Engineering Commons^™

Designing Bioinspired Materials With Tunable Structures And Properties From Natural And Synthetic Polymers, Anandavalli Varadarajan

Theses and Dissertations

Biological systems are composed of complex materials which are responsible for performing various functions, such as providing structural support, mobility, functional adaptation to the environment, damage repair, and self-healing. These complex materials display excellent mechanical properties and can rapidly adapt to external stimuli. Thus, nature inspires in terms of source materials, functions, and designs to develop new-generation structural and functional materials. Polymers (natural or synthetic) are excellent sources of developing materials to mimic the functions of soft segments in biological systems. This dissertation focuses on synthesizing and characterizing two different materials with tunable structures and properties: complexes from natural polysaccharides …

Superhydrophobic And Oleophobic Surfaces. Synthesis And Applications, Zirui Liu

Electronic Theses and Dissertations

Surface patterning is an overwhelming approach to mechanically modifying metal surfaces and improving their tribological properties, such as repellency, lower friction, and more excellent corrosion resistance. Patterned surfaces can be applied to various industrial uses, such as cutting tools, submarines, and self-cleaning surfaces. In this paper, the novel nature-inspired flat-top-pillar "double-undercut" designs were proposed to achieve an apparent angle that satisfies super-hydrophobicity and endure higher pressure on which external forces are exerted. The main objective is to enlarge the change in Gibbs free energy for the system to exhibit a heterogeneous wetting to a homogeneous one by excavation on the …

Mimicking The Namib Desert Beetle With Hydrophilic And Hydrophobic Surfaces, Tyler Bracewell

Williams Honors College, Honors Research Projects

The Namib Desert beetle, Stenocara gracilipes, condenses fog that rolls in off the west coast of Namibia to provide itself with the water it needs for the day. By lifting its abdomen into the air to collect the water vapor, it condenses on hydrophilic bumps that are about 500μm in diameter and are spaced apart about 500-1500μm. Once the water reaches a critical size, the droplet rolls off the hydrophilic bump and onto the flat hydrophobic surface of the elytra. Since the beetle is angled with its abdomen in the air, the water rolls down to its mouth. A …

Wetting Transition On 3d-Printed Surfaces, Isabelle Moryan

Williams Honors College, Honors Research Projects

Taking the previous research conducted, this project aims to further the study and research of the wettability of surfaces. Surface features and types are important factors to their wettability. The geometric properties of a surface can make it more hydrophobic and hydrophilic. Extreme cases of hydrophobic and hydrophilic surfaces lead to water repulsion or water absorption, even under extreme conditions. The goal of this project is to gain further insight on how fabricated 3D-printed featured surfaces and examine the wetting transition on these surfaces. In particular, cylindrical pillars will be studied with varied pillar spacing, height and diameter. In addition, …

Hydrophobically Modified Isosorbide Dimethacrylates As Biomaterials For Bisphenol A Free Dental Fillings, Bilal Marie

Dissertations

Amalgam and Bisphenol A glycerolate dimethacrylate (BisGMA) are the main dental filling materials in use today. Because of the negative perception of amalgam and its lower esthetic appeal, as well as the desire to replace the endocrine disruptor Bisphenol A, which is the building block of BisGMA, there has been a critical need to search for safer alternatives to these dental filling materials.

Isosorbide is a sugar-based molecule generally recognized as safe. It has been extensively studied as a replacement to the Bisphenol A core in various materials. However, isosorbide is extremely hygroscopic, and water uptake in dental fillings causes …

Wetting Metamorphosis Of Hydrophobic Fluoropolymer Coatings Submerged In Water And Ultrasonically Vibrated, Matthew Trapuzzano, Nathan B. Crane, Rasim Guldiken, Andrés Tejada-Martínez

