Inspired by the unique, agile and efficient flapping flight of insects, we present a novel sub-100 mg, electromagnetically driven, tailless, flapping-wing micro robot. This robot utilizes two optimized electromagnetic actuators placed back to back to drive two wings separately, then kinematics of each wing can be independently controlled, which gives the robot the ability to generate all three control torques of pitch, roll and yaw for steering. To quantify the performance of the robot, a simplified aerodynamic model is used to estimate the generated lift and torques, and two customized test platforms for lift and torque measurement are built for this robot. The mean lift generated by the robot is measured to be proportional to the square of the input voltage amplitude. The three control torques are measured to be respectively proportional to three decoupled parameters of the control voltages, therefore the modulation of three control torques for the robot is independent, which is helpful for the further controlled flight. All these measured results fit well with the calculated results of the aerodynamic model. Furthermore, with a total weight of 96 mg and a wingspan of 3.5 cm, this robot can generate sufficient lift to take off.

Wing deformation capture with simulation is a mixed experimental-numerical approach whereby the wing deformation during flapping is captured using high-speed cameras and used as an input for the numerical solver. This is an alternative approach compared to pure experiment or full fluid structure interaction simulation. This study is an update to the previous paper by Tay et al., which aims to address the previous limitations. We show through thrust and vorticity contour plots that this approach can simulate Flapping Micro Aerial Vehiclex (FMAVs) with reasonable accuracy. Next, we use this approach to explain the thrust improvement when an additional rib is added to the original membrane wing, which is due to longer duration for the new wing to open during the fling stage. Lastly, by decreasing the number of points and frames per cycle on the wing, we can simplify and shorten the digitization process. These results show that this approach is an accurate and practical alternative which can be applied to general bio-inspired research.

The click beetle can jump up with a hinge when it is on the dorsal side. This jumping mechanism is simple and suitable as an inspiration for designing a simple, small, and reliable hopping robot. We report a single-legged robot inspired by the jumping mechanism of click beetles. It is 85 mm high, 60 mm long, and 41 mm wide, and weighs about 49 g. The robot has good hopping performance that the hopping height is about 4 times – 4.3 times of its body height. It is capable for rescue missions that require to enter enclosed spaces through cracks and narrow channels. In addition, hopping dynamics of the robot is important to understand its jumping mechanism and improve the robot’s hopping performance. But existing dynamic study does not complete the analysis including all stages in the hopping which are pre-hopping, take-off, and air-flying. We propose the decomposition method to study dynamics of the three stages separately, and synthesize them with related parameters. The dynamic synthesis of multi-motion states in a hopping cycle of the single-legged hopping robot is implemented. The hopping performance and dynamic synthesis theory of the robot are verified by simulations and experiments. Our study helps lay the foundation for design and hopping control of simple hopping robot systems.

Performing complex tasks by soft robots in constrained environment remains an enormous challenge owing to the limitations of flexible mechanisms and control methods. In this paper, a novel biomimetic soft robot driven by Shape Memory Alloy (SMA) with light weight and multi-motion abilities is introduced. We adapt deep learning to perceive irregular targets in an unstructured environment. Aiming at the target searching task, an intelligent visual servo control algorithm based on Q-learning is proposed to generate 
distance-directed end effector locomotion. In particular, a threshold reward system for the target searching task is proposed to enable a certain degree of tolerance for pointing errors. In addition, the angular velocity and working space of the end effector with load and without load based on the established coupling kinematic model are presented. Our framework enables the trained soft robot to take actions and perform target searching. Realistic experiments under different conditions demonstrate the convergence of the learning process and effectiveness of the proposed algorithm.

Under the requirement of the force controller of hydraulic quadruped robots, the goal of this work is to accurately track the force commands at the level of the hydraulic drive unit. The main contribution focuses on the development of a force-controlled compensation scheme, which is specifically aimed at the key issues affecting the hydraulic quadrupedal locomotion. With this idea, based on a P-Q valve-controlled asymmetric cylinder, we first establish a mathematical model for the hydraulic drive unit force control system. With the desired force commands, a force feed-forward algorithm is presented to improve the dynamic performance of the system. Meanwhile, we propose a disturbance compensation algorithm to reduce the influence induced by external disturbances due to foot-ground impacts. Afterwards, combining with a variable gain PI controller, a series of experiments are implemented on a force control performance test platform to verify the proposed scheme. The results demonstrate that the force-controlled compensation scheme has the ability to notably improve the force tracking accuracy, reduce the response time and redundant force.

