Biomimetic Micro Research Articles

Nature-Inspired Micro/Nano-Structured Antibacterial Surfaces.

The problem of bacterial resistance has become more and more common with improvements in health care. Worryingly, the misuse of antibiotics leads to an increase in bacterial multidrug resistance and the development of new antibiotics has virtually stalled. These challenges have prompted the need to combat bacterial infections with the use of radically different approaches. Taking lessons from the exciting properties of micro-/nano-natural-patterned surfaces, which can destroy cellular integrity, the construction of artificial surfaces to mimic natural functions provides new opportunities for the innovation and development of biomedicine. Due to the diversity of natural surfaces, functional surfaces inspired by natural surfaces have a wide range of applications in healthcare. Nature-inspired surface structures have emerged as an effective and durable strategy to prevent bacterial infection, opening a new way to alleviate the problem of bacterial drug resistance. The present situation of bactericidal and antifouling surfaces with natural and biomimetic micro-/nano-structures is briefly reviewed. In addition, these innovative nature-inspired methods are used to manufacture a variety of artificial surfaces to achieve extraordinary antibacterial properties. In particular, the physical antibacterial effect of nature-inspired surfaces and the functional mechanisms of chemical groups, small molecules, and ions are discussed, as well as the wide current and future applications of artificial biomimetic micro-/nano-surfaces. Current challenges and future development directions are also discussed at the end. In the future, controlling the use of micro-/nano-structures and their subsequent functions will lead to biomimetic surfaces offering great potential applications in biomedicine.

Numerical investigation on energy absorption characteristics of impact-resistant lightweight structure of bio-mimetic micro aerial vehicle

With the increasing development of micro aerial vehicle, the impact resistance of the structure has gradually become a research hotspot. The beetle's exoskeleton not only provides important protection for its body and flexible wings but also ensures its good flight performance. Therefore, the beetle's exoskeleton has become an important research content in the field of bio-mimetic micro aerial vehicles. In this study, taking the internal structure of the beetle's exoskeleton as the research object, a kind of bio-mimetic lightweight thin-walled impact-resistant structure that can be used in the micro aerial vehicle is proposed. The energy absorption characteristics of the bio-mimetic structure under axial impact loading are calculated and analyzed by the numerical simulation method, and the important parameters such as impact angle, protective layer thickness, and wall thickness are optimized and discussed. The main results include that the filling method of the hollow column has a certain correlation with the energy absorption characteristics of the structure under different impact angles, and among the different cross-sectional shapes, the hollow column with a circular cross-sectional configuration has the best energy absorption ability. In addition, as the internal space of the structure increase exponentially, the decrease of specific energy absorption value of the bio-mimetic structure is relatively small. Finally, the wall thickness with good energy absorption characteristics is about 1.5 mm, while the preferred span length of the structure is between 90 and 120 mm.

Multi-objective design and optimization of wings

Nowadays, with the fast development of technology, aircrafts have been successful advanced. As we all know, wings are one of the most significant parts of the aircrafts, therefore, multi-objective design and optimization of wings has become a critical issue among many researchers. This paper mainly introduces several approaches to improve the wing in different conditions, including optimization design of civil airplanes, design and optimization of aircraft wing structure at low Reynolds numbers, Wing Design and Aerodynamic Characteristics of Biomimetic Flapping Wing Micro Air Vehicles and so on, the purpose of this article is to give a brief introduction to these relatively new research methods and make the public understand more about this field. The primary approaches of this article are literature analysis and review. This paper finds that algorithm and artificial intelligence are fundamental to improving wings, and all the design needs to reduce the amount of energy as much as possible, which is also the most important requirement.

Vortex dynamics and on the mechanism of vertical force enhancement in inclined stroke flapping wings

The rigorous numerical investigation of the class of inclined stroke plane flapping wings has brought to light the vertical force enhancement due to dipole jet interaction. In this study, the class of inclined stroke plane flapping wings with varying inter-plane distances and stroke inclinations are studied for vertical force generation. The configurations with stroke plane angles of 60° and 75° are found to produce significantly high vertical forces. Further, wake structures of the tandem flapping wing in an inclined stroke plane show various types of dipole vortex shedding and dipole jet interactions. The identified types of dipole jet interactions help in the understanding of vertical force trends of the forewing, hindwing, and hence the tandem wing configuration as a whole. It reveals the potential dipole jet interaction producing the highest vertical force in tandem wing configurations. In all, the study can classify the flows of the tandem wing configurations based on vortex shedding during hovering conditions and understand its vertical force enhancements. This not only helps in getting physical insights into the vortex dynamics of inclined stroke plane flapping wings but also in the design optimisation of the tandem wing configurations in biomimetic Micro Air vehicles (MAVs).