Faculty Publications

Many important processes, from manufacture of integrated circuit boards, to an insect’s ability to walk on water, depend on the wetting of liquids on surfaces. Wetting is commonly controlled through material selection, coatings, and/or surface texture. However, wetting is sensitive to environmental conditions. In particular, some hydrophobic fluoropolymer coatings are sensitive to extended water exposure as evidenced by a declining contact angle and increasing contact angle hysteresis. Understanding “degradation” of these coatings is critical to applications that employ them. The durability of a series of fluoropolymer coatings were tested by measuring the contact angle before, during, and after extended submersion …

A Model For Condensation Heat Transfer In Hydrophobic-­Hydrophilic Surfaces, Abdulwahab E. Alhashem

Theses and Dissertations

The primary focus of this research is to provide a validated model for a comprehensive understanding of hydrophobic-­‐hydrophilic condensation on patterned-­‐ hybrid surface. Establishing the model requires the modeling of fully dropwise condensation (DWC) before applying modifications to evaluate heat transfer performance of patterned-­‐hybrid condensation surface.

The model for fully DWC consists of defining expressions for heat transfer through a single drop, maximum radius of the drop and drop-­‐size distribution which all are primarily based on the work in the literature. In this work the author utilized a proposed modified version of the simulation for drop-­‐size distribution for fully DWC, …

Droplet Impact Onto Super-Hydrophobic Surfaces And Determining The Response To Heat And Light Of Terrestrial Cyanobacteria, Benjamin B. Lovett

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

This thesis examines droplets striking water repelling surfaces as well as the movement of a soil based bacteria under various light and heat conditions. Droplet impact studies have shown that introducing a macroscopic feature to a water repelling surface can reduce the amount of time that droplet is in contact with the surface. By manipulating water droplets to impact different sized needles at varying speeds, we present how a needle can induce a similar reduction in the residence time of the droplet to more widely studied features. Results show the spreading and lift-off characteristics of the droplet are dependent on …

Development Of Low Cost, Environmentally Friendly And High Strength Carbon Foams From Bread And Cake, Laura Mountain-Tuller

Materials Engineering

Carbon foam is a high niche material that consists of a highly porous, three-dimensional cellular network that is characterized by extremely high strength-to-weight ratios and low thermal conductivity. Due to these properties, carbon foams excel in structural and thermal applications, especially in the aerospace industry. Typically, carbon foams are formed through a heating process called pyrolysis of polymer precursors with high carbon content. This process is done at high temperatures in an oxygen free environment. These precursors are expensive to make and use toxic chemicals to produce, therefore, there is a push to find an environmentally friendly and cost-effective method …

Optimization Of Superhydrophobic Surface Production Using Ambient-Dried Silica-Based Aerogels, Elizabeth Donlon

Honors Theses

Superhydrophobic surfaces exhibit particular properties that make them functional in various anti-sticking, anti-contamination, self-cleaning and drag reduction applications. Though such surfaces are found in nature - most notably the lotus leaf - they are difficult to produce. There are numerous methods and techniques for fabricating superhydrophobic surfaces. One such method is the sol-gel method, in which aerogel, a highly porous and lightweight material that can be made hydrophobic or superhydrophobic, is coated onto a surface. The purpose of this project is to devise a simple and repeatable procedure for making hydrophobic silica aerogel coatings that can be used for drag …

Micropillar Arrays Fabricated By Light Induced Self-Writing: An Opportunity For Rapid, Scalable Formation Of Hydrophobic Surfaces, Hansheng Li

Theses - ALL

Superhydrophobic surfaces naturally exist in plants and animals, which have inspired the development of artificial hydrophobic surfaces. The hydrophobic surfaces have drawn attention in multiple areas in recent years. Multiple approaches were carried out and achieved different levels of hydrophobicity. In this thesis, a series of hydrophobic surface structures have been prepared with a photo-inducted self-writing method and then coated with fluorocarbon compounds. Various fiber heights and different coating methods have been tested for differences and influences in hydrophobicity. Section views using optical microscope showed uniform cone structures fabricated with photo-curing; contact angle measurements that exhibited static contact angles greater …

