Smart actuators refer to integrated devices that are composed of smart and artificial materials, and can provide actuation and dampening capabilities in response to single/multi external stimuli (such as light, heat, magnetism, electricity, humidity, and chemical reactions). Due to their capability of dynamically sensing and interaction with complex surroundings, smart actuators have attracted increasing attention in different application fields, such as artificial muscles, smart textiles, smart sensors, and soft robots. Among these intelligent material, functional hydrogels with fiber structure are of great value in the manufacture of smart actuators. In this review, we summarized the recent advances in stimuli-responsive actuators based on functional materials. We emphasized the important role of functional nano-material-based additives in the preparation of the stimulus response materials, then analyzed the driving response medium, the preparation method, and the performance of different stimuli responses in detail. In addition, some challenges and future prospects of smart actuators are reported.
Smart actuators with multistimuli synergistic response functions can be widely used in complex environments. In this study, a torsion side-by-side sodium alginate-sodium alginate/graphene oxide (SA-SA/GO) fiber-based smart actuator with an intermittent spiral structure is reported by the side-by-side wet spinning and twisting methods. With the excellent humidity response of SA and the photothermal properties of GO, the side-by-side fiber can produce a twisting motion of 449 rpm and untwisting rotation motion of 201 rpm at full speed when stimulated by infrared (IR) light (0.5 W/cm2) or moisture (90% RH). Meanwhile, due to the unique bicomponent intermittent spiral structure of the side-by-side fiber, the SA component and the SA/GO component in the spiral structure show different response speeds to infrared light and humidity stimulus, and the actuator can complete a controllable and programmable “forward–stagnation–reverse” synergistic drive response behavior under the co-stimulation of IR light and humidity using the alternating transformation of torque force and solvation force. In addition, owing to the excellent flexibility and synergistic responsiveness of the side-by-side SA-SA/GO smart actuator, it can be prepared to form a series of programmable smart devices for the design of bionic muscles and multifunctional load devices in complex environments, which has important applications in future smart device development.
Particulate matter and formaldehyde (HCHO) in closed indoor environments are seriously harmful to human health; hence, techniques for the improvement of air quality have attracted significant attention.
Small extracellular vesicles (sEVs) miRNAs are promising diagnosis and prognosis biomarkers for ischemic stroke (IS). This study aimed to determine the impact of IS on the serum sEVs miRNA profile of IS patients and a transient middle cerebral artery occlusion (tMCAO) mouse model. Small RNAseq was used to define the serum sEVs miRNA profile in IS patients and healthy controls (HC), and tMCAO mice and sham controls. Among the 1,444 and 1,373 miRNAs identified in human and mouse serum sEVs, the expression of 424 and 37 miRNAs was significantly altered in the IS patients and tMCAO mice, respectively (| Log2FC| ≥ 1, p < 0.01). Notably, five of the top 25 upregulated miRNAs in IS patients were brain-specific or enriched, including hsa-miR-9-3p, hsa-miR-124-3p, hsa-miR-143-3p, hsa-miR-98-5p, and hsa-miR-93-5p. Upregulation of these four miRNAs was further validated by qPCR. Nine of the 20 upregulated miRNAs in tMCAO mice were also brain-specific or enriched miRNAs. Temporal analysis indicated that the dynamics of mmu-miR-9-5p, mmu-miR-124-3p, mmu-miR-129-5p, and mmu-miR-433-3p were closely correlated with the evolution of ischemic brain injury, as their expression increased at 0.5 days after the onset of ischemia, peaked at day 1 or 3, and returned to normal levels at day 7 and 14. Notably, with the exceptions of mmu-miR-128-3p, the expression of the other eight miRNAs in the mouse serum sEVs was unaffected in the lipopolysaccharide (LPS)-induced neuroinflammation model. Together, in this study, we provided a comprehensive view of the influences of IS on the serum sEVs miRNA profile of IS patients and tMCAO mice and demonstrated the increment of a set of brain-specific miRNAs in serum sEVs after acute cerebral ischemia, which could be promising candidates directly reflecting the ischemic brain injury.
Flame retardant and antibacterial sodium alginate (SA) fiber were fabricated using the bio-based flame retardant of phytic acid and DL-arginine successively, and then the morphological structures, combustion behavior, thermal stability, and mechanical as well as antibacterial properties of SA fiber were investigated carefully. It is found that when the additional amount of PADL (reaction products of phytic acid and DL-arginine) in SA composite fiber is 20 wt%, its limiting oxygen index (LOI) is 40.0 ± 0.3%, and UL−94 is V−0 grade. The combustion behavior of composite fiber shows that PADL can effectively reduce combustion heat and promote carbon formation. Its peak of HRR (pkHRR) is 5.9% of pure SA fiber, and the residual carbon increases from 23.0 ± 0.1% to 44.2 ± 0.2%. At the same time, the density of the residual carbon increases gradually. PADL can promote SA to form expanded carbon with increasing density, and isolate the heat and volatilization of combustible gases. The guanidine group of DL-arginine can interact with the cell membrane to kill bacteria, and the antibacterial property of SA composite fiber is increased by 30%. This study provides a very ecological, safe, environmentally friendly and simple method to prepare flame retardant and antibacterial SA composite fiber with bio-based materials.
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