“Label-free” biomolecule sensors for detection of inflammatory cardiovascular biomarker associated with vulnerable coronary vascular plaque were designed and fabricated using micro and nano-textured polystyrene structures that functioned as sensing elements coupled with electronic measurement equipment. We demonstrated that scaling down the surface texturing from the micro to the nanoscale enhances the amplitude of the measured signal strength. We believe that the nanoscale fiber morphology provides size matched spaces for trapping and immobilizing the protein biomolecules resulting in enhanced detection and signal strength. We selected polystyrene as the model system and demonstrated the detection of human serum C-reactive protein (hs-CRP). We employed these findings in designing a platform “lab-on-a-chip” protein sensor. Comparative studies were performed on two different polystyrene textured surfaces: a polystyrene microsphere mat, and an electrospun polystyrene nanofiber matrix.

Carbon nanotube (CNT) has emerged as potential candidate for replacement of conventional metal patch in antenna application. The principal objective of our research is to develop nanostructured flexible patch antenna array for multi- frequency operation in industrial, scientific and medical (ISM) band. Patch antenna design using CNT on flexible cotton sheets has been simulated with cotton as a substrate and CNT as conductive patch and ground plane. Due to high conformability and conductivity of CNT all antenna parameters like VSWR, return loss, gain and radiation pattern obtained using FEKO EMSS software meet design criteria. Our simulated antenna design shows a return loss less than -10 dB and VSWR less than 2 at 2.06 GHz, 2.38 GHz and 2.49 GHz. We have also simulated a versatile and conformable antenna design where the whole geometry is rolled up like patch array on cylindrical surface. Conformability to curved surfaces and integration with the structure brings about a unique antenna design. An inset fed square patch array is also proposed for RF energy harvesting operating in the 2.45 GHz ISM band that can harvest and store energy from the surrounding environment. Simulation result shows that dc voltage of 0.215 V can be achieved at -6 dbm received energy level at 2.45 GHz IEEE 802.11b band. This would correspond to potential working distance of 10m.

We have synthesized a series of ion exchange functionalized fibers (IXF) from polystyrene (PS) and polyacrylonitrile (PAN). To obtain strong-acid cation exchange fibers, polystyrene was sulfonated using specific sulfonation protocols. Micron sized fibers (average diameter of 100m) were then produced from the functionalized polystyrene using a single-screw extruder equipped with a 30 hole spinneret with orifice diameter of 0.5 mm with a precise screw speed of 5 rpm, pump speed of 15 rpm, and with a feed rate of 2.4 cc/min. The extruder zone temperature was kept at 250 – 270 °C. Fiber was drawn at 120 degree with a draw ratio of 2. Electrospinning of functionalized polystyrene was also carried out to produce ultrafine functionalized fibers of 100 nm in average diameter. We have also electrospun polystyrene and polyisoprene blended nanofibers to increase the strength of the resulting blend nanofibers compared to pure PS nanofibers. To synthesize weak-acid cation exchange fibers polyacrylonitrile (PAN) was electrospun and the nanofibers obtained were alkaline hydrolyzed with 2 N NaOH for 20 minutes at room temperature to convert nitrile bonds to carboxylate. Cation exchange capacity (CEC) of the microfibers and nanofibers was determined. Sulfonated PS microfibers show high CEC of 4.0 meq/gm compared to that of nanofibers with 2.5 meq/gm. CEC of blended nanofibers of PS and polyisoprene was 2.0 meq/gm. In case of PAN fibers, nanosized electrospun fibers were found to show a CEC of 1.5 meq/gm. Weak-base anion exchange fiber synthesis was undertaken using appropriate protocol and its CEC was measured. For all IXF synthesized, fiber diameter was measured using SEM, degree of functionalization was qualitatively determined using FTIR and ion exchange capacity was computed after mass balance on a binary exchange system after equilibrium.

Electrospinning is a technique of producing nanofibers from polymer solution/melt solely under the influence of electrostatic forces. In this research, we investigated the formation of nanofibers by melt electrospinning polycaprolactone (PCL). The effect of process parameters such as molecular weight, applied voltage, and electrode separation on the fiber diameter was investigated. Controlling the process parameters could help increase the proportion of ultrafine fibers in the melt electrospun nonwoven mat. The velocity of the straight jets was in the range of 0.2-1 m/s. The melt electrospun fibers were characterized with respect to fiber diameter, distribution, mechanical properties and birefringence. Melt electrospun polycaprolactone fibers had a diameter distribution of the order of 5 -20 μm. The birefringence of the melt electrospun fibers increased with decrease in fiber diameter.

