Nature creatures have evolved excellent receptors, such as sensory hairs in arthropods, lateral line system of fishes. Researchers inspired by nature creatures have developed various mechanical sensors. Here, we provide an overview on the development of Artificial Hair-Like (AHL) sensors based on the inspiration of hair flow sensory receptors, especially sensory hairs in arthropods and lateral line systems of fishes. We classify the developed AHL sensors into several categories according to the operating principles they based on, for example, piezoresistive and piezoelectric effects. The current challenges and existing problems in the development of AHL sensors are also present, which were primarily restricted by the exploratory tools of sensing mechanism of creatures and current manufacturing technologies. In future, more efforts are required in order to further improve the performance of AHL sensors. We expect that intelligent multi-functional AHL sensors can be applied not only in applications like navigation of underwater automatic vehicles, underwater search and rescue, tap-water metering, air monitoring and even in medicare, but also potentially be used in space robots to detect complex to-pography.

Three-dimensional (3D) printing is a novel process used to manufacture bone tissue engineered scaffolds. This process allows for easy control of the architecture at the micro structure. However, the scaffold properties are typically limited in terms of cellular activity at the scaffold surface due to the printed materials properties. In this study, we developed a polycaprolactone (PCL) blended with polyeth-ylene glycol (PEG) 3D printed scaffold using a rapid prototyping system. The manufactured scaffolds were then washed out to form small pores on the surface in order to improve the scaffolds hydrophilicity. We analyzed the resultant material by using Scanning Electron Microscopy (SEM), water absorption, water contact angle, in vitro WST-1, and the Bradford assay. Additionally, cells incubated on the fabricated scaffolds were visualized by Confocal Laser Scanning Microscopy (CLSM). The developed scaffolds exhibited small pores on the strand surface which served to increase hydrophilicity as well as improve cellular proliferation and increase total protein content. Our findings suggest that the presence of small pores on the scaffolds can be used as an effective tool for improving implant cellular interaction. This research indicates that these modified scaffolds can be considered useful for bone tissue engineering applications to improve human health.

Custom-made pelvic prostheses are normally employed to reconstruct the biomechanics of the pelvis for improving patient’s life quality. However, due to the large demand of biomechanical performance around the pelvic system, the customized prosthesis needs to be studied for its strength and stability. A hemi-pelvic finite element model, including a custom-made prosthesis and the surrounded main ligaments, was created to study the strength and stability of the system. Based on the developed finite element model, the relationship between the pre-stress of the screws and the biomechanical performance of the reconstructed pelvis was investigated. Results indicate that the pre-stress should not exceed 1000 N during surgery in order to prevent fatigue fractures from happening to screws. Moreover, four screws were removed from the pelvic system without affecting the fixing stability of the system, which provide surgical guidance for surgeons in terms of safety and fixation.

Hybrid wetting surfaces have been developed to enhance condensation heat transfer, water collection and seawater desalination, due to the advantages of high droplet nucleation efficiency and excellent removal effect. However, there are still many difficulties to overcome before a simple, operable and low-cost system can be exploited in large-scale practical applications. In the present report, an applicable way to fabricate sprayable hybrid wetting coatings mixed with superhydrophobic and hydrophilic particles is described. Conventional condensation tests are carried out for comparison of the nucleation, growth, coalescence and ejection behaviors of dewdrops on a hybrid wetting surface with different hydrophilic particles. Test results showed that a hybrid wetting surface with superhydrophobic and hy-drophilic particles has a higher drop number density than a homogeneous superhydrophobic surface has. As expected, this advantage was exhibited also in the water collection test.

The aim of this study is to investigate the effect of the contents of modified 3, 4-dihydroxyphenyl-L-alanine (DOPA), named as do-pamine methacrylamide (DMA), on the adhesion of mussel-inspired adhesives in air and water. A series of adhesives, p(DMA-co-MEA), were synthesized by copolymerized DMA and methoxy ethylacrylate (MEA) with the content of DMA from 2 mol.% to 10 mol.%. Results of 1H NMR show that the contents of DMA in all adhesives are near to the theory ratios of DMA in the staring reagents. Adhe-sives with more than 5 mol.% of DMA appear adhesion, while adhesives with 2 mol. % and 3 mol. % of DMA show almost no adhesion in air and water. Adhesive with 7 mol.% of DMA has the highest molecular weight and adhesion either in air or in water in all adhesives. Adhesion of adhesive is synergistically influenced by the content of DMA, molecular weight and elastic modulus of adhesive. It is because that higher content of DMA would provide more DOPA, which leads to the coordination bond between DOPA and metal ions. It is feasible to develop the mussel-inspired adhesive through incorporating DMA into polymers, which will have potential application in the clinic.

