Marine fouling is a worldwide problem, which is harmful to the global marine ecological environment and economic benefits. The traditional antifouling strategy usually uses toxic antifouling agents, which gradually exposes a serious environmental problem. Therefore, green, long-term, broad-spectrum and eco-friendly antifouling technologies have been the main target of engineers and researchers. In recent years, many eco-friendly antifouling technologies with broad application prospects have been developed based on the low toxicity and non-toxicity antifouling agents and materials. In this review, contemporary eco-friendly antifouling technologies and materials are summarized into bionic antifouling and non-bionic antifouling strategies (2000–2020). Non-bionic antifouling technologies mainly include protein resistant polymers, antifoulant releasing coatings, foul release coatings, conductive antifouling coatings and photodynamic antifouling technology. Bionic antifouling technologies mainly include the simulated shark skin, whale skin, dolphin skin, coral tentacles, lotus leaves and other biology structures. Brief future research directions and challenges are also discussed in the end, and we expect that this review would boost the development of marine antifouling technologies.

Any phenomenon in nature is potential to be an inspiration for us to propose new ideas. Lateral line is a typical example which has attracted more interest in recent years. With the aid of lateral line, fish is capable of acquiring fluid information around, which is of great significance for them to survive, communicate and hunt underwater. In this paper, we briefly introduce the morphology and mechanism of the lateral line first. Then we focus on the development of artificial lateral line which typically consists of an array of sensors and can be installed on underwater robots. A series of sensors inspired by the lateral line with different sensing principles have been summarized. And then the applications of artificial lateral line systems in hydrodynamic environment sensing and vortices detection, dipole oscillation source detection, and autonomous control of underwater robots have been reviewed. In addition, the existing problems and future foci in this field have been further discussed in detail. The current works and future foci have demonstrated that artificial lateral line has great potentials of applications and contributes to the development of underwater robots.

In industrial applications, climbing robots are widely used for climbing and detection of rough or smooth pipe surfaces. Inspired by the special claws of longicorn is that can crawl on rough surfaces and the array of tiny bristles of geckos that can crawl on smooth surfaces, a new type of wall-climbing robot for rough or smooth surfaces is proposed in this paper. The bionic palms of the robot are suggested with special bionic hooks inspired by the longicorn and bionic adhesive materials inspired by the gecko with a good performance on adhering on the surfaces. The special bionic hooks are manufactured by the 3D printing method and the bionic adhesive materials are made by the polymer print lithography technology. These two different bionic adhere accessory are used on the robot’s palm to achieve climbing on the different surfaces. This foldable climbing robot can not only bend its own body to accommodate the cylindrical contact surfaces of different diameters, but also crawl on vertical rough and smooth surfaces using their bionic palms.

Evolutionary Computation (EC) has strengths in terms of computation for gait optimization. However, conventional evolutionary algorithms use typical gait parameters such as step length and swing height, which limit the trajectory deformation for optimization of the foot trajectory. Furthermore, the quantitative index of fitness convergence is insufficient. In this paper, we perform gait optimization of a quadruped robot using foot placement perturbation based on EC. The proposed algorithm has an atypical solution search range, which is generated by independent manipulation of each placement that forms the foot trajectory. A convergence index is also introduced to prevent premature cessation of learning. The conventional algorithm and the proposed algorithm are applied to a quadruped robot; walking performances are then compared by gait simulation. Although the two algorithms exhibit similar computation rates, the proposed algorithm shows better fitness and a wider search range. The evolutionary tendency of the walking trajectory is analyzed using the optimized results, and the findings provide insight into reliable leg trajectory design.

In this study, a human-chair model was developed as the basis for a wearable-chair design. A prototype chair, HUST-EC, based on the model was fabricated and evaluated. Employing the optimization under the golden divisional method, an optimized simulation of the operating mode with the lowest chair height was implemented. A novel multi-link support structure has been established with parameters optimized using Matlab software. The stress analysis of the solid models was conducted to ensure the adequate support from the designed chair for the user. Ten subjects participated in the evaluation experiment, who performed both static tasks and dynamic tasks. The experimental results consisted of subjective evaluation and objective evaluation. The experimental data demonstrate that (1) the HUST-EC can effectively reduce the activation level of related muscles at a variety of tasks; (2) the plantar pressure was reduced by 54% – 67%; (3) the angle between the upper body and the vertical axis was reduced by 59% – 77%; (4) the subjective scores for chair comfortability, portability, and stability were all higher than 7. The results further revealed that the designed chair can reduce the musculoskeletal burden and may improve work efficiency.

