Browsing by Author "Li, Yan Vivian, advisor"
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Item Open Access Bacterial culture components activating colorimetric transition in polydiacetylene nanofiber composites(Colorado State University. Libraries, 2020) Bhattacharjee, Abhishek, author; Li, Yan Vivian, advisor; Gentry-Weeks, Claudia, committee member; Diddi, Sonali, committee memberPolydiacetylene (PDA) demonstrates colorimetric transition behaviors due to conformational changes in π conjugated backbone of PDA macromolecules at external stimuli of bacteria, suggesting potential applications in biosensors. However, the bacterial culture components activating colorimetric transition in PDAs are still undetermined due to the complexity of the bacterial system. In this study, PU-PDA nanofiber composite was prepared via electrospinning and tested with components from Escherichia coli (E. coli) culture including supernatant fluid, cell pellet, and extracellular polymeric substances (EPS). When PU-PDA nanofiber was tested with supernatant fluid, it changed color from blue to red. In contrast, bacterial cell pellets could not induce a color change, suggesting the color-changing substances (CCS) are not cell-associated, rather can be found in the spent media (supernatant fluid) generated by E. coli during its growth phase. Intense color change in the nanofiber by the autoclaved supernatant fluid indicated that the CCS may not be a protein, DNA, or RNA since they denature in high heat and pressure from the autoclaving process. With an increase in storage time of the supernatant fluid, the color-changing rate was reduced significantly, suggesting a degradation in CCS with time. Free EPS from the supernatant fluid could induce a color change in the nanofibers, which confirmed that EPS contains the CCS. No significant changes were found in the morphology of PU-PDA nanofibers before and after the exposure of E. coli culture components. Critical bacterial concentration (CBC) was found approximately 9 × 108 CFU/ml, suggesting the efficiency of the PU-PDA nanofiber composite to be used as a biosensor. Additionally, solvatochromism of the nanofiber composite was investigated using organic solvents commonly used in extracting bacterial culture components. The results from this study provided a guideline for using PU-PDA nanofiber composite as a biosensor in point-of-care applications.Item Open Access Colorfastness properties of persimmon dye on cotton and wool substrates(Colorado State University. Libraries, 2014) Malensek, Nicholas, author; Li, Yan Vivian, advisor; Miller, Nancy, advisor; Kissell, Kevin, committee member; Hess, Ann, committee memberPersimmon dye is a natural dye that imparts unique properties, including fungal resistance and water resistance. This study investigated persimmon dye's performance on cotton and wool fabric. Color strength and appearance of dyed cotton and wool fabrics at various dyeing conditions (mordanting order, dye concentration, and dyeing time length) were evaluated. Dyed fabrics had high color strength when using a mordant. Color strength on dyed cotton and wool increased with increased dye concentration and dyeing time. In this study, post-mordanting, 200% dye concentration, and 60 minutes dyeing length yielded the highest color strength for cotton and wool. These samples were then assessed using AATCC laundering, perspiration, and crocking colorfastness tests. Cotton samples received a 2-3 to 4 shade change rating, while wool received a 3 to 4 depending on the test. Cotton and wool samples received a 4 to 5 staining rating except in crocking, where they received a 2-3 and 3, respectively. FTIR analysis showed that the persimmon dye formed weak bonds on both fabrics, resulting in minimal chemical changes. The results suggest that natural persimmon dye can provide good colorfastness and minimal chemical changes on wool and cotton. The comparison between dyed cotton and wool suggests wool fabric is better suited for persimmon dye application than cotton because of its slightly better colorfastness ratings and significantly higher color strength.Item Embargo Development and characterizations of mycelium-based composites(Colorado State University. Libraries, 2024) Davis, Morgan N., author; Li, Yan Vivian, advisor; Morris, Kristen, committee member; Stewart, Jane, committee memberThe current materials economy produces linear materials without regard to their end of life. As the demand for these materials rises, the demand for a new textile economy increases: regenerative by design, minimizing resource input, and waste systems. Mycelium-based composites (MBC) is a lightweight biodegradable material, with good thermal insulation, fire resistance, and acoustic attenuation. The role of MBC lies at a crossroads between biology and design, where designers incorporate biological principles and need to understand the mechanisms of material growth. The study's specific aims include the