Abstract
Microcatheters have enabled diverse minimally invasive endovascular operations and notable health benefits compared with open surgeries. However, with tortuous routes far from the arterial ...puncture site, the distal vascular regions remain challenging for safe catheter access. Therefore, we propose a wireless stent-shaped magnetic soft robot to be deployed, actively navigated, used for medical functions, and retrieved in the example M4 segment of the middle cerebral artery. We investigate shape-adaptively controlled locomotion in phantoms emulating the physiological conditions here, where the lumen diameter shrinks from 1.5 mm to 1 mm, the radius of curvature of the tortuous lumen gets as small as 3 mm, the lumen bifurcation angle goes up to 120
°
, and the pulsatile flow speed reaches up to 26 cm/s. The robot can also withstand the flow when the magnetic actuation is turned off. These locomotion capabilities are confirmed in porcine arteries ex vivo. Furthermore, variants of the robot could release the tissue plasminogen activator on-demand locally for thrombolysis and function as flow diverters, initiating promising therapies towards acute ischemic stroke, aneurysm, arteriovenous malformation, dural arteriovenous fistulas, and brain tumors. These functions should facilitate the robot’s usage in new distal endovascular operations.
The oscillatory pitch motion at the leading edge of a millimeter‐scale flexible sheet on the water surface can generate undulatory locomotion for swimming, similar to a honeybee vibrating its wings ...for propulsion. The influence of various parameters on such swimming strategy remains unexplored. This study uses magnetic milliswimmers to probe the propulsion mechanics and impact of different parameters. It is found that this undulatory propulsion is driven by capillary forces and added mass effects related to undulatory waves of the milliswimmers, along with radiation stress stemming from capillary waves at the interface. Modifying the parameters such as actuation frequency, pitch amplitude, bending stiffness, and hydrofoil length alters the body waveform, thus, affecting the propulsion speed and energy efficiency. Although undulatory motion is not a prerequisite for water surface propulsion, optimizing body stiffness to achieve a proper undulatory waveform is crucial for efficient swimming, balancing energy consumption, and speed. The study also reveals that the induced water flow is confined near the water surface, and the flow structures evolve with varying factors. These discoveries advance the understanding of undulatory water surface propulsion and have implications for the optimal design of small‐scale swimming soft robots in the future.
The water‐surface propulsion of an undulatory swimmer stems from the complex interplay of various forces that are generated by the body's waveform and the waves at the water‐air interface. Adjusting the material and dimensions of the body, along with the excitation manner of the head, allows for tuning of the swimmer's waveform that is crucial for optimizing propulsion performance.
Mechanical model of hook-loop adhesion Ouyang, Zi; Chen, Yan; Yan, Yingbo ...
International journal of solids and structures,
05/2022, Letnik:
243
Journal Article
Recenzirano
Odprti dostop
The hook-loop like adhesion is a common phenomenon in nature, widely used in our daily life with robust adhesion ability, i.e. the Velcro on our clothes. In general, the hook-loop adhesion can be ...divided into two stages, i.e., the loop hooked up and pull-out stages. At present, the intrinsic factors that affect the hook-loop adhesion are still unknown, and quantitative models describing the two stages are still lacked. Herein, these issues are rationalized through combining experiments, theoretical analysis, and numerical simulations. The theoretical models for fibrous loops hooked on single hook and pull-out of one loop on curved hook are developed. Furthermore, the loop hooked up stage is further simulated by introducing a spring-sandwich element to describe the resilience and compaction effects of fibrous loops. The results show good agreements among theoretical predictions, numerical simulations, and experiments. It is shown that the number of hooked loops is mainly determined by the length of hook-arm and hook angle, friction coefficient, and expulsion displacement of fibrous loops. While, the pull-out force of single loop on hook mainly depends on the bending stiffness, hook arc angle and arc length. Combining with hooked loop number and pull-out force, a general algorithm is proposed to optimize the adhesion property of Velcro, by considering the parameters of hook interspace, hook arc angle and arc length. The results presented in this work not only explore the adhesion mechanism of hook-loop adhesion, but also provide quantitative models to predict its adhesion behaviors, which may offer a rational design strategy for high-performance hook-loop adhesive.