Bio-inspired optical structures for enhancing luminescence.

Luminescence is an essential signal for many plants, insects, and marine organisms to attract the opposite sex, avoid predators, and so on. Most luminescent living organisms have ingenious optical structures which can help them get high luminescent performances. These remarkable and efficient structures have been formed by natural selection from long-time evolution. Researchers keenly observed the enhanced luminescence phenomena and studied how these phenomena happen in order to learn the characteristics of bio-photonics. In this review, we summarize the optical structures for enhancing luminescence and their applications. The structures are classified according to their different functions. We focus on how researchers use these biological inspirations to enhance different luminescence processes, such as chemiluminescence (CL), photoluminescence (PL), and electroluminescence (EL). It lays a foundation for further research on the applications of luminescence enhancement. Furthermore, we give examples of luminescence enhancement by bio-inspired structures in information encryption, biochemical detection, and light sources. These examples show that it is possible to use bio-inspired optical structures to solve complex problems in optical applications. Our work will provide guidance for research on biomimetic optics, micro- and nano-optical structures, and enhanced luminescence.

12.1: Biomimetic micro structured flexible graphene pressure sensor and its application in wearable intelligent gloves

12.1: Biomimetic micro structured flexible graphene pressure sensor and its application in wearable intelligent gloves

Stone rubbing–inspired biomimetic multi–scale surface with highly robust superhydrophobicity

It has been widely recognized that the key issue limiting practical applications of superhydrophobic surfaces is the insufficient robustness. Combining robust microstructure and superhydrophobic material is an effective way to achieve robust superhydrophobicity. Mechanical robustness and superhydrophobicity are usually realized individually and sometimes cannot appear simultaneously in some local regions of the surface. Here, a stone rubbing–inspired strategy was explored to create biomimetic multi–scale surface (BMS) with highly robust superhydrophobicity. The strategy fused mechanical robustness and superhydrophobicity for the entire surface to be created, rather than realizing them individually. BMS was constructed on the substrate of cemented carbide considering the structure features of both honeycomb and lotus leaf. Biomimetic hexagonal recessed microstructures, biomimetic protrusion microstructures and biomimetic micro–/nano–structures layer were superimposed together to form BMS. The resulting BMS with stand protrusion microstructures (BMSS) and tilted protrusion microstructures (BMST) were analyzed to reveal the influences induced by the side length lm (260 μm to 350 μm) of the hexagon and the laser angle φ (110° to 140°). It was found that the strategy effectively synthesized the advantages and circumvented the disadvantages of the microstructures and the micro–/nano–structures layer. BMSS and BMST separately well maintained low-adhesive and high-adhesive superhydrophobicity under sandpaper abrasion, Taber abrasion, knife-scratch and tape peel. The abraded BMS was able to perform self-cleaning, resist slurry impact and manipulate water droplets. The proposed strategy can be extended to various combinations of materials with high wear resistance or low surface energy.

A Review on Fabrication and Application of Tunable Hybrid Micro–Nano Array Surfaces

AbstractThe wettability and adhesion of biological surfaces often depend on their periodically arranged hybrid micro–nano array structures. Various fabrication processes are designed to mimic biomimetic micro–nano array surfaces. This review summarizes the types of micro–nano array structures and analyzes fabrication methods based on top‐down and bottom‐up construction, including templating, etching, self‐assembly, and electrospinning/electrospraying. This review focuses on the shape reconfiguration of surface micro–nano array structures under physical stimuli, as well as the changes in material surface properties during the reconfiguration process. In addition, the applications of biomimetic micro–nano array composite surfaces in the fields of droplet transport, adhesion properties, sensors, and soft robotics are also discussed, and the current challenges and prospects in this field are identified.

