Morpho butterfly, famous for its iridescence wing scales, has gradually evolved a diversity of functions and has attracted much attention recently. On the other hand, it is known that the wing surface of Morpho butterfly has some complex and so-phisticated structures. In fact, they are composed of an alternating multilayer film system of chitin and air layers, which have different refractive indexes. More importantly, these structures can interact strongly with visible light because the feature size of the structures is in the same order of magnitude with light wavelength. It is noteworthy that it is these optical architectures that cause the excellent multifunction including structural color, antireflection, thermal response, selective vapour response, direc-tional adhesion, superhydrophobicity and so on. This review mainly covers the excellent multifunctional features of Morpho butterfly wings with representative functional structures of multilayer film system, photonic crystal and ridges. Then, the mechanism of the structure-based optical multifunction of Morpho butterfly is analyzed. In order to facilitate mechanism analysis, the models of bionic functional structures are reported, as well as the interaction process between the multiscale structures and the external media It is concluded that these functions of Morpho butterfly wings have inevitable and corre-sponding regularity connection with the structural parameters and the dielectric coefficient of the filled medium. At last, the future direction and prospects of this field are briefly addressed. It is hoped that this review could be beneficial to provide some innovative inspirations and new ideas to the researchers in the fields of engineering, biomedicine, and materials science.

Caterpillar crawling is distinct from that of other limbless animals. It is simple but efficient. This paper presents a novel mechanism to duplicate the movement to a modular caterpillar-like robot. First, how caterpillars move in nature is investigated and analyzed systematically. Two key locomotive properties are abstracted from the body shape of caterpillars during crawling. Then, based on a morphological mapping, a hypothesis of asymmetric oscillation with a ratio of two is proposed, followed by a thorough analysis of the kinematics of the caterpillar-like robot. The asymmetric oscillating mechanism is proved capable of generating stable caterpillar-like locomotion. Next, taking advantage of the two locomotive properties and the hypothesis, a new Central Pattern Generator (CPG) model is designed as the controller of the robot. The model can not only generate the signal as expected, but also provide explicit control parameters for online modulation. Finally, simulation and on-site experiments are carried out. The results confirm that the proposed method is effective for caterpillar-like locomotion.

Freshwater stingrays undulate their flexible disc-like pectoral fins to perform cruising, manoeuvring, and other motions. This undulatory propulsion has a higher propulsive efficiency and more precise manoeuvrability than most other species at low swimming velocity. In the current study, a new robotic fish inspired by the freshwater stingray was developed and tested. First, the morphology and kinematic patterns of the freshwater stingray were presented. A kinematic model of the pectoral fin was established based on several assumptions. Then a robotic stingray with an undulatory pectoral fin was designed and developed. Experiments were conducted to investigate the effects of various fin actuation parameters on its linear swimming velocity and the forces generated by the robotic stingray. The controllable fin parameters include oscillation frequency, wave number, maximal angular deflection of the fin rays, and the amplitude pattern of the pectoral fin. The experimental results indicate that the developed prototype is able to generate adequate thrust for self-propulsion. Linear swimming velocity and surge force increase rapidly with oscillation frequency, angular deflection, and wave number. A maximum velocity of 4.3 cm•s−1 (nearly 0.18 Body Lengths per second (BL•s−1)) and a maximum surge force of 102 mN are achieved at an oscillation frequency of
0.5 Hz, a wave number of 1, a maximum angular deflection of 30?, and an equal amplitude pattern. The sway force of the robotic fish fluctuates around 0 mN. The heave force varies with wave number and reaches its minimum at a wave number of 1.