Bone connection with robot is an important topic in the research of robot assisted fracture reduction surgery. With the method to achieve bone-robot connection in current robots, requirements on reliability and low trauma can not be satisfied at the same time. In this paper, the design, manufacturing, and experiments of a novel Bone Connection Robotic Hand (BCRH) with variable stiffness capability are carried out through the bionics research on human hand and the principle of particle jamming. BCRH’s variable stiffness characteristic is a special connection between “hard connection” and “soft connection”, which is different from the existing researches. It maximizes the reliability of bone-robot connection while minimizes trauma, meets the axial load requirement in clinical practice, and effectively shortens the operating time to less than 40 s (for mode 1) or 2 min (for mode 2). Meanwhile, a theoretical analysis of bone-robot connection failure based on particle jamming is carried out to provide references for the research in this paper and other related studies.

The fabrication of multi-material medical phantoms with both patient-specificity and realistic mechanical properties is of great importance for the development of surgical planning and medical training. In this work, a 3D multi-material printing system for medical phantom manufacturing was developed. Rigid and elastomeric materials are firstly combined in such application for an accurate tactile feedback. The phantom is designed with multiple layers, where silicone ink, Thermoplastic Polyurethane (TPU), and Acrylonitrile Butadiene Styrene (ABS) were chosen as printing materials for skin, soft tissue, and bone, respectively. Then, the printed phantoms were utilized for the investigation of needle-phantom interaction by needle insertion experiments. The mechanical needle-phantom interaction was characterized by skin-soft tissue interfacial puncture force, puncture depth, and number of insertion force peaks. The experiments demonstrated that the manufacturing conditions, i.e. the silicone grease ratio, interfacial thickness and the infill rate, played effective roles in regulating mechanical needle-phantom interaction. Moreover, the influences of material properties, including interfacial thickness and ultimate stress, on needle-phantom interaction were studied by finite element simulation. Also, a patient-specific forearm phantom was printed, where the anatomical features were acquired from Computed Tomography (CT) data. This study provided a potential manufacturing method for multi-material medical phantoms with tunable mechanical properties and offered guidelines for better phantom design.

Micron/nano scale topographic modification has been a significant focus of interest in current titanium (Ti) surface design. However, the influence of micron/nano structured surface on cell or bacterium behavior on the Ti implant has rarely been systematically evaluated. Moreover, except for popular microgrooves, little work has been carried out on the reaction of cells to the bionic structure. In this study, several micro-pillars mimicking cell morphology were prepared on Ti surfaces by lithography and contact printing (ICP) method, and they were further decorated with nanotube arrays by anodization technology. These surface modifications remarkablly increased the surface roughness of pristine Ti surface from 91.17 nm ± 5.57 nm to be more than 1000 nm, and reduced their water contact angles from 68.3? ± 0.7? to be 16.9? ± 2.4?. Then, the effects of these hierarchical micron/nano scale patterns on the behaviors of MG63 osteoblasts, L929 fibroblasts, SCC epithelial cells and P. gingivalis were studied, aiming to evaluate their performance in osseointegration, gingival epithelial sealing and antibacterial ability. Through an innovative scoring strategy, our findings showed that square micro-pillars with 6 μm width and 2 μm height combined with 85 nm diameter nanotubes was suitable for implant neck design, while square micro-pillars with 3 μm width and 3.6 μm height combined with 55 nm diameter nanotubes was the best for implant body design. Our study reveals the synergistic effect of the hierarchical micron/nano scale patterns on MG63 osteoblasts, L929 fibroblasts, SCC epithelial cells and P. gingivalis functions. It provides insight into the design of biomedical implant surfaces.

