Magnetically actuated microswimmers have attracted researchers to investigate their swimming characteristics and controlled actuation. Although plenty of studies on actuating helical microswimmers ...have been carried out, robust closed-loop controls should be still explored for practical applications. In this paper, we proposed a data-driven model-free method using Image-Based Visual Servoing (IBVS), which uses features directly extracted in the image space as feedbacks. The IBVS method can eliminate camera calibration errors. We have demonstrated with experiments that the proposed IBVS method can enable velocity-independent path following of an arbitrarily given path on the plane, which permits a better experience of user interaction. The proposed control method is successfully applied to obstacle avoidance tasks and has the potential for the application in complex circumstances. This approach is promising for biomedical applications.
As the controller parameter adjustment process is simplified significantly by using learning algorithms, the studies about learning-based control attract a lot of interest in recent years. This ...article focuses on the intelligent servo control problem using learning from desired demonstrations. Compared with the previous studies about the learning-based servo control, a control policy using the broad learning system (BLS) is developed and first applied to a microrobotic system, since the advantages of the BLS, such as simple structure and no-requirement for retraining when new demos' data is provided. Then, the Lyapunov theory is skillfully combined with the complex learning algorithm to derive the controller parameters' constraints. Thus, the final control policy not only can obtain the movement skills of the desired demonstrations but also have the strong ability of generalization and error convergence. Finally, simulation and experimental examples verify the effectiveness of the proposed strategy using MATLAB and a microswimmer trajectory tracking system.
Nature provides much inspiration for developing soft millirobots. However, compared with smart and adaptations of lives in nature, these robotic systems still suffer from insufficiency of ...intelligence. Here, a new untethered soft millirobot with magnetic actuation in the head and function in the tail is presented via implementing control, actuation, and sensing directly in the materials, thereby endowing robots with multimodal locomotion and environment‐adaptive functions. Due to the soft and asymmetric structure, the millirobot not only shows robust multimodal locomotion, including controllable and transformable crawling, swinging and rolling, but also achieves an excellent capability of helical propulsion in water. Moreover, the robot also possesses outstanding obstacle‐crossing abilities, including helically propelling over obstacles (>2 body length), crawling within a 2 mm height tunnel and swinging through a 450 µm width channel. Furthermore, the robot can even squeeze its body to crawl through a tube easily via near‐infrared irradiation, which triggers the osmotic shrinking of its body. Notably, the robots also possess extraordinary environment‐adaptive functions, for example, leptocephali‐like optical camouflage in water, octopus‐like controllable delivery and variable appearance via visible color–shifting for interaction with the changing environment. These smart robotic systems would be of benefit in various fields via seamless integration of bioinspired design and smart materials.
The bioinspired hydrogel‐based millirobots not only possess excellent capabilities of controllable and transformable locomotion, but also outstanding obstacle‐crossing abilities. Furthermore, the robots even have extraordinary environment‐adaptive functions, including leptocephali‐like optical camouflage, octopus‐like controllable delivery, and variable appearance via visible color–shifting for interaction with the changing environment, which would benefit a wide range of areas such as biomedical and environmental fields.
We herein develop a two-in-one molecular design strategy for facile synthesis of 2D imine based covalent organic frameworks (COFs). The integration of two different functional groups (i.e., formyl ...and amino groups) in one simple pyrene molecule affords a bifunctional building block: 1,6-bis(4-formylphenyl)-3,8-bis(4-aminophenyl)pyrene (BFBAPy). Highly crystalline and porous Py-COFs can be easily prepared by the self-condensation of BFBAPy in various solvents, such as CH2Cl2, CHCl3, tetrahydrofuran, methanol, ethanol, acetonitrile, and dimethylacetamide, etc. The current work, to the best of our knowledge, is a rare case of COF synthesis that exhibits excellent solvent adaptability. Highly crystalline Py-COF thin films have been facilely fabricated on various substrates and exhibit potential applications in hole transporting layers for perovskite solar cells. Furthermore, the versatility of this two-in-one strategy was also verified by two additional examples. The current work dramatically reduces the difficulty of COF synthesis, and such two-in-one strategy is anticipated to be applicable for the synthesis of other COFs constructed by different building blocks and linkages.
