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The last two decades have witnessed the emergence of micro‐ and nanoswimmers (MNSs). Researchers have invested significant efforts in engineering motile micro‐ and nanodevices to address current limitations in minimally invasive medicine. MNSs can move through complex fluid media by using chemical fuels or external energy sources such as magnetic fields, ultrasound, or light. Despite significant advancements in their locomotion and functionalities, the gradual deterioration of MNSs in human physiological media is often overlooked. Corrosion and biodegradation caused by chemical reactions with surrounding medium and the activity of biological agents can significantly affect their chemical stability and functional properties during their lifetime performance. It is therefore essential to understand the degradation mechanisms and factors that influence them to design ideal biomedical MNSs that are affordable, highly efficient, and sufficiently resistant to degradation (at least during their service time). This review summarizes recent studies that delve into the physicochemical characteristics and complex environmental factors affecting the corrosion and biodegradation of MNSs, with a focus on metal‐based devices. Additionally, different strategies are discussed to enhance and/or optimize their stability. Conversely, controlled degradation of non‐toxic MNSs can be highly advantageous for numerous biomedical applications, allowing for less invasive, safer, and more efficient treatments. [ABSTRACT FROM AUTHOR]

With the increase in the scale of breeding at modern pastures, the management of dairy cows has become much more challenging, and individual recognition is the key to the implementation of precision farming. Based on the need for low-cost and accurate herd management and for non-stressful and non-invasive individual recognition, we propose a vision-based automatic recognition method for dairy cow ear tags. Firstly, for the detection of cow ear tags, the lightweight Small-YOLOV5s is proposed, and then a differentiable binarization network (DBNet) combined with a convolutional recurrent neural network (CRNN) is used to achieve the recognition of the numbers on ear tags. The experimental results demonstrated notable improvements: Compared to those of YOLOV5s, Small-YOLOV5s enhanced recall by 1.5%, increased the mean average precision by 0.9%, reduced the number of model parameters by 5,447,802, and enhanced the average prediction speed for a single image by 0.5 ms. The final accuracy of the ear tag number recognition was an impressive 92.1%. Moreover, this study introduces two standardized experimental datasets specifically designed for the ear tag detection and recognition of dairy cows. These datasets will be made freely available to researchers in the global dairy cattle community with the intention of fostering intelligent advancements in the breeding industry. [ABSTRACT FROM AUTHOR]

Highlights: This review discusses the potential of degradable metallic micromotors for a variety of biomedical and environmental applications. The design principles, fabrication techniques and degradation mechanisms of degradable metallic micromotors are reviewed in detail. Challenges and future directions for the development of degradable metallic micromotors for real-life applications are presented. Synthetic micromotor has gained substantial attention in biomedicine and environmental remediation. Metal-based degradable micromotor composed of magnesium (Mg), zinc (Zn), and iron (Fe) have promise due to their nontoxic fuel-free propulsion, favorable biocompatibility, and safe excretion of degradation products Recent advances in degradable metallic micromotor have shown their fast movement in complex biological media, efficient cargo delivery and favorable biocompatibility. A noteworthy number of degradable metal-based micromotors employ bubble propulsion, utilizing water as fuel to generate hydrogen bubbles. This novel feature has projected degradable metallic micromotors for active in vivo drug delivery applications. In addition, understanding the degradation mechanism of these micromotors is also a key parameter for their design and performance. Its propulsion efficiency and life span govern the overall performance of a degradable metallic micromotor. Here we review the design and recent advancements of metallic degradable micromotors. Furthermore, we describe the controlled degradation, efficient in vivo drug delivery, and built-in acid neutralization capabilities of degradable micromotors with versatile biomedical applications. Moreover, we discuss micromotors' efficacy in detecting and destroying environmental pollutants. Finally, we address the limitations and future research directions of degradable metallic micromotors. [ABSTRACT FROM AUTHOR]

Based on the fact that most of real networks are directed and weighted, and the breeding of new connections generally affects the communication capacity of neighbor nodes, this paper proposes a strength-based instead of degree-based directed weighted scale-free network model where an adaptive weight evolution mechanism is introduced, and the newly added edges between existing nodes besides between existing nodes and the new node are involved in. Theoretical analysis shows the strength (in-strength and out-strength) distribution as well as degree (in-degree and out-degree) distribution of networks generated by our presented model follow a power law distribution, indicating the network is with scale-free characteristic, and the power-law exponent is independent of network size, but depends on the basic edge weight, the weight increment and the number of newly added edges. Numerous simulations further verify that numerical results are well consistent with the theoretical results, and the dependence of power-law exponents on the aforementioned parameters are also analyzed and discussed. In addition, the topological characteristics of the directed weighted scale-free network, such as the average clustering coefficient and the average path length, are demonstrated as well. • The model aims at the directed and weighted network, and it is based on node's strength distribution. • An adaptive evolution mechanism is introduced in generating networks. • The new edges are bred not only between the new node and existing nodes, but between existing nodes. • The model is verified by theoretical analysis and numerical simulations. • The impact of initial setting parameters on the scale-free characteristic is discussed. [ABSTRACT FROM AUTHOR]