This paper presents the design and control of a pneumatically actuated transtibial prosthesis, which utilizes a pneumatic cylinder-type actuator to power the prosthetic ankle joint to support the user’s locomotion. The pneumatic actuator has multiple advantages over the traditional electric motor, such as light weight, low cost, and high power-to-weight ratio. The objective of this work is to develop a compact and lightweight transtibial prosthesis, leveraging the multiple advantages provided by this highly competitive actuator. In this paper, the design details of the prosthesis are described, including the determination of performance specifications, the layout of the actuation mechanism, and the calculation of the torque capacity. Through the authors’ design calculation, the prosthesis is able to provide sufficient range of motion and torque capacity to support the lo-comotion of a 75 Kg individual.  The controller design is also described, including the underlying biomechanical analysis and the formulation of the finite-state impedance controller. The testing results of human subject indicate that the prosthesis is able to generate a natural walking gait and sufficient power output for its amputee user.

Power requirements in vertical flight in the dronefly (Eristarlis tenax; also known as hoverfly) are studied using the method of computational fluid dynamics. The flow solution provides the aerodynamic forces and torques; the inertial torques due to the acceleration of the wing-mass are computed analytically. From the aerodynamic and inertial torques, the mechanical power is obtained. It has been shown that at hovering flight, the specific power with 100% elastic energy storage is 43.51 W•kg−1 and that without elastic energy storage is 60.12 W•kg−1. During vertical flight, the specific power increases with the ascending ratio K (ratio of the ascending velocity to the tip velocity); it is proportional to K to the power of about 1.37. When flying upward at an ascending ratio of about 0.3, the power required is the same as that when the insect carries a load of about 50% of its weight.

A gecko’s habitat possesses a wide range of climbing slopes that pose a number of postural challenges for climbing lo-comotion. Few studies have examined the relationship between the lateral bending of the trunk of a gecko and other aspects of locomotion when climbing. In this paper, three-dimensional reaction forces and high-speed videos of Gekko geckos moving on different slopes are used to reveal how the lateral bending of the animal’s trunk responds to changing slopes. The results of such observations indicate that the minimum bending radius continually decreases with an increase in the slope, illustrating that the degree of bending of the trunk becomes significantly greater. Moreover, a lateral bending mechanical model is used to show the interrelation between the lateral bending in the frontal plane and the sagittal deformation of the trunk caused by gravity. Taken together, these results have advanced our understanding of the role of lateral bending of vertebrates when climbing on a slope.

Bioinspiration can be considered one of the keys for future smart and versatile robotic systems. Plants could be an im-portant source of ideas despite the fact that they have not yet been deeply observed and considered. In this paper, climbing tendril-bearer plants that, by means of irritable ?liform organs called tendrils, search for a support, grasp it and climb to gain height, have been used to study and develop an effective climbing robot. The study aimed ?rst to evaluate the main movements and behaviors of the tendril from a biomimetic point of view. The tendril complexity was then simpli?ed, a robotic model was developed and a kinematic simulator was designed and implemented to visualize and evaluate the chosen system. Finally, based
on the biological, technical and numerical evaluations, the main tendril behaviors were replicated by proof of concept devices made of smart materials to move towards a practical realization and to replicate the simulated results.  The designed proof of concept prototypes showed good repeatability and feasibility.

Polymeric visual decoys of beetle of an invasive species called the Emerald Ash Borer (EAB), Agrilus planipennis, are highly efficacious in luring and trapping EAB males. Although industrially scalable, the bioreplication process to fabricate these decoys involves several operational steps. In a simpler bioreplication process devised by us, a multi-cavity negative die of nickel is made from an array of several EAB females. This die is used to fabricate multiple decoys simultaneously by casting and thermal curing of poly(dimethyl siloxane). Finally, the decoys are sprayed by first a black paint and then a metallic green paint. The new bioreplication process has considerably fewer operational steps than its predecessor and can be adopted by industry.

