Tough, Transparent, and Slippery PVA Hydrogel Led by Syneresis.

Slippery and transparent polyvinyl alcohol (PVA) hydrogels with mechanical robustness exhibit broad applications in artificial biological soft tissues, flexible wearable electronics, and implantable biomedical devices. Most of the current PVA hydrogels, however, are unable to integrate these features, which compromises its performance in biological and engineering applications. To achieve such purpose, herein, a novel tactic is proposed, salting-out-after-syneresis of PVA, to realize a mechanically robust and highly transparent slippery PVA hydrogel. The syneresis of PVA sol is first conducted to form highly dense and transparent PVA polymer networks, then the salting-out effect tunes the aggregation of the polymer chains to rapidly induce the phase separation and crystallization. The resultant hydrogels show the transparency up to 98% in the visible region, the tribological coefficient down to 0.0081, and the excellent mechanical properties with strength, modulus, and toughness of 26.72 ± 1.05, 6.66 ± 0.29 MPa, and 55.21 ± 1.62 MJ m-3 , respectively. To reveal the potentials, PVA contact lens that combine remarkable lubrication, anti-protein adhesion, biocompatibility, and drug-loading functions are demonstrated. This strategy provides a simple and new avenue for developing the mechanically robust, transparent, and hydrated hydrogels, showing the potential in biomedicine and wearable devices.

Sophisticated Structural Ceramics Shaped from 3D Printed Hydrogel Preceramic Skeleton.

Shaping ceramic materials into sophisticated architecture with 3D hierarchical structure is desirable in multiapplication yet remains challenge due to their brittle and stiff nature. Herein, a new method to achieve ceramic architectures with unsupported and large-spanning structure by shaping vat photopolymerization 3D printed hydrogel preceramic skeleton with unique flexible and deformable character is proposed. Specifically, the present photopolymerizable hydrogel preceramic achieves one stone, two birds: the photosensitive polymer matrix coupled with ceramic nanoparticles for the first shaping by vat photopolymerization 3D printing and the secondary plasticity of the 3D printed ceramic body through flexible shape deformation of hydrogel networks. Inorganic binder aluminum dihydrogen phosphate serves as hydrogel dispersion medium to achieve ultralow shrinkage photopolymerization ceramic. Compared with conventional polymer-derived photocuring ceramics, the linear shrinkage of lamina structure is solely 2%, and which of cubic ceramic structure is just 13.3%. More importantly, one 3D printed preceramic is conducted to reshape repeatedly myriad constructions, realizing reusability of intrinsic brittle ceramic, improving manufacturing fault tolerance rate. Finally, a variety of paradigms for ceramic structure applications are proposed toward stereo circuit, biomedicine, and catalytic applications, breaking the limitation of intrinsic brittleness of ceramic in high-precision manufacturing of complex ceramic devices.

[Observation of clinical efficacy of acupuncture for cerebral vasospasm after embolization of ruptured aneurysms].

OBJECTIVE: To observe the improvement of acupuncture in cerebral vasospasm (CVS) after embolization of ruptured aneurysms. METHODS: Sixty cases were randomly divided into two groups, an acupuncture-medication group and a conventional treatment group, 30 cases in each one. The cases of CVS in conventional treatment group were treated with Nimodipine. In acupuncture-medication group, on the basis of the treatment as conventional treatment group, Baihui (GV 20) and Fengchi (GB 20) were selected as the main acupoints in the treatment of CVS. The treatment lasted for 3 weeks. Hunt-Hess scale for the standard assessment was adopted to determine the severity of disease before and after treatment and compare the efficacy between two groups. The transcranial Doppler (TCD) was conducted on the 1st, 4th, 7th, 10th, 14th and 21st days successively after operation, and the average flow velocity of 3 pairs of vessels (ACA, MCA, and PCA) was recorded. CT perfusion (CTP) was taken to test cerebral blood flow (CBF), cerebral blood volume (CBV) and mean transit time (MTT) on the 1st, 7th, 14th and 21st days successively. RESULTS: The improvement of Hunt-Hess scale in acupuncture-medication group was superior to that in conventional treatment group (P < 0.05). The analysis of variance (ANOVA) was adopted in the comparison of ACA, MCA, PCA, CBF, CBV and MTT between two groups. The results showed that the therapy in either group achieved the effect on CVS (all P < 0.05). But, the improvements in the above mentioned indices in acupuncture-medication group were superior to those in conventional treatment group (all P < 0.05). CONCLUSION: Acupuncture at Baihui (GV 20) and Fengchi (GB 20) down-regulates the peak values or upregulates the valley values. It releases the peak of CVS effectively, improves the clinical prognosis significantly and is the effective therapy for CVS after subarachnoid hemorrhage.