A comprehensive review on bio-inspired fish robots has been done in this article with an enhanced focus on swimming styles, actuators, hydrodynamics, kinematic-dynamic modeling, and controllers. Swimming styles such as body and/or caudal fin and median and/or paired fin and their variants are discussed in detail. Literature shows that most fish robots adapt carangiform in body and/or caudal fin type swimming as it gives significant thrust with a maximum speed of 3.7 m?s?1 in iSplash-II. Applications of smart or soft actuators to enhance real-time dynamics was studied from literature, and it was found that the robot built with polymer fiber composite material could reach a speed of 0.6 m?s?1. However, dynamic modeling is relatively complex, and material selection needs to be explored. The numerical and analytical methods in dynamic modeling have been investigated highlighting merits and demerits. Hydrodynamic parameter estimation through the data-driven model is widely used in offline, however online estimation of the same need to be explored. Classical controllers are frequently used for navigation and stabilization, which often encounters the linearization problem and hence, can be replaced with the state-of-the-art adaptive and intelligent controller. This article also summarizes the potential research gaps and future scopes.

This paper presents a study of a three-row opposed gripping mechanism made of bioinspired spiny toes. An insect Serica orientalis Motschulsky’s tarsal system was first described and studied. A compliant single spiny toe model was established assuming that the contact asperities were spheres. Following the single toe contact model, a spiny toe array’s contact model was then developed using asperity height’s distribution function. By studying the engaging and disengaging process of the single toe, the mechanical behavior of the toe and toe array were addressed. The toes as well as the arrays were manufactured via rapid prototyping. A customized apparatus using displacement-control method has been carried out to measure the pull-in forces and pull-off positions of the single toe and toe array under various compression conditions. Based on the understanding, a three-row opposed gripping mechanism with radial configuration for wall-climbing robots was designed and fabricated according to the mechanical behaviors of the toe and array. Using an opposed spoke configuration with 3 rows of 31 toes on each linkage array, the mechanism designed as a foot of climbing robots can vertically resist at least 1 kg of load on rough inverted surface, while the maximum normal load is as high as 31 N. The findings may provide a way in developing a high payload wall-climbing robot system for practical applications.

In nature, with the help of lateral lines, fish is capable of sensing the state of the flow field and recognizing the surrounding near-field hydrodynamic environment in the condition of weak light or even complete darkness. In order to study the application of lateral lines, an improved pressure distribution model was proposed in this paper, and the pressure distributions of the lateral line carrier under different working conditions were obtained using hydrodynamic simulations. Subsequently, a visualized pressure difference matrix was constructed to identify the flow fields under different working conditions. The role of the lateral lines was investigated from a visual image perspective. Instinct features of different flow velocities, flow angles and obstacle offset distances were mapped into the pressure difference matrix. Lastly, a four-layer Convolutional Neural Network (CNN) model was built as a recognition tool to evaluate the effectiveness of the pressure difference matrix method. The recognition results demonstrate that the CNN can identify the flow field state with 2 s earlier than the current time. Hence, the proposed method provides a new way to identify flow field information in engineering applications. 

The challenges we are faced with in localizing objects are the complex environments, such as tunnels, high-rise areas and underground parking lots. This paper develops a bionic vibration source localization device to estimate the direction of the object which is inspired by the unique and precise hunting localization mechanism of scorpions. The localization device uses the sensor array, which is patterned after the scorpions’ biological sensory structure, and imitates the coding mode of scorpions’ sensory neurons for determination of the prey (vibration source) bearing. To verify the effectiveness of the localization device, some experiments were performed through real collected vibration signals. The Average Estimated Error (AEE) and the Relative Estimated Error (REE) of the experimental results were calculated to be 3.64? ± 2.44? and ?1.43? ± 4.14?, respectively. It indicates that the device has a good performance to estimate the bearings of vibration sources at different distances and azimuths. This bionic localization device lays the foundation for the development of locating the moving object in some special conditions.

This study reports a simple imprinting method for the fabrication of biomimetic moth-eye antireflective polymethyl methacrylate (PMMA) nanostructures on the surface of the substrate. The antireflection structured silicon was obtained by Reactive Ion Etching (RIE) method. By using the antireflection structured silicon substrate as the imprinting stamp, the biomimetic moth-eye polymer structures showed tapered holes, whose depth and periodicity were around 780 nm and 580 nm, respectively. The reflectance of the resulting PMMA structures was reduced from 10% to less than 1% in the wavelength range from 300 nm to 1600 nm. This simple methodology can be scaled up via self-loading and nanoimprinting, which may have a promising application in optoelectronic devices and solar cells.

