Design and fabrication of a novel 4D-printed customized hand orthosis to treat cerebral palsy.

This research study is dedicated to additive manufacturing of the shape memory polymer hand orthosis to treat patients with cerebral palsy. The treatment process for cerebral palsy is a step-by-step process that needs different adjustments for the spastic hand to stretch it towards a normal posture, whereas meeting these requirements using conventional methods or complicated mechanisms is expensive, less flexible, time-consuming, and less practical. A comprehensive investigation was conducted to design and fabricate novel thermally actuated customized hand orthosis via digital light processing (DLP). The highly precise scanning device was used to derive the hand model, and subsequently, the Blender software was used to design the customized orthosis. The results showed that fabricated orthosis could represent a strong potential to become an alternative treatment for cerebral palsy. The shape memory actuation of the orthosis indicated that 100 % shape recovery is achievable in different actuating conditions with recovery temperatures higher than 55°C. Besides, it was found that the response time and shape recovery percentage could be tailored in the range of 5 to 40 s and 45 to 100%, respectively, by adjusting programming and actuation temperatures. Further, the repeatability of the shape memory effects in the printed orthosis was investigated as well, which proved that until 17 repetitions, 100 % shape recovery was achievable.

The role of foaming process on shape memory behavior of polylactic acid-thermoplastic polyurethane-nano cellulose bio-nanocomposites.

In this study the effects of foaming process on the shape memory properties of Polylactic acid/thermoplastic polyurethane/cellulous-nanofiber bio-nanocomposites were investigated. The samples of cylindrical shapes as well as sheets were manufactured and foamed. The results indicated that while the foaming process presented a microcellular structure, it can cause a tangible increase (up to 40%) in force recovery ratio and an intense reduction (up to 10 times) in actuation force. It is statistically shown that the existence of cellulose nano-fibers within the foamed matrix causes a significant increase in actuation force and reduction in the force recovery ratio. Analytical evaluation on the sheet form samples, in the foamed state using rheological model, was carried out that indicated satisfying description of their shape memory behaviors. It was also demonstrated that there exists significant deviation between the shape memory properties extracted from experimental and analytical assessments.