Water snails developed a distinct appendage, the operculum, to better protect the body against predators. When the animal is active and crawling, part of the underside of the shell rests on the outer surface of the operculum. We observed the water snails (Pomacea ca-naliculata) spend ~3 hours per day foraging, and the relative angular velocity between the shell and operculum can reach up to 10 ?•s−1, which might inevitably lead to abrasion on the shell and operculum interface. However, by electron microscopy images, we found that the underside of the shell and outer surface of the operculum is not severely worn, which indicates that this animal might have a strategy to reduce wear. We discovered the superimposed rings distributed concentrically on the surface, which can generate micro-grooves for a hydrodynamic lubrication. We theoretically and experimentally revealed the mechanism of drag reduction combing the groove geometry and hydrodynamics. This textured operculum surface might provide a friction coefficient up to 0.012 as a stability-resilience, which protects the structure of the snail’s shell and operculum. This mechanism might open up new paths for studies of micro-anti-wear struc-tures used in liquid media.

It is known that the tribological behaviors of snake skins are contributed by the synergistic action of multiple factors, such as surface morphology and mechanical properties, which has inspired fabrication of scale-like surface textures in recent years. However, the coupling effect and mechanism remain to be elucidated. In this work, the morphology and mechanical properties of the scales from different body sections (leading body half, middle trunk and tailing body half) and positions (dorsal, lateral and ventral) of Boa constrictor and Eryx tataricus were characterized and compared to investigate the corresponding effects on the tribological behaviors and to probe the possible coupling mechanism. The morphological characterizations of scanning electron microscopy and atomic force microscopy revealed sig-nificant differences between the two species that the scales from Boa constrictor are rougher in general. The mechanical properties measured by nanoindentation corroboratively demonstrated substantial differences in elastic modulus and hardness. Interestingly, the ventral scales with lower surface roughness, together with relatively larger elastic modulus and hardness, manifest higher friction coeffi-cients. A “double-crossed” hypothesis was proposed to explain the observed coupling effect of morphology and mechanical properties on friction, which may afford valuable insights for the design of bionic surface with desirable tribological performance.

Flight stabilization in insects is normally achieved through a closed-loop system integrating the internal dynamics and feedback control. Recent studies have reported that flight instability may exist in most flying insects but how insects achieve the flight stabilization still remains poorly understood. Here we propose a control model specified for bumblebee hovering stabilization by applying a three-axis PD (proportional-derivative)-controller to a free-flying bumblebee computational model with six Degrees of Freedom (DoFs). Morpho-logical and kinematic models of a realistic bumblebee in hovering are built up based on measurements whereas a versatile bio-inspired dynamic flight simulator is employed in simulations. A simplified flight dynamic model is further developed as a fast model for control parameter tuning. Our results demonstrate that the stabilizing control model is capable of achieving the hovering stabilization with small perturbations in terms of 6-DoF, implying that the simplified linear algorithms can still work reasonably for bumblebee hovering. A further sensitivity analysis of the control parameters reveals that yaw control via manipulating pitch angle of the wing is mostly sensitive, im-plicating that bumblebee may utilize alternative yaw control strategies.

Flap-bounding, a form of intermittent flight, is often exhibited by small birds over their entire range of flight speeds. Its purpose is unclear during low to medium speed (2 m•s−1 – 8 m•s−1) flight: aerodynamic models suggest continuous flapping would require less power output and lower cost of transport. To explore its functional significance at low speeds, we measured body trajectory and kinematics of wings and tail of two zebra finches (Taeniopygia guttata) during flights between two perches in a laboratory. The flights consisted of three phases: initial, descending and ascending. Zebra finch first accelerated using continuous flapping, then descended, featuring intermittent bounds. The flight was completed by ascending using nearly-continuous flapping. When exiting bounds in descending phase, they achieved higher velocity than that of pre-bound forward by swinging their body forward similar to pendular motion with conserved me-chanical energy. We recorded takeoffs of three black-capped chickadees (Poecile atricapillus) in the wild and also found similar kine-matics. Our modeling of power output indicated finch achieved higher velocity (13%) with lower cost of transport (9%) when descending, compared with continuous flapping in previously studied pigeons. Flap-bounding could be useful for unmanned aerial vehicle design by mimicking descending flight to achieve rapid take-off and transition to forward flight.

Semi-aquatic arthropods skate on water surfaces with synergetic actions of their legs. The sculling forward locomotion of water striders was observed and analyzed in situ to understand and reproduce the abovementioned feature. The bright–edged elliptical shadows of the six legs of a water strider were recorded to derive the supporting force distributions on legs. The propulsion principles of water striders were quantitatively disclosed. A typical sculling forward process was accomplished within approximately 0.15 s. Water striders lifted their heads slightly and supported their weight mainly by the two driving legs to increase the propulsion force and reduce the water resistance during the process. The normalized thrust–area ratio (defined as the ratio of the propulsion force to the projected area) was usually lower than 0.4 after sculling for approximately 0.08 s. The entire normal supporting force remained nearly constant during a stroke to reduce the mass center fluctuation in the normal direction. In addition, water striders could easily control the locomotion direction and speed through the light swinging of the two hind legs as rudders. These sculling principles might inspire sophisticated biomimetic wa-ter-walking robots with high propulsion efficiency in the future.

