Fabrication of Embedded Microvalve on PMMA Microfluidic Devices through Surface Functionalization

The integration of a PDMS membrane within orthogonally placed PMMA microfluidic channels enables the pneumatic actuation of valves within bonded PMMA-PDMS-PMMA multilayer devices. Here, surface functionalization of PMMA substrates via acid catalyzed hydrolysis and air plasma corona treatment were investigated as possible techniques to permanently bond PMMA microfluidic channels to PDMS surfaces. FTIR and water contact angle analysis of functionalized PMMA substrates showed that air plasma corona treatment was most effective in inducing PMMA hydrophilicity. Subsequent fluidic tests showed that air plasma modified and bonded PMMA multilayer devices could withstand fluid pressure at an operational flow rate of 9 mircoliters/min. The pneumatic actuation of the embedded PDMS membrane was observed through optical microscopy and an electrical resistance based technique. PDMS membrane actuation occurred at pneumatic pressures of as low as 10kPa and complete valving occurred at 14kPa for 100 micrometers x 100 micrometers channel cross-sections.Comment: Submitted on behalf of EDA Publishing Association (http://irevues.inist.fr/handle/2042/16838

Design, Fabrication, and Testing of an Electrospinning Apparatus for the Deposition of PMMA Polymer for Biomedical Applications

This paper describes the successful design and fabrication of a deposition system for synthesis and assembly of nanoscale and submicron sized fibers of poly(methylmethacrylate)(PMMA) polymer. To optimize the electrospinning deposition process, the distance between the needle and the electrically grounded substrate, the applied voltage, and the concentration of PMMA polymer in the solution were varied. PMMA fibers as small as 500 nanometers were observed using scanning electron microscopy (SEM). The chemical signature of PMMA was confirmed for best quality and retention of chemistry using Fourier Transformed Infrared spectroscopy (FT-IR). PMMA is a biocompatible polymer, and nanofibers of PMMA are key building blocks for scaffolds and other biomanufacturing applications, such as bioprinting for regenerative medicine and tissue engineering of synthetic organs (Mo, 2004)

Enhancement of optical response in nanowires by negative-tone PMMA lithography

The method of negative-tone-PMMA electron-beam lithography is investigated to improve the performance of nanowire-based superconducting detectors. Using this approach, the superconducting nanowire single-photon detectors (SNSPDs) have been fabricated from thick 5-nm NbN film sputtered at the room temperature. To investigate the impact of this process, SNSPDs were prepared by positive-tone and negative-tone-PMMA lithography, and their electrical and photodetection characteristics at 4.2 K were compared. The SNSPDs made by negative-tone-PMMA lithography show higher critical-current density and higher photon count rate at various wavelengths. Our results suggest a higher negative-tone-PMMA technology may be preferable to the standard positive-tone-PMMA lithography for this application

Thermal Degradation Studies on PMMA–HET Acid Based Oligoesters Blends

Imparting thermal stability to polymethyl methacrylate (PMMA) without affecting its optical clarity is attempted by incorporating HET acid based oligoesters. Pure PMMA and PMMA containing five and 20 wt% of four different oligoesters are separately prepared using bulk polymerization. The thermal properties of the materials studied using DSC, TG, TG–FTIR and Pyr–GC–MS are presented. The main volatile degradation products identified are CO, HCl, CO2, H2O, hexachlorocyclopentadiene, hexachloroendomethylene tetrahydrophthalic acid/anhydride and methyl methacrylate. A detailed mechanism for the influence of the degradation products of HET acid based oligoesters on the thermal degradation of PMMA is also presented

Surface structure of thin asymmetric PS-b-PMMA diblock copolymers investigated by atomic force microscopy

Asymmetric poly(styrene-b-methyl methacrylate) (PS-b-PMMA) diblock copolymers of molecular weight M-n = 29,700g mol(-1) (M-PS = 9300 g mol(-1) M-PMMA = 20,100 g mol(-1), PD = 1.15, chi(PS) = 0.323, chi(PMMA) = 0.677) and M-n = 63,900 g mol(-1) (M-PS = 50,500 g mol(-1), M-PMMA = 13,400 g mol(-1), PD = 1.18, chi(PS) = 0.790, chi(PMMA) = 0.210) were prepared via reversible addition-fragmentation chain transfer (RAFT) polymerization. Atomic force microscopy (AFM) was used to investigate the surface structure of thin films, prepared by spin-coating the diblock copolymers on a silicon substrate. We show that the nanostructure of the diblock copolymer depends on the molecular weight and volume fraction of the diblock copolymers. We observed a perpendicular lamellar structure for the high molar mass sample and a hexagonal-packed cylindrical patterning for the lower molar mass one. Small-angle X-ray scattering investigation of these samples without annealing did not reveal any ordered structure. Annealing of PS-b-PMMA samples at 160 degrees C for 24 h led to a change in surface structure

New Phosphated Poly(methyl Methacrylate) Polymers for the Prevention of Denture-induced Microbial Infection: an In Vitro Study