In this paper we present a method to create a hydrophobicity gradient on the surface of a Polydimethylsiloxane (PDMS) dry adhesive. The method consists of the partial silanization of the surface of the dry adhesive by Chemical Vapour Deposition (CVD) of octadecyltrichlorosilane (OTS). The partial silanization of the surface of the sample results in a hydrophobic to hy-drophilic gradient across the surface of the dry adhesive. The resulting change in hydrophobicity across the surface of the dry adhesive results in the uphill motion of a droplet of water, which appears to be directly proportional to the area of contact between the droplet and the adhesive. Normal adhesion testing is performed to quantify the effect of the hydrophobic gradient across the surface of the sample. While a variation in adhesion strength across the sample is measured, the adhesive properties are only minimally affected by the silanization, and the motion of the droplet of water doesn’t cause any loss of adhesion.

The microstructures of Atrina pectinata and freshwater mussel shells are investigated by optical microscopy and scanning electron microscopy. The mechanical properties of these shells are characterized by nanoindentation and three-point bending tests. Results show that both shells possess a prismatic microstructure mainly composed of columnar crystals and an organic matrix. The fracture toughness of the prismatic structure of Atrina pectinata and freshwater mussel are approximately
1.15 MPa•m1/2 and 0.87 MPa•m1/2, respectively, while the fracture toughness of natural calcite is approximately 0.2 MPa•m1/2. Calculated results from indentations agree with those obtained from the three-point bending tests. The columnar crystal material shows excellent fracture toughness due to grain refinement. In addition, the organic matrix of the prismatic layer can arrest cracks, and thereby improves the fracture toughness.

This paper presents a new method of delivering shRNA with biodegradable, thermosensitive PLGA-PEG-PLGA hydrogels for gene treatment of osteoarthritis (OA). OA is a chronic debilitating disease. Without the proper treatment and prognosis, it may result in the loss of joint function in aged people. Currently, gene therapy targeted on WISP-1 has emerged as an alternative method for OA treatment. In order to constantly release shRNA at 37.0 ?C, we synthetized the hydrogels via ring-opening copolymerization of lactide (LA) and glycolide (GA) using Polyethylene glycol (PEG Mn = 1000) and stannous octoate (Sn(Oct)2, 95%) as the macroinitiator and catalyst. First, the PLGA-PEG-PLGA copolymer was mixed with WISP-1shRNA and PEI-Lys in distilled water at 4.0 ?C. Then, the WISP-1shRNA/PEI-Lys loaded hydrogel was formed after incubation of the mixed solution at 37.0 ?C. During tests, the plasmid was released from this hydrogel complex constantly, and enhanced the transfection efficiency of WISP-1shRNA. In addition, silencing WISP-1 results to lower expression of MMP-3 and ADAMTS, and the accumulation of HBP1 in synoviocytes. Therefore, the hydrogel containing WISP-1shRNA is demonstrated an efficient way for the treatment of OA.

The regional microstructural variations in femoral head from proximal femoral fracture patients were investigated. Mi-cro-CT scanning was performed on seven femoral heads from proximal femoral fracture patients. Each femoral head was divided into three regions according to the trabecular orientation from the fovea of femoral head to the femoral neck. Eight three-dimensional trabecular cube models were reconstructed from each region. A total of 154 trabecular cubic models were reconstructed because the corresponding areas for 14 cubic models were damaged during the surgeries. Eight trabecular mor-phological parameters were measured and analyzed, namely, trabecular thickness (Tb.Th), trabecular separation (Tb.Sp), spe-cific bone surface (BS/BV), bone volume fraction (BV/TV), structural model index (SMI), degree of anisotropy (DA), trabe-cular pattern factor (Tb.Pf), and trabecular number (Tb.N). Bivariate correlation analyses were performed for all morphological parameters. One-way ANOVA tests were performed to analyze the differences of each parameter among three regions. Post-hoc multiple comparisons (Student-Newman-Keuls method) were performed to analyze the morphological difference between two regions. Trabecular bone of proximal femoral fracture patients significantly degenerated in all regions of femoral heads. BV/TV was statistically correlated with Tb.Th, Tb.Sp, BS/BV, Tb.Pf, and Tb.N (p < 0.05). Statistical differences in morphological parameters were observed between regions (p < 0.05). The trabecular strength in the middle regions was significantly higher than that in other regions because of the relationships between morphological parameters and mechanical parameters. Trabe-culae in the medial region were more uniform and stable along each direction than those in the lateral region. Most trabeculae in the lateral region only grew along the weight-bearing direction, and those along the other directions degenerated significantly. This study provides detailed trabecular morphological information on fractured femoral heads, as well as references for the prevention of high fracture risk in the elderly.