Microrobots have great potential for multiple applications, such as targeted drug delivery and micromanipulation. Several kinds of microrobots assembled by nanoparticles have been proposed by ...researchers. However, they are difficult to adapt for complex environments, for example, traversing porous materials or climbing over obstacles. Many such environments require multimodal motion control. In this article, we proposed a needle-like microrobot assembled by ferromagnetic nanoparticles, which enables three types of locomotion, defined as axial motion, lateral motion, and rolling motion. The influence of velocities by input frequencies and the lengths of the microrobots are investigated theoretically and experimentally. Moreover, visual feedback path-following control methods are designed for each motion type, and experimentally verified. The needle-like microrobots enable traversing the nonwoven layer of a clinical mask and a seaweed silk barrier by axial motion, which showed a separation and a reaggregation during the traversing process. The needle-like microrobots with rolling motion are capable of climbing over obstacles, which expands its motion scene from 2-D to 3-D. They can overcome even higher obstacles by assembling themselves to form the longer needle-like microrobots. We further expect that with the proposed multimodal motion control of nanoparticle microrobots, they may achieve complex tasks at the microscale.
Untethered microrobots have attracted extensive attention due to their potential for biomedical applications and micromanipulation at the small scale. Soft microrobots are of great research ...importance because of their highly deformable ability to achieve not only multiple locomotion mechanisms but also minimal invasion to the environment. However, the existing microrobots are still limited in their ability to locomote and cross obstacles in unstructured environments compared to conventional legged robots. Nature provides much inspiration for developing miniature robots. Here, we propose a bionic quadruped soft thin-film microrobot with a nonmagnetic soft body and 4 magnetic flexible legs. The quadruped soft microrobot can achieve multiple controllable locomotion modes in the external magnetic field. The experiment demonstrated the robot's excellent obstacle-crossing ability by walking on the surface with steps and moving in the bottom of a stomach model with gullies. In particular, by controlling the conical angle of the external conical magnetic field, microbeads gripping, transportation, and release of the microrobot were demonstrated. In the future, the quadruped microrobot with excellent obstacle-crossing and gripping capabilities will be relevant for biomedical applications and micromanipulation.
Paramagnetic nanoparticles are considered as attractive building blocks, particularly for robotic delivery of drugs. Although paramagnetic nanoparticles can be effectively gathered and transported ...using external magnetic fields, the disassembly process is yet to be fully investigated to avoid the formation of aggregations. In this paper, we report a novel method of controllable disassembly of paramagnetic nanoparticle chains using a predefined dynamic magnetic field. The dynamic field is capable of performing spreading and fragmentation of the particle chains simultaneously. Using the magnetic dipole-dipole repulsive forces, the final area covered by the particle chains swells up to 545% of the initial area. The final length distribution presents a strong relationship with the frequency of the dynamic field in deionized (DI) water and two kinds of biofluids. An analytical model of phase lag is proposed, which shows good agreement with the experimental results. Furthermore, we also present an assembly process using a rotating magnetic field, indicating that the assembly disassembly process is reversible. In addition, batch-cargo delivery of polystyrene microbeads using the nanoparticle chains as swarm-like nanorobots is demonstrated.