TiO2 nanotubes (NTs) have a great potential in improving the osetointegration of titanium (Ti)-based biomaterials. Much efforts have been made to evaluate the biological performance of the TiO2 nanotube in regulating protein adsorption and cells attachments. As often used in orthopaedic applications, although biotribological performance and biocorrosion are important issues in these applications, few researches have been reported on the biotribological performance of NT layers. This paper reports the preparation of a structure-optimised TiO2 NT (SO-NT) material via a multi-step oxidation strategy, as well as its biotribological and biocorrosion behaviours. In this procedure, an interfacial bonding layer of approximately 120 nm – 150 nm was first formed on the titanium substrate, which was then joined to the NT bottoms. The mechanical testing with respect to impact, bending, and biotribological performance have demonstrated the resultant SO-NT layer possess improved mechanical stability compared to conventional NT. The uniform hyperfine interfacial bonding layer with nano-sized grains exhibited a strong bonding to NT layer and Ti substrate. It was observed that the layer not only effectively dissipates external impacts and shear stress but also acts as a good corrosion resistance barrier to prevent the Ti substrate from corrosion. Theoretical models were proposed to analyze and predict the shear performance and corrosion-resistance mechanisms of the resultant material. The obtained results demonstrated that the SO-NT material has great potential in orthopaedic applications.

Direct oxidation is a simple and effective method for titanium surface treatment. In this research, a titanium sample was directly oxidized at the high temperature in two different atmospheres, air and pure oxygen, to obtain better atmosphere for titanium surface treatment. The results of the Raman spectroscopy indicated that in both atmospheres, the rutile bioactive phase (TiO2) has been formed on the titanium surface. The results of X-ray diffraction (XRD) also revealed that the surface of oxygen-treated sample was composed of the rutile phase and titanium monoxide (TiO), while at the surface of the air-treated sample, the rutile phase and titanium dioxide had been formed. Further, the results of Field Emission Scanning Electron Microscopy (FE-SEM) showed that by the surface treatment of titanium in both atmospheres, some micro-features including cracks thinner than 30 nm were formed on the surface. Because of more apatite forming ability and fewer water contact angle and more L-929 cell attachment of the air-treated titanium, it seemed that air, in comparison to the pure oxygen, is more promising atmosphere for the direct oxidation of titanium and improving its biofunctionalization.

Recent development concerning underwater superoleophobic surface has been motivated by fish scales, which are rendered capable of preventing their surfaces from contamination in oil-polluted water. In this paper, for the first time, the variations in surface topography and chemical composition of crucian fish scales at different growth stages have been investigated. The water and oil contact angles, surface morphology and chemical composition of the fish scales were measured by means of contact angle measurements, scanning electron microscopy and Fourier transform infrared spectroscopy, respectively. It is found that surface morphology and chemical composition both have influences on surface wettability of fish scales; fish scale at infant period seems to possess better hydrophilicity than that of fish scales at mature and senescent period. What is more, it is believed that the wettability heavily depends on the surface structures during their growth procedure, which enlightens us to design and fabricate biomimetic multifunctional underwater superoleophobic surfaces inspired by nature.

In this paper, the tribological properties of cuttlebone (CB)-reinforced high density polyethylene (HDPE) and Red Coral (RC)-reinforced HDPE composites were investigated. The composite specimens were prepared with a hot compression molding machine using different weight proportions of fillers blended with HDPE. The tribological behavior of the composite disks was studied using pin-on-disk tribometer under dry condition against stainless steel M30NW pins. The coefficient of friction as well as wear rate were examined to study the effects of the two fillers on the tribological performance of both composites. After wear tests, different composites were examined using a Scanning Electron Microscope (SEM). It was found that the use of cuttlebone (CB) and Red Coral (RC) as reinforcement improved the tribological properties of HDPE.

A photocatalyst of Au/ZnO (s-Au/ZnO) has been prepared via an approach, which uses spinach leaves with interconnected hierarchical structure as sacrificial biological template. The resultant s-Au/ZnO has well maintained the physical characteristics of the spinach leaf and demonstrated superior photocatalytic performance as well as enhanced photocurrent generation capability. Moreover, functional sacrificial agents (AgNO3, ammonium oxalate (AO) and tert-butyl alcohol (TBA)) have been employed to quench electrons, holes and hydroxyl radicals respectively to identify the active species of photocatalytic reaction and to investigate the mechanism of photocatalytic degradation. The facile method herein presented provides a convenient option for the preparation of bio-inspired leaf-like photocatalysts of ZnO-based nano-materials, holding potential applications in not only environmental purification but also solar-to-electric energy conversion. 

