Browsing by Author "Pearce, Oliver"

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    Bactericidal surfaces: an emerging 21st century ultra-precision manufacturing and materials puzzle
    (American Institute of Physics (AIP), 2021-04-06) Larrañaga-Altuna, Mikel; Zabala, Alaitz; Llavori, Iñigo; Pearce, Oliver; Nguyen, Dinh T.; Caro, Jaume; Mescheder, Holger; Endrino, José L.; Goel, Gaurav; Ayre, Wayne Nishio; Seenivasagam, Rajkumar Kottayasamy; Tripathy, Debendra Kumar; Armstrong, Joe; Goel, Saurav
    Progress made by materials scientists in recent years has greatly helped the field of ultra-precision manufacturing. Ranging from healthcare to electronics components, phenomena such as twinning, dislocation nucleation and high-pressure phase transformation have helped to exploit plasticity across a wide range of metallic and semiconductor materials. One current problem at the forefront of the healthcare sector that can benefit from these advances is that of bacterial infections in implanted prosthetic devices. The treatment of implant infections is often complicated by the growth of bacterial biofilms on implant surfaces, which form a barrier that effectively protects the infecting organisms from host immune defences and exogenous antibiotics. Further surgery is usually required to disrupt the biofilm, or to remove the implant altogether to permit antibiotics to clear the infection, incurring considerable cost and healthcare burdens. In this review, we focus on elucidating aspects of bactericidal surfaces inspired by the biological world to inform the design of implant surface treatments that will suppress bacterial colonization. Alongside manufacturing and materials related challenges, the review identifies the most promising natural bactericidal surfaces and provides representative models of their structure, highlighting the importance of the critical slope presented by these surfaces. The scalabl production of these complex hierarchical structures on freeform metallic implant surfaces has remained a scientific challenge to date and as identified by this review, is one of the many 21st Century puzzles to be addressed by the field of applied physics.
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    Critical review of nanopillar-based mechanobactericidal systems
    (American Chemical Society, 2022-01-05) Hawi, Sara; Goel, Saurav; Kumar, Vinod; Pearce, Oliver; Nishio Ayre, Wayne; Ivanova, Elena P.
    The rise of multidrug-resistant bacteria is the biggest threat to human health globally, as described by the World Health Organization. Mechanobactericidal surfaces provide a sustainable approach to addressing this concern by eradicating pathogens, especially bacteria, “right-at-the-point” of contacting the surface. However, the lack of a “design to manufacture” approach due to our limited understanding of the mechanobactericidal mechanism has impeded engineering optimization to develop scalable exploitation routes in various healthcare applications. It can be argued that the reason, most particularly, is the limitations and uncertainties associated with the current instrumentation and simulation capabilities, which has led to several streams of test protocols. This review highlights the current understanding on the mechanobactericidal mechanisms in light of the contributing factors and various techniques that are used to postulate these mechanisms. The review offers a critique on the variations observed on how nanostructured surfaces found in the literature have been evaluated such that the test protocols and outcomes are incomparable. The review also shows a strong need for developing more accurate models of a bacterium because the currently reported experimental data are insufficient to develop bacterial material models (constitutive equations). The review also alludes to the scarcity of direct experimental evidence of the mechanobactericidal mechanism, suggesting a strong need for further in situ monitoring as a future research direction.
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    Fabrication of functionalised surfaces on gum metal (Ti-30Nb) using micromachining
    (euspen, 2019-06-30) Hawi, Sara; Dickins, Andrew; Pardal, Goncalo; Giusca, Claudiu; Pearce, Oliver; Goel, Saurav
    Structured surfaces are attracting deep interest, as they allow tailoring the functionality via changes in the surface topography. Applications for these surfaces range greatly, including, optical surfaces for antireflective surfaces, thermal structures to assist in heat dispersion and anti-fouling surfaces to reduce micro-organisms from adhering to components. Gum metal is a relatively newer kind of beta titanium alloy that has earmarked its place as the next generation Ortheopedic implant material. In a timely effort, this work investigated the generation of micron level structured surfaces on Gum metal (Ti-30Nb – a beta titanium alloy) to explore micromilling as the robust scalable process to achieve low dimensional surfaces in titanium alloy. During micromilling, the feedrate, spindle speed, axial depth of cut and tool step over were varied to optimise these parameters for achieving superior quality of machining.
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    Precision laser manufacturing and metrology of nature-inspired bioactive surfaces for antibacterial medical implants
    (Elsevier, 2025-04-01) Hawi, Sara; Goel, Saurav; Kumar, Vinod; Giusca, Claudiu; Pearce, Oliver; Ayre, Wayne Nishio
    Femtosecond laser ablation presents a highly promising method to create bioactive nano/micro-structured metallic surfaces, offering numerous avenues for fabricating diverse types of surface structures. However, the relationship between surface properties and biological functionality, leading to the observed bioactivity remains unclear. This study aimed to investigate the relationship between structured/patterned steel surfaces and bioactivity, identifying key factors that enhance their performance. As opposed to the commonly used controversial parameter, arithmetic surface roughness (Ra), fractal dimension analysis was discovered to be strongly representative in quantifiably evaluating the adhesion of Staphylococcus aureus NCTC 7791 and MG-63 osteoblast-like cells. Surface chemistry and surface energy of structured surfaces showed no significant influence on bacterial adhesion. A specific type of laser-induced periodic structured surfaces with sub-micron wavelengths, high fractal dimension, and high texture aspect ratio demonstrated a 63 % reduction in bacterial adhesion compared to flat surfaces while avoiding cytotoxicity to MG-63 cells. Our findings underline the importance of scale-dependent analysis and the use of fractal analysis in evaluating the effectiveness of laser-structured surfaces for orthopaedic implant applications.
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    Resilient and agile engineering solutions to address societal challenges such as coronavirus pandemic
    (Elsevier, 2020-05-28) Goel, Saurav; Hawi, Sara; Goel, Gaurav; Thakur, Vijay Kumar; Agrawal, Anupam; Hoskins, Clare; Pearce, Oliver; Hussain, Tanvir; Upadhyaya, Hari M.; Cross, Graham; Barber, Asa H.
    The world is witnessing tumultuous times as major economic powers including the US, UK, Russia, India, and most of Europe continue to be in a state of lockdown. The worst-hit sectors due to this lockdown are sales, production (manufacturing), transport (aerospace and automotive) and tourism. Lockdowns became necessary as a preventive measure to avoid the spread of the contagious and infectious “Coronavirus Disease 2019” (COVID-19). This newly identified disease is caused by a new strain of the virus being referred to as Severe Acute Respiratory Syndrome CoronaVirus 2 (SARS CoV-2; formerly called 2019-nCoV). We review the current medical and manufacturing response to COVID-19, including advances in instrumentation, sensing, use of lasers, fumigation chambers and development of novel tools such as lab-on-the-chip using combinatorial additive and subtractive manufacturing techniques and use of molecular modelling and molecular docking in drug and vaccine discovery. We also offer perspectives on future considerations on climate change, outsourced versus indigenous manufacturing, automation, and antimicrobial resistance. Overall, this paper attempts to identify key areas where manufacturing can be employed to address societal challenges such as COVID-19.