The ability of natural living organisms, transferring deformations into locomotion, has attracted researchers’ increasing attention in building bionic actuators and smart systems. As a typical category of functional materials, magnetoresponsive composite elastomers, comprised of flexible elastomer matrices and rigid magnetic particles, have been playing critical roles in this field of research due to their dynamic changes in response to applied magnetic field direction and intensity. The magnetically driven bionic actuators based on mag-netoresponsive composite elastomers have been developed to achieve some specific functions in some special fields. For instance, under the control of the applied magnetic field, the bionic actuators can not only generate time-varying deformation, but also motion in diverse environments, suggesting new possibilities for target gripping and directional transporting especially in the field of artificial soft robots and biological engineering. Therefore, this review comprehensively introduces the component, fabrication, and bionic locomotion application of magnetoresponsive composite elastomers. Moreover, existing challenges and future perspectives are further discussed.

Research on antistatic superhydrophobic surfaces has attracted widespread attention in some fields. However, in the application of superhydrophobic materials, fabricating stable and practical superhydrophobic surfaces through facile and low-cost approaches still faces considerable challenges. Herein, a polyphenylene sulfide (PPS)-based antistatic superhydrophobic composite coating with a high water contact angle (166?) and a low sliding angle (2?) was fabricated on a Q345 steel surface through a simple spray-coating method without any modifier. Furthermore, the as-prepared superhydrophobic coating also displayed excellent superhydrophobicity for water droplets at different pH values, as well as self-cleaning, anti-fouling and anti-icing properties. Importantly, the superhydrophobic coating still exhibited superhydrophobicity after calcination at 350 ?C for 1 h, indicating its outstanding thermal stability. Excellent antistatic and anticorrosion properties were obtained on the prepared coating surface, which allows the coating to be applied under harsh conditions. Benefiting from the above characteristics, compared with the commercial coating, the as-obtained antistatic superhydrophobic coating may be applied more widely in related fields.

Wettability plays a vital role in fundamental researches and practical applications. Wettability control and patterning have been widely studied in various fields. Although researches have grown rapidly, the methods are still restricted by limitations including complicated processes, high equipment requirements and shortage of methods to treat complex surfaces. Here we report a simple, low cost, array-based wettability control and patterning method via in-situ modification by flexible plasma stamp. Wettability control and patterning on surfaces of superhydrophobic aluminum, superhydrophobic PDMS and silicon, even plant leaf and fruit are achieved. The relationships between the wettability and the treatment time are investigated. We elucidate that the wetting states can also be reversible. The surface modification mechanism of in-situ plasma treatment is further investigated. Utilizing the step by step treatment, gradient and arbitrary wettability patterning on surfaces have been obtained. Notably, the patterned wettability on the inner surface of a tube has been realized, which has never been reported. Finally, in-situ wettability patterning is applied to achieve microfluidics channels on the inner surface of superhydrophobic tube. This work will bring new insights into the study of wetting field and stimulate more applications on wettability control and patterning.

Wet adhesion is widely adopted in biological adhesion systems in nature, and it is beneficial to design new materials with desired properties based on the underlying physics of wet adhesion. The aim of this work is to develop a design criterion to regulate the wet adhesion. The effects of different contact shapes (flat and sphere) and morphologies of the substrate (smooth, microstructure and nanostructure) on the adhesion force are investigated. Combining with the theoretical models,  the dominated factors in the separation process and isolating the viscous contributions from the capillary interactions are evaluated. The results demonstrate that the adhesion mechanisms depend significantly on the capillary numbers of the interstitial liquid and the contact geometry, and the ratio of capillary force to viscous force is a key to regulate the wet adhesion mechanism. These findings can not only explain some phenomena of wet adhesion to organisms, but also provide some inspirations to design new adhesion technology for robotic fingers that can grasp objects in wet environments.

Tissue engineered skeletal muscle is expected to treat muscle defects caused by trauma and disease. However, designing and manufacturing thick and complex tissue engineered skeletal muscle requires vascularization to ensure its internal cell viability and nutrient supply in vitro. In this article, we developed a set of Direct-Writing (DW) bio-printing procedure to manufacture a prevascularized composite construct with Human Umbilical Vein Endothelial Cell (HUVEC) and C2C12 cells for muscle tissue engineering application. We put the cells into the construct during the DW process to obtain the prevascularization and intend to promote its vascularization in vivo later. The constructs with cells or without cells were implanted respectively into nude mice back for 3 weeks, after which the mice healthily live for all the time and all the implants are tightly bonded to the host. From immunohistochemical analysis, CD31-positive blood vessels existed in the implanted samples with cells are more substantial than those without cells, but the implanted samples with HUVEC and C2C12 cells have much more number of small blood vessels distributing evenly. Moreover, the implants with cells, especially that with HUVEC and C2C12 cells, are able to get better fusion with the host skin and subcutaneous tissues. Histological analysis demonstrates that our DW-based constructs have the potential to be getting to vascularize the tissue engineered muscle.

