Bio-inspired Micro Research Articles

From conventional to bioinspired: Evolution of tail surface designs in micro air vehicles

The paper presents the evolution of the tail surface design of a micro air vehicle based on adaptive wing geometry. The initial prototype was conceived as a tailless aircraft geometry, waiting for future innovations and stability augmentations. An initial experimental test bench will be presented to characterize the variation of wing profile curvature as a function of the voltage, through MFC actuators. Once these results have been analyzed, the process of conceiving a conventional T-tail was initiated, ultimately evolving toward the proposal of a bioinspired tail based on the tail shape of various birds. The results obtained in wind tunnel tests using PIV techniques will be presented. The results validate the selected tail surface design as an appropriate geometry for a bioinspired micro air vehicle.

Bio-Inspired Micro- and Nano-Scale Surface Features Produced by Femtosecond Laser-Texturing Enhance TiZr-Implant Osseointegration.

Surface design plays a critical role in determining the integration of dental implants with bone tissue. Femtosecond laser-texturing has emerged as a breakthrough technology offering excellent uniformity and reproducibility in implant surface features. However, when compared to state-of-the-art sandblasted and acid-etched surfaces, laser-textured surface designs typically underperform in terms of osseointegration. This study investigates the capacity of a bio-inspired femtosecond laser-textured surface design to enhance osseointegration compared to state-of-the-art sandblasted & acid-etched surfaces. Laser-texturing facilitates the production of an organized trabeculae-like microarchitecture with superimposed nano-scale laser-induced periodic surface structures on both 2D and 3D samples of titanium-zirconium-alloy. Following a boiling treatment to modify the surface chemistry, improving wettability to a contact angle of 10°, laser-textured surfaces enhance fibrin network formation when in contact with human whole blood, comparable to state-of-the-art surfaces. In vitro experiments demonstrate that laser-textured surfaces significantly outperform state-of-the-art surfaces with a 2.5-fold higher level of mineralization by bone progenitor cells after 28 days of culture. Furthermore, in vivo evaluations reveal superior biomechanical integration of laser-textured surfaces after 28 days of implantation. Notably, during abiological pull-out tests, laser-textured surfaces exhibit comparable performance, suggesting that the observed enhanced osseointegration is primarily driven by the biological response to the surface.

Design of Three Elements Lotus Leaf Shape Wideband Antenna for Wireless Communication Applications

The work presents a three-elements lotus leaf-shaped wideband antenna (BIMS) designed for wireless communication applications. The antenna's size is reduced without compromising performance. The BIMS uses bio-inspired shapes like leaves, trees, animals, or insects as preference. The antenna is simulated using fiberglass laminate (FR4) as a substrate, offering maximum gain and occupying less area compared to conventional patch antennas. The work demonstrates the potential of BIMS in reducing antenna size without compromising performance. Key Words: BIMS (Bio-inspired Micro Strip), Antenna, Size, Shape, Work

The role of bio-inspired micro-/nano-structures in flexible tactile sensors

This review focuses on the development of tactile sensors for parameters such as pressure, strain and integration of multiple functions. The application prospect of bionic sensors in e-skin, human–computer interaction, and bionic robots is envisioned.

Laser texturing of additively manufactured implants: A tool to programme biological response