High utility sequential pattern (HUSP) mining aims to mine actionable patterns with high utilities, widely applied in real-world learning scenarios such as market basket analysis, scenic route ...planning and click-stream analysis. The existing HUSP mining algorithms mainly attempt to improve computation efficiency while maintaining the algorithm stability in the setting of large-scale data. Although these methods have made some progress, they ignore the relationship between additional items and underlying sequences, which directly leads to the generation of redundant sequential patterns sharing the same underlying sequence. Hence, the mined patterns' actionability is limited, which significantly compromises the performance of patterns in real-world applications. To address this problem, we present a new method named Combined Utility-Association Sequential Pattern Mining (CUASPM) by incorporating item/sequence relations, which can effectively remove redundant patterns and extract high discriminative and strongly associated sequential pattern combinations with high utilities. Specifically, we introduce the concept of actionable combined mining into HUSP mining for the first time and develop a novel tree structure to select discriminative high utility sequential patterns (HUSPs) for downstream tasks. Furthermore, two efficient strategies (i.e., global and local strategies) are presented to facilitate mining HUSPs while guaranteeing utility growth and high levels of association. Last, two parameters are introduced to evaluate the interestingness of patterns to choose the most useful actionable combined HUSPs (ACHUSPs). Extensive experimental results demonstrate that the proposed CUASPM outperforms the baselines in terms of execution time, memory usage, mining high discriminative and strongly associated HUSPs.
Silicosis is a kind of irreversible pulmonary fibrosis induced by the long-term inhalation of silica particles. The therapeutic strategy based on the microRNAs might be an effective way for the ...treatment of silicosis. Our previous miRNA microarray data indicated that miR-326 was decreased in the mouse lung tissues of silica-induced pulmonary fibrosis. However, the specific functions of miR-326 on silica-induced pulmonary fibrosis remain unclear. The objective was to determine the expression and the biological effects of miR-326 in silica-induced pulmonary fibrosis. Methods included mouse models of silica-induced pulmonary fibrosis and miR-326 intervention that were established separately to explore the effect of miR-326 in vivo. The cell models of SiO2-treated lung epithelial cells (HBE and A549) and TGF-β1-stimulated lung fibroblast cells (MRC-5 and NIH/3T3) were used to investigate the mechanism of miR-326 in vitro. Hematoxylin and eosin staining was used to evaluate the severity and distribution of fibrosis of mouse lung tissues. Western blot and immunofluorescence assays were performed to measure the downstream molecules of miR-326. Transmission electron microscopy pictures showed the autophagy activity. The results showed miR-326 is down-regulated in the fibrotic lung tissues of silica-treated mice, while increased expression of miR-326 attenuates silica-induced pulmonary fibrosis in vivo. Tumor necrosis factor superfamily-14 (TNFSF14) and polypyrimidine tract-binding protein 1 (PTBP1) are identified as the targets of miR-326. MiR-326 dampens pulmonary inflammation through targeting TNFSF14 and promotes autophagy activity of fibroblasts through targeting PTBP1. LncRNA HOTAIR facilitates inflammation via sponging miR-326. In conclusion, we demonstrate that miR-326 inhibits inflammation and promotes autophagy activity by targeting TNFSF14 and PTBP1 separately to alleviate silica-induced pulmonary fibrosis. Our results might shed new light on the therapeutic strategies for silica-induced pulmonary fibrosis.
Abstract
Based on the DEA-Malmquist method, this study analyzes water resource utilization efficiency in six cities of the northern Anhui region. The input indicators covered per capita water ...resources, industrial water consumption, agricultural water consumption, domestic water consumption, fixed assets investment, and number of employees. The output indicator was per capita GDP of each city. The findings of the study revealed that only Huaibei achieved efficiency according to the DEA model, while the other cities in the northern Anhui region did not exhibit the same level of efficiency. The overall water resource utilization efficiency in the region was low, with significant variations among the cities (p ≤ 0.05; ANOVA test). The order of water resource utilization efficiency from high to low was Huaibei, Huainan, Bengbu, Bozhou, Suzhou, and Fuyang. An analysis of investment redundancy revealed that a large number of employees and an unreasonable water use structure were key factors that restricted the efficiency of water resource utilization in the region. The overall TFP index of water resource utilization efficiency in the region showed an upward trend, with a value of 1.02. By addressing them, decision-makers can work toward promoting sustainable economic development and effective water resource management in the region.