A phenyl-containing highly cross linked polyborosiloxane (PBSiO) was synthesized as a flame retardant for polyethylene terephthalate (PET). We coated montmorillonite (MMT) clay, a very high aspect ratio and high specific surface area layered silicate with synthesized PBSiO to introduce synergism in flame retardation to the PET nanocomposite film that retained thermal and mechanical properties. This PBSiO has high thermal stability at the processing temperature (270-285° C) of PET and acts as a compatibilizer between PET and clay that are otherwise incompatible. During burning, the flame retardant PET containing PBSiO and MMT forms a protective borosilicatecarbonaceous intumescent char on the surface. Cone calorimeter tests were performed to evaluate key fire properties of the PET/PBSiO/MMT. The peak heat release rate (PHRR) of PET that contains 5 wt% PBSiO and 2.5 wt% MMT was reduced by 60% and similar trend in the reduction of mass loss rate of the nanocomposite was observed.

We investigated the effect of organically modified clay on the thermal and flammability behavior of nylon 6 nanocomposites. We also used zinc borate along with layered silicate with an aim of achieving synergistic effect in flame retardancy. It is found that addition of 10 wt% clay reduced the onset decomposition (5% wt loss) temperature of nylon 6 by 20°C, while addition of 5 wt% zinc borate and 5 wt% clay in combination reduced it by around 10°C. Differential thermogravimetric analysis indicated that the peak decomposition temperature was not affected by the addition of clay, but the rate of weight loss decreased with increasing clay concentration. The horizontal burning behavior of the nanocomposite films of approximately 0.5mm thickness changed with additive concentration. The nanocomposites with 2.5 wt% and 5 wt% clay burned for almost the same duration as neat nylon 6 but dripping was reduced. The 10 wt% clay nanocomposite sample burned without any dripping and the flame spread rate was reduced by 25-30%. The burn rate of 5 wt % zinc borate/5 wt% clay nanocomposite sample was about 20% higher than that of 10 wt% clay nanocomposite sample, which could be attributed to varying char morphology. Scanning electron microscopy images of the 10wt% clay nanocomposite char surface and cross- section revealed an integrated layer of clay platelets with increasing density gradient from the center to the surface, while the 5 wt% zinc borate/5 wt% clay nanocomposite char appeared foamy and porous. The 5 wt% zinc borate and 5 wt% clay sample developed into a very good intumescent system in cone calorimeter test, swelling about 10-13mm height prior to ignition forming a cellular char structure. This was as effective as the 10wt% clay nanocomposite sample in reducing the heat release and mass loss rate of nylon 6 by around 65%. Fourier transform infrared spectroscopy of the 10 wt% clay nanocomposite char showed the presence of amides, indicating possible residual polymer within the shielded char.

Polymer materials such as Kevlar that are susceptible to UV degradation may be protected by appropriate coatings. We are using zinc oxide and titanium dioxide nanoparticles with an average particle size ranging from 25 to 70 nm. Five weight percent nanoparticles were dispersed in acrylic coatings, the dispersion is assisted by addition of a non-ionic surfactant, mechanical stirring and ultrasonication. The UV protective mechanism of nanoparticle-embedded coatings is theoretically explained using Mie theory. We estimated the minimum thickness of a 5 weight % nanoparticle-embedded coatings that is required to prevent the UV radiation from reaching the base of the substrate. Results obtained from nanoparticle-embedded acrylic-coated Kevlar fabric and neat acrylic-coated Kevlar fabric after exposure to UV radiation in QUV weatherometer show that the nanoparticle coating offers protection. UV-visible spectroscopy was used to obtain quantitative results.

The flame retardancy of nylon 6/laponite and nylon 6/montmorillonite nanocomposites was investigated. The pronounced effect of layered silicates on heat release and mass loss rates of nylon 6 was examined. We found that nylon 6/laponite has 46 % and nylon 6/montmorillonite has 52.5 % lower peak heat release rates than that of neat nylon 6. The 6.5 % difference between the peak heat release rates of laponite- and montmorillonite-based nanocomposites was attributed to differences in aspect ratio and surface charge density of the nanoparticles.