Cilia are finger-like cell-surface organelles that are used by certain varieties of aquatic unicellular organisms for motility, sensing and object manipulation. Initiated by internal generators and external mechanical and chemical stimuli, coordinated undulations of cilia lead to the motion of a fluid surrounding the organism. This motion transports micro-particles towards an oral cavity and provides motile force. Inspired by the emergent properties of cilia possessed by the pond organism P. caudatum, we propose a novel smart surface with closed-loop control using sensor-actuators pairings that can manipulate objects. Each vibrating motor actuator is controlled by a localised microcontroller which utilises proximity sensor information to initiate actuation. The circuit boards are designed to be plug-and-play and are infinitely up-scalable and reconfigurable. The smart surface is capable of moving objects at a speed of 7.2 millimetres per second in forward or reverse direction. Further development of this platform will include more anatomically similar biomimetic cilia and control.

In this paper, a miniaturized bionic electronic nose system is developed in order to solve the problems arising in oil and gas detection for large size and inflexible operation in downhole. The bionic electronic nose chamber is designed by mimicking human nasal turbinate structure, V-groove structure on shark skin surface and flow field distribution around skin surface. The sensitivity of the bionic electronic nose system is investigated through experimentation. Radial Basis Function (RBF) and Support Vector Machines (SVM) of 10-fold cross validation are used to compare the recognition performance of the bionic electronic nose system and common one. The results show that the sensitivity of the bionic electronic nose system with bionic composite chamber (chamber B) is significantly improved compared with that with common chamber (chamber A). The recognition rate of chamber B is 4.27% higher than that of chamber A for the RBF algorithm, while for the SVM algorithm, the recognition rate of chamber B is 5.69% higher than that of chamber A. The three-dimensional simulation model of the chamber is built and verified by Computational Fluid Dynamics (CFD) simulation analysis. The number of vortices in chamber B is fewer than that in chamber A. The airflow velocity near the sensors inside chamber B is slower than that inside chamber A. The vortex intensity near the sensors in chamber B is 2.27 times as much as that in chamber A, which facilitates gas molecules to fully contact with the sensor surface and increases the intensity of sensor signal, and the contact strength and time between odorant molecules and sensor surface. Based on the theoretical investigation and test validation, it is believed that the proposed bionic electronic nose system with bionic composite chamber has potential for oil and gas detection in downhole.

Inspired by the coupling phenomena in biological systems, to improve the solid particle erosion resistance of Thermal Barrier Coatings (TBCs), different kinds of bionic units were made on the coating surfaces using Bionic Coupled Laser Remelting (BCLR) process. The NiCoCrAlYTa/ZrO2–7wt%Y2O3 double-layer structured TBCs were prepared by air plasma spraying. The microstructure, microhardness and phase composition of the as-sprayed and bionic specimens were examined. The solid particle erosion behaviors of bionic specimens as function of bionic unit shape were investigated. The results indicated that the bionic specimens had better erosion resistance than the as-sprayed specimen. The specimen with striation and grid bionic units had the better erosion resistance, while the dot showed the worse. The bionic units were characterized by the dense columnar crystal structure and the high hardness, which are the main reasons for improving the erosion resistance. Under the synergistic action of the shear stress and normal stress on the protrusive coating surface, the erosion failure of the as-sprayed TBCs was proved to be the fracture and spallation of the splats. By contrast, the spallation of segmented bionic unit occurred in the overlapping area between the adjacent laser irradiation, and the erosive unit surface presented the clear and deep furrows, which revealed that the erosion failure mechanism of bionic TBCs was dominated by brittle and some ductile erosion. These results showed more opportunities for bionic application in improving the solid particle erosion resistance of components in the windy and sandy environment.

In this work, Eucalyptus Capsule Fibers (ECF) are proposed as a new natural fiber reinforcement to produce bio-composites due to their biological origin, specific smell and color. High Density Polyethylene (HDPE) is used as the matrix to compare three reinforcement types, raw ECF, alkali treated ECF, and ECF treated with PE-graft-maleic anhydride (PE-g-MA) as a coupling agent at three concentra-tions (5 wt.%, 10 wt%, and 15 wt%). A complete set of characterization is performed including tension, torsion, hardness, Melt Flow Index (MFI), Attenuated Total Reflection Fourier Transform Infrared Spectroscopy (ATR-FTIR), Contact Angle (CA), Scanning Electron Mi-croscopy (SEM), Thermogravimetric Analysis (TGA) and Dynamic Mechanical Analysis (DMA). The results show that the best me-chanical and rheological improvements are obtained by using the coupling agent with alkali treated fibers.

To design effective and easy-to-manufacture conductive heat channels, a heuristic method by emulating the natural branch systems is suggested. The design process of the method is divided into two steps, which are the principal channel design and the lateral channel design. During the process, the width of each channel is controlled by the bifurcation law, and the end point of the channel is located at the point with the maximum temperature while the start points of the principal channel and the lateral channel are respec-tively determined by the location of the heat sink and the law of the minimum thermal resistance. Four design examples with different boundary conditions are studied by the suggested method, and the design results are compared with that of the traditional structural topology optimization method. Not only lower maximum temperature and relatively uniform distribution of temperature are obtained by the suggested method, but also straight channels are achieved without gray element, which is easy to manufacture. The suggested method inspired by the natural branch systems can provide an effective solution for heat channel design in the heat dissipation structures.