Nature‐Inspired Biomimetic Surfaces for Controlling Bacterial Attachment and Biofilm Development

AbstractThe use of antibacterial and antifouling materials is widely being investigated to combat the increasing risk associated with bacterial infections and the evolution of drug‐resistant bacteria. Efficient antibacterial materials can be fabricated by mimicking the topography found on the surface of natural antibacterial materials. Natural materials such as the wings of cicadas and dragonflies have evolved to use the structural features on their surface to attain bactericidal properties. The nanopillars/nanospikes present on these natural materials physically damage the bacterial cells that settle on the nanostructures resulting in cell lysis and death. This article reviews the role of nanostructures found on the surface of some of these natural antibacterial and antifouling materials such as lotus leaf, cicadas and dragonflies wings, shark skin, and rose petals. These natural structures provide guidelines for the design of synthetic bio‐inspired materials. This review article also presents some novel fabrication techniques used to produce biomimetic micro‐ and nano‐structures on synthetic material surfaces. The role of size, shape, aspect ratio, and spacing between the micro/nano‐structures on the bactericidal properties is also discussed. Finally, the review is finished with the author's view on the future of the field.

Recent Advancements in Biological Microelectromechanical Systems (BioMEMS) and Biomimetic Coatings

Biomimetic micro- and nanotechnology have substantially grown in recent years, contributing to significant progress in the pharmaceutical and biomedical domains [...]

Bio-Inspired Micro- and Nanorobotics Driven by Magnetic Field.

In recent years, there has been explosive growth in the number of investigations devoted to the development and study of biomimetic micro- and nanorobots. The present review is dedicated to novel bioinspired magnetic micro- and nanodevices that can be remotely controlled by an external magnetic field. This approach to actuate micro- and nanorobots is non-invasive and absolutely harmless for living organisms in vivo and cell microsurgery, and is very promising for medicine in the near future. Particular attention has been paid to the latest advances in the rapidly developing field of designing polymer-based flexible and rigid magnetic composites and fabricating structures inspired by living micro-objects and organisms. The physical principles underlying the functioning of hybrid bio-inspired magnetic miniature robots, sensors, and actuators are considered in this review, and key practical applications and challenges are analyzed as well.

Design study of outboard wing incorporating MFC for a morphing vehicle

A novel biomimetic morphing micro aerial vehicle was designed using macro fiber composites (MFCs) as control actuators. The vehicle features variable-sweep, multi-curved wings, and a tail, both of which were embedded with MFC bimorphs. The wing design has a span of 1.1 m unswept (wings fully extended) and 0.65 m swept, resembling falcons (Falco Peregrinus). A design study was conducted on the outboard wing’s MFC and carbon fiber substrate orientation to enhance the roll authority of the wings when fully extended. Finite element modeling, wind tunnel testing, and flight testing were conducted to model and optimize the design to obtain linear aerodynamic control with given MFC deflections. In addition, this research explores several configurations to increase roll authority of MFCs using segmented and overlapped sections resembling avian feathers. An overlapped wing configuration was discovered to have the potential to increase roll authority at the expense of adverse yaw. Flight testing proved that MFC-actuated, continuous outboard wings provide sufficient roll authority and handling quality without added compensation for the non-linear behavior of MFCs. This research showed that MFCs can be incorporated into a morphing wing design for manual flight and autonomous flight through feedback from inertial sensors onboard the vehicle.

Nanogenerators integrated self-powered multi-functional wings for biomimetic micro flying robots

Under rigorous weight and power constraints, improving the energy systems and the onboard sensing approaches for flapping-wing micro air vehicles (FWMAVs) are monumental challenges. Mechanical energy transformation and integrated self-powered sensing hold great promising features to improve the flying performance of FWMAVs. Herein, we introduce novel triboelectric nanogenerators (TENGs) integrated multi-functional wings to address these challenges. Synthetically, The TENGs integrated wings can realize the mechanical energy transformation, the motion monitoring of flapping wings, and the pneumatic functions for FWMAVs. Firstly, a lightweight and ultra-thin sandwich structure integration technique with silk-fibroin film as the coated friction layer is realized for the TENGs integrated wings. Secondly, the wind tunnel test verifies the feasibility of the mechanical transformation and reveals the effects of the operating conditions of the FWMAVs on the triboelectric energy performance. The triboelectric energy performance of the TENGs integrated wings, whose entire thickness and the weight increases are less than 20 µm and 0.2 g respectively is verified to achieve 468.7 V voltage, 100.6 μA current, and 379.8 μW power. Likewise, as an attractive potential application, it is demonstrated to provide an accurate self-powered measurement of the flapping mechanism frequency based on the triboelectric principle. The aerodynamic measurements verify that the TENGs integrated wings maintain the pneumatic functions, which guarantee flight stability, and they positively enhance 29.89% of the onboard load of the FWMAV.

