Soft dielectric elastomer actuators (DEAs) exhibit interesting muscle-like behavior for the development of soft robots. However, it is challenging to model these soft actuators due to their material ...nonlinearity, nonlinear electromechanical coupling, and time-dependent viscoelastic behavior. Most recent studies on DEAs focus on issues of mechanics, physics, and material science, while much less importance is given to quantitative characterization of DEAs. In this paper, we present a detailed experimental investigation probing the voltage-induced electromechanical response of a soft DEA that is subjected to cyclic loading and propose a general constitutive modeling approach to characterize the time-dependent response, based on the principles of nonequilibrium thermodynamics. In this paper, some of the key observations are found as follows: 1) Creep exhibits the drift phenomenon, and is dominant during the first three cycles. The creep decreases over time and becomes less dominant after the first few cycles; 2) a significant amount of hysteresis is observed during all cycles and it becomes repeatable after the first few cycles; 3) the peak of the displacement is shifted from the peak of the voltage signal and occurs after it. To account for these viscoelastic phenomena, a constitutive model is developed by employing several dissipative nonequilibrium mechanisms. The quantitative comparisons of the experimental and simulation results demonstrate the effectiveness of the developed model. This modeling approach can be useful for control of a viscoelastic DEA and paves the way to emerging applications of soft robots.
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After surgical treatment of osteoarticular tuberculosis (TB), it is necessary to fill the surgical defect with an implant, which combines the merits of osseous regeneration and local ...multi-drug therapy so as to avoid drug resistance and side effects. In this study, a 3D-printed macro/meso-porous composite scaffold is fabricated. High dosages of isoniazid (INH)/rifampin (RFP) anti-TB drugs are loaded into chemically modified mesoporous bioactive ceramics in advance, which are then bound with poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) through a 3D printing procedure. The composite scaffolds show greatly prolonged drug release time compared to commercial calcium phosphate scaffolds either in vitro or in vivo. In addition, the drug concentrations on the periphery tissues of defect are maintained above INH/RFP minimal inhibitory concentrations even up to 12weeks post-surgery, while they are extremely low in blood. Examinations of certain serum enzymes suggest no harm to hepatic or renal functions. Micro-CT evaluations and histology results also indicate partly degradation of the composite scaffolds and new bone growth in the cavity. These results suggest promising applications of our hierarchical composite scaffold in bone regeneration and local anti-TB therapy after osteoarticular TB debridement surgery.
The dimensional tolerance of flexible, thin-walled aerospace parts can be violated by the excessive static deflections during milling. This paper proposes a method to predict the dimensional surface ...form errors caused by deflections of both flexible workpiece and slender end-mill in five-axis flank milling of thin-walled parts. The end-mill is modeled as a cantilevered beam. The stiffness of the thin-walled part varies as the metal is removed and the tool-part contact location changes. The time varying stiffness of the thin-walled part is predicted by an efficient structural stiffness modification method that only needs the FE model of the initial workpiece and avoids re-meshing the part at each cutter location. The cutting forces are distributed over both the cutting tool and the part in the engagement zone, and the effect of deflections on the immersion is calculated. The effect of radial runout of the tool is considered in chip thickness, hence in the cutting force prediction. Finally, the cutter and the workpiece deflections are considered to predict the surface errors left on the finished part. The proposed method has been proven in five-axis blade milling experiments.
•Dimensional form errors are predicted in five-axis flank milling of thin-walled parts.•Varying static stiffness of the flexible part is efficiently updated without re-meshing as the material is removed.•Effect of the combined tool and flexible part deflections on the cutter-workpiece engagement is considered.•The chip thickness is analytically calculated along the tool axis considering the five-axis process kinematics.•The proposed surface error prediction model is experimentally validated in five-axis flank milling of a sample blade.
New nanostructure means new nanotechnology and nanoscience. The need of complex nanostructure‐based advanced functional nanomaterials has promoted the appearance of several kinds of multifluid ...electrospinning processes, such as tri‐axial electrospinning, quad‐fluid coaxial electrospinning, tri‐fluid side‐by‐side electrospinning, and coaxial electrospinning with a side‐by‐side core. These multifluid processes can greatly expand the capability of electrospinning in generating new types of nanostructures with different organization manner of the inner parts, and from both spinnable and unspinnable working fluids. The key elements for conducting a multifluid electrospinning lie in a well‐designed spinneret, compatibility of the working fluids, and special operational parameters. The complex nanostructures can be created through direct electrospinning of multiple fluids, through after‐treatment of the electrospun products, and through ingenious design of the components, compositions and their spatial distributions as well. This article provides a simple review on the most recent publications about the multifluid electrospinning processes and the corresponding complex nanostructures.
This article is characterized under:
Therapeutic Approaches and Drug Discovery > Emerging Technologies
Implantable Materials and Surgical Technologies > Nanomaterials and Implants
Multifluid electrospinning for the generation of complex nanostructures.
Although lithium–sulfur (Li–S) batteries are promising next‐generation energy‐storage systems, their practical applications are limited by the growth of Li dendrites and lithium polysulfide ...shuttling. These problems can be mitigated through the use of single‐atom catalysts (SACs), which exhibit the advantages of maximal atom utilization efficiency (≈100%) and unique catalytic properties, thus effectively enhancing the performance of electrode materials in energy‐storage devices. This review systematically summarizes the recent progress in SACs intended for use in Li‐metal anodes, S cathodes, and separators, briefly introducing the operating principles of Li–S batteries, the action mechanisms of the corresponding SACs, and the fundamentals of SACs activity, and then comprehensively describes the main strategies for SACs synthesis. Subsequently, the applications of SACs and the principles of SACs operation in reinforced Li–S batteries as well as other metal–S batteries are individually illustrated, and the major challenges of SACs usage in Li–S batteries as well as future development directions are presented.
