Pretreatment of polycaprolactone-20% tricalcium phosphate (PCL-TCP) scaffolds under alkaline conditions can be utilized to alter surface characteristics for enhanced early bone formation. PCL-TCP scaffolds were treated with sodium hydroxide (NaOH) at various time intervals (group A: untreated, group B: 3M NaOH for 48 h, and group C: 3M NaOH for 96 h). In vitro results showed a greater degree of physical changes in the NaOH-treated scaffolds (B and C) than the untreated group (A). Clearly, the NaOH-treated scaffolds showed an increased surface roughness than the untreated ones. A significantly large number of "channel-like" pits and greater average pit sizes were detected in groups B (14.51 +/- 10.9 microm) and C (20.27 +/- 14.3 microm); and absent in group A. In addition, treated scaffolds had a significant reduction of the water contact angle (40.9-58.2%). Favorably, the pore dimensions and scaffold rod thickness remained unchanged throughout the experiment. When implanted in the calvaria of rabbits, NaOH-treated scaffolds reported greater early matrix deposition and bone formation from scanning electron images and Micro-computed tomography analyses. In conclusion, pretreatment of PCL-TCP scaffolds with NaOH increases the wettability and surface area for initial matrix deposition and early bone ingrowth.
In this follow-on study, macro fiber composite actuators are used to change the shape of the upper surface of an airfoil model with geometry close to that of the NACA 4415 type. In the design discussed, these thin and light piezoelectric actuators are bonded to the inside and become an integral part of the skin of the upper surface of the airfoil. The model used in this study incorporates some structural changes that allow a smoother shaping of the surface closer to the leading edge of the airfoil. Still-air and wind-tunnel measurements in different flow regimes are performed to assess the characteristics of the deformation of the upper surface. The results obtained can be used to design a wing with morphing upper surface for improved aerodynamics, for maneuvering without ailerons, and/or for active control of the flow over the wing.
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