Investigation Of Nanomaterial Based Photovoltaic Panel Packaging Materials, Xingeng Yang

Graduate Theses and Dissertations

In this research, nanomaterial-based packaging materials for photovoltaic (PV) panels are investigated. A hydrophobic/anti-reflective surface coating which not only repels water from the top glass of a PV panel but at the same time reduces its light reflectance is investigated. COMSOL simulation results indicate that taller ellipsoid rod (aspect ratio = 5) reflects less light than shorter rod (aspect ratio = 0.5) in the desired spectrum for solar energy harvest from 400nm-700nm. The addition of a polymer layer on these ellipsoid rods broadens the light incident angle from 23° to 34°, from which light can be efficiently absorbed. Based on …

Silane Modulation Of Protein Conformation And Self-Assembly, Abul Bashar Mohammad Giasuddin

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

This research focused on development of nanoparticle- based therapeutics against amyloid fibrils. Amyloid fibrils are associated with various diseases such as Parkinson’s, Huntington’s, mad cow disease, Alzheimer’s, and cataracts. Amyloid fibrils develop when proteins change their shape from a native form to a pathogenic “misfolded” form. The misfolded proteins have the ability to recruit more native proteins into the pathogenic forms, which self-assemble into amyloid fibrils that are hallmarks of the various protein-misfolding diseases listed above. Amyloid fibrils are highly resistant to degradation, which may contribute to the symptoms of amyloid diseases. Synthetic drugs, natural compounds, and antibodies are widely …

Mitigation Of Corrosion Under Insulation (Cui) Of Carbon Steel Of Different Insulating Materials: A Literature Review And Testing Analysis, Michael Alexander Lowes

Materials Engineering

Equipment often found in refineries may be enveloped in insulation and weathering jackets to maintain internal processing temperatures. In many cases moisture from the environment will penetrate the weathering jacket and infiltrate the insulation, leaching corrosive ions to the surface of metal equipment, effectively creating a corrosion cell. The goal of this project is to investigate different insulating materials for their ability to inhibit corrosion under insulation (CUI). The inhibiting mechanism utilizes water ingress that leaches ions from the insulator to bond with the surface metal and create a passive layer, inhibiting any further corrosion. This study will follow ASTM …

Corrosion Characteristics Of Magnesium Under Varying Surface Roughness Conditions, Yahya Efe Yayoglu

USF Tampa Graduate Theses and Dissertations

The biggest challenge with magnesium alloy biodegradable implants is the rapid corrosion at the earlier stages of the healing process after implantation. In this research, the impact of surface roughness generated by different means on the corrosion rate of AZ31 magnesium alloy in a simulated biologic environment is investigated. In order to perform accurate experimentation, an in vitro setup is assembled that simulates the human body environment accurately has been prepared using Schinhammer’s in vitro immersion testing setup and Kokubo’s Simulated Body Fluid (SBF). For the immersion test of Mg in SBF, several surface texture groups of Mg have been …

Water Condensation And Protein Adsorption On Hybrid Superhydrophobic-Hydrophilic Surfaces, Bikash Mondal

Dissertations, Theses, and Capstone Projects

This thesis describes the study of protein adsorption and water condensation on hybrid superhydrophobic-hydrophilic surfaces for various technological applications such as diagnostics, artificial organs and medical devices, water collection, and heat transfer.

In the chapter 1, a general introduction to wetting theories, superhydrophobic surface, and hybrid surfaces is given. In chapter 2, design and fabrication of a hybrid superhydrophobic surface for studying dropwise condensation and heat transfer is discussed. Effect of surface chemistry and wettability on protein adsorption is discussed in the chapter 3. Finally, in chapter 4, the protein adsorption study on hybrid superhydrophobic surfaces made by 3D-printing and …

Microstructure Alone Induced Wetting Transition From Hydrophilic To Hydrophobic On Silicon And Graphene, Henry L. Ems