Smart acoustic 3D cell construct assembly with high-resolution

Precise and flexible three-dimensional (3D) cell construct assembly using external forces or fields can produce micro-scale cellular architectures with intercellular connections, which is an important prerequisite to reproducing the structures and functions of biological systems. Currently, it is also a substantial challenge in the bioengineering field. Here, we propose a smart acoustic 3D cell assembly strategy that utilizes a 3D printed module and hydrogel sheets. Digitally controlled six wave beams offer a high degree of freedom (including wave vector combination, frequency, phase, and amplitude) that enables versatile biomimetic micro cellular patterns in hydrogel sheets. Further, replaceable frames can be used to fix the acoustic-built micro-scale cellular structures in these sheets, enabling user-defined hierarchical or heterogeneous constructs through layer-by-layer assembly. This strategy can be employed to construct vasculature with different diameters and lengths, composed of human umbilical vein endothelial cells and smooth muscle cells. These constructs can also induce controllable vascular network formation. Overall, the findings of this work extend the capabilities of acoustic cell assembly into 3D space, offering advantages including innovative, flexible, and precise patterning, and displaying great potential for the manufacture of various artificial tissue structures that duplicate in vivo functions.

Aerodynamic Performance of a Dragonfly-Inspired Tandem Wing System for a Biomimetic Micro Air Vehicle.

The flying agility demonstrated by dragonflies is accomplished by means of complex aerodynamic forces produced by flapping their four wings arranged in a tandem configuration. The current study presents a novel tandem flapping wing mechanism for a biomimetic air vehicle that was designed and manufactured to experimentally investigate the aerodynamic forces. By optimizing the configuration and using spatial network analysis, it is shown that the designed structure can flap the wings in a linear up–down stroke motion and is capable of maintaining good consistency and aerodynamic performance. Such a mechanism could be used in a future biomimetic micro air vehicle (BMAV) design. The mechanism uses an electromagnetic actuator to flap the wings with a variable beat frequency (30–210 Hz) at various angles of attack (−10°–20°). The results show that the tandem wings generate approximately 50% higher lift than the forewing or hindwing pairs acting alone. Tandem wings also improve stability, which could potentially allow hovering.

Nanoimprinting of Biomimetic Nanostructures

Biomimetic micro- and nano- structures have attracted considerable interest over the last decades for various applications ranging from optics to life sciences. The complex nature of the structures, however, presents significant challenges for fabrication and their application in real-life settings. Nanoimprint lithography could provide an interesting opportunity in this respect. This article seeks to provide an overview of what has already been achieved using nanoscale replication technologies in the field of biomimetics and will aim to highlight opportunities and challenges for nanoimprinting in this respect in order to inspire new research.

A comparison of plunging- and pitching-induced deep dynamic stall on an SD7003 airfoil using URANS and LES simulations

Dynamic stall is a fluid dynamics phenomenon experienced by airfoils undergoing a rapid variation in their operating conditions, such as in the presence of pitching or plunging motions, when the effective angle of attack exceeds the static stall angle. The flow field near the airfoil is characterized by the presence of a strong clockwise vortex originating near the leading edge, which is convected downstream along the suction side, generating a low-pressure region and a continuous rise in lift. A controlled form of dynamic stall is involved in the flight mechanism of some natural flapping-wing flyers, and this is currently a matter of interest for the design of biomimetic micro aerial vehicles. Dynamic stall is also responsible for limitations in helicopters' forward-flight velocity, it can lead to flutter in fixed-wing aircraft and vibration-induced damage in wind turbine blades. In this work, 2D URANS and LES numerical simulations have been carried out for incompressible dynamic stall flow cases over an SD7003 airfoil at a Reynolds number of 6⋅104 and at a reduced frequency of 0.25, with the aim of assessing the validity and the role of low fidelity simulations in dynamic stall prediction, at operating conditions relevant for micro air vehicles. Simulations have been conducted both in the case of periodic pitching and plunging, in order to investigate similarities and differences in the resulting flow fields and aerodynamic coefficients. The effect of the reduced frequency on the agreement between 2D URANS and LES has also been evaluated for an airfoil under periodic plunging.