The advent of additive manufacturing (AM) is rapidly shaping healthcare technologies pushing forward personalisation and enhanced implant functionalisation to improve clinical outcomes. AM techniques such as powder bed fusion (PBF) have been adopted despite the need to modify the as-built surface post manufacture. Medical device manufacturers have focused their efforts on refining various physical and chemical surface finishing approaches, however there is little consensus and some methods risk geometry alteration or contamination. This has led to a growing interest in laser texturing technologies to engineer the device surface. Herein, several bioinspired micro and nano textures were applied to laser PBF Ti-6Al-V4 substrates to alter physicochemical properties and in-turn we sought to understand what influences these alterations had on a human osteosarcoma cell line (MG63). Significant variations in roughness and time dependent contact angles were revealed between different patterns provide a tool to elicit desired biological responses. All surface treatments effectively enhanced early cell behaviour and in particular coverage was increased for the micro-textures. Influence of the patterns on cell differentiation was less consistent with alkaline phosphatase content increased only for the channel, grid and dual textures. While long term (21 days) mineralisation was found to be significantly enhanced in grids, dual, triangles and shark skin textures. Further regression analysis of all physicochemical and biological variables indicated that several properties should be used to strongly correlate cell behaviour, resulting in 82 % of the 21 day mineralisation dataset explained through a combination of roughness kurtosis and glycerol contact angle. Overall, this manuscript demonstrates the ability of laser texturing to offer tailored cell-surface interactions, which can be tuned to offer a tool to drive functional customisation of anatomically customised medical devices.

Aerodynamic Exploration on Rough Airfoil Based on Overlapping Feathers of a Swift-Wing Structure

To investigate the flow mechanism of feather-like rough airfoils based on swift wings, computational simulations were employed to explore their overall aerodynamic characteristics in comparison to equivalent smooth airfoils. The study focused on angles of attack ranging from 0° to 20° at low Reynolds numbers. The results reveal that the rough airfoil exhibits higher lift and lower drag compared to the smooth airfoil at moderate angles of attack ranging from 6° to 10°, resulting in significantly improved aerodynamic efficiency. Notably, at an angle of attack of 8°, the aerodynamic efficiency is increased by 19%. However, at angles of attack smaller than 6°, the increase in drag outweighs the increase in lift, leading to lower aerodynamic efficiency for the rough airfoil. Conversely, when the angle of attack exceeds 16°, both airfoils experience separated flow-dominated flow fields, resulting in comparable effective aerodynamic shapes and similar aerodynamic efficiencies. Furthermore, the study found that increasing the Reynolds number results in greater pressure differences in the flow field, leading to higher aerodynamic efficiency. These preliminary conclusions are valuable for elucidating the flight mechanisms of bird-feather-like wings and can inform the design or morphing design of bio-inspired micro aerial vehicles in the near future.

Performance enhancement of a bioinspired micro air vehicle by integrating a smart composite in its morphing wing

The purpose of this paper is to show the advantages of using a smart composite in a micro air vehicle (MAV) equipped with morphing wing technology. A Macro Fiber Composite (MFC) actuator is attached to the wing’s bottom surface to modify the wing camber during the mission. This material allows the MAV to be optimized according to each flight, thus making it more versatile and attractive to the market. The elongation of the lower surface when a positive voltage is applied to the actuator is translated to an increment in camber, which results in an increment in the maximum lift coefficient, thus enabling the vehicle to fly slower to adapt to any payload. Besides, a reduction in camber results in an increase in aerodynamic efficiency, which improves range and endurance. Several tests of the MAV at prototype level have been carried out at INTA, so as to demonstrate the feasibility of implementing MFC actuators to control and manoeuvre these vehicles. The use of this material in aerospace industry opens up various fields of research in aerospace engineering, such as new features in flight mechanics and aerodynamic performance and new strategies in the design of flight stability and control laws.

Bio-inspired micro area concentrated array assisted perovskite photodetector toward weak light imaging

A perovskite photodetector with bio-inspired micro area concentrated structures has been fabricated for weak light imaging. The photodetector exhibits high detectivity (1.37 × 1013Jones), and it can achieve weak light imaging under 0.64 μW cm−2.

