as a mask for deep-UV patterning or as a mask for metal sputtering. A microfluidic device was also fabricated to demonstrate the feasibility of this method. The device has two layers: the first layer is a 1-mm thick PMMA substrate that was patterned by deep-UV exposure to create microchannels. The mask used in this process was the laser-cut wax paper. The second layer, also a 1-mm thick PMMA layer, was gold sputtered with patterned wax paper as the shadow mask. These two pieces of PMMA were then bonded to form microchannels with exposed electrodes. This process is a simple and rapid method for creating integrated microfluidic systems that do not require cleanroom facilities.

Development and characterization of a capillary-flow microfluidic device for nucleic acid detection

We have developed a capillary flow-driven microfluidic biosensor to meet the needs of diagnostics for resource-limited areas. The device combined elements of lateral flow assays and microfluidic technology resulting in a hybrid with benefits of both formats. The biosensor was achieved by bonding two pieces of polymethyl methacrylate with channels ablated by a CO2 laser, and enclosing an absorbent pad. The channels were UV/ozone treated to increase hydrophilicity which enabled capillary flow. The absorbent pad allowed for continuous flow in the channels once filled. The application of biosensor was demonstrated by detection of DNA with a sandwich assay. The target DNA was hybridized with nucleic acid modified magnetic beads as well as Ru(bpy)32+ doped silica nanoparticles. Fluorescent signals were quantified in a holder fabricated to fit in a fluorescent microtiter plate reader. The capillary flow microfluidic was capable to detect 1 pmol target. The assay format which features rapid analysis and does not require the use of pumps could allow for inexpensive point of care diagnostics in the future.

Optical PMMA Chip Suitable for Multianalyte Detection

A new optical platform for the interrogation of a polymethylmethacrylate (PMMA) multichannel array for chemical and biochemical parameters is described. It consists of a plastic chip formed by two pieces of PMMA properly shaped in order to obtain different microchannels, 500 mum in width and 400 mum in height. A fluorescent sensing layer is immobilized on the internal wall of the microchannel. The emitted light travels along the thickness of the upper PMMA piece and it is detected with an optical fiber connected with a spectrum analyzer. The anisotropy of the fluorescence emitted by the fluorophore immobilized at the liquid/plastic interface gives rise to preferential directions of the emitted fluorescence. The collection of the fluorescence at an angle of 50deg implies an amplification of roughly one order of magnitude in the ratio between the fluorescence signal and the scattered light. The optical platform was further characterized as a pH sensor and as potential chip for immunoassay. In the first case, the fluorescein dye is directly immobilized onto the internal wall of the channel and the fluorescence changes are measured as a function of the pH of the flowing sample. In the second case, a direct antigen-antibody interaction is carried out. The mouse-IgG is covalently immobilized onto the internal wall of the channel and the Cy5-labeled anti-mouse IgG is used for the specific interaction.

An analysis of bottom stagnation region combustion of polymeric material pieces under natural convection

Bottom surface combustion of polymeric material pieces in free convective flows is studied theoretically. The radiative heat exchange at the gas-condensed material interface and the difference of the diffusion coefficient for the pyrolysis gas from that for other species are considered in the analysis. Numerical calculations are performed for cases of cylindrical and spherical PMMA (polymethylmethacrylate) pieces. For each case, the gas temperature, gas velocity, and species profiles across a flame established at the bottom stagnation region and the surface regression rate are examined. Several novel aspects are elucidated. As the diameter d of the cylindrical or spherical PMMA piece increases, the flame temperature T f decreases and the distance y f from the gas-condensed material interface to the flame front increases. At a small but finite value of d − 1 4 , T f decreases rapidly as d − 1 4 decreases. When the Schmidt number Sc F for the pyrolysis gas is small, i.e., when the diffusion coefficient D F for the pyrolysis gas is large, a maximum of y f appears at a near-extinction condition. As Sc F increases, both T f and y f decrease. Since the effects of T f and y f on the regression rate ν s counteract each other, the dependence of ν s on Sc F is very slight. The experimentally obtained values of y f and ν s for cylindrical PMMA pieces are compared with their numerically obtained values. The numerical results are shown to coincide with the experimental results when a large value of Sc F is assumed.

Theoretical and Experimental Research on Hydraulic Fracturing

We are conducting a joint theoretical/experimental research program on hydraulic fracturing. Newly developed two-dimensional numerical models (which include complete descriptions of the elastic continuum and porous flow fluids) have been applied to analyze the effects of pore pressure on the fracturing process. By means of small-scale experiments, we are acquiring a better understanding of the effects of the in-situ stress field, the porosity and permeability of the solid, and the presence of interfaces or layering in the solid. Experimentally, we have been studying the growth of cracks near an interface in several materials, including polymethylmethacrylate (PMMA), Nugget sandstone, and Indiana limestone. Results have shown that the mechanical properties of the interface relative to the properties of the materials on either side are important. A crack will not cross a well-bonded interface between two pieces of PMMA, even in the presence of a 13.79-MPa (2000-psi) normal load. Cracks will cross a well-bonded interface from PMMA to limestone, but not vice versa. Similarly, cracks will propagate across a bonded interface from Nugget sandstone to limestone, but not the other way. Pressure-driven cracks will cross an unbonded interface between limestone blocks at normal loads as low as 3.45 MPa (500 psi).