Structural colorful cholesterics show impressive susceptibility to external stimulation, leading to applications in electro/mechano‐chromic devices. However, out‐of‐plane actuation of structural ...colorful actuators based on cholesterics and the integration with other stimulation remains underdeveloped. Herein, colorful actuators and motile humidity sensors are developed using humidity‐responsive cholesteric liquid crystal networks (CLCNs) and magnetic composites. The developed colorful actuator can exhibit synergistic out‐of‐plane shape morphing and color change in response to humidity, with CLCNs as colorful artificial muscles. Through the integration with magnetic control, the motile sensor can be navigated to open and confined spaces with the aid of friction to detect local relative humidity. The integration of multi‐stimulation actuation of cholesteric magnetic actuators will expand the research frontier of structural colorful actuators and motile sensors for confined spaces.
Humidity‐sensitive cholesteric liquid crystal network polymers combined with magnetic composite are developed into colorful actuators and motile sensors, which can be controlled and actuated using humidity and magnetic field. The actuators show synergistic color change and shape morphing while the motile sensors can locomote in open and confined spaces under magnetic actuation.
Methodologies based on intravascular imaging have revolutionized the diagnosis and treatment of endovascular diseases. However, current methods are limited in detecting, i.e., visualizing and ...crossing, complicated occluded vessels. Therefore, we propose a miniature soft tool comprising a magnet-assisted active deformation segment (ADS) and a fluid drag-driven segment (FDS) to visualize and cross the occlusions with various morphologies. First, via soft-bodied deformation and interaction, the ADS could visualize the structure details of partial occlusions with features as small as 0.5 millimeters. Then, by leveraging the fluidic drag from the pulsatile flow, the FDS could automatically detect an entry point selectively from severe occlusions with complicated microchannels whose diameters are down to 0.2 millimeters. The functions have been validated in both biologically relevant phantoms and organs ex vivo. This soft tool could help enhance the efficacy of minimally invasive medicine for the diagnosis and treatment of occlusions in various circulatory systems.
Active and passive deformations of miniature soft robotic tools assist in detecting complex occlusions in lumens.
Layered materials and structures (LMS), such as van der Waals two-dimensional (2D) layered materials and nacre-like layered structures, often exhibit highly anisotropic mechanical properties, i.e., ...strong in in-plane directions but weak in out-of-plane direction. Despite the strong anisotropy in their mechanical properties, Timoshenko beam model (TBM) is usually used to describe the bending deformation of LMS. We note, however, that there are two fundamental issues in using TBM to describe LMS: First, the stiffness of LMS approaches zero when the interlayer shear modulus G approaches zero; and second, the first derivative of deflection becomes discontinuous at the point of concentrated force. Clearly, both are not true for LMS. In this work, by introducing the bending energy of monolayer into the potential energy of TBM, we develop a modified Timoshenko beam model (MTBM), which is able to not only address these two issues, but also correctly predict the bending stiffness of LMS without any fitting parameters. Our analysis shows that the bending behaviors of LMS are determined by a dimensionless parameter λL, where L is the length of the beam and λ=kGA∕D0+kGA∕(nDbend), where, kGA and D0 are, respectively, the shear and bending rigidity of the beam cross-section, Dbend is the bending rigidity of monolayer, and n is the number of layer. When λL→0, the MTBM degenerates to the multi-beam model with bending stiffness of nDbend; while it degenerates to the TBM whenλL→∞. Furthermore, if kGA is much larger than D0, both MTBM and TBM degenerate to the classical Euler–Bernoulli beam model. We further perform molecular dynamics simulations, finite element simulations and experiments to validate the MTBM. Based on the MTBM, a couple of interesting applications of LMS are also demonstrated. Hence, the MTBM presented here captures the necessary intrinsic deformation modes of LMS and provides an accurate tool for the prediction and optimization of the mechanical properties of LMS.
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Emerging evidence indicates that tumor cells release a large amount of exosomes loaded with cargos during tumorigenesis. Exosome secretion is a multi-step process regulated by certain related ...molecules. Long non-coding RNAs (lncRNAs) play an important role in hepatocellular carcinoma (HCC) progression. However, the role of lncRNA HOTAIR in regulating exosome secretion in HCC cells remains unclear.
