Surface structuring and functionalization of aluminium alloys using multimodal laser processing

This thesis explores advanced multimodal laser processing techniques to fabricate nano- and micro-scale structures on aluminum alloys, targeting the marine, aerospace, and automotive industries. Aluminum alloys are known for their physical and mechanical properties but are prone to degradation from fouling, corrosion, and wear. Conventional methods for mitigating these issues are insufficient, leading to the investigation of laser-based texturing as a more robust, environmentally friendly, and scalable alternative. Chapter 2 reviews aluminum alloys as marine materials, the mechanisms of surface fouling, and traditional mitigation methods, alongside the principles of laser-based nano- and micro-fabrication techniques. Femtosecond and continuous wave (CW) fiber lasers were used to induce surface modifications that enhance antifouling, corrosion resistance, and wear performance. Chapter 3 examines ultrafast laser texturing to increase hydrophobicity in aluminum alloy 7075. By optimizing parameters such as laser power and scan speed, the water contact angle was increased from 85° to 142°, showing a highly hydrophobic surface. Environmental aging further contributed to these improvements. In Chapter 4, five laser patterns were tested for biofouling and corrosion resistance. The star pattern texture reduced biofilm coverage by 79% and improved corrosion resistance by 25%. Further, three optimized patterns were subjected to CW laser heat treatment, resulting in a 17.8% increase in microhardness and an 83% reduction in the friction coefficient. Amount of wear was reduced by 80% in the most hardened sample. Regression models were developed to fine-tune these characteristics, enhancing tribological performance. This research highlights the potential of multimodal laser processing for creating robust and ecofriendly surface modifications on aluminum alloys, significantly improving their functional properties

AN INVESTIGATION OF EXPERIMENTAL PARAMETERS REQUIRED TO STUDY HYDROCARBON PHASE BEHAVIOR UNDER CONSTANT VOLUME AND CONSTANT COMPOSITION CONDITIONS

Accurate fluid phase behavior evaluation is essential for reservoir engineers to predict the type of reservoir, oil and gas in place, and develop proper production strategies. The change in phase behavior and phase equilibrium are key to understand the reservoir condition and estimate production from a particular formation. In shale reservoirs, hydrocarbon phase behavior in nanopores can be affected by various factors such as pore proximity and pore size distribution. In many shale and tight oil and gas reservoirs, pore sizes are in the ranges of nanometers. Various simulation models are seen in literature attempting to predict phase behavior under confinement but there is no good reference of experimental results for verification. Our research team is trying to conduct phase behavior tests for single, binary, and multi-component hydrocarbon mixtures under confinement to validate and test the various simulation models. Since that’s not an easy endeavor, each of us in the research team has taken on one of the challenging tasks to accomplish the goal. My particular goal is to examine the feasibility of a new experimental procedure for detecting the edge of the phase envelope. The new experimental approach for detecting the phase envelope was examined through numerical simulation of binary hydrocarbon mixtures in bulk since these bulk simulation numbers have been verified experimentally in the past. The binary hydrocarbon mixtures we examined were Ethane with Propane, Pentane, Heptane and Hexane with 50-50 mole percentage. As per the experimental feasibility in the laboratory and lower temperature and pressure ranges available, various compositions of Ethane-Pentane system were studied in order to design the experimental parameters. The results of this study will be used by the rest of the members in the research team to conduct the experiments as it provided them with the most suitable system to explore in the laboratory

Topical Clear Aqueous Nanomicellar Formulation for Anterior and Posterior Ocular Drug Delivery

