• Effect of laser treatment on the attachment and viability of mesenchymal stem cell responses on shape memory NiTi alloy

      Chan, Chi-Wai; Hussain, Issam; Waugh, David G.; Lawrence, Jonathan; Man, Hau-Chung; Queen's University, Belfast ; University of Lincoln ; University of Chester ; University of Chester ; Hong Kong Polytechnic University (Elsevier, 2014-05-22)
      The objectives of this study were to investigate the effect of laser-induced surface features on the morphology, attachment and viability of mesenchymal stem cells (MSCs) at different periods of time, and to evaluate the biocompatibility of different zones: laser-melted zone (MZ), heat-affected zone (HAZ) and base metal (BM) in laser-treated NiTi alloy.
    • Laser melting of NiTi and its effects on in-vitro mesenchymal stem cell responses

      Waugh, David G.; Lawrence, Jonathan; Chan, Chi-Wai; Hussain, Issam; Man, Hau-Chung; University of Chester ; University of Chester ; University of Lincoln ; University of Lincoln ; Hong Kong Polytechnic University (Woodhead Publishing, 2014-10-14)
    • Laser surface treatment of polyamide and NiTi alloy and the effects on mesenchymal stem cell response

      Waugh, David G.; Lawrence, Jonathan; Shukla, Pratik; Chan, Chi-Wai; Hussain, Issam; Man, Hau-Chung; Smith, Graham C.; University of Chester ; University of Chester ; University of Chester ; Queen's University, Belfast ; University of Lincoln ; Hong Kong Polytechnic University ; University of Chester (2015-03-18)
      Mesenchymal stem cells (MSCs) are known to play important roles in development, post-natal growth, repair, and regeneration of mesenchymal tissues. What is more, surface treatments are widely reported to affect the biomimetic nature of materials. This paper will detail, discuss and compare laser surface treatment of polyamide (Polyamide 6,6), using a 60 W CO2 laser, and NiTi alloy, using a 100 W fiber laser, and the effects of these treatments on mesenchymal stem cell response. The surface morphology and composition of the polyamide and NiTi alloy were studied by scanning electron microscopy (SEM) and X-ray photoemission spectroscopy (XPS), respectively. MSC cell morphology cell counting and viability measurements were done by employing a haemocytometer and MTT colorimetric assay. The success of enhanced adhesion and spreading of the MSCs on each of the laser surface treated samples, when compared to as-received samples, is evidenced in this work.
    • 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.