We analyzed the relationship between HOTAIR expression and exosome secretion-related genes using gene set enrichment analysis (GSEA). Nanoparticle tracking analysis was performed to validate the effect of HOTAIR on exosome secretion. The transport of multivesicular bodies (MVBs) after overexpression of HOTAIR was detected by transmission electron microscopy and confocal microscopy analysis of cluster determinant 63 (CD63) with synaptosome associated protein 23 (SNAP23). The mechanism of HOTAIR's regulation of Ras-related protein Rab-35 (RAB35), vesicle associated membrane protein 3 (VAMP3), and SNAP23 was assessed using confocal co-localization analysis, phosphorylation assays, and rescue experiments.
We found an enrichment of exosome secretion-related genes in the HOTAIR high expression group. HOTAIR promoted the release of exosomes by inducing MVB transport to the plasma membrane. HOTAIR regulated RAB35 expression and localization, which controlled the docking process. Moreover, HOTAIR facilitated the final step of fusion by influencing VAMP3 and SNAP23 colocalization. In addition, we validated that HOTAIR induced the phosphorylation of SNAP23 via mammalian target of rapamycin (mTOR) signaling.
Our study demonstrated a novel function of lncRNA HOTAIR in promoting exosome secretion from HCC cells and provided a new understanding of lncRNAs in tumor cell biology.
In contrast to normal cells, which use the aerobic oxidation of glucose as their main energy production method, cancer cells prefer to use anaerobic glycolysis to maintain their growth and survival, ...even under normoxic conditions. Such tumor cell metabolic reprogramming is regulated by factors such as hypoxia and the tumor microenvironment. In addition, dysregulation of certain signaling pathways also contributes to cancer metabolic reprogramming. Among them, the Hippo signaling pathway is a highly conserved tumor suppressor pathway. The core oncosuppressive kinase cascade of Hippo pathway inhibits the nuclear transcriptional co-activators YAP and TAZ, which are the downstream effectors of Hippo pathway and oncogenic factors in many solid cancers. YAP/TAZ function as key nodes of multiple signaling pathways and play multiple regulatory roles in cancer cells. However, their roles in cancer metabolic reprograming are less clear. In the present review, we examine progress in research into the regulatory mechanisms of YAP/TAZ on glucose metabolism, fatty acid metabolism, mevalonate metabolism, and glutamine metabolism in cancer cells. Determining the roles of YAP/TAZ in tumor energy metabolism, particularly in relation to the tumor microenvironment, will provide new strategies and targets for the selective therapy of metabolism-related cancers.
Hypoxia-inducible factor 1α (HIF-1α) is essential in hepatocellular carcinoma (HCC) glycolysis and progression. Yes-associated protein (YAP) is a powerful regulator and is overexpressed in many ...cancers, including HCC. The regulatory mechanism of YAP and HIF-1α in HCC glycolysis is unknown.
We detected YAP expression in 54 matched HCC tissues and the adjacent noncancerous tissues. The relationship between YAP mRNA expression and that of HIF-1α was analyzed using The Cancer Genome Atlas HCC tissue data. We cultured HepG2 and Huh7 HCC cells under normoxic (20% O
) and hypoxic (1% O
) conditions, and measured the lactate and glucose levels, migration and invasive capability, and the molecular mechanism of HCC cell glycolysis and progression.
In this study, we detected YAP expression in 54 matched HCC tissues and the adjacent noncancerous tissues. We observed that hypoxia-induced YAP activation is crucial for accelerating HCC cell glycolysis. Hypoxia inhibited the Hippo signaling pathway and promoted YAP nuclear localization, and decreased phosphorylated YAP expression in HCC cells. YAP knockdown inhibited HCC cell glycolysis under hypoxic. Mechanistically, hypoxic stress in the HCC cells promoted YAP binding to HIF-1α in the nucleus and sustained HIF-1α protein stability to bind to PKM2 gene and directly activates PKM2 transcription to accelerate glycolysis.
Our findings describe a new regulatory mechanism of hypoxia-mediated HCC metabolism, and YAP might be a promising therapeutic target in HCC.
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