Nanoengineered parylene-C sculptured thin films (STFs) are deposited on glass and silicon substrates using a direct one-step growth technique. The deposited STFs support fibroblast cell attachment and proliferation in vitro, which is an early indication of biocompatibility and bioactivity of this emerging class of biomaterials. Surface modification of endoprostheses of the small joints of the hand, which heal with fibrous stabilization, may be greatly enhanced by such nanoengineered biomaterials.
Microscale sliding friction experiments were performed on nanostructured poly-chloro-p-xylylene (PPX-Cl, a.k.a, parylene) films. Oblique-angle vapour-phase deposition resulted in nanostructured columnar films tilted 57°–63° relative to the surface. The mechanical response to sliding was studied relative to the film structural anisotropy by examining contact friction and deformation in three sliding orientations: ‘with’, ‘against’ and ‘perpendicular’ to the tilt axis of the columns. Friction coefficients were uniformly high (0.5–1.5) for all orientations. Neither frictional anisotropy nor depth hysteresis was observed for sliding perpendicular to the column tilt axis. However, sliding ‘with’ and ‘against’ the column tilt axis resulted in measurable friction anisotropy as well as depth hysteresis, with larger contact depths and higher friction coefficients for sliding ‘with’ the column tilt. In comparison, planar films did not exhibit either frictional anisotropy or depth hysteresis. The depth hysteresis during sliding parallel to the tilt axis is attributed to the lateral force contribution to the total contact loading. Contacts formed when the sliding orientation was perpendicular to the column tilt axis were nominally Hertzian, allowing estimation of elastic moduli of the films from the load–displacement data during sliding. These films may have applications in the area of tissue engineering for directional cell sheet growth, MEMS developments for directional microfluidic pumps and sensors for deformation induced detection.
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