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 of Non-Conventional Flight Control Systems for Bioinspired Micro Air Vehicles

This research focuses on the development of two bioinspired micro air vehicle (MAV) prototypes, based on morphing wings and wing grid wingtip devices. The morphing wings MAV tries to adapt the aerodynamics of the vehicle to each phase of flight by modifying the vehicle geometry, while the wing grid MAV aims to minimize the aerodynamic and weight penalty of these vehicles. This work focuses on the design methodology of the flight control system of these MAVs. A preliminary theoretical conceptual design was used to verify the requirements, wind tunnel tests were performed to determine aerodynamic characteristics, and suitable materials were selected. The hardware and software configuration designed for the control system, which fulfills the objective of adaptive and optimal control in the wingtip-based prototype of the wing grid, is described. Finally, the results of the flight control on the prototype MAVs are analyzed.

Fabrication of an ordered micro-/nanotextured titanium surface to improve osseointegration

Ordered microscale titanium (Ti) surface topography with homogeneous cell-sized microholes (20 µm in diameter) was fabricated using simple electrochemical etching. The as-prepared surface imposed with uniform titania nanotubes (TNTs, 70 nm in diameter) through electrochemical anodization showed no considerable change in the initial microscale morphology. Bone marrow mesenchymal stem cells (BMSCs) were used in evaluating the bioactivity. Compared with polished Ti and unordered microtextured Ti, the ordered microtextured Ti formed by electrochemical etching remarkably promoted cell attachment, alkaline phosphatase activity, collagen secretion, extracellular matrix mineralization, and osteogenesis-related gene expression but considerably inhibited cell proliferation. After TNTs were introduced to the ordered microtextured Ti, cell attachment and osteogenic differentiation indexes were further enhanced, and cell proliferation recovered over time. The ordered micro-/nanotextured Ti surface was more conducive to the cell attachment, proliferation, and osteogenesis of BMSCs than polished Ti with and without TNTs, unordered microtextured Ti with and without TNTs, and unitary ordered microtextured Ti. Thus, the novel ordered bio-inspired micro-/nanotextured structure composed of cell-sized microholes and TNTs on the Ti surface possessed a favorable interfacial environment that improved osseointegration, potentially optimizing Ti implant surface topography.

The function of pitching in Beetle's flight revealed by insect-wearable backpack

The study of insect flight orientation is important for investigating flapping-wing aerodynamics and designing bioinspired micro air vehicles (MAVs). Pitch orientation plays a vital role in flight control, which has been explored less than directional control. In this study, the role of pitching maneuvers in flight was revealed by mounting an insect-wearable backpack on a beetle, which transformed the live insect into a bioelectronic device. The flight status of the cyborg beetle in a large chamber was recorded wirelessly. Accordingly, the pitch angle and forward acceleration showed a strong linear relationship. The coupling of pitch angle and forward acceleration was due to a tilted net aerodynamic force and the induced air drag. Moreover, the left and right subalar muscles of the beetle, a pair of major flight muscles, were electrically stimulated in free flight on demand to pitch up the beetle's body. We demonstrated that the induced nose-up movements were effective for decelerating the beetle in air. The flight orientation findings from the flying cyborgs would inspire a new approach to the study of flapping-wing flight and control of flapping-wing MAVs.

Study on piezo-electric flapping wing mechanism for bio-inspired micro aerial vehicles

The Micro Aerial Vehicle (MAV) with a flapping wing configuration is much more efficient and capable of generating substantial lift at low flight speeds and has excellent maneuverability. Different motor-driven mechanisms have been developed to mimic this flapping motion, but these mechanisms introduced mechanical complexity and heavy weight to the system. Piezo-electric based mechanisms have been used to solve these problems, but provide very small flapping amplitudes within the size limitation of MAVs. So some kind of amplification mechanism is needed. In this paper, a flexible wing is created by attaching a polymer skin to a pair of carbon fiber reinforced plastic spars. This wing is connected by means of an elastic-element (EE) to a pair of piezoelectric unimorphs (piezofan). The motion from the piezofan to the wing is transferred through this EE. Simulation has been done by applying sinusoidal voltages of varying frequency to this piezofan and observations have been made for the flapping amplitude of the wing for different stiffness of the EE. It is observed that the amplitude of the peak flapping amplitude initially increases, attains a maximum value, then decreases again with an increase in the stiffness of the EE. It is also observed that as the EE stiffness increases, the corresponding peak of the flapping amplitude shifts towards higher frequency.