Fingers are the basic components of anthropomorphic hands. At present, most anthropomorphic fingers utilize rigid joints, which have obvious fabrication and assembly complexities as well as limited flexibility and adaptability. Thus, some anthropomorphic fingers were attempted to utilize compliant joints learned from bioinspiration, but they have a limited self-resetting ability and lateral deformation resistance, as well as occupying a large space and having a non-anthropomorphic appearance. In this paper, nine compliant joints for anthropomorphic fingers were analyzed using Finite Element Analysis (FEA), based on which two combined compliant joints were proposed, and the optimal one was obtained through FEA and experiments. An anthropomorphic finger that embeds parts of the compliant joint into the adjacent phalanxes was then designed. Finally, the anthropomorphic finger was fabricated and experiments were conducted. Experimental results show that the anthropomorphic finger with the proposed combined compliant joints has a better self-resetting ability and lateral deformation resistance while ensuring a large range of motion similar to that of the human finger, and the required actuating force is reasonable. Furthermore, the embedded joint structure can reduce the occupied space of the joint so as to improve the anthropomorphic appearance of the finger, and enhance its lateral deformation resistance.

Exoskeleton robots have demonstrated the potential to rehabilitate stroke dyskinesia. Unfortunately, poor human-machine physiological coupling causes unexpected damage to human of muscles and joints. Moreover, inferior humanoid kinematics control would restrict human natural kinematics. Failing to deal with these problems results in bottlenecks and hinders its application. In this paper, the simplified muscle model and muscle-liked kinematics model were proposed, based on which a soft wrist exoskeleton was established to realize natural human interaction. Firstly, we simplified the redundant muscular system related to the wrist joint from ten muscles to four, so as to realize the human-robot physiological coupling. Then, according to the above human-like musculoskeletal model, the humanoid distributed kinematics control was established to achieve the two DOFs coupling kinematics of the wrist. The results show that the wearer of an exoskeleton could reduce muscle activation and joint force by 43.3% and 35.6%, respectively. Additionally, the humanoid motion trajectories similarity of the robot reached 91.5%. Stroke patients could recover 90.3% of natural motion ability to satisfy for most daily activities. This work provides a fundamental understanding on human-machine physiological coupling and humanoid kinematics control of the exoskeleton robots for reducing the post-stroke complications.'

To help walking, using assistive devices can be considered to reduce the loads caused by weight and to effectively decrease the propulsive forces. In this study, a mobility Saddle-Assistive Device (S-AD) supporting body weight while walking was evaluated on two healthy volunteers. This device is based on the support of body weight against gravity with the help of a saddle, which is not used in other passive mobility assistive devices. To prove the efficiency of this device, the experimental results obtained while walking with this device were compared with those related to walking without the assistive device. The results showed that this device could significantly reduce the forces and torque of the lower and upper limbs when walking. By distributing the load on the saddle, the vertical force and the propulsive force in the best conditions were decreased to 46.7% and were increased to 13.7% in body weight, respectively. Using a S-AD can help patients with lower limbs weakness and elderly people to walk.

Tantalum (Ta) alloys have been widely used as bone repair materials due to their excellent biocompatibility. In present work, zinc (Zn) incorporated ceramic coatings with micro/nano hierarchical structure were successfully fabricated on Ta by micro-arc oxidation and hydrothermal treatment. The content of Zn ions is about (1.35 ± 0.3) wt%. Cortex-like rough morphology (Ra: 1.504 μm) with irregular vermiform slots can be clearly observed on the surface of Ta. More importantly, the coatings resembling the structure of natural bone can release Zn, Ca, and P ions in a controlled and sustained manner. The corrosion resistance of Ta is greatly improved after functionalized with ceramic coatings, confirming by potentiodynamic polarization tests. The bonding strength between the coatings and substrates can be up to 18.9 N. Furthermore, the surface of MAOs-HT@Ta is covered by bonelike apatite after immersed in Simulated Body Fluid (SBF) for three weeks, showing excellently bioactivity. These results suggest that the innovative Zn-incorporated micro/nano hierarchical coatings on Ta may be used as promising candidates for orthopedic implants.

The past decade has witnessed significant efforts in addressing the global metallic corrosion challenge, with a focus on avoiding or mitigating huge economic losses incurred by corrosion and on the development of protective coatings on metals. Herein, a synergistic anti-corrosion coating with both superhydrophobicity and self-healing properties was reported, through a facile replica molding method by mixing the polyvinylidene fluoride (PVDF) matrix with nano-sized SiO2 particles and 2-mercaptobenzothiazole (MBT) loaded halloysites (HNTs). The surface exhibits robust self-cleaning behavior under harsh conditions and high liquid repellence to withstand the osmosis of corrosive ions. The self-healing performance of the coating, due to the introduction of MBT-loaded HNTs, enhances the anticorrosion capability, which is still valid once the protective layer is damaged. Potentiodynamic polarization (PDP) and Electrochemical Impedance Spectroscopy (EIS) measurements demonstrate that the synergetic effects in anticorrosion performances significantly enhance the long-term corrosion protection of metals. Hence, this type of dual-action coating may find unique applications in metal corrosion resistance where both super-repellency and self-healing properties are desired.