The cycling stability and rate performance of Li–S batteries are adversely affected by the formation of Li dendrites and the polysulfide shuttle effect. Single‐atom catalysts (SACs) can effectively guide Li deposition and suppress polysulfide migration, thus holding great promise for Li–S batteries. The recent progress in the development of SACs for Li–S batteries is systematically summarized and analyzed.
An intramolecular dearomatization of indole derivatives based on visible-light-promoted 2+2 cycloaddition was achieved via energy transfer mechanism. The highly strained cyclobutane-fused angular ...tetracyclic spiroindolines, which were typically unattainable under thermal conditions, could be directly accessed in high yields (up to 99%) with excellent diastereoselectivity (>20:1 dr) under mild conditions. The method was also compatible with diverse functional groups and amenable to flexible transformations. In addition, DFT calculations provided guidance on the rational design of substrates and deep understanding of the reaction pathways. This process constituted a rare example of indole functionalization by exploiting visible-light-induced reactivity at the excited states.
In flank milling of thin-walled parts, the profile tolerance would usually be violated by the excessive static deformations. This paper presents a comprehensive method to compensate deformation ...errors in five-axis flank milling from the aspect of tool path optimization. Firstly, the machined surface is constructed by imprinting the predicted tool/workpiece deformations on the cutter envelope surface. Secondly, the signed distances from the sample points on the design surface to the machined surface are calculated for the machining error evaluation. Their differential increments that characterize the variation of surface errors with respect to the adjustment of tool path are then derived. On this basis, the mathematical model and algorithm for minimizing the deformation-induced surface errors are developed through slightly optimizing the shape parameters of the tool path surface. Finally, five-axis blade milling experiments are conducted to validate the effectiveness of the proposed method. The results demonstrate that the surface errors mainly caused by machining deformations in flank milling of flexible blades can be largely reduced by using the developed algorithm.
•The deformations in flank milling of blades are compensated via tool path optimization.•The machined surface is modeled by imprinting deformations on cutter envelope surface.•Machining errors are minimized by optimizing the shape parameters of tool path surface.•The tool path optimization is formulated as a MILP problem.•The proposed compensation method is experimentally validated via blade machining.
Nanoscale drug-delivery systems (DDSs) have great promise in tumor diagnosis and treatment. Platelet membrane (PLTM) biomimetic DDSs are expected to enhance retention in vivo and escape uptake by ...macrophages, as well as minimizing immunogenicity, attributing to the CD47 protein in PLTM sends "don't eat me" signals to macrophages. In addition, P-selectin is overexpressed on the PLTM, which would allow a PLTM-biomimetic DDS to specifically bind to the CD44 receptors upregulated on the surface of cancer cells.
In this study, porous nanoparticles loaded with the anti-cancer drug bufalin (Bu) were prepared from a chitosan oligosaccharide (CS)-poly(lactic-co-glycolic acid) (PLGA) copolymer. These were subsequently coated with platelet membrane (PLTM) to form PLTM-CS-pPLGA/Bu NPs. The PLTM-CS-pPLGA/Bu NPs bear a particle size of ~ 192 nm, and present the same surface proteins as the PLTM. Confocal microscopy and flow cytometry results revealed a greater uptake of PLTM-CS-pPLGA/Bu NPs than uncoated CS-pPLGA/Bu NPs, as a result of the targeted binding of P-selectin on the surface of the PLTM to the CD44 receptors of H22 hepatoma cells. In vivo biodistribution studies in H22-tumor carrying mice revealed that the PLTM-CS-pPLGA NPs accumulated in the tumor, because of a combination of active targeting effect and the EPR effect. The PLTM-CS-pPLGA/Bu NPs led to more effective tumor growth inhibition over other bufalin formulations.
Platelet membrane biomimetic nanoparticles played a promising targeted treatment of cancer with low side effect.
Rational design of optimal bifunctional oxygen electrocatalyst with low cost and high activity is greatly desired for realization of rechargeable Zn–air batteries. Herein, we fabricate mesoporous ...thin-walled CuCo2O4@C with abundant nitrogen-doped nanotubes via coaxial electrospinning technique. Benefiting from high catalytic activity of ultrasmall CuCo2O4 particles, double active specific surface area of mesoporous nanotubes, and strong coupling with N-doped carbon matrix, the obtained CuCo2O4@C exhibits outstanding oxygen electrocatalytic activity and stability, in terms of a positive onset potential (0.951 V) for oxygen reduction reaction (ORR) and a low overpotential (327 mV at 10 mA cm–2) for oxygen evolution reaction (OER). Significantly, when used as cathode catalyst for Zn-air batteries, CuCo2O4@C also displays a low charge–discharge voltage gap (0.79 V at 10 mA cm–2) and a long cycling life (up to 160 cycles for 80 h). With desirable architecture and excellent electrocatalytic properties, the CuCo2O4@C is considered a promising electrocatalyst for Zn–air batteries.
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