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

In the present work, transition from hydrophilic to hydrophobic wetting states for an intrinsically hydrophilic surface (contact angle less than 45 degrees) using only surface microstructuring is presented. The surface microstructures are re-entrant microcavities (inverted trapezoidal microstructures) which promote air entrapment below the water droplet causing a Cassie wetting state as opposed to a Wenzel state where the surface is completely wetted. The microstructures were fabricated on a Silicon-On-Insulator (SOI) wafer through steps of deposition, photolithography, etching, and bonding. Contact angle measurements demonstrated the ability of the microfabricated surfaces to sustain large contact angles above 100°, in comparison to a …

Investigation Of Boat Hull Performance With Superhydrophobic Coating, Nolan Sayre

Honors Theses

Aerogels are a nano-porous material that have the ability to be made chemically superhydrophobic. A durable boat hull coating of superhydrophobic aerogels could form the boundary conditions necessary to reduce drag in water and in turn improve overall boat performance. This project investigated whether a superhydrophobic aerogel coating could effectively reduce skin friction drag on a boat. Various techniques for superhydrophobic surface fabrication were researched and tested with the goal of maximizing the surface water contact angle. It was concluded that Nafion solution is not an effective material to adhere aerogels to a surface. Hydrophobic and non-hydrophobic aerogels were adhered …

The Effectiveness Of Silane And Siloxane Treatments On The Superhydrophobicity And Icephobicity Of Concrete Surfaces, Sunil M. Rao

Theses and Dissertations

Icy roads lead to treacherous driving conditions in regions of the U.S., leading to over 450 fatalities per year. De-icing chemicals, such as road salt, leave much to be desired. In this report, commercially available silane, siloxane, and related materials were evaluated as solutions, simple emulsions, and complex emulsions with incorporated particulates, for their effectiveness as superhydrophobic treatments. Through the development and use of a basic impact test, the ease of ice removal (icephobicity) was examined as an application of the targeted superhydrophobicity.

A general correlation was found between icephobicity and hydrophobicity, with the amount of ice removed on impact …

Nf/Ro Filtration Of The Hydrophobic Ionogenic Com#163 Triclosan: Transport Mechanisms And The Influence Of Membrane Fouling, Long Nghiem, Poppy Coleman

Long D Nghiem

Filtration phenomena of the hydrophobic ionogenic compound triclosan by three commercially availablenanofiltration (NF)/reverse osmosis (RO) membranes were investigated in this study. The separationbehaviour of triclosan was systematically related to the compound physicochemical properties and themembranes as well as the solution pH. The influence of membrane fouling on the rejection of triclosanby the three selected NF/RO membranes were also examined using three model organic foulants and onemodel colloidal foulants. Having a unique hydrophobic ionogenic profile, even when triclosan was fullydeprotonated at pH 10, considerable adsorption of the compound to the membrane could still be observed.The adsorption of triclosan to the membrane …

Comparison Of The Removal Of Hydrophobic Trace Organic Contaminants By Forward Osmosis And Reverse Osmosis, Ming Xie, Long D. Nghiem, William E. Price, Menachem Elimelech

Long D Nghiem

We compared the rejection behaviours of three hydrophobic trace organic contaminants, bisphenol A, triclosan and diclofenac, in forward osmosis (FO) and reverse osmosis (RO). Using erythritol, xylose and glucose as inert reference organic solutes and the membrane pore transport model, the mean effective pore size of a commercial cellulose-based FO membrane was estimated to be 0.74 nm. When NaCl was used as the draw solute, at the same water permeate flux of 5.4 L/m2 h (or 1.5 mm/s), the adsorption of all three compounds to the membrane in the FO mode was consistently lower than that in the RO mode. …

Comparison Of The Removal Of Hydrophobic Trace Organic Contaminants By Forward Osmosis And Reverse Osmosis, Ming Xie, Long D. Nghiem, William E. Price, Menachem Elimelech