evaluation of the chemical, mechanical, and physical properties of MBC developed in various conditions and nutrient substrates. Essential to this process is the cultivation of the mycelium, where careful considerations of fungal species, nutrient substrate, and growing parameters are critical. A component of the first critical factor emerges: verification of the fungal DNA. The nutrient substrate hemp fabric demonstrates great compatibility, with the fungal species Pleurotus fossulatus, as it has the largest hyphae diameter, and offers solutions to incorporate waste. In contrast to the strong hydrophilic nature inherent in many natural cellose, mycelium exhibits hydrophobic properties, a critical feature in terms of product implication. The results provide insight for the future design and optimization of mycelium-based composites for product development innovation.Item Open Access Development and thermal characterization of polydiacetylene (PDA) nanofiber composites for smart wound dressing applications(Colorado State University. Libraries, 2016) Alam, A K M Mashud, author; Li, Yan Vivian, advisor; Park, Juyeon, committee member; Gentry-Weeks, Claudia, committee memberConventional methods of identification of microbiological pathogens infection in wound have many challenges such as the need for specialized instruments and trained personnel, and the long detection time. There is a critical need for an innovative method that is simple, accurate, sensitive, reliable, and rapid in pathogen detection practices. Wound dressings containing PDA nanofibers could be used as a diagnostic tool for the detection of onsite bacterial infection. By early wound infection diagnosis, the smart wound dressing would allow physicians to start timely treatment which would reduce hospitalization time and patient suffering. PDAs are of great interest in the development of chromatic sensors due to their unique optical property of undergoing a chromatic transition from blue to red upon external stimuli. 10,12-Pentacosadiynoic acid (PCDA) and poly (ethylene oxide) (PEO) were used in this study to develop fiber composites via an electrospinning method at various mass ratios of PEO to PCDA, solution concentrations, and injection speeds. High mass ratios of PEO to PCDA, low polymer concentrations, and low injection speed promoted fine fibers with smooth surfaces. The colorimetric transition of the fibers was investigated by heating the fibers at temperatures ranging from 25 °C to 120 °C. A color switch from blue to red was observed when the fibers were treated at temperatures higher than 60 °C. The color transition was more sensitive in the fibers made with a low mass ratio of PEO to PCDA due to the high fraction of PDA in the fibers. The large diameter fibers also promoted the color switch due to the high reflectance area in the fibers. All of the fibers were analyzed using Fourier transform infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC) and compared before and after the color change occurred. The colorimetric transitional mechanism is proposed to occur due to conformational changes in the PDA macromolecules.Item Open Access Fluorescent nanosphere transport: groundwater tracing and implications for nanoparticle migration through groundwater systems(Colorado State University. Libraries, 2015) King, Charlene N., author; Sanford, William E., advisor; Li, Yan Vivian, advisor; Ronayne, Michael J., committee member; Sale, Thomas, committee memberEngineered nanoparticles (NPs) are being introduced to water supplies and many NPs have been shown to have deleterious effects on plants and animals; however, their behavior in natural substrates is not well characterized. In an effort to characterize nanoparticle migration through porous media a dual-tracer of fluorescent carbon nanospheres (CNP) and bromide (Br) were deployed through columns of porous media designed to be homogeneous, have dual-porosity, or be reactive. The CNP are hydrophilic, non-toxic, inert, and only 5 to 10 nm in diameter. Unlike other colloid tracers CNP are designed to be inexpensive, easy to identify, and not susceptible to pore throat filtering or settling making them an ideal particle tracer. The results of the homogeneous tests show that CNP and Br had identical breakthrough curves with retardation factors close to 1, confirming that CNP transport conservatively through silica sand. The results of the dual-porosity tests suggested that CNP may undergo slightly less transverse diffusion (mass transfer) into the immobile zone than the solute tracer Br. However the differences were less than expected because molecular diffusion was overwhelmed by the high pore velocities in the experiments. The results of the reactive media tests showed that in columns with surface-modified zeolite (SMZ) the CNP transported conservatively, while Br had a retardation factor 11 to 18 times higher, due to sorption. This means that the CNP can function as the conservative species used