Some true bug species use droplet-shaped, open-capillary structures for passive, unidirectional fluid transport on their body surface in order to spread a defensive fluid to protect themselves against enemies. In this paper we investigated if the shape of the structures found on bugs (bug-structure) could be optimised with regard to better performance in unidirectional fluid transportation. Furthermore, to use this kind of surface structure in technical applications where fluid surface interaction occurs, it is necessary to adapt the structure geometry to the contact angle between fluid and surface. Based on the principal of operation of the droplet-shaped structures, we optimised the structure shape for better performance in targeted fluid flow and increase in flexibility in design of the structure geometry. To adapt the structure geometry and the structure spacing to the contact angle, we implemented an equilibrium simulation of the, the structure surrounding, fluid. In order to verify the functionality of the optimised structure, we designed and manufactured a prototype. By testing this prototype with pure water used as fluid, the functionality of the optimised structure and the simulation could be proved. This kind of structure may be used on technical surfaces where targeted fluid transport is needed, e.g. evacuation of condensate in order to prevent the surface from mold growth, microfluidics, lab-on-a-chip applications and on microneedles for efficient drug/vaccine coating.

Herein, self-assembled superhydrophobic composite coatings were successfully prepared using a one-step dip-coating method on different irregular parts. The fluorinated nano-SiO2 particles spread into a uniform layer owing to the viscosity of the composite resin. After the optimization of the process, the fabricated nanoporous-structured coating has low adhesion properties with chemical and high thermal stabilities. After baking at 250 ?C for 2 h or soaking in a solution of pH = 1 or pH = 13 for 10 days, the coating could maintain its good superhydrophobicity. The self-ejecting effects of the condensed dewdrops and droplet bounce phenomenon indicate that the coatings can be well-distributed on components of different structures, and they have significant application prospects in irregular parts and industrial production in the near future.

Recently, there are hesitations in the application scope of the classical Cassie theory and Wenzel theory. In this paper, Molecular Dynamics (MD) simulations are used to study these two theories used in the nanoscale and find their limitations. The effect of parameters including solid fractions (or roughness factors), arrangement of pillars (with same solid fractions), pillar height, and droplet size on contact angles was investigated. It shows that the Cassie equation is suitable for droplets on uniform pillared surfaces including different solid fractions, arrangement of pillars and pillar height, when there is no meniscus of droplets. The Wenzel equation is also suitable for droplets on uniform pillared surfaces including different roughness factors, arrangement of pillars and pillar heights. Moreover, whether the droplet size has an influence on the contact angle depends on the pinned place of the contact line. In the Wenzel state, the contact line is pinned although increasing the droplet size, resulting in increasing the contact angle, while the contact angle decreases to the initial value again when the droplet size increases enough to allow the contact line moving to the next pillar. The results provide insights toward the wettability of droplets on surfaces in nanoscale.

To improve the mechanical properties of Trabecular Beetle Elytron Plates (TBEPs, a type of biomimetic sandwich structure inspired by the beetle elytron) under transverse loads, three-point bending tests are performed to investigate the influence of the trabecular and chamfer radii of the core structure on the mechanical performance of TBEPs manufactured by 3D printing technology. The results show that the three-point bending performance of TBEPs can be improved by setting reasonable trabecular and chamfer radii; however, excessive increases in these radii can cause a decline in the mechanical performance. For the reason, these two structural parameters can enhance the deformation stiffness of the whole structure and the connection property between the core and skin, which is also the mechanical reason why Prosopocoilus inclinatus beetle elytra have thick, short trabeculae with a large chamfer radius. However, when these radii increase to a certain extent, the cracks are ultimately controlled between two adjacent trabeculae, and the failure of the plate is determined by the skin rather than the core structure. Therefore, this study suggests a reasonable range for trabecular and chamfer radii, and indicates that TBEPs are better suited for engineering applications that have high compression requirements and general bending requirements.

To better understand dragonflies’ remarkable flapping wing aerodynamic performance, we measured the kinematic parameters of the wings in two different flight modes (Normal Flight Mode (NFM) and Escape Flight Mode (EFM)). When the specimens switched from normal to escape mode the flapping frequency was invariant, but the stroke plane of the wings was more horizontally inclined. The flapping of both wings was adjusted to be more ventral with a change of the pitching angle that resulted in a larger angle of attack during downstroke and smaller during upstroke to affect the flow directions and the added mass effect. Noticeably, the phasing between the fore and hind pair of wings varies between two flight modes, which affects the wing-wing interaction as well as body oscillations. It is found that the momentum stream in the wake of EFM is qualitatively different from that in NFM. The change of the stroke plane angle and the varied pitching angle of the wings diverts the momentum downwards, while the smaller flapping amplitude and less phase difference between the wings compresses the momentum stream. It seems that in order to achieve greater flight maneuverability a flight vehicle needs to actively control positional angle as well as the pitching angle of the flapping wings.

