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Hydroxyapatite (HA) and fluorapatite (FA) coatings were deposited on Ti-6Al-4V substrates with an Nd-YAG laser and then immersed in simulated body fluid (SBF) for up to 21 days to evaluate their bioactivity. Prior to SBF immersion, the coating layer of the HA specimen had a coral-like structure, and was mainly composed of Ti, CaTiO 3 , TiO 2 , Al 2 O 3 , and Ca 2 P 2 O 7 , whereas that of the FA specimen had a dense cellular-like structure, and was mainly composed of Ti, CaTiO 3 , TiO 2 , Al 2 O 3 , and residual FA. The Ca/P ratios of the HA and FA coating layers were 7.61 and 2.12, respectively. After 21 days of immersion in SBF, only a very small amount of precipitates, mainly consisting of CaCO 3 with some hydroxycarbonated apatite (HCA) and HA, formed on the HA coating layer, whose Ca/P ratio retained a high value of 6.34. In contrast, a dense accumulation of granulated precipitates, mainly consisting of HCA, formed on the FA coating layer after just 7 days of SBF immersion, with a corresponding Ca/P ratio of 1.63. The SBF immersion test shows that FA coatings produced via an Nd-YAG laser cladding technique on a Ti-6Al-4V substrate have better bioactivity than that of their HA counterparts.

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Abstract-Wheelchairs are an essential assistive device for many individuals with injury or disability. Manual wheelchairs provide a relatively low-cost solution to the mobility needs of such individuals. Furthermore, they provide an effective means of improving the user's cardiopulmonary function and upperlimb muscle strength. However, manual wheelchairs have a gross loss of mechanical efficiency, and thus the risk of user fatigue and upper-limb injury is increased. Electric-powered wheelchairs reduce the risk of injury and provide a more convenient means of transportation. However, they have a large physical size and are relatively expensive. Accordingly, the present study utilizes a quality function deployment method to develop a wheelchair with a user-selectable manual/electric propulsion mode and an auxiliary solar power supply system. The auxiliary solar power supply increased the travel range of the wheelchair by approximately 26% compared with that of a wheelchair powered by battery alone. Moreover, the wheelchair has a modular design and can be disassembled and folded for ease of transportation or storage. Overall, the present results suggest that the proposed wheelchair provides an effective and convenient means of meeting the mobility needs of individuals with mobility difficulties.

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To study the effect of titania (TiO2) addition on the surface microstructure and bioactivity of fluorapatite coatings, fluorapatite was mixed with TiO2 in 1:0.5 (FA + 0.5TiO2), 1:0.8 (FA + 0.8TiO2), and 1:1 (FA + TiO2) ratios (wt%) and clad on Ti-6Al-4V substrates using an Nd:YAG laser system. The experimental results show that the penetration depth of the weld decreases with increasing TiO2 content. Moreover, the subgrain structure of the coating layer changes from a fine cellular-like structure to a cellular-dendrite-like structure as the amount of TiO2 increases. Consequently, as the proportion of TiO2 decreases (increase in fluorapatite content), the Ca/P ratio of the coating layer also decreases. The immersion of specimens into simulated body fluid resulted in the formation of individual apatite. With a lower Ca/P ratio before immersion, the growth of the apatite was faster and then the coating layer provided a better bioactivity. X-ray diffraction analysis results show that prior to simulated body fluid immersion, the coating layer in all three specimens was composed mainly of fluorapatite, CaTiO3, and Al2O3 phases. Following simulated body fluid immersion, a peak corresponding to hydroxycarbonated apatite appeared after 2 days in the FA + 0.5TiO2 and FA + 0.8TiO2 specimens and after 7 days in the FA + TiO2 specimen. Overall, the results show that although the bioactivity of the coating layer tended to decrease with increasing TiO2 content, in accordance with the above-mentioned ratios, the bioactivity of all three specimens remained generally good.

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