In this paper, the effect of stereom structure on the mechanical behavior of the Sea Urchin Inorganic Skeleton (SUIS) has been studied. The stereom microstructure of both Anthocidaris crassispina and Tripnenstes gratilla was characterized by Scanning Electron Microscopy (SEM). Results indicate that a three-layer porous structure consisting of a growth, a support, and a resorption (GSR) layer is a common denominator for both species. The effect of GSR layer order on the mechanical behavior of the SUIS was studied by a finite element method. The results show that the GSR model could effectively reduce the maximum tensile stress on its meridional sutures under unidirectional pressure, hydrostatic pressure, and self-weight situation. For a fabricated three-layered ceramic test strips with different layer orders, the mechanical properties have a completely opposite performance compared with the compressive properties of the calculated SUIS-like models. This indicates that the GSR structure can effectively improve the mechanical properties of the SUIS, but it cannot be applied to bionics without considering its synergistic effect with the macro-structure of the SUIS. This is a typical example of bionic invalidation by single structure, where multi-level structure bionics may be an effective solution.

This paper introduces the design and fabrication of a smart and Hybrid Composite Finger (HCF) to achieve finger-like motions, such as holding and tapping motions. Bionic research on tapping motion of the index finger was conducted to obtain its structural and tapping parameters. The HCF, actuated by Shape Memory Alloy (SMA) wires, possesses a hybrid structure which is composed of a rigid structure to be its metacarpal part and a deformable structure to produce bending movement just like the function of the finger. Owing to an adhesive bonding technology, the HCF was fabricated with a composite structure which is reliable under impulsive responses, and had a worklife of more than 630000 times. A bending model was built by synthesizing the phase transformation dynamic model of the SMA wires and quasi-static analysis of the HCF. Structural optimization of the HCF was conducted by synthesizing the bending model together with experimental analyses. To produce a holding motion like as the finger, a holding heating strategy was proposed to adaptively heat the HCF to keep holding state based on the resistance feedback of SMA wires and a Proportion Differentiation (PD) algorithm. Besides, we used an impulsive heating method to heat the HCF to produce a high fidelity tapping motion with a maximum tapping force (6.83 N) at a response time (43 ms) which considerably coincided with those (about 
5.8 N, 45 ms) from tapping bionics of the index finger. Finally, a soft prosthetic hand system which had a hand-like appearance was manufactured based on the HCFs and several tests like as anthropomorphic gesture motions and human-like tapping motions to tap a keyboard were conducted to prove potential application of the HCF.

Anthropomorphic hands have received increasing research interest in the fields of robotics and prosthetics. But it is not yet clear how to evaluate their anthropomorphism. Similarity in the kinematic chain is essential to achieve both functionality and cosmesis. A few previous works have addressed the definition of anthropomorphism indexes, although they have some limitations in its definition. In this study, three different anthropomorphism indexes have been defined to compare the kinematic chain of artificial hands with that of the human hand. These indexes are based on the comparison of: (1) the parameters of the kinematic chain (dimensions, type of joints, orientations and ranges of motion), (2) the reachable workspace, and (3) common grasping postures. Five artificial hands with different degrees of anthropomorphism have been compared using the three Anthropomorphism Indexes of the Kinematic Chain (AIKC). The results show a high correlation between the first and third AIKC for the hands compared. The second AIKC presents much lower values than the other two, although they are higher for hands that combine abduction/adduction and flexion/extension movements in the kinematic chain of each finger. These indexes can be useful during the initial stage of designing artificial hands or evaluating their anthropomorphism.

Foothold identification is a key ability for legged robots that allows generating terrain adaptive behaviors (e.g., gait and control parameters) and thereby improving mobility in complex environment. To this end, this paper addresses the issue of foothold characterization and identification over rugged terrain, from the terrain geometry point of view. For a terrain region that might be a potential foothold of a robotic leg, the characteristic features are extracted as two first-order partial derivatives and two curvature parameters of a quadric regression surface at this location. These features are able to give an intuitive and, more importantly, accurate characterization towards the specific geometry of the ground location. On this basis, a supervised learning technique, Support Vector Machine (SVM), is employed, seeking to learn a foothold identification policy from human expert demonstration. As a result, an SVM classifier is learnt using the extracted features and human-demonstrated labels, which is able to identify whether or not a certain ground location is suited as a safe foot support for a robotic leg. It is shown that over 90% identification rate can be achieved with the proposed approach. Finally, preliminary experiment is implemented with a six-legged robot to demonstrate the effectiveness of the proposed approach.