The effect of concurrent attendance of two inhibitors of bone degradation, namely Alendronate (Ald) sodium trihydrate and Strontium (Sr), on Calcium Phosphate Cement (CPC) characteristics was explored. To this aim, 5 wt% Strontium and 21 mM Alendronate sodium trihydrate were used in calcium phosphate cement and setting time, ion and drug release were analyzed. RAW264.7 and G cell were cultured on cement samples and Tartrate-Resistant Acid Phosphatase (TRAP), Alkaline phosphatase (ALP) activity and MTT assay were studied. The results of structural analysis indicated that 21 mM Ald did not let the cement set. Therefore, colloidal silica was added to the cement formula and successfully decreased the setting time. In vitro tests showed Sr-loaded sample had a greater inhibitory effect on biocompatibility of G cells than Ald-loaded and Sr-Ald-loaded samples. In addition, the findings about osteoblast MTT and ALP activity indicated that Sr was more effective in osteogenic activity of G cells. The simultaneous presence of Ald and Sr in Calcium Phosphate Cement (CPC) was not as effective in its biocompatibility as the presence of Sr alone.

Human shoulder joints exhibit stable but highly active characteristics due to a large amount of soft tissues. Finite Element (FE) modelling plays an important role in enhancing our understanding of the mechanism of shoulder disorders. However, the previous FE shoulder models largely neglected the Three-Dimensional (3D) volume of soft tissues and their sophisticated interactions with the skeletons. This study develops a 3D model of the rotator cuff and deltoid muscles and tendons. It also includes cartilage and, for the first time, main ligaments around the joint to provide a better computational representation of the delicate interaction of the soft tissues. This model has potential value for studying the force transfer mechanism and overall joint stability variation caused by 3D pathological changes of rotator cuff tendons.  Motion analysis systems and Magnetic Resonance (MR) scans were used to collect shoulder movement and geometric data from a young healthy subject, respectively. Based on MR images, a FE model with detailed representations of the musculoskeletal components was constructed. A multi-body model and the measured motion data were utilised to estimate the loading and boundary conditions. Quasi-static FE analyses simulated four instants of the measured scapular abduction. Simultaneously determined glenohumeral motion, stress/strain distribution in soft tissues, contact area, and mean/peak contact pressure were found to increase monotonically from 0? to 30? of abduction. The results of muscle forces, bone-on-bone contact force, and superior-inferior movement of the humeral centre during motion were consistent with previous experimental and numerical results. It is concluded that the constructed FE shoulder model can accurately estimate the biomechanics in the investigated range of motion and may be further used for the comprehensive study of shoulder musculoskeletal disorders.

Due to its real-time control, high folding ratio, and structure self-locking, flexible large curvature self-folding devices have broad application prospects, such as foldable human implants, flexible electronics, and flexible robots. Driven by this background, flexible large curvature folding butterfly (Polyura eudamippus) proboscises were studied in this work. The folding ratio of the proboscises was about 15. The curvature of coiled proboscises ranged from about 150 m?1 to 880 m?1. The external and internal structures of the proboscises were studied by different methods. Three main strategies for large-curvature folding of proboscises were identified: a gradual decrease in thickness, a lower elastic modulus, and (most importantly) large numbers of regular corrugated cracks arranged on the surface. These corrugated cracks can effectively accommodate the coiled strain and provide space for the large curvature folding of proboscises. Finally, a 4D printed coiled sample with corrugated cracks was fabricated to mimic the proboscises stretching process. Large-curvature folding strategies, based on these proboscises, provide insights for the biomimetic design of artificial highly folded components.

Misalignment is one of the most common causes of wear in bush bearings. Design improvements have been proposed by many re-searchers. Unfortunately, it did not efficiently reduce the misalignment. Classic geometrical designs sometimes reach their limits. For this reason, a bio-inspired design is proposed to solve the impediment. In this article, a bio-inspired bearing suited to misalignment was tested and compared to a classical bush bearing. The contact pressures of both bearings were compared with static Finite Element (FE) simulations for off-center load. Due to the complex shape of the involved contact, the performances of both bearings were also studied over time. Their wear behaviors were predicted with a numerical method. The methodologies emplaced to simulate the wear were described in this paper. Particularly, the wear coefficient determination obtained by experimental testing was detailed. The pressure value, the contact zone and the wear depth were compared and discussed. The wear results for the classical bearing are in accordance with the literature. The simulations show a deeper wear on the classical bush bearing than on the bio-inspired bearing. This leads to a longer period of service life for the bio-inspired bearing.

This work deals with the investigation of the synergistic effect of bagasse ash with sisal-banana-kenaf-flax fibers reinforced epoxy composite for their flexural behavior. The composites with three combinations of hybrid fibers viz. sisal/kenaf (HSK), banana/kenaf (HBK), and banana/flax (HBF) with bagasse ash (BGA) as filler material are fabricated using vacuum bag assisted resin transfer molding. Experiments were conducted based on L27 orthogonal array to understand the influence of control factor viz. fiber volume, alkali concentration & BGA over output response. X-ray micro computed tomography analysis was conducted over the developed sample to infer the uniform dispersion of fiber and filler material. The experimental results reveal that the addition of fiber up to 30 vol% depicts better strength and further addition results in a negative impact. Increasing in order of BGA decreases the flexural strength of the developed composites.