Covalent Adaptable Liquid Crystal Networks Enabled by Reversible Ring-Opening Cascades of Cyclic Disulfides.

The development of covalent adaptable liquid crystal networks (LCNs) enabled by introducing dynamic covalent bonds has endowed liquid crystal actuators with self-healing properties and reversible shape programmability, broadening their applications in diverse soft robotic devices. However, the finite molecular design strategy limits the recyclability and the architectural diversity of these materials. Here, a strategy is first reported for fabricating photoresponsive polydisulfide-based covalent adaptable LCNs by ring-opening polymerization of cyclic dithiolane groups. Based on the disulfide metathesis, the resulting materials are self-healable, reshapable, and reprogrammable. Importantly, the equilibrium between the polymer backbones and the dithiolane-functionalized monomers enables catalytic depolymerization to recycle monomers, which could significantly weaken the disadvantage of subtractive manufacturing of photomechanical devices. This work rooted in chemistry would provide an economical and environmentally friendly strategy for the fabrication of functional soft robotics with excellent programmability and renewability and beyond.

Effects of a 3D-printed orthosis compared to a low-temperature thermoplastic plate orthosis on wrist flexor spasticity in chronic hemiparetic stroke patients: a randomized controlled trial.

OBJECTIVE: The aim of this study was to compare the effects of two kinds of wrist-hand orthosis on wrist flexor spasticity in chronic stroke patients. DESIGN: This is a randomized controlled trial. SETTING: The study was conducted in a rehabilitation center. PARTICIPANTS: A total of 40 chronic hemiparetic stroke patients with wrist flexor spasticity were involved in the study. INTERVENTIONS: Patients were randomly assigned to either an experimental group (conventional rehabilitation therapy + 3D-printed orthosis, 20 patients) or a control group (conventional rehabilitation therapy + low-temperature thermoplastic plate orthosis, 20 patients). The time of wearing orthosis was about 4-8 hours per day for six weeks. MAIN MEASURES: Primary outcome measure: Modified Ashworth Scale was assessed three times (at baseline, three weeks, and six weeks). Secondary outcome measures: passive range of motion, Fugl-Meyer Assessment score, visual analogue scale score, and the swelling score were assessed twice (at baseline and six weeks). The subjective feeling score was assessed at six weeks. RESULTS: No significant difference was found between the two groups in the change of Modified Ashworth Scale scores at three weeks (15% versus 25%, P = 0.496). At six weeks, the Modified Ashworth Scale scores (65% versus 30%, P = 0.02), passive range of wrist extension (P < 0.001), ulnar deviation (P = 0.028), Fugl-Meyer Assessment scores (P < 0.001), and swelling scores (P < 0.001) showed significant changes between the experimental group and the control group. No significant difference was found between the two groups in the change of visual analogue scale scores (P = 0.637) and the subjective feeling scores (P = 0.243). CONCLUSION: 3D-printed orthosis showed greater changes than low-temperature thermoplastic plate orthosis in reducing spasticity and swelling, improving motor function of the wrist and passive range of wrist extension for stroke patients.