Behnam Pourdeyhimi

Fundamentals and applications of micro- and nanofibers

1. Introduction 2. Polymer physics and rheology 3. General quasi-one-dimensional equations of dynamics of free liquid jets. Capillary and bending instability 4. Melt and solution blowing 5. Electrospinning of micro and nanofibers 6. Additional methods and materials used to form micro and nanofibers 7. Tensile properties of micro and nanofibers 8. Post-processing 9. Applications of micro and nanofibers 10. Military applications of micro and nanofibers 11. Applications of micro and nanofibers and micro and nanoparticles: healthcare, nutrition, drug delivery and personal care.

Solution Blowing of Soy Protein Fibers

Solution blowing of soy protein (sp)/polymer blends was used to form monolithic nanofibers. The monolithic fibers were blown from blends of soy protein and nylon-6 in formic acid. The sp/nylon-6 ratio achieved in dry monolithic nanofibers formed using solution blowing of the blend was equal to 40/60. In addition, solution blowing of core-shell nanofibers was realized with soy protein being in the core and the supporting polymer in the shell. The shells were formed from nylon-6. The sp/nylon-6 ratio achieved in dry core-shell fibers was 32/68. The nanofibers developed in the present work contain significant amounts of soy protein and hold great potential in various applications of nonwovens.

Texture Evaluation of Carpets Using Image Analysis

This paper explores in detail new image enhancement techniques for assessing tuft geometry and concomitant appearance changes in new and worn carpets. Using im proved algorithms and more advanced tuft geometry, saxony tufted carpets of nylon and polyester BCF yams are capable of being extensively and reliably characterized as to texture and changes in appearance with laboratory or floor wear. While still using a relatively low resolution grey level imaging system, the newly developed al gorithms demonstrate how tuft size distribution, number of tufts, evenness of tuft spatial distribution, and aspect ratio (shape factor) of tufts can be objectively measured. Statistical analysis confirms that customary wear levels, and their visual appearance change in carpet, can be separated and correctly grouped by these new techniques. Some limitations of these and other texture-sensitive image analysis techniques are also discussed.

Fiber Cross-Sectional Shape Analysis Using Image Processing Techniques:

. Quantitative characterization of fiber cross sections has attracted considerable in terlst, since cross-sectional size and shape have an important impact on the physical and mechanical properties of fibers, as well as the performance of end-use products. We present one application of automated measurement using image processing tech niques that extract basic shape features from fiber cross sections. Cross-sectional shapes are characterized with the aid of geometric and Fourier descriptors. Geometric de scriptors measure attributes such as area, roundness, and ellipticity. Fourier descriptors are derived from the Fourier series for the cumulative angular function of the cross- sectional boundary and are used to characterize shape complexity and other geometric attributes. Shape reconstruction based on Fourier coefficients is also discussed. We present the results of shape analysis for a wide variety of fiber types.

Assessing Changes in Texture Periodicity Due to Appearance Loss in Carpets: Gray Level Co-occurrence Analysis

Texture may be defined with respect to the global properties of an image or to the repeating units that compose it. We have attempted to isolate the periodic components of texture in wool carpets for the purpose of assessing the effects of wear on carpet textures. Texture is defined as any recurring spatial pattern of sampled gray level intensities. We restrict attention to textural features that reflect the physical charac teristics of the carpet tuft assemblies. Our test materials consist of four kinds of double ply wool carpets of differing textures divided into control, light, and heavy wear samples. Video images were recorded under several magnifications using a Truevision Vista board. Image files with 256 gray levels were converted to 32 levels using histogram equalization. Textural features were evaluated by computing gray level differences and second-order gray level statistics. We discuss results for spatial gray level depen dence (SGLDM) and gray level difference (GLDM) methods for a range of intersam pling distances. Results for our carpet series show that SGLDM and GLDM yield very similar trends, statistical trends within each method are correlated, overall, these mea sures are generally effective for differentiating the degree of wear as well as providing an indication of textural periodicity, and changes in frequency may be examined by subjecting SGLDM and GLDM statistics to spectral analysis.