The barrier properties of nanocomposite chars was evaluated by examining the peak heat release and mass loss rate reductions of stacks of layers, with the bottom layer being neat nylon 6 polymer and the top layers being nanocomposites that formed chars during the experiments. We observed that the peak heat release rate of a 10×10×0.3 cm neat nylon 6 slab was reduced by about 45 % when protected with a char-forming nylon 6/montmorillonite slab of same dimensions. The dramatic reduction of the peak heat release rate of neat nylon 6 when covered with a nanocomposite char was consistent with the notion that the flame retardancy of polymer/clay nanocomposites is affected by the (thermal and/or mass) barrier properties of the char. In order to test the thermal insulation of the char, temperature profiles of the layered samples were measured during cone calorimeter experiments. We observed that the nanocomposite char that brought about a 44.5 % reduction in peak heat release and mass loss rates reduced the heating rate of the same neat nylon 6 by about 31.2 %. The reduction in the heating rate increased with the amount of nanocomposite char formed.

The main issues related with preparation of nanocomposites are dispersion, alignment and adhesion between carbon nanotubes and matrix. We are designing an approach where these issues are fully addressed. We combined a functionalization approach with in-situ technique of nanocomposites preparation. A good dispersion and intercalation of carbon nanotubes were observed in the prepared nanocomposites. A presence of strong interfacial region was also noted. It is also found that orientation of carbon nanotubes inside matrix can be done by mechanically stretching of nanocomposites. DSC analysis shows that inclusion of carbon nanotubes affects crystallization behavior of nylon 6 significantly and it is found that CNTs acts as nucleating agents.

With an average diameter of 80–200 nm, nylon fibers embedded with ferrite nanoparticles were electrospun using a point to plate geometry. The nickel-ferrite particles with a diameter range of 20–30 nm were used to prepare the composite electrospun nanofibers. The ferrite nanoparticles were dispersed in the polymer solution using a surfactant dodecyl benzene sulfonic acid (DBSA). Ultrasonication was used to dissolve nylon-6 into the formic acid/particle dispersion. Electrospinning of virgin polymer solution and particle filled polymer system was carried out with polymer concentration of 15% w/v. The particle loading was 3%w/w. SEM of the particle filled fibers show some bead formations and a diameter distribution of about 80–200 nm. The DSC analyses of the neat nylon polymer fibers and ferrite filled nanofibers show an increase in glass transition temperature from 55°C to 72°C. The melting temperature showed a decrease from 226°C to 201°C. The TEM images show the presence and some alignment of particles in the polymer. The electron diffraction pattern of ferrite nanoparticles confirms its crystalline nature.

Nanocomposite fibers involve the concept of integrally dispersing nanosized particles of the second phase inorganic material into fiber forming polymers such as nylon or polyester. The material goal involves obtaining bi-phasic fibers with high mechanical stiffness and strength, electrical conductivity and/or enhanced other features such as thermal stability. Thus far, the main difficulties toward achieving nanocomposite fibers are: (1) the inability of obtaining large quantities of nanoparticles in a pure, un-agglomerated state and (2) obtaining a uniform, intimate dispersion of single entity nanoparticles in a fiber polymer matrix. These problems have been approached in the context of studying the properties of experimentally prepared nano-silica reinforced fibers and attempts to prepare carbon nanotube, CNT, containing fiber material. Modulus and tenacity tests on experimentally prepared nanosilica filled PET (polyethyleneterephthalate) fibers showed the silica nanoparticles reduced the modulus and tenacity (tensile strength) of the filled PET fiber materials. DSC and shrinkage studies on nano-silica/PET fiber show that polymer crystallinity is influenced by the presence of the silica nano-particles. Heats of melting are found to increase as the filler loading increases. In further shrinkage studies, the “shrinkage modulus” of these nanosilica/PET fibers was found to increase by the addition of silica nanoparticles. Attempts to prepare nylon reinforced CNTs (multi-wall) from a commercially available CNT/nylon resin “concentrate” failed due to the poor melt dispersion processing of the blended polymer. Only very weak CNT reinforced nylon fibers could be prepared.