Purpose: Poly(methyl methacrylate) (PMMA) has been widely used as a denture-base acrylic resin due to its excellent physical and mechanical properties. However, the material is highly prone to microbial fouling that often leads to Candida-associated denture stomatitis. Incorporation of phosphate groups into PMMA could facilitate adsorption of salivary antimicrobials and inhibit microbial adherence on the polymer surface. An in vitro study evaluated PMMA polymers containing varying amounts of phosphate group for their efficacy to inhibit Candida albicans adhesion, adsorb salivary histatin 5, and exhibit candidacidal activity. Methods: Six PMMA polymers containing 0%, 5%, 15%, 10%, 20%, and 25% of phosphate group were synthesized by bead (suspension) polymerization technique using mixtures of methyl methacrylate and methallyl phosphate as monomers. The efficacy of the polymers to inhibit the adherence of C. albicans was examined by using human saliva-coated polymer beads and radio-labeled C. albicans cells, as compared with that of PMMA. The potency of the phosphated PMMA polymers to adsorb histatin 5 was determined by measuring the radioactivity of the adsorbed labeled-peptide on the polymer surface. The candidacidal activity of the histatin 5-adsorbed polymers was assessed by using the fluorescence technique. The percent release of the fluorescent probe calcein from the C. albicans membrane caused by the disruption of the cell membrane was determined. The data were analyzed statistically by one-way ANOVA followed by Scheffé’s test (α = 0.05 and n = 6). Results: The presence of ≥15% phosphate content in PMMA significantly reduced the saliva-mediated adhesion of C. albicans. Phosphated PMMA polymers showed significantly enhanced adsorption of histatin 5 in a phosphate density-dependent manner. The candidacidal activity of the histatin 5-bound polymers increased significantly with the increase in the phosphate content of the polymer. Conclusion: Phosphated PMMA polymers have the potential to serve as novel denture-base resins, which may reduce C. albicans colonization and prevent denture stomatitis

Experimental ex-vivo validation of PMMA-based bone cements loaded with magnetic nanoparticles enabling hyperthermia of metastatic bone tumors

Percutaneous vertebroplasty comprises the injection of Polymethylmethacrylate (PMMA) bone cement into vertebrae and can be used for the treatment of compression fractures of vertebrae. Metastatic bone tumors can cause such compression fractures but are not treated when injecting PMMA-based bone cement. Hyperthermia of tumors can on the other hand be attained by placing magnetic nanoparticles (MNPs) in an alternating magnetic field (AMF). Loading the PMMA-based bone cement with MNPs could both serve vertebra stabilization and metastatic bone tumor hyperthermia when subjecting this PMMA-MNP to an AMF. A dedicated pancake coil is designed with a self-inductance of 10 mu H in series with a capacitance of 0.1 mu F that acts as resonant inductor-capacitor circuit to generate the AMF. The thermal rise is appraised in beef vertebra placed at 10 cm from the AMF generating circuit using optical temperatures sensors, i. e. in the center of thePMMA-MNPbone cement, which is located in the vicinity of metastatic bone tumors in clinical applications; and in the spine, which needs to be safeguarded to high temperature exposures. Results show a temperature rise of about 7 degrees C in PMMA-MNP whereas the temperature rise in the spine remains limited to 1 degrees C. Moreover, multicycles heating of PMMA-MNP is experimentally verified, validating the technical feasibility of having PMMA-MNP as basic component for percutaneous vertebroplasty combined with hyperthermia treatment of metastatic bone tumors

Morphological and Tribological Properties of PMMA/Halloysite Nanocomposites

From an environmental and cost-effective perspective, a number of research challenges can be found for electronics, household, but especially in the automotive polymer parts industry. Reducing synthesis steps, parts coating and painting, or other solvent-assisted processes, have been identified as major constrains for the existing technologies. Therefore, simple polymer processing routes (mixing, extrusion, injection moulding) were used for obtaining PMMA/HNT nanocomposites. By these techniques, an automotive-grade polymethylmethacrylate (PMMA) was modified with halloysite nanotubes (HNT) and an eco-friendly additive N,N′-ethylenebis(stearamide) (EBS) to improve nanomechanical properties involved in scratch resistance, mechanical properties (balance between tensile strength and impact resistance) without diminishing other properties. The relationship between morphological/structural (XRD, TEM, FTIR) and tribological (friction) properties of PMMA nanocomposites were investigated. A synergistic effect was found between HNT and EBS in the PMMA matrix. The synergy was attained by the phase distribution resulted from the selective interaction between partners and favourable processing conditions. Modification of HNT with EBS improved the dispersion of nanoparticles in the polymer matrix by increasing their interfacial compatibility through hydrogen bonding established by amide groups with aluminol groups. The increased interfacial adhesion further improved the nanocomposite scratch resistance. The PMMA/HNT-EBS nanocomposite had a lower coefficient of friction and lower scratch penetration depth than PMMA/HNT nanocomposite.Financial support by the EU Commission through Project H2020-686165-IZADINANO2INDUSTRY is gratefully acknowledged

Rapid fabrication of polymer microfluidic systems for the production of artificial lipid bilayers

A polymer microfluidic device has been fabricated using rapid prototyping techniques. The device was built up to allow the formation and subsequent investigation of artificial bilayer lipid membranes (BLMs). A simple dry film photoresist stamp was used to hot emboss microfluidic channels into PMMA films. Laser micromachining was employed to form an aperture into PMMA films. Laser micromachining was employed to form an aperture through the PMMA channels, across which the BLM was later formed. The dry film phororesist was also used as a simple etch mask for the deep etching of glass substrates in buffered HF solutions, which was used in this work for the production of glass embossing stamps. We show that bilayer films can be successfully produced across laser micromachined apertures in PMMA films

Low-energy vibrational density of states of plasticized poly(methyl methacrylate)

The low-energy vibrational density of states (VDOS)of hydrogenated or deuterated poly(methyl methacrylate)(PMMA)plasticized by dibutyl phtalate (DBP) is determined by inelastic neutron scattering.From experiment, it is equal to the sum of the ones of the PMMA and DBP components.However, a partition of the total low-energy VDOS among PMMA and DBP was observed.Contrary to Raman scattering, neutron scattering does not show enhancement of the boson peak due to plasticization.Comment: 9 pages, 2 figures (Workshop on Disordered Systems, Andalo