VitaTitle from PDF of title page, viewed on August 31, 2016Dissertation advisor: Ashim K. MitraVitaIncludes bibliographical references (pages 329-352)Thesis (Ph.D.)--School of Pharmacy and Department of Chemistry. University of Missouri--Kansas City, 2015The objective of this study was to develop a clear, aqueous drug loaded nanomicellar formulation (NMF) for the back-of-the-eye delivery. Hydrophobic drugs such as cyclosporine, resolvin analog (RX-10045), dexamethasone, rapamycin were entrapped in the core of polymeric micelles and solubilized. Polymeric amphiphilic molecules (e.g., hydrogenated castor oil – 40 (HCO-40) and Vit. E TPGS) are known to generate nanomicellar constructs with hydrophobic core and hydrophilic corona. However, constructs prepared from a single polymer are unstable and easily fall apart at high temperature. Inclusion of a second polymer such as Oc-40 improves stability and prevents nanomicellar destabilization. Such stable nanomicellar constructs can encapsulate hydrophobic drugs in their lipophilic core while the hydrophilic corona helps solubility in aqueous solution. We screened resolvin for efflux pumps and prepared resolvin analog nanomicelles. Studies showed that NMFs were tolerable and delivered high drug concentrations to back-of-the-eye tissues with topical eye drop application to rabbits. Negligible drug levels were quantified in systemic circulation. These nanomicellar constructs efficiently utilize their hydrophilic corona and evade the wash-out into the systemic circulation from both the conjunctival and choroidal blood vessels and lymphatics, thus overcoming the dynamic barrier. Moreover, this pathway might overcome the major drawback associated with steroid therapy (glaucoma and cataract), since a trans-scleral route of absorption is accessed. In summary, for the first time we identified that resolvin analog was substrate/inhibitor for BCRP and MRP but not P-gp. Moreover, resolvin analog was identified as a strong inhibitor of influx transporter (OCT-1). Clear, aqueous NMF encapsulating hydrophobic drugs were successfully developed. Ocular bioavailability and pharmacokinetic studies demonstrated a very high drug levels in retina-choroid (place of drug action) with a negligible drug partitioning into lens and vitreous humor. These results suggest that drug and/or NMFs cannot reach back-of-the-eye tissues following corneal pathway. Alternatively, ~12 nm - 20 nm nanomicelles efficiently permeate through 20 nm to 80 nm scleral pores and reach back-of-the-eye tissues (retina-choroid) following conjunctival-scleral pathway. In the lipoidal posterior ocular tissues, these nano-constructs may release the cargo into Bruch’s membrane/retina-choroid generating high drug levels.Introduction -- Literature review -- Topical aqueous clear cyclosporine nanomicellar formulation: optimization, in vivo ocular toxicity evaluation and pharmacokinetic study -- Topical aqueous clear resolvin E1 analog (RX-10045) nanomicellar formulation -- Part A: interaction studies of resolvin E1 analog with efflux transporters -- Part B. formulation optimization and in vivo evaluation -- Topical aqueous clear dexamethasone nanomicellar formulation: optimization and in vivo tissue distribution -- Topical aqueous clear rapamycin (sirolimus) nanomicellar formulation: develop,emt and in vivo issue distribution -- Summary and recommendations -- Appendi

Topology and FEA modeling and optimization of a patient-specific zygoma implant

Additive manufacturing has proven to be a very beneficial production technology in the medical and healthcare industries. While existing for over four decades, recent work has seen great improvements in the quality of products; particularly in medical devices such as implants. Improved customization reduced operating time and increased cost-effectiveness associated with Metal AM for these products offers a new value proposition. This paper investigates and evaluates modelling methods for the zygoma bone (human jawbone) and explores the most suitable material and optimum design for this critical biomedical implant. This paper proposes an innovative and efficient pre-process methodology that includes modelling, design validation, topological optimization, and numerical analysis. The method includes the generation of the model using reverse engineering of CT scan data and a topology optimization technique which makes the implant lightweight without causing excessive stress concentration. Static structural Finite Element Analysis was conducted to test three different biocompatible materials (Ti6Al4V, stainless steel 316L and CoCr alloys) which are commonly available for metal additive manufacturing. The stresses and conditions in the analysis were that of the human mastication process and all the implant design were tested with the three material types. The Taguchi method was used to determine the optimum design which was found to result in the highest mass reduction of 25% with Ti6Al4V as the implant material

Quality assessment and features of microdrilled holes in aluminum alloy using ultrafast laser

In this work, we present the use of an ultrafast laser system for the high aspect ratio micro-drilling of aluminum alloy thin foils. Hole sizes in between 20 and 40 lm were fabricated in arrays with sub-micron level precision in terms of diameter and hole location. The Design of Experiment approach was employed to analyze the influences of the laser process parameters like laser power, frequency, and exposure time on the resulting quality of the produced micro-holes. The outputs measured were hole size, location and the variability in these measures. The metallurgical and geometrical features were examined using a scanning electron microscope and optical microscope. Processing throughput is also important in industrial laser processes. The parametric effect on circularity and taper has been observed to understand the features of the hole. The features of holes help in fabrication in a plethora of industries to produce applications such as fins, filters, microgrid circuits, and biomedical devices

Ultrafast laser-induced surface structuring of anti-fouling steel surfaces for biomedical applications

