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4D printing, the fabrication of dynamic 3D objects, has emerged as a frontier in additive manufacturing, benefiting from rapid advancements in 3D printing technologies and the development of new stimuli-responsive materials. Among the diverse materials explored for 4D printing, the hydrogel, renowned for its exceptional flexibility, biocompatibility, and tunable mechanical properties, is a class of soft materials well-suited for 4D printing. In addition to selecting and developing appropriate stimuli-responsive materials, it is important to devise suitable printing strategies to enable the fabrication of hydrogel-based structures that can perform complex shape-changing under external stimuli in various applications, such as soft robotics and biomedical areas. In view of this, various printing strategies, including structural design, printing scheme, and stimuli control are systematically summarized. This review aims to provide an up-to-date evolution of 4D-printed hydrogels and insights into the utilization of these printing strategies and printing techniques, such as direct ink writing, stereolithography, and two-photon polymerization, in the 4D printing of hydrogel structures for specific functions and applications.

Objective: To analyze the clinical characteristics of alcohol-flame burns and the correlation with COVID-19 epidemic. Methods: A retrospective analysis was conducted on the medical records of 134 patients with alcohol-flame burns who were admitted to the Second People's Hospital of Chengdu City from January 2015 to December 2022. Demographics, time of first hospital visit, burn size, depth and site, month and place of burn, inhalation injury, surgical intervention, length of hospital stay, hospital costs were recorded annually. Data from the COVID-19 epidemic period (2020–2022) were compared to those from the non-epidemic period (2015–2019) for analysis. Results: The number of patients with alcohol-flame burns showed a consistent annual increase. During the epidemic period, the proportion of alcohol-flame burns among burn patients was significantly higher (2.43% ± 0.16%) than during the non-epidemic period (1.70% ± 0.15%) (P = 0.00). Alcohol-flame burns primarily affected adult men, occurring mainly in massage parlors and homes. The peak incidence was between May and August. Patients sought medical attention promptly, with a median time to first hospital visit of 2 h post-burn. Alcohol-flame burns mostly involved the trunk and upper extremities. Median total burn size was 7% TBSA, median full-thickness burn size was 1% TBSA. Over 20% of patients had combined inhalation injuries, and a similar proportion required surgical intervention. Alcohol burn patients had a median hospital stay of 14 days and incurred median medical costs of ¥16,600($2300). During the epidemic, the basic characteristics of patients with alcohol-flame burns did not change much. However, the time to first hospital visit was significantly shorter (2 h) during the epidemic period than non-epidemic period (3 h). Furthermore, alcohol-flame burn patients during the epidemic exhibited significantly larger total burn sizes, higher burn indices, and longer hospital stays compared to non-epidemic patients. The incidence of combined inhalation injuries was also significantly higher during the epidemic. Surgical requirements and medical costs were not significantly associated with the COVID-19 epidemic. Conclusion: Alcohol-flame burns exhibit distinct clinical characteristics, including severe injuries, prolonged hospital stays, and elevated costs, particularly in the context of the COVID-19 pandemic.

Micro/nano-fabrication technology via two-photon polymerization (TPP) nanolithography is a powerful and useful manufacturing tool that is capable of generating two dimensional (2D) to three dimensional (3D) arbitrary micro/nano-structures of various materials with a high spatial resolution. This technology has received tremendous interest in cell and tissue engineering and medical microdevices because of its remarkable fabrication capability for sophisticated structures from macro- to nano-scale, which are difficult to be achieved by traditional methods with limited microarchitecture controllability. To fabricate precisely designed 3D micro/nano-structures for biomedical applications via TPP nanolithography, the use of photoinitiators (PIs) and photoresists needs to be considered comprehensively and systematically. In this review, widely used commercially available PIs are first discussed, followed by elucidating synthesis strategies of water-soluble initiators for biomedical applications. In addition to the conventional photoresists, the distinctive properties of customized stimulus-responsive photoresists are discussed. Finally, current limitations and challenges in the material and fabrication aspects and an outlook for future prospects of TPP for biomedical applications based on different biocompatible photosensitive composites are discussed comprehensively. In all, this review provides a basic understanding of TPP technology and important roles of PIs and photoresists for fabricating high-precision stimulus-responsive micro/nano-structures for a wide range of biomedical applications.

We systematically reviewed published clinical trials to evaluate the effectiveness of virtual reality (VR) technology on functional improvement, pain relief, and reduction of mental distress among burn patients undergoing rehabilitation. Systematic searches were conducted in 4 databases, including PubMed, the Cochrane Library, Embase, and Web of Science, from inception to August 2021. Randomized controlled trials (RCTs) evaluating any type of VR for the rehabilitation in burn patients with dysfunction were included. Two reviewers evaluated the eligibility, and another 2 reviewers used the Cochrane risk of bias assessment tool to assess the risk of bias. The extracted data included the main results of rehabilitation evaluation (quality of life [QOL], work performance, range of motion [ROM] of joints, hand grip and pinch strength, pain, fun, anxiety), the application performance of VR (realness and presence), adverse effects (fatigue and nausea), and characteristics of the included studies. Heterogeneity was evaluated using the chi-square tests and I 2 statistics. Random- or fixed-effects models were conducted to pool the effect sizes expressed as standardized mean differences (SMDs). Sixteen RCTs with 535 burn patients were included. VR-based interventions were superior to usual rehabilitation in QOL and work performance of burn patients and produced positive effect on the average gain of ROM (SMD=0.72) as well. VR was not associated with improved hand grip and pinch strength (SMD=0.50, 1.22, respectively) but was associated with reduced intensity, affective, and cognitive components of pain (SMD=−1.26, −0.71, −1.01, respectively) compared with control conditions. Ratings of fun in rehabilitation therapy were higher (SMD=2.38), and anxiety scores were lower (SMD=−0.73) than in control conditions. VR-based burn rehabilitation significantly improves the QOL and work performance of burn patients, increases the ROM gain in the joints, reduces the intensity and unpleasantness of pain and the time spent thinking about pain, increases the fun in the rehabilitation therapy, reduces the anxiety caused by the treatment, and has no obvious adverse effects. However, it did not significantly improve hand grip or pinch strength. [ABSTRACT FROM AUTHOR]