in a multiple tracer test to quantify the surface area exposure of other minerals or contaminants with a surface charge along preferential flow paths. During each of these experiments the average mass recovery for CNP was 95% indicating that there was minimal mass loss from pore throat filtering, settling, or sorption. Not only are CNP an extremely useful new tracer for groundwater systems, but they also provide insight as to how other NPs might be transported once introduced into the subsurface. NPs with surfaces that have been functionalized to be hydrophobic or preferentially sorb to a target constituent behave differently. If NPs which sorb to a particular contaminant are introduced to the subsurface it could facilitate transport of that contaminant or facilitate sorption. Similarly the rapid transport properties of hydrophilic NPs should be considered where any toxic NP is being introduced to natural systems.Item Open Access Mechanical and antimicrobial performance analysis of a shark skin bio-mimicked fabric swatch via 3D printing(Colorado State University. Libraries, 2020) Purandare, Saloni Prasanna, author; Li, Yan Vivian, advisor; Yan, Ruoh-Nan, committee member; Prawel, David, committee memberBiomimicry is a long-practiced concept concerned with development of products with nature as the source of inspiration. Bio mimicked textiles is a branch of textiles wherein textile products are developed to replicate desirable elements of nature such as lotus-leaf inspired water repellent fabric, high-strength spider silk inspired by the spider web and shark skin biomimicry. The scaled texture on shark skin, known as riblet effect, exhibits drag reduction and antimicrobial properties. Accurate biomimicry of shark skin is an on-going continual process This study is concerned with 3D printing bio mimicked fabric swatches by replication of riblet effect followed by characterization of the developed fabric swatches. The swatches were printed using Autodesk Ember photopolymer 3D printer, allowing printing of minutely detailed denticles in the base. The materials used were polycarbonate/acrylonitrile butadiene styrene (PC/ABS) and polyurethane (PU) material. PU allowed creation of rigid tough denticles embedded in flexible and soft base, indicating as a better raw material to 3D print bio-mimicked swatches for functional clothing. The PU swatches were studied further in morphological, mechanical, and antimicrobial analysis. The morphological analysis resulted into optical images exhibiting the developed texture resembling characteristic riblet effect of shark skin. Mechanical analysis in terms of tensile stress testing exhibited stronger and tougher fabric samples with thick (1.05mm) base in comparison with those having thin (0.75mm) base. Also, the mechanical analysis indicated good elastomeric properties for the fabric swatches suggesting potential in functional clothing. Lastly, the antimicrobial test conducted exhibited reduced antimicrobial growth for samples with riblet texture against untextured samples, copper foil as well as aluminum foil thus exhibiting potential use of the textured fabric swatches as non-toxic antimicrobial material. Shark skin biomimicry through riblet effect replication has been studied majorly for hydrodynamic properties while shark skin inspired material intended for antimicrobial properties such as by Sharklet® technology is not concerned with riblet effect replication. Thus, to our best knowledge study focusing on mechanical and antimicrobial analysis of shark skin biomimicry through replication of riblet effect is missing. This study will help determine potential of shark skin biomimicry by replication of riblet effect in functional clothing, through mechanical and antimicrobial analysis.Item Open Access Nanofiber based smart wound dressing combined with bacteria detection and drug delivery(Colorado State University. Libraries, 2018) Hassan, Faqrul, author; Li, Yan Vivian, advisor; Park, Juyeon, committee member; Popat, Ketul, committee memberSince the emergence of Nanotechnology in the past decades, the development and design of nanofibers demonstrated the great potential for applications in wound treatment. Proliferation of bacteria in wound site is a major challenge in combating wounds. Bio-sensing wound dressing composed of nanofibers has proven to be an effective tool in detecting bacterial presence at wound sites. Though wound dressing with antibacterial property is available but they are not quite effective in terms of bioavailability and sustained release of drugs. Biodegradable polymeric nanoparticles have been proven to increase bioavailability, encapsulation, and control release of drugs with less toxic properties. In this study, poly diacetylene (PDA)-based composite nanofibers were prepared to study the microstructure and mechanical properties, and to investigate relationship between these two. It was found that mixing polyurethane (PU) polymer with the PDA yielded