Graphene-based PANI composite coatings with fine-controllable 3D hierarchical structures prepared from bio-inspired photo-/colloidal-lithography technique for flexible supercapacitor application

In this study, various bio-inspired micro-/nano-scaled cylindrical patterns were designed by controlling their width and interspacing over a silicon substrate by using 3D photo/colloidal lithography techniques. The surface morphology and cross-sectional images confirmed the exact fabrication of bio-inspired textures. The as-prepared bio-inspired surface textures were coated with polydimethylsiloxane as a soft negative template and then covered with polyaniline (PANI) to investigate the morphology effect in supercapacitor application. Results showed that the bio-inspired texture with micro-/nano-architectured surface of two different widths and interspacing of 5 µm and 500 nm provided the best PANI capacitance performance of 429 F/g amongst other single and non-patterned (plain) templates with capacitance performances of 364 and 316 F/g, respectively, at 5 mV/s. Moreover, reduced graphene oxide was successfully incorporated into PANI; characterised using Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and transmission electron microscopy; and investigated for supercapacitor performance by using the bio-inspired micro/nano-template. A synergistic performance of 614 F/g was observed at 1 A/g with excellent capacitive retention of 85% after 10,000 cycles. Efficient flexibility was also found over long-term cycling without defects in the performance. Thus, these novel bio-inspired electrodes could open the door for developing further portable bio-inspired electronic devices in the future.

Numerical and Experimental Study of Aerodynamic Performances of a Morphing Micro Air Vehicle

The present work is focused on the investigation of the aerodynamic performances of a novedous bioinspired morphing Micro Air Vehicle (MAV) with an adaptive wing structure geometry. For this purpose, a numerical study of Computational Fluid Dynamics (CFD) implemented by Ansys Fluent 15.0 was performed in order to obtain insight about the aerodynamic effect of wing structure deformation when morphing devices are used, and its influence on the global aerodynamic parameters related with aircraft performances. On the other hand, an experimental study using the Particle Image Velocimetry technique and balance measurements in a Low-Speed Wind Tunnel was conducted to obtain experimental information about performances measured to establish a comparison between both, experimental and numerical results. The Micro Air Vehicle (MAV) presents a Zimmerman wing with an Eppler 61 airfoil. Three different wing configurations according to curvature and thickness variations and for all angles of attack have been studied. A comparative analysis based on aerodynamic features is performed by an assessment of lift coefficient (CL), total aerodynamic drag coefficient (CD) and aerodynamic efficiency as lift/drag ratio (CL/CD) in order to conclude the best wing configuration in terms of aerodynamic performance.

Numerical and Experimental Analysis of 3D Micro-Corrugated Wing in Gliding Flight

Abstract In this study, computational fluid dynamics analysis was performed on a three-dimensional model of a Libellulidae wing to determine aerodynamic performance in gliding flight. The wing is comprised of various corrugated features alongside the spanwise and chordwise directions, as well as twist. The detailed features of real 3D dragonfly wing models, including all the corrugations through both span and chord, have not been considered in the past for a detailed aerodynamic analysis. The simulations were conducted by solving the Navier-Stokes equations to demonstrate gliding performance over a range of angles of attack at low Reynolds numbers. The numerical model was validated against experimental data obtained from a fabricated corrugated wing model using particle image velocimetry. The numerical results demonstrate that bio-inspired wings with corrugations compared to flat profile wings generate more lift with lower drag, trapping the vortices in the valleys of wing corrugation leading to delayed flow separation and delayed stall. The experimental and numerical results demonstrate that the methodology presented in this study can be used to measure bio-inspired 3D wing flow characteristics, including the influence of complex corrugations on aerodynamic performance. These findings contribute to the advancement of knowledge required for designing an optimized bioinspired micro air vehicle.

