Browsing by Subject "Nanofibers"

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Conductive nickel nanostrand-reinforced polymer nanocomposites
(2013-05) Lu, Chunhong; Krifa, Mourad
Conductive and flexible nanocomposites can have wide applications in textiles, including wearable sensors, antenna, electrodes, etc. The objective of this research is to develop electrically conductive fibers and films that are flexible and deformable for use in textile structures able to accommodate the drape and movement of the human body. To achieve this objective, we evaluate the electrical properties of PEDOT:PSS/nickel nanostrand as well as nylon 6/nickel nanostrand nanocomposites. Nickel nanostrands (NiNS) were first used to reinforce an intrinsically conductive polymer, Poly(3,4-ethylenedioxythiophene) (PEDOT:PSS), in order to fabricate nanocomposite films with high electrical conductivity. The electrical properties of the films were evaluated by the Van der Pauw method. The addition of 10 wt% nanostrands in PDOT:PSS provided a two order of magnitude improvement in electrical conductivity. In addition to PDOT:PSS, nylon 6/NiNS nanocomposite fibers were produced using electrospinning and exhibited diameters in the sub-micron range. The NiNS-reinforced fibers had electrical conductivity that exceeded the ESD range, which offers the potential for use in protective textile applications.
Experimental characterization of thermoplastic polyurethane nanocomposites under extreme conditions
(2007-12) Nguyen, Khiet Chi; Koo, Joseph H.
The thermal insulation properties of thermoplastic polyurethane elastomer nanocomposites (TPUN) were characterized at different heat flux levels. Thermoplastic polyurethane elastomer (TPU) was modified with montmorillonite nanoclays (Cloisite® 30B) and carbon nanofibers (PR24PS) via twin screw extrusion processing. Several loadings of these two types of nanoparticles were incorporated into the thermoplastic polyurethane elastomer to create polymer nanocomposites. It was found that TPU with 10% PR24PS and TPU with 5% Cloisite 30B gave the best thermal insulation performance. Surface temperatures of these polymer nanocomposites were measured using an infrared pyrometer. The surface temperatures of the TPUN-clay material did not vary much while the surface temperatures of the TPUN-CNF material varied substantially.
Flame retardant polyamide 6 nanocomposites and nanofibers : processing and characterization
(2012-05) Yin, Xiaoli; Koo, Joseph H.; Krifa, Mourad
Polyamide 6 (PA6) was melt-blended with an intumescent flame retardant (FR) and nanoparticles (multi-wall carbon nanotubes [MWNTs] and nanoclays) to produce multi-component FR-PA6 nanocomposites. Thermal, flammability properties, char residue morphology, and mechanical properties of FR-PA6 nanocomposites were characterized. The flame retardant properties were enhanced according to UL 94 and microscale combustion calorimeter (MCC) measurements, whereas the thermal stability was decreased. Mechanical properties of the bulk material, especially elongation at break, were severely reduced, with the exception of tensile modulus which increased significantly. FR-PA6 nanofibers were processed via electrospinning. Electrospinnability, morphology of the nanofibers, combustion, and thermal properties were also analyzed. As for the bulk-form nanocomposite, improved combustion properties of these nanofibers were successfully achieved though thermal stability was compromised. With proper FR additive, the synergism between MWNTs and nanoclays was observed in PA6 resin.
Nanostructured PVDF-TrFE based piezoelectric pressure sensors on catheter for cardiovascular applications
(2012-12) Sharma, Tushar; Zhang, John X. J.; Gill, Brijesh S.
The objective of this research is to develop a new class of miniaturized sensors on-catheter technology through the integration of functional nanomaterials and flexible microsystems, with high sensitivity, fast recovery time, reduced form factor, for in situ blood pressure and flow monitoring with minimal invasiveness. Real-time endovascular pressure measurement techniques are crucial to evaluate the hemodynamics, which indicates the physiological state of the cardiovascular system. Current technology relies on fluid filled catheter coupled to remote transducers to measure endovascular pressures and gradients. The fluid filled catheters are bulky, inherently inaccurate due to the tubing mechanical resonance, and with low signal integrity due to the vibration noises from the environment. Silicon based conventional pressure sensors have complications due to issues of catheter stiffness, biocompatibility or small form factor integration. We propose a paradigm shift in designing the endovascular pressure sensing technology, through developing compact flexible sensing structures using nanoengineered piezoelectric polymers which can be integrated on catheters without consuming the internal lumen space. We focused on designing novel nanostructures using PVDF-TrFE (Polyvinyledene fluoride trifluoroethylene), with well controlled [Beta]-crystalline phase to significantly improve the resulting sensor performance. The research objectives include: (1) Thin-film structures for higher piezoelectric effect without any mechanical stretching or poling requirements, (2) High density highly-aligned electrospun nanofibers through electrospinning towards enhanced sensitivity; (3) Core-shell electrospun nanofiber for tapping the near [Beta]-crystalline phase formation and high cyrstallinity by virtue of inherent stress and stretching involved in the fabrication procedure. For pressure sensor design and characterization, we worked on two main form factors designs: thin-film, and aligned electrospun nanofiber based sensors patterned on catheter tips which are ready to be deployed in intra-vascular environment. Testing results showed promising results from PVDF based pressure sensors. The average sensitivity of the PVDF sensors was found to be four times higher than commercial pressure sensor while the PVDF sensor had five fold shorter response time than commercial pressure sensor, making the PVDF sensors highly suitable for real-time pressure measurements using catheters.