William E. Price

We compared the rejection behaviours of three hydrophobic trace organic contaminants, bisphenol A, triclosan and diclofenac, in forward osmosis (FO) and reverse osmosis (RO). Using erythritol, xylose and glucose as inert reference organic solutes and the membrane pore transport model, the mean effective pore size of a commercial cellulose-based FO membrane was estimated to be 0.74 nm. When NaCl was used as the draw solute, at the same water permeate flux of 5.4 L/m2 h (or 1.5 mm/s), the adsorption of all three compounds to the membrane in the FO mode was consistently lower than that in the RO mode. …

Comparison Of The Removal Of Hydrophobic Trace Organic Contaminants By Forward Osmosis And Reverse Osmosis, Ming Xie, Long D. Nghiem, William E. Price, Menachem Elimelech

Faculty of Engineering - Papers (Archive)

We compared the rejection behaviours of three hydrophobic trace organic contaminants, bisphenol A, triclosan and diclofenac, in forward osmosis (FO) and reverse osmosis (RO). Using erythritol, xylose and glucose as inert reference organic solutes and the membrane pore transport model, the mean effective pore size of a commercial cellulose-based FO membrane was estimated to be 0.74 nm. When NaCl was used as the draw solute, at the same water permeate flux of 5.4 L/m2 h (or 1.5 mm/s), the adsorption of all three compounds to the membrane in the FO mode was consistently lower than that in the RO mode. …

Time Dependence Of Self-Assembly Process For The Formation Of Inorganic-Organic Hybrid Nanolayers, Alexandre Dhôtel

Department of Engineering Mechanics: Dissertations, Theses, and Student Research

There is increasing interest in self-assembled materials for energy storage, flexible electronics and hydrophobic barriers. Inorganic/organic hybrid thin films and especially organosilane-based coatings already have demonstrated their ability to achieve those goals. However, some fundamental points of their formation process by molecular self-assembly remain unexplained. Although the literature widely reports the effect of temperature on the final nanostructure, until now, no one has taken into account the importance of time during their synthesis.

The main objective of this study was to improve and complete the understanding of mechanisms responsible for the self-organization of organic/inorganic molecules into a highly ordered, layered …

Laminar And Turbulent Flow Of A Liquid Through Channels With Superhydrophobic Walls Exhibiting Alternating Ribs And Cavities, Brady L. Woolford

Theses and Dissertations

There is significant interest in reducing the frictional resistance that occurs along a surface in contact with a liquid. A novel approach to reducing the frictional resistance across a liquid-solid interface is the use of superhydrophobic surfaces. superhydrophobic surfaces are created in this work by the use of micro-fabrication techniques where systematic roughness is fabricated on a substrate surface which is subsequently treated with a hydrophobic coating. This work reports an experimental study of superhydrophobic surfaces used to reduce drag in both laminar and turbulent channel flows. In the laminar flow regime reductions in frictional resistance greater than 55% were …

Surface Modification Of Bricks By Chitosan Coatings, S Nilpairach, S T. Dubas

Journal of Metals, Materials and Minerals

Bricks were successfully modified by application of a chitosan coating in order to provide their surface with a water repellant character. The chitosan coating was prepared by depositing solutions of variable chitosan concentration (1% or 2.5% w/w) onto the brick surface and let to dry under ambient condition. In order to improve the water repellant property, the films were cross-linked with a 1% solution of sodium citrate, sodium sulfate or sodium tri - polyphosphate. The effect of the chitosan concentration on the morphology of the coating at the brick surface was observed by scanning electron microscope (SEM). It was found …

Cationic Surfactant Mediated Hybridization And Hydrophobization Of Dna Molecules At The Liquid/Liquid Interface And Their Phase Transfer, Murali Sastry, Ashavani Kumar, Mrunalini Pattarkine, Vidya Ramakrishnan, Krishna N. Ganesh

Faculty Works

Hybridization of complementary oligonucleotides mediated by a cationic surfactant at the water/hexane interface leads to hydrophobic, double-helical DNA which may be readily phase transferred to the organic phase and cast into thin films on solid substrates.