• Influencing the attachment of bacteria through laser surface engineering

      Gillett, Alice R.; Waugh, David G.; Lawrence, Jonathan; University of Chester (Laser Institute of America, 2015-10-31)
      Bacteria have evolved to become proficient at adapting to both extracellular and environmental conditions, which has made it possible for them to attach and subsequently form biofilms on varying surfaces. This has resulted in major health concerns and economic burden in both hospital and industrial environments. Surfaces which prevent this bacterial fouling through their physical structure represent a key area of research for the development of antibacterial surfaces for many different environments. Laser surface treatment provides a potential candidate for the production of anti-biofouling surfaces for wide ranging surface applications within healthcare and industrial disciplines. In the present study, a KrF 248 nm Excimer laser was utilized to surface pattern Polyethylene terephthalate (PET). The surface topography and roughness were determined with the use of a Micromeasure 2, 3D profiler. Escherichia coli (E. coli) growth was analysed at high shear flow using a CDC Biofilm reactor for 48 hours, scanning electron microscopy was used to determine morphology and total viable counts were made. Through this work it has been shown that the surface modification significantly influenced the distribution and morphology of the attached E. coli cells. What is more, it has been evidenced that the laser-modified PET has been shown to prevent E. coli cells from attaching themselves within the laser-induced micro-surface-features.
    • Modifications of surface properties of beta Ti by laser gas diffusion nitriding

      Ng, Chi-Ho; Lawrence, Jonathan; Waugh, David G.; Chan, Chi-Wai; Man, Hau-Chung; University of Chester (Laser Institute of America, 2015-10)
      β -type Ti-alloy is a promising biomedical implant material as it has a low Young’s modulus but is also known to have inferior surface hardness. Various surface treatments can be applied to enhance the surface hardness. Physical vapour deposition (PVD) and chemical vapour deposition (CVD) are two examples of this but these techniques have limitations such as poor interfacial adhesion and high distortion. Laser surface treatment is a relatively new surface modification method to enhance the surface hardness but its application is still not accepted by the industry. The major problem of this process involves surface melting which results in higher surface roughness after the laser surface treatment. This paper will report the results achieved by a 100 W CW fiber laser for laser surface treatment without the surface being melted. Laser processing parameters were carefully selected so that the surface could be treated without surface melting and thus the surface finish of the component could be maintained. The surface and microstructural characteristics of the treated samples were examined using X-ray diffractometry (XRD), optical microscopy (OM), 3-D surface profile & contact angle measurements and nano-indentation test.
    • Modulating the wettability characteristics and bioactivity of polymeric materials using laser surface treatment

      Waugh, David G.; Lawrence, Jonathan; Shukla, Pratik; University of Chester (Laser Institute of America, 2015-10)
      It has been thoroughly demonstrated previously that lasers hold the ability to modulate surface properties of materials with the result being utilization of such lasers in both research and industry. What is more, these laser surface treatments have been shown to affect the adhesion characteristics and bio-functionality of those materials. This paper details the use of a Synrad CO2 laser marking system to surface treat nylon 6,6 and polytetrafluoroethylene (PTFE). The laser-modified surfaces were analyzed using 3D surface profilometry to ascertain an increase in surface roughness when compared to the as-received samples. The wettability characteristics were determined using the sessile drop method and showed variations in contact angle for both the nylon 6,6 and PTFE. For the PTFE it was shown that the laser surface treatment gave rise to a more hydrophobic surface with contact angles of up to 150° being achieved. For the nylon 6,6, it was observed that the contact angle was modulated approximately ±10° for different samples which could be attributed to a likely mixed state wetting regime. The effects of the laser surface treatment on osteoblast cell and stem cell growth is discussed showing an overall enhancement of biomimetic properties, especially for the nylon 6,6. This work investigates the potential governing parameters which drives the wettability/adhesion characteristics and bioactivity of the laser surface treated polymeric materials.