Wall-climbing robots can work on steep terrain and obtain environment information in three dimensions for human in real time, which can improve operation efficiency. However, traditional single-mode robots cannot ensure the stable attachment on complex wall surfaces. Inspired by the structure characteristics of flies and clingfishes, three bionic structures including the flexible spine wheel, the adhesive material and the adsorption system are proposed. Aiming at task requirements on multiple walls and based on the above three bionic structures, a wall-climbing robot with the composed mode of ‘‘grabbing+adhesion+adsorption’’ is presented via the law of mechanism configuration synthesis. Using static analysis, the safe attachment conditions for the robot on smooth and rough walls are that the adsorption force is 30 N or more. Based on Newton’s Euler and Lagrange formulas, the dynamic equations of the robot on vertical walls are established to deduce that the maximum theoretical torque of the driving motor is 1.43 N?m at a uniform speed. Finally, the prototype of the wall-climbing robot is manufactured and tested on the vertical lime wall, coarse sandpaper wall and acrylic ceiling wall. Meanwhile, experiment results imply that the average maximum moving speed and the corresponding load are 7.19 cm?s?1 and 0.8 kg on the vertical lime wall, 7.78 cm?s?1 and 0.6 kg on the coarse sandpaper wall, and 5.93 cm?s?1 and 0.2 kg on the acrylic ceiling wall respectively. These findings could provide practical reference for the robot’s application on walls.

The effects of hybrid porous-serrated trailing edge on flow structure and sound source of NACA65(12)-10 at moderate Reynolds number (Rec = 5 × 105) have been investigated by Delayed Detached Eddy Simulation (DDES). Compared with conventional serrated trailing edge, the pressure fluctuation in the vicinity of hybrid porous-serrated trailing edge is further decreased significantly. The typical necklace vortex structures stretching across adjacent serrations are suppressed by the porous additive. It is found that porous media changes the shear stress distribution along the serration edge and inside the serration gap, which consequently eliminates the generation of necklace vortex. Therefore, the deformation of vortex tube caused by velocity vector is weakened. The underlying mechanisms associated to the sound source modification are analyzed based on vortex sound theory. The magnitude of Lamb vector and the angle between 
vorticity and velocity vectors are synchronously reduced by the porous additive, which implies that the present hybrid porous-serrated trailing edge has important influence on the further attenuation of far-field aerodynamic noise.

Drosophila melanogaster, a.k.a. the common fruit fly, is a simple organism that may give a rapid, high-throughput response in regard to the therapeutic efficacy of nanoparticles and drugs, while circumventing the high environmental and monetary cost of today’s typical in vivo assays involving more complex animals, along with the immeasurable suffering imposed onto them. Here we give the progress report on our effort to turn D. melanogaster into a model organism for the in vivo testing of Blood-Brain Barrier (BBB) penetration of nanoparticles and the treatment of infectious disease. We show that orally ingested superparamagnetic nanoparticles successfully cross the BBB in D. melanogaster and localize to the optic lobes of the third instar larval brain, while causing no adverse effects to the invertebrate organisms. We also show that both orally ingested calcium phosphate nanoparticles and biofilm-forming P. aeruginosa localize to the Drosophila crop, the food storage organ of the fly, which shrinks in response to infection. The model does not induce mortality consequential to infection and the effects of the internalization and proliferation of the microbes are evaluable by measuring the crop parameters, including fluorescence intensity and size. Continued development of these two models could simplify the preclinical testing of medical treatments and of pharmaceutical agents for neurological and infectious disease, while ensuring robust and reliable levels of statistical significance at low cost.

Discoveries in geckos locomotion have advanced the bio-inspired robotics. However, the gecko-inspired robots still lag behind animals in attachments and maneuvers due to our failure to understand and implement gecko bionics thoroughly. Here, we studied the toe deployments that facilitate the upside-down motion of geckos by focusing on the directions and contact area of toes to offer inspirations for the design and control of feet of legged robots that must operate on inverted surfaces. Instead of clustering toes, geckos align toes in varying directions. They distribute adhesion to toes by controlling the magnitude of contact area, with one square millimeter setae generating ~153.8 mN shear force and ~39.5 mN attractive force on ceilings. Front feet deploy toes in a ~190? span that centers on ~16? from the motion direction. Toes distribute uniformly and contribute similarly. Whereas, hind feet deploy toes in a ~220? span centering around ~90? relative to the fore-aft direction. The last two toes point toward the rear and contribute most in hind feet while the first two toes adhere barely. Such deployments involving distributed control among toes not only provide insight into biological adhesion but will also deliver useful information to the next generation of climbing robotics.