Remote radio control of insect flight reveals why beetles lift their legs in flight while other insects tightly fold

In the research and development of micro air vehicles, understanding and imitating the flight mechanism of insects presents a viable way of progressing forward. While research is being conducted on the flight mechanism of insects such as flies and dragonflies, research on beetles that can carry larger loads is limited. Here, we clarified the beetle midlegs' role in the attenuation and cessation of the wingbeat. We anatomically confirmed the connection between the midlegs and the elytra. We also further clarified which pair of legs are involved in the wingbeat attenuation mechanism, and lastly demonstrated free-flight control via remote leg muscle stimulation. Observation of multiple landings using a high-speed camera revealed that the wingbeat stopped immediately after their midlegs were lowered. Moreover, the action of lowering the midleg attenuated and often stopped the wingbeat. A miniature remote stimulation device (backpack) mountable on beetles was designed and utilized for the free-flight demonstration. Beetles in free flight were remotely induced into lowering (swing down) each leg pair via electrical stimulation, and they were found to lose significant altitude only when the midlegs were stimulated. Thus, the results of this study revealed that swinging down of the midlegs played a significant role in beetle wingbeat cessation. In the future, our findings on the wingbeat attenuation and cessation mechanism are expected to be helpful in designing bioinspired micro air vehicles.

Biocompatible and Bio-Inspired Micro- and Nano-Structures for Nanotheranostics

Biocompatible and Bio-Inspired Micro- and Nano-Structures for Nanotheranostics

Advancing of Additive-Manufactured Titanium Implants with Bioinspired Micro- to Nanotopographies.

There is an increasing demand for low-cost and more efficient titanium (Ti) medical implants that will provide improved osseointegration and at the same time reduce the likelihood of infection. In the past decade, additive manufacturing (AM) using metal selective laser melting (SLM) or three-dimensional (3D) printing techniques has emerged to enable novel implant geometries or properties to overcome such potential challenges. This study presents a new surface engineering approach to create bioinspired multistructured surfaces on SLM-printed Ti alloy (Ti6Al4V) implants by combining SLM technology, electrochemical anodization, and hydrothermal (HT) processes. The resulting implants display unique surfaces with a distinctive dual micro- to nano-topography composed of micron-sized spherical features, fabricated by SLM and vertically aligned nanoscale pillar structures as a result of combining anodization and HT treatment. The fabricated implants enhanced hydroxyapatite-like mineral deposition from simulated body fluid (SBF) compared to control. In addition, normal human osteoblast-like cells (NHBCs) showed strong adhesion to the nano-/microstructures and displayed greater propensity to mineralize compared to control surfaces. This engineering approach and the resulting nature-inspired multiscale-structured surface offers desired features for improving osseointegration and antibacterial performance toward the development of next-generation orthopedic and dental implants.

Energy absorbed ability and damage analysis for honeycomb sandwich material of bio-inspired micro aerial vehicle under low velocity impact

Because of the advantages of light weight, small size, and good maneuverability, the bio-inspired micro aerial vehicle has a wide range of application prospects and development potential in military and civil areas, and has become one of the research hotspots in the future aviation field. The beetle’s elytra possess high strength and provide the protection of the abdomen while being functional to guarantee its flight performance. In this study, the internal microstructure of beetle’s elytra was observed by scanning electron microscope (SEM), and a variety of bionic thin-walled structures were proposed and modelled. The energy absorption characteristics and protective performance of different configurations of thin-walled structures with hollow columns under impact loading was analyzed by finite element method. The parameter study was carried out to show the influence of the velocity of impactor, the impact angle of the impactor and the wall thickness of honeycomb structure. This study provides an important inspiration for the design of the protective structure of the micro aerial vehicle.