Melamine-formaldehyde acrylamide (MFA) copolymer was prepared and vacuum impregnated into wood in presence of 1,3-dimethylol 4,5-dihydroxyethylene urea (DMDHEU) as crosslinker, vinyltrichlorosilane (VTCS) modified montmorillonite (MMT) and Gum Polymer (GP) derived from Moringa oleifera as a flame retarding agent under catalyst heat treatment. The formation of MFA and DMDHEU was confirmed by Nuclear Magnetic Resonance (NMR) and Fourier Transform Infrared Spectroscopy (FTIR) studies. The crystallinity of the composites and interaction among them was studied by X-ray Diffrac-tometry (XRD) and FTIR study. Maximum interaction was found in wood samples treated with MFA/DMDHEU/GP
(3 phr)/MMT as shown by FTIR. Scanning Electron Microscopy (SEM) revealed the presence of polymer and MMT in the composites. Transmission Electron Microscopy (TEM) study indicated the incorporation of MMT into the wood polymer composite. Thermal stability and flammability were checked by Thermogravimetric Analyser (TGA) and Limiting Oxygen Index (LOI) instrument. The treatment of wood with GP had a significant influence on the thermal stability and flame retardant properties of the composites. Remarkable improvement in water repellency and chemical resistance was found for the treated wood samples. The composites showed significant improvement in mechanical properties due to treatment.

Two new feature extraction methods, window sample entropy and window kurtosis, were proposed, which mainly aims to complete the surface Electromyography (sEMG)-muscle force pattern recognition for intelligent bionic limb. The inspiration is drawn from physiological process of muscle force generation. Five hand movement tasks were implemented for sEMG-muscle force data record. With two classical features: Integrated Electromyography (IEMG) and Root Mean Square (RMS), two new features were fed into the wavelet neural network to predict the muscle force. To solve the issues that amputates’ residual limb couldn’t provide full train data for pattern recognition, it is proposed that force was predicted by neural network which is trained by contralateral data in this paper. The feasibility of the proposed features extraction methods was demonstrated by both ipsi-lateral and contralateral experimental results. The ipsilateral experimental results give very promising pattern classification accuracy with normalized mean square 0.58 ± 0.05. In addition, unilateral transradial amputees will benefit from the proposed method in the contralateral experiment, which probably helps them to train the intelligent bionic limb by their own sEMG.

Based on the Cockroach Swarm Optimization (CSO) algorithm, a new Cockroach Colony Optimization (CCO) algorithm is presented and applied to the Robot Path Planning (RPP) problem in this paper. In the CCO algorithm, an improved grid map is used for environment modeling, and 16-geometry and 8-geometry are introduced, respectively, in food division and cockroach search operation. Moreover, the CCO algorithm adopts a non-probabilistic search strategy, which avoids a lot of invalid searches. Furthermore, by introducing a novel rotation scheme in the above CCO algorithm, an Adaptive Cockroach Colony Optimization (ACCO) algorithm is presented for the 2-D Rod-Like Robot Path Planning (RLRPP) problem. The simulation results show that the CCO algorithm can plan an optimal or approximately optimal collision-free path with linear time com-plexities. With the ACCO algorithm, the robot can accomplish intelligent and adaptive rotations to avoid obstacles and pass through narrow passages along the better path.