Metallic surfaces are increasingly used in medical applications due to their favorable material properties such as high strength and biocompatibility. In medical applications antifouling properties are an important requirement especially for implants and medical devices which come into contact with different types of fluid streams. These should be anti-fouling in order to prevent contamination and corrosion. Laser processing methods such as ultrafast laser processing is a one-step and scalable process for surface texturing. This process can be used to produce well-defined surface nano- and microscale superficial textures such as Laser-induced Periodic Surface Structures (LIPSS) which can enhance the anti-fouling capability of the surface. In this study, micro and nano scaled LIPSS structures are manufactured on a biocompatible grade stainless steel 316L substrate using an ultrafast (<370 fs) and low power (<4 W) laser system. With an aim to optimize the anti-fouling properties, laser process parameters such as pulse energy, pulse repetition rate and beam scanning speed were varied to produce microstructures on the stainless-steel surface of varying dimensions. Surface roughness was analyzed using a laser surface profilometer and changes in the hydrophobicity were examined using water contact angle goniometry

Advances in laser-based surface texturing for developing antifouling surfaces: A comprehensive review

Surface fouling is a major challenge faced within various engineering applications, especially in marine, aerospace, water treatment, food and beverage, and the energy generation sectors. This can be prevented or reduced in various ways by creating artificial surface textures which have fouling resistance properties. Ultrafast laser texturing provides an efficient method for the texturing of surfaces of different materials with high accuracy, precision, and repeatability. Laser texturing methods can enhance the production of well-defined surface nano- and microscale patterns. These surfaces with nano- and micro-scale patterning can be tailored to have inherent properties such as hydrophobicity, hydrophilicity, and resistance to fouling. This review gives an overview of the various types of fouling that can occur, the properties affecting a surface's fouling resistance, as well as the latest physical and chemical strategies for the generation of antifouling surfaces. Surfaces architectures which have inherent antifouling capabilities are presented. This review focuses on the utilization of the higher precision laser-based texturing offered from femtosecond laser systems for enhance fouling resistance. The process parameters to fabricate these textures and the current state of art femtosecond laser sources are presented and discussed. The challenges and future research requirements in the field of laser-based methods to fabricate antifouling surfaces are presented

Innovative laser manufacturing processes at nano scale within the NewSkin Open Innovation Test Bed

Laser nanotechnologies have enormous potential for bringing products with new surface functionalities to market, while meeting sustainable development objectives. However, SMEs and start-ups are not benefiting fully from these technologies because of their cost and the necessary access to testing and validation infrastructures. The Horizon 2020-funded NewSkin project has thus created an Open Innovation Test Bed (OITB) focused on surface nanotechnologies to overcome these challenges. It provides access to scale-up and testing facilities to enhance surface properties in different relevant sectors. Regarding laser nanotechnologies, NewSkin provides access to different laser up-scaling facilities that integrate innovative manufacturing processes, including surface texturing, roll-to-roll femtosecond laser texturing, heat-treatment laser, multimodal laser processing. Several companies and research organisations have benefited from these technologies to improve surface functionalities such as wettability properties, improved heat exchange, friction reduction, wear resistance. The creation of NewSkin AISBL will further accelerate the uptake of innovative laser processes to manufacture new nanoenabled products

Parametric investigation of ultrashort pulsed laser surface texturing on aluminium alloy 7075 for hydrophobicity enhancement

Hydrophobicity plays a pivotal role in mitigating surface fouling, corrosion, and icing in critical marine and aerospace environments. By employing ultrafast laser texturing, the characteristic properties of a material’s surface can be modified. This work investigates the potential of an advanced ultrafast laser texturing manufacturing process to enhance the hydrophobicity of aluminium alloy 7075. The surface properties were characterized using goniometry, 3D profilometry, SEM, and XPS analysis. The findings from this study show that the laser process parameters play a crucial role in the manufacturing of the required surface structures. Numerical optimization with response surface optimization was conducted to maximize the contact angle on these surfaces. The maximum water contact angle achieved was 142º, with an average height roughness (Sa) of 0.87 ± 0.075 μm, maximum height roughness (Sz) of 19.4 ± 2.12 μm, and texture aspect ratio of 0.042. This sample was manufactured with the process parameters of 3W laser power, 0.08 mm hatch distance, and a 3 mm/s scan speed. This study highlights the importance of laser process parameters in the manufacturing of the required surface structures and presents a parametric modeling approach that can be used to optimize the laser process parameters to obtain a specific surface morphology and hydrophobicity