better mechanical properties as PU and PDA mixed homogeneously and this helped to form large crystalline regions in the fiber microstructure. In the second part of this thesis, poly(D, Lactide-co-glycolide) acid (PLGA) nanoparticles were synthesized by double emulsion solvent evaporation technique to encapsulate hydrophilic gentamicin antibiotics. The effects of different formulation parameters on the particle size and structure were examined thoroughly which included copolymer ratios of PLGA, molecular weight and concentration of stabilizing agents or surfactants, volume of both aqueous and organic phase, sonication and stirring rate and time. The molecular weight and concentration of surfactants had the most impact on the size and morphology of particles. Higher molecular weight of surfactants caused agglomeration of particles. Increasing the concentration of surfactants resulted in smaller particles. PLGA particles with different morphologies were obtained where the average size ranged 300 nm to several microns.Item Open Access Preparation and characterization of poly lactic-co-glycolic nanoparticles encapsulated with gentamicin for drug delivery applications(Colorado State University. Libraries, 2019) Sun, Yu, author; Li, Yan Vivian, advisor; Bailey, Travis, committee member; Wang, Zhijie, committee memberWound treatment has always been a popular topic around the world. Since the emergence of nanotechnology, the development and design of novel wound dressing materials have been dramatically improved. The ues of nanoparticles encapsulated with antibiotics to deliver drugs has been shown to be a potentially effective approach to control bacterial infections at a wound position. Recently, biodegradable and biocompatible polymers have drawn lots of attention for the manufacture of drug-loaded nanoparticles in the pharmaceutical industry. In this work, poly-lactic-co-glycolic acid (PLGA) was used in nanoparticle synthesis due to its biodegradability, biocompatibility, and nontoxicity. For this work, gentamicin was loaded into the PLGA nanoparticles as an antibiotic because it is a broad-spectrum antibiotic effective in wound treatments. PLGA nanoparticles were prepared while gentamicin was loaded in the nanoparticles via a double emulsion evaporation method. Poly vinyl alcohol (PVA) was a surfactant that was an important factor in determining the most probable nanoparticle size and morphology. When the PVA concentrations were 9% and 12%, the nanoparticles demonstrated a spherical structure with a porous surface. The porous surface of a nanoparticle was promising for the purpose of releasing encapsulated antibiotics. Another important factor in determining the formation of nanoparticles was the PLGA concentration. Poly lactic-co-glycolic acid (PLGA) was the main material affecting PLGA nanoparticles' properties. PLGA nanoparticles would have various release profiles, morphology, and size distribution with different PLGA concentrations. The results suggested that different PLGA concentrations can endow PLGA nanoparticles with various properties which can lead to different applications of PLGA nanoparticles.Item Open Access Study of mechanical and antimicrobial properties of biomimetic shark skin fabrics with different denticle size via 3D printing technology(Colorado State University. Libraries, 2022) Wen, Jiayi, author; Li, Yan Vivian, advisor; Chisholm, Sandra, committee member; Prawel, David, committee memberPrevious studies have shown that biomimetic shark skin fabrics can reduce water drag and increase swimming speed. It was also known that the smaller the denticle was, the higher water drag reduction was. In nature, the size of the denticles on shark skin is between 100 μm and 500 μm. However, the minimum size of the 3D printed denticles on a biomimetic shark skin fabric previously reported was about 2mm, which was still much larger than the natural size. In this study, different sizes of denticles ranging from 0.65mm to 1.30mm were fabricated using a Form3 3D printer and Flexible80A resin, and the effect of denticle size on mechanical properties and antimicrobial properties of biomimetic shark skin fabric were evaluated for the applications in functional clothing. The results suggested that when the size of the denticle was decreased, the stiffness of the fabrics was increased. In the tensile testing, the tensile strength and the breaking elongation of the 3D printed fabric with 1.04mm denticles were largest in the tested fabrics, which was larger than those of some common fabric materials used in commercial swimwear, suggesting great potential of functional clothing applications. In addition, mechanical anisotropy was observed in the 3D printed fabrics, which is commonly seen in textile fabrics. In antimicrobial testing, the shark skin fabrics with 0.65mm and 1.04mm denticles were found to be less susceptible to bacterial attachment, suggesting good potential for functional clothing applications.