Biomimetic Aligned Micro-/Nanofibrous Composite Membranes with Ultrafast Water Transport and Evaporation for Efficient Indoor Humidification.

Humidifying membranes with ultrafast water transport and evaporation play a vital role in indoor humidification that improves personal comfort and industrial productivity in daily life. However, commercial nonwoven (NW) humidifying membranes show mediocre humidification capability owing to limited wicking capacity, low water absorption, and relatively less water evaporation. Herein, we report a biomimetic micro-/nanofibrous composite membrane with a highly aligned fibrous structure using a humidity-induced electrospinning technique for high-efficiency indoor humidification. Surface wettability and roughness are also tailored to achieve a high degree of superhydrophilicity by embedding hydrophilic silicon dioxide nanoparticles (SiO2 NPs) into the fiber matrix. The synergistic effect of the highly aligned fibrous structure and surface wettability endows composite membranes with ultrafast water transport and evaporation. Strikingly, the composite membrane exhibits an outstanding wicking height of 19.5 cm, a superior water absorption of 497.7%, a fast evaporation rate of 0.34 mL h-1, and a relatively low air pressure drop of 14.4 Pa, thereby achieving a remarkable humidification capacity of 514 mL h-1 (57% higher than the commercial NW humidifying membrane). The successful synthesis of this biomimetic micro-/nanofibrous composite membrane provides new insights into the development of micro-/nanofibrous humidifying membranes for personal health and comfort as well as industrial production.

Dynamic Stability and Flight Control of Biomimetic Flapping-Wing Micro Air Vehicle

This paper proposes an approach to analyze the dynamic stability and develop trajectory-tracking controllers for flapping-wing micro air vehicle (FWMAV). A multibody dynamics simulation framework coupled with a modified quasi-steady aerodynamic model was implemented for stability analysis, which was appended with flight control block for accomplishing various flight objectives. A gradient-based trim search algorithm was employed to obtain the trim conditions by solving the fully coupled nonlinear equations of motion at various flight speeds. Eigenmode analysis showed instability that grew with the flight speed in longitudinal dynamics. Using the trim conditions, we linearized dynamic equations of FWMAV to obtain the optimal gain matrices for various flight speeds using the linear-quadratic regulator (LQR) technique. The gain matrices from each of the linearized equations were used for gain scheduling with respect to forward flight speed. The reference tracking augmented LQR control was implemented to achieve transition flight tracking that involves hovering, acceleration, and deceleration phases. The control parameters were updated once in a wingbeat cycle and were changed smoothly to avoid any discontinuities during simulations. Moreover, trajectories tracking control was achieved successfully using a dual loop control approach. Control simulations showed that the proposed controllers worked effectively for this fairly nonlinear multibody system.

Thermal analysis of double diffusive electrokinetic thermally radiated TiO2-Ag/blood stream triggered by synthetic cilia under buoyancy forces and activation energy

Second law analysis of double diffusive cilia endorsed transport of thermally radiated hybrid nanofluid through an electroosmotic pump is deliberated in this study. Joint effects of applied Lorentz force, activation energy and Joule heating on the proposed stream are also examined. Channel inner surface is shielded with artificial cilia carpet that ensures flow induction and micro-mixing activity in the fluid. After applying the lubrication and the Debye-Huckel estimations, numerical solutions of the envisioned problem are calculated. The analysis reveals that the elevated electric potential and prolonged cilia assist directional flow spreads over large distances. The augmentation in fluid stream is seen near the channel surface for higher electroosmotic parameter. Presence of activation energy input and thin electric double layer supports mass dispersion and control heat indulges. The present model provides an immediate understanding about the promising role of fabricated cilia in electroosmotic pumps for the future biomimetic micro and nanofluidic devices.