In Situ Collagen Polymerization of Layered Cell-Seeded Electrospun Scaffolds for Bone Tissue Engineering Applications

Electrospun scaffolds have been studied extensively for their potential use in bone tissue engineering applications. However, inherent issues with the electrospinning approach limit the thickness of these scaffolds and constrain their use for repair of critical-sized bone defects. One method to increase overall scaffold thickness is to bond multiple electrospun scaffolds together with a biocompatible gel. The objective of this study was to determine whether multiple human adipose-derived stem cell (hASC-seeded electrospun, nanofibrous scaffolds could be layered via in situ collagen assembly and whether the addition of laser-ablated micron-sized pores within the electrospun scaffold layers was beneficial to the bonding process. Pores were created by a laser ablation technique. We hypothesized that the addition of micron-sized pores within the electrospun scaffolds would encourage collagen integration between scaffold layers, and promote osteogenic differentiation of hASCs seeded within the layered electrospun scaffolds. To evaluate the benefit of assembled scaffolds with and without engineered pores, hASCs were seeded on individual electrospun scaffolds, hASC-seeded scaffolds were bonded with type I collagen, and the assembled ∼3-mm-thick constructs were cultured for 3 weeks to examine their potential as bone tissue engineering scaffolds. Assembled electrospun scaffolds/collagen gel constructs using electrospun scaffolds with pores resulted in enhanced hASC viability, proliferation, and mineralization of the scaffolds after 3 weeks in vitro compared to constructs using electrospun scaffolds without pores. Scanning electron microscopy and histological examination revealed that the assembled constructs that included laser-ablated electrospun scaffolds were able to maintain a contracted structure and were not delaminated, unlike assembled constructs containing nonablated electrospun scaffolds. This is the first study to show that the introduction of engineered pores in electrospun scaffolds assists with multilayered scaffold integration, resulting in thick constructs potentially suitable for use as scaffolds for bone tissue engineering or repair of critical bone defects.

Flexible, durable printed electrical circuits

This study investigates the screen printing of transmission lines into a variety of nonwoven substrates using different conductive inks for durable and wearable electronic textile applications. The viscosity of the ink dictated the performance of the printed media during washing trials. The printed inks begin to degrade and display lower conductivity after 25 wash cycles. A method to control the durability of the printed circuits, which includes coating of the printed lines with a meltblown layer, has been developed.

ASSESSING WRINKLING USING IMAGE ANALYSIS AND REPLICATE STANDARDS

This paper describes the application of digital image processing to the grading of fabric wrinkle recovery. Degrees of fabric wrinkling of AATCC replicate standards are analyzed using a combination of texture and profile analysis techniques. Results in dicate that wrinkling can be reliably measured using gray level and surface statistics, co-occurrence analysis, and power spectral density of image profiles.

A comparison of mechanical properties of discontinuous Kevlar 29 fibre reinforced bone and dental cements

A comparative study of the fracture behaviour of Kevlar 29 reinforced bone and dental cements is undertaken using both linear elastic and non-linear elastic fracture mechanics approaches. Results from both approaches reflect improved fracture toughness at very low fibre contents. Flexural modulus is not apparently improved in either system, and flexural strength is only improved in the bone cement system probably because of poor interfacial bonding and the presence of voids in the dental cement. In all cases, however, bone cement is seen to be superior to dental cement. This is interpreted in terms of smaller voids and better fibre distribution due to the lower viscosity of the bone cement material. When compared to carbon-polymethyl methacrylate (PMMA) cements, Kevlar 29 reinforced systems appear to be superior. More work is underway to optimize the properties of these systems with regard to structural parameters.

Nonwoven Fabric Active Electrodes for Biopotential Measurement During Normal Daily Activity

Body movement is responsible for most of the interference during physiological data acquisition during normal daily activities. In this paper, we introduce nonwoven fabric active electrodes that provide the comfort required for clothing while robustly recording physiological data in the presence of body movement. The nonwoven fabric active electrodes were designed and fabricated using both hand- and screen-printing thick-film techniques. Nonstretchable nonwoven (Evolon 100) was chosen as the flexible fabric substrate and a silver filled polymer ink (Creative Materials CMI 112-15) was used to form a transducer layer and conductive lines on the nonwoven fabrics. These nonwoven fabric active electrodes can be easily integrated into clothing for wearable health monitoring applications. Test results indicate that nonwoven textile-based sensors show considerable promise for physiological data acquisition in wearable healthcare monitoring applications.