Passive micromixing can efficiently mix laminar flows through molecular and convective diffusion. Microstructures are expected to be efficient, easily integrated into micromixers, and suitable for micromixers over a wide range of Re. This paper presents the enhancement effects of the multiscale lateral microstructures on the flow field characteristics and mixing efficiency through numerical simulations at Re = 0.01–50. Inspired by the regulation of lateral microstructures on the local flow field, cross-scale staggered baffles (CSBs) were established and applied in typical passive micromixers. For low-Re conditions, the paired trapezoidal microstructures (PTMs) of the CSBs improved the mixing effect by increasing the local streamline tortuosity. For high-Re conditions, the PTMs of CSBs increased the number of expanding vortices in the microchannel, which could increase the size of the fluid interfaces, and an optimal mixing index with relatively little pressure drop was achieved. Moreover, the CSBs were applied to the serpentine curved channel, which caused large expanding vortices on the inner side of the curved channel, and then the state of the Dean vortices on the cross section of the curved channel changed. Therefore, compared with the conventional micromixer channel structure, lateral microstructures regulate the local flow field through the enhancement of the streamlines and the secondary flow effects, and lateral microstructures have great potential to improve the mixing efficiency over a wide range of Re.

Inspired by the impressive shape reconfigurability in natural systems, stimulus-responsive soft materials have been exploited to enable reconfigurable surface changes, relying on controllable deformations inner soft materials and spatiotemporally varying external stimuli. Among these, light stimulus, due to its high degree of spatial and temporal control manner, has been becoming a particularly powerful actuation means. Especially, photothermal shape transformations induced by bilayered structures, combining light absorption layer and an active layer of hydrogels, SMPs (Shape Memory Polymers), and nanocomposites, have provided a facile reconfigurable scheme. Here, we proposed reconfigurable shape-morphing flexible surfaces with individually addressable photoactuators arrays. By adjusting near-infrared radiation intensity and actuators thickness, the deformations of each actuator can be desirably tuned up to 350 μ m. Additionally, actuator arrays can be individually photoactuated one by one due to the remote and straightforward control manner, which give rise to distinct surface morphology. Furthermore, multiple actuators are enabled to demonstrate coupled photomechanical actuation, causing broader area surface reconfigurations. Finally, we tried to explore shape-morphing flexible surfaces applications in a deformable mirror prototype with 19 actuator arrays. Based on photomechanical deformation simulation from COMSOL MultiPhysics, surface change capability was preliminarily researched. We envision that our proposed photoactuated deformable mirror will have a significant impact on the novel design in the future deformable mirrors and metasurfaces.

Graphene oxide (GO) was prepared using metal-catalyzed crystallization of amorphous carbon on a carbon fiber surface to improve the mechanical properties of the carbon fiber (CF). The deposited GO was used for repairing of surface structure defects on CF, thereby improving the tensile strength and interfacial strength force of CF. The grown morphology of GO and the changes in CF surface microstructure before and after remediation were investigated in detail by scanning tunneling microscopy and Raman spectroscopy. The effects of surface repair on the mechanical properties of the CF and the resulting composites were investigated systematically. The results of scanning tunneling microscopy show that the graphene oxide formed on the surface of carbon fiber present uniform dispersion. Raman spectroscopy curves indicate that CF successfully remediated the defects in the CF surface. The results of mechanical properties testing show that such a remediation method could significantly enhance the tensile strength of CF and increase the interfacial strength versus raw fibers; that is, the tensile strength of CF was enhanced by 42% and the interfacial strength by 33.7%.