It is generally known that forelimbs and hindlimbs play different roles during locomotion, but the possible differences in the bio-mechanical functions of the metacarpal pad and metatarsal pad remain unknown. This study combined kinematic and pressure data from dogs to investigate the key roles of the metacarpal and metatarsal pads. The peak vertical ground reaction force of the metacarpal pad was found to be larger than that of the metatarsal pad, whereas the peak vertical ground reaction force of the fore toes was equal to that of hind toes, and the vertical deformations of the metacarpal and metatarsal pads were almost equal; moreover, the obtained stiffness of the metacarpal pad was several times greater than that of metatarsal pad based on in vivo measurement data. The results showed that the metacarpal pad demonstrated the biomechanical characteristics of cushion and support; however, the support characteristics of the metatarsal pad were weak. Furthermore, magnetic resonance imaging was performed to gather evidence to interpret the various roles played by the metacarpal pad and the metatarsal pad. It was found that the morphology and volumes of internal adipose tissues were closely related to the functions played by the metapodial pad during movement.

As a bionic therapy, hand-foot crawling has been reported to be used for the rehabilitation of low back pain. However, there have been few relevant biomechanical studies about this type of exercise. The purpose of this study was to calculate muscle activation and lumbar spinal load based on the examined limb kinematics and kinetics, which associated with hand-foot crawling at the different Centre of Mass (CoM) heights. A total of 14 men performed hand-foot crawling at three CoM heights. The kinematics and kinetics data were collected. One-way repeated measure analysis of variance was used to analyze the effect of the CoM height on crawling parameters. The crawling data from one subject at the three heights were used to calculate the muscle activation and compressive lumbar load with an OpenSim musculoskeletal model. The CoM heights had no significant effect on kinematics, kinetics or muscle activation. The spinal load was larger at higher heights. Hand-foot crawling was associated with lower trunk muscle activity. This study helps us to understand hand-foot crawling from the perspective of biomechanics. The findings from this study may help physical therapists choose hand-foot crawling as an appropriate exercise for patients with low back pain during early rehabilitation.

When humans jump down from a high position, there is a risk of serious injury to the lower limbs. However, cats can jump down from the same heights without any injury because of their excellent ability to attenuate impact forces. The present study aims to investigate the macro/micro biomechanical features of paw pads and limb bones of cats, and the coordination control of joints during landing, providing insights into how cats protect themselves from landing injury. Accordingly, histological analysis, radiological analysis, finite element method, and mechanical testing were performed to investigate the mechanical properties, microstructure, and biomechanical response of the pads and limb bones. In addition, using a motion capture system, the kinematic/kinetic data during landing were analysed based on inverse dynamics. The results show that the pads and limb bones are major contributors to non-impact-injuries, and cats actively couple their joints to adjust the parameters of movement to dissipate the higher impact. Therefore, the paw pads, limb bones, and coordinated joints complement each other and constitute a multi-level buffering mechanism, providing the cat with the sophisticated shock absorption system. This biomechanical analysis can accordingly provide biological inspiration for new approaches to prevent human lower limb injuries.

Scientists have long looked to nature and biology in order to understand and model solutions for complex real-world problems. The study of bionics bridges the functions, biological structures and functions and organizational principles found in nature with our modern technologies, numerous mathematical and metaheuristic algorithms have been developed along with the knowledge transferring process from the lifeforms to the human technologies. Output of bionics study includes not only physical products, but also various optimization computation methods that can be applied in different areas. Related algorithms can broadly be divided into four groups: evolutionary based bio-inspired algorithms, swarm intelligence-based bio-inspired algorithms, ecology-based bio-inspired algorithms and multi-objective bio-inspired algorithms. Bio-inspired algorithms such as neural network, ant colony algorithms, particle swarm optimization and others have been applied in almost every area of science, engineering and business management with a dramatic increase of number of relevant publications. This paper provides a systematic, pragmatic and comprehensive review of the latest developments in evolutionary based bio-inspired algorithms, swarm intelligence based bio-inspired algorithms, ecology based bio-inspired algorithms and multi-objective bio-inspired algorithms.