• In vitro mesenchymal stem cell response to a CO2 laser modified polymeric material

      Waugh, David G.; Hussain, Issam; Lawrence, Jonathan; Smith, Graham C.; Toccaceli, Christina; University of Chester; University of Lincoln (Elsevier, 2016-05-16)
      With an ageing world population it is becoming significantly apparent that there is a need to produce implants and platforms to manipulate stem cell growth on a pharmaceutical scale. This is needed to meet the socio-economic demands of many countries worldwide. This paper details one of the first ever studies in to the manipulation of stem cell growth on CO2 laser surface treated nylon 6,6 highlighting its potential as an inexpensive platform to manipulate stem cell growth on a pharmaceutical scale. Through CO2 laser surface treatment discrete changes to the surfaces were made. That is, the surface roughness of the nylon 6,6 was increased by up to 4.3 µm, the contact angle was modulated by up to 5° and the surface oxygen content increased by up to 1 atom%. Following mesenchymal stem cell growth on the laser treated samples, it was identified that CO2 laser surface treatment gave rise to an enhanced response with an increase in viable cell count of up to 60,000 cells/ml when compared to the as-received sample. The effect of surface parameters modified by the CO2 laser surface treatment on the mesenchymal stem cell response is also discussed along with potential trends that could be identified to govern the mesenchymal stem cell response.
    • Laser surface engineering of polymeric materials and the effects on wettability characteristics

      Waugh, David G.; Avdic, Dalila; Woodham, K. J.; Lawrence, Jonathan; University of Lincoln (Scrivener/John Wiley & Sons., 2014-12-23)
      Wettability characteristics are believed by many to be the driving force in applications relating to adhesion. So, gaining an in-depth understanding of the wettability characteristics of materials before and after surface treatments is crucial in developing materials with enhanced adhesion properties. This chapter details some of the main competing techniques to laser surface engineering followed by a review of current cutting edge laser surface engineering techniques which are used for wettability and adhesion modulation. A study is provided in detail for laser surface treatment (using IR and UV lasers) of polymeric materials. Sessile drop analysis was used to determine the wettability characteristics of each laser surface treated sample and as-received sample, revealing the presence of a mixed-state wetting regime on some samples. Although this outcome does not follow current and accepted wetting theory, through numerical analysis, generic equations to predict this mixed state wetting regime and the corresponding contact angle are discussed.
    • Modifications of surface properties of beta Ti by laser gas diffusion nitriding

      Ng, Chi-Ho; Chan, Chi-Wai; Man, Hau-Chung; Waugh, David G.; Lawrence, Jonathan; University of Chester; Queen's University; The Hong Kong Polytechnic University (AIP Publishing, 2016-03-31)
      b-type Ti-alloy is a promising biomedical implant material as it has a low Young’s modulus and is also known to have inferior surface hardness. Various surface treatments can be applied to enhance the surface hardness. Physical vapor deposition and chemical vapor deposition 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 100W 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, optical microscopy, three-dimensional surface profile and contact angle measurements, and nanoindentation test.
    • 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.
    • On the study of oil paint adhesion on optically transparent glass: Conservation of reverse paintings on glass

      Bayle, M.; Waugh, David G.; Colston, Belinda J.; Lawrence, Jonathan; University of Chester (Elsevier, 2015-12-01)
      Reverse painting on glass is a technique which consists of applying a cold paint layer on the reverse-side of glass. The main challenge facing these artworks is the fragile adhesion of the pictorial layer – a simple movement can modify the appearance of the painting. This paper details a study into the adhesion parameters of pigments on glass and the comparison between different pigments. The relationships between the binder (linseed oil) with pigments and the glass with or without the use of an adhesive are studied. Physical analyses by surface characterisation have been carried out to better understand the influence of the pigment. The use of a sessile drop device, optical microscopy, scanning electron microscopy (SEM), a surface 3D profiler and a pencil hardness scratch tester were necessary to establish a comparison of the pictorial layer adhesion. A comparison of the effect of two adhesives; namely ox gall and gum arabic, has shown that the adhesion is not only linked to the physical parameters but that possible chemical reactions can influence the results. Finally, a treatment based on humidity-extreme storage has shown the weakness of some pictorial layers.
    • Surface treatments to modulate bioadhesion: A critical review

      Waugh, David G.; Toccaceli, Christina; Gillett, Alice R.; Ng, Chi-Ho; Hodgson, Simon D.; Lawrence, Jonathan; University of Chester (Scrivener Publishing, 2016-03-01)
      On account of the recent increase in importance of biological and microbiological adhesion in industries such as healthcare and food manufacturing many researchers are now turning to the study of materials, wettability and adhesion to develop the technology within these industries further. This is highly significant as the stem cell industry alone, for example, is currently worth £3.5 million in the United Kingdom (UK) alone. This paper reviews the current state-of-the-art techniques used for surface treatment with regards to modulating biological adhesion including laser surface treatment, plasma treatment, micro/nano printing and lithography, specifically highlighting areas of interest for further consideration by the scientific community. What is more, this review discusses the advantages and disadvantages of the current techniques enabling the assessment of the most attractive means for modulating biological adhesion, taking in to account cost effectiveness, complexity of equipment and capabilities for processing and analysis.