Inspired by the movement of bacteria and other microorganisms, researchers have developed artificial helical micro‐ and nanorobots that can perform corkscrew locomotion or helical path swimming under external energy actuation. In this paper, for the first time the locomotion of nonhelical multifunctional nanorobots that can swim in helical klinotactic trajectories, similarly to rod‐shaped bacteria, under rotating magnetic fields is investigated. These nanorobots consist of a rigid ferromagnetic nickel head connected to a rhodium tail by a flexible hydrogel‐based hollow hinge composed of chemically responsive chitosan and alginate multilayers. This design allows nanoswimmers switching between different dynamic behaviors—from in‐plane tumbling to helical klinotactic swimming—by varying the rotating magnetic field frequency and strength. It also adds a rich spectrum of swimming capabilities that can be adjusted by varying the type of applied magnetic fields and/or frequencies. A theoretical model is developed to analyze the propulsion mechanisms and predict the swimming behavior at distinct rotating magnetic frequencies. The model shows good agreement with the experimental results. Additionally, the biomedical capabilities of the nanoswimmers as drug delivery platforms are demonstrated. Unlike previous designs constitute metallic segments, the proposed nanoswimmers can encapsulate drugs into their hollow hinge and successfully release them to cells. [ABSTRACT FROM AUTHOR]

We describe a double template-assisted electrodeposition of porous metal microstructures. The method combines two-dimensional photolithography and electrophoretic assembly of polystyrene beads, in order to confine the electrochemical growth of a porous magnetic cobalt–nickel alloy within well-defined microscale boundaries. Polystyrene beads are electrophoretically deposited onto a sulfonate derivatized gold substrate where a patterned photoresist layer (first template) is applied. The polystyrene beads trapped in the first template act as the second template, and cobalt–nickel alloy is electrochemically grown through the voids between the beads. After removal of both templates, magnetic microstructures with well-defined shapes and porosity are successfully obtained. Additionally, we demonstrate the capabilities of these magnetic microstructures as wireless cargo microtransporters by loading their pores with a stimulus-responsive hydrogel. Magnetic manipulation experiments are also demonstrated. [ABSTRACT FROM AUTHOR]

The development of 3D soft‐robotic components is currently hindered by material limitations associated with conventional 3D printing techniques. To overcome this challenge, an indirect 3D printing approach based on the fabrication of 3D printed sacrificial templates is proposed. High‐resolution micromolds produced by direct laser writing are infused with polymers and then dissolved, leading to the final 3D printed soft microstructures. This method is used to indirectly print 3D and 4D soft microrobots. The versatility of this technique is shown through the fabrication and actuation of gelatin helices filled with magnetic nanoparticles. In addition, it is shown that stent‐like microstructures with shape memory properties can be manufactured with minimum features of 5 µm, which is 40 times smaller than those reported to date. In summary, the utilization of this technique can overcome obstacles associated with the fabrication of soft microrobots and surgical tools for minimally invasive surgery. [ABSTRACT FROM AUTHOR]

Poly(vinylidenefluoride-trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)) is a ferroelectric terpolymer relaxor with a static dielectric constant of 50, which was developed using defect modification to eliminate remnant polarization in the normal ferroelectric PVDF. In this work, this solution processable terpolymer was used as the gate insulator in bottom gated organic thin-film transistors with a pentacene semiconductor layer. Due to the high dielectric constant of P(VDF-TrFE-CFE), a large capacitive coupling between the gate and channel can be achieved which causes a high charge concentration at the interface of the semiconductor and dielectric layers. In this device, an on/off ratio of 104 and a low minimum operation gate voltage (5-10 V) were attained. [ABSTRACT FROM AUTHOR]

We present directly measured electrocaloric effect (ECE) from the poly(vinylidenefluoride-trifluoroethylene) 65/35 mol. % copolymer. The data reveal a large difference in the ECE between that measured in applying and in removing the electric field. The difference is significantly reduced by modifying the copolymer with 20 Mrad of high energy electron irradiation. Moreover, an isothermal entropy change ΔSint = 160 J kg-1 K-1 and an adiabatic temperature change ΔTint = 35 °C can be induced in the irradiated copolymer. These results demonstrate the promise of achieving a significant ECE in ferroelectric polymers near first-order ferroelectric-paraelectric transition where multiple intermediate phases can exist. [ABSTRACT FROM AUTHOR]