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In this study we evaluated methods to reduce the friction of an extrasynovial tendon under a pulley in vitro. The surface of canine peroneus longus (PL) tendons was modified with gelatin and/or hyaluronic acid (HA) under different conditions. The gliding resistance between treated or control tendons and the canine digital flexor pulley was measured during 500 cycles of simulated flexionlextension. After 500 cycles, the gliding resistance of normal PL tendon increased 10-fold (p < 0.05), while the gliding resistance of tendons coated with carbodiimide derivatized gelatin (cd-gelatin) or carbodiimide derivatized gelatidHA (cdgelatin-HA) did not increase significantly. The PL tendon treated with cd-gelatin-HA had a similar friction response during the repetitive motion as the intrasynovial flexor digitorum profundus (FDP) tendon. Scanning electron microscopy after 500 cycles of motion showed that the tendon surface in the group treated with cd-gelatin-HA appeared smoother than tendons in the other groups.

A conducting polymer-based hydrogel (PPy/CPH) with a polypyrrole-poly(vinyl alcohol) interpenetrating network was prepared by utilization of a chemical cross-linked poly(vinyl alcohol)-HSO hydrogel (CPH) film as flexible substrate followed by vapor-phase polymerization of pyrrole. Then an all-solid-state polymer supercapacitor (ASSPS) was fabricated by sandwiching the CPH film between two pieces of the PPy/CPH film. The ASSPS is mechanically robust and flexible with a tensile strength of 20.83 MPa and a break elongation of 377% which is superior to other flexible conducting polymer hydrogel-based supercapacitors owing to the strong hydrogen bonding interactions among the layers and the high mechanical properties of the PPy/CPH. It exhibits maximum volumetric specific capacitance of 13.06 F/cm and energy density of 1160.9 μWh/cm. The specific capacitance maintains 97.9% and 86.3% of its initial value after 10 000 folding cycles and 10 000 charge-discharge cycles, respectively. The remarkable electrochemical and mechanical performance indicates this novel ASSPS device is promising for flexible electronics.

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