Accepted Manuscripts

Tahseen Jwad, Sunan Deng, Haider Butt and Stefan Dimov
J. Micro Nano-Manuf   doi: 10.1115/1.4038097
Fresnel zone plates (FZPs) have been gaining a significant attention by industry due to their compact design and light weight. Different fabrication methods have been reported and used for their manufacture but they are relatively expensive. This research proposes a new low-cost one-step fabrication method that utilises nanosecond laser selective oxidation of titanium coatings on glass substrates and thus to form TiO2 nano-scale films with different thicknesses by controlling the laser fluence and the scanning speed. In this way phase-shifting FZPs was manufactured where the TiO2 thin-films acted as a phase shifter for the reflected light while the gain in phase depended on the film thickness. A model was created to analyse the performance of such FZPs based on the scalar theory. Finally, phase-shifting FZPs were fabricated for different operating wavelengths by varying the film thickness and a measurement setup was built to compare experimental and theoretical results. A good agreement between these results was achieved and an FZP efficiency of 5.5% to 20.9% was obtained when varying the wavelength and the oxide thicknesses of the zones.
TOPICS: Thin films, Manufacturing, Plates (structures), Lasers, Film thickness, Wavelength, Scalars, Weight (Mass), Fluence (Radiation measurement), Design, Nanoscale phenomena, oxidation, Titanium, Coatings, Glass
Deepak Patil, S. Aravindan, Mishi Kaushal Wasson, P. Vivekanandan and P. V. Rao
J. Micro Nano-Manuf   doi: 10.1115/1.4038093
The method for fast fabrication of superhydrophobic surfaces was proposed to resist the formation of biofilm ofEscherichia coli (E.coli) and Staphylococcus aureus (S. aureus) for orthopedic and dental implants. Laser beam machining with nanosecond pulsed laser (Nd:YAG) was used to fabricate pit structure on Grade-5 Ti-6Al-4V alloy followed by annealing (at 3000C with different time scales) in order to reduce the transition time from hydrophilic to superhydrophobic surface generation. Field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD) techniques were used to characterize the textured samples. The surface wettability of plain and textured samples was measured by the sessile drop method using goniometer. The biofilm formation was quantitatively and qualitatively evaluated by crystal violet binding assay and field emission scanning electron microscopy respectively. The biofilm formation is observed on plain (hydrophilic) surface for both the types of bacteria, whereas significantly less biofilm formation is observed on the laser textured (superhydrophobic) surfaces. The proposed methodhelps in reducing the risk of infection associated with implants without using cytotoxic bactericidal agents.
TOPICS: Manufacturing, Titanium alloys, Lasers, Scanning electron microscopy, Electron field emission, Laser beam machining, Orthopedics, Bacteria, Risk, Alloys, X-ray diffraction, Annealing, Crystals

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