In order to study the relationship between the important parameters of internal flow and the effect of drag and noise reduction, the internal flow field and sound field characteristics of bionic centrifugal pump are studied in this paper. Based on the methods of theoretical analysis, numerical simulation and test, the relationship between wall average shear stress, drag reduction rate, increasing efficiency and noise reduction rate of internal sound field is studied. Internal flow parameters to judge and predict the effect of drag and noise reduction are revealed. The results show that the bionic pit can effectively increase the thickness of the boundary layer and reduce the Reynolds stress on the wall. The resistance on the wall is reduced and the hydraulic efficiency of the centrifugal pump is increased. The noise reduction rate is basically consistent with the changing trend of the drag reduction rate, increasing efficiency and wall average shear stress in the flow field. Wall average shear stress can reveal the effect of drag and noise reduction, so the effect of drag and noise reduction can be predicted and judged by the change of wall average shear stress.

In order to meet the requirements for miniaturization detection of oil shale pyrolysis process and solve the problem of low sensitivity of oil and gas detection devices, a small bionic electronic nose system was designed. Inspired by the working mode of the olfactory receptors in the mouse nasal cavity, the bionic spatial arrangement strategy of the sensor array in the electronic nose chamber was proposed and realized for the first time, the sensor array was used to simulate the distribution of mouse olfactory cells. Using 3D printing technology, a solid model of the electronic nose chamber was manufactured and a comparative test of oil shale pyrolysis gas detection was carried out. The results showed that the proposed spatial arrangement strategy of sensor array inside electronic nose chamber can realize the miniaturization of the electronic nose system, strengthen the detection sensitivity and weaken the mutual interference error. Moreover, it can enhance the recognition rate of the bionic spatial strategy layout, which is higher than the planar layout and spatial comparison layout. This bionic spatial strategy layout combining naive bayes algorithm achieves the highest recognition rate, which is 94.4%. Results obtained from the Computational Fluid Dynamics (CFD) analysis also indicate that the bionic spatial strategy layout can improve the responses of sensors.

With the measurement of the Earth’s magnetic field, magnetic compass can provide high frequency heading information. However, it suffers from local magnetic interference. An intelligent ellipsoid calibration method based on the grey wolf is proposed to generate optimal parameters for magnetic compass to generate high performance heading information. With the analysis of the projection relationship among the navigation coordinate frame, the body frame and the local horizontal frame, the heading ellipsoid equation is constructed. Furthermore, an improved grey wolf algorithm is proposed to find optimization solution in a large solution space. With the improvement of the convergence factor and the evolutionary mechanism, the improved grey wolf algorithm can generate optimized solution for heading ellipsoid equation. The effectiveness of the proposed method has been verified by a series of vehicle and flight tests. The experimental results show that the proposed method can eliminate errors caused by sensor defects, hard-iron interference, and soft-iron interference effectively. The heading error generated by the magnetic compass is less than 0.2162 degree in real flight tests.

Multi Access Interference (MAI) is the main source limiting the capacity and quality of the Multiple-Input Multiple-Output Orthogonal Frequency Division Multiplexing (MIMO-OFDM) system which fulfills the demand of high-speed transmission rate and high quality of service for future underwater acoustic (UWA) communication. Multi User Detection (MUD) is needed to overcome the performance degradation caused by MAI. In this research, both local and global optimal solutions are obtained in Bionic Binary Spotted Hyena Optimizer (BBSHO) algorithm using the Position Coordinate Vectors (PCVs) of the social behavior of spotted hyenas to achieve MUD. Further, Extremal Optimization (EO) is introduced in BBSHO algorithm to improve the local search ability within the search space. Hence, a hybrid BBSHO algorithm is proposed for achieving MUD at the receiver of the MIMO-OFDM system whose transceiver model in underwater is implemented using BELLHOP simulation system. By MATLAB simulation, it is shown that the Bit Error Rate (BER) performance of the proposed hybrid algorithm outperforms with best optimal solution within the search space towards MUD for Interference to Noise Ratio (INR) at 10 dB, 20 dB, and 40 dB over conventional detectors and metaheuristic approaches such as Binary Spotted Hyena Optimizer (BSHO), Binary Particle Swarm Optimization (BPSO) in the UWA network.