Customized prostheses are normally employed to reconstruct the biomechanics of the pelvis after resection due to tumors or accidents. The objective of this study is to evaluate the biomechanics of the pelvis under different daily activities and to establish a functional evaluation methodology for the customized prostheses. For this purposes, finite element model of a healthy pelvis as well as a reconstructed pelvic model after type II+III resection were built for biomechanical study. The biomechanical performance of the healthy and reconstructed pelvic model was studied under routine activities including standing, knee bending, sitting down, standing up, walking, stair descent and stair ascent. Subsequently, the strength and stability of the prosthesis were evaluated under these activities. Results showed that, for the heathy pelvic model, the stresses were mainly concentrated around the upper part of the sacrum and the sacroiliac joint undergoing different activities, and the maximum stress occurred during stair ascent. As for the reconstructed pelvis, the stress distribution and the tendency of the maximum stress variation predicted for the bone part during all the activities were similar to those of the natural pelvic model, which indicated that the load transferring function of the reconstructed pelvis could be restored by the prosthesis. Moreover, the predicted maximum von Mises stress of the screws and prosthesis was below the fatigue strength of the 3D printed Ti-6Al-4V, which indicated the prosthesis can provide a reliable mechanical performance after implantation.

Despite the success of cementless hip stem, stress shielding still presents a serious problem leading to bone resorption. Stems in-corporating porous cellular structures represent a promising solution. Therefore, this study validates the finite element models of titanium (Ti) alloy (Ti-6Al-4V) porous stem and effective porous stems. Several effective porous stems with strut thicknesses 0.33 mm –1.25 mm (18% – 90% porosity) under different loading conditions were analyzed. The results of finite element models revealed that changing the load type and porosity affect stress shielding. Climbing loads yield the maximum stress levels while walking loads result in the lowest stresses in the stems. Furthermore, the point load results in the maximum stress shielding and micromotions (?19% to 18%, 40 μm  to 703 μm), as compared to walking (?17.5% to 3%, 35 μm to 242 μm) and climbing loads (?7% to 1.6%, 30 μm to 221 μm). Finally, effective porous stems of strut thickness 0.87 mm exhibit the lowest stress shielding signals (<5%) under all loading conditions.

In Magnetic Resonance Imaging (MRI) guided intervention procedures, the flexibility and reliability of the mammary gland fixation device are important indicators for ensuring the quality of surgery. This paper presents a bionic flexible fixation system for MRI-guided breast biopsy, and establishes a mathematical model of the palm-type curved plate and a breast compression model. The bending angle, eccentricity, and tightening stroke of the palm-type curved plate are considered the main influencing factors. The bending angle and eccentricity of the bionic palm-type curved plate and flexible fingers are optimized, and a prototype of the breast fixation system is developed. The experimental results show that when the external force is 10 N, the average repetitive accuracy of four lesion points is 
0.71 mm, 0.60 mm, 0.63 mm, and 0.68 mm, respectively. When the pressures are 8 N, 10 N, and 12 N, the thickness of the compressed tissue is 76.27 mm, 72.8 mm and 68.73 mm, respectively. It has good repetitive accuracy and is compatible with the concept of flexible fixation that reduces the uncomfortable feeling of the human body. We propose that by optimizing the flexible tightening mechanism, it is feasible to properly control the external compression force to effectively reduce the compression pain for patients while guaranteeing the tightening reliability in breast biopsy.

The purpose of the work is to prepare and characterize hybrid fillers of cereal straw – perlite as well as to examine their impact on the functional properties of elastomeric biocomposites. Natural rubber was used as the polymer matrix, vulcanized with a sulfuric crosslinking system. The subject matter of the work included an interdisciplinary knowledge segment in the field of polymertechnology – hybrid biomaterials. The work investigated the effect of physical (mechanical) modification of lignocellulosic filler. The process of milling and homogenization of cereal straw with the addition of perlite was carried out in a planetary ball mill. The properties of biocomposites were examined in terms of two key aspects: The amount of hybrid filler and its ratio (cereal straw to natural mineral). The plate-like structure of natural minerals and the fibrous structure of cereal straw created a two-component filler, which influenced the properties of the produced biomaterials. A significant improvement in barrier, crosslinking density, hardness, mechanical and damping properties has been noted for systems containing hybrid fillers. Moreover, all vulcanizates proved to be resistant to the rmooxidative aging. Furthermore, the straw modificated with perlite formed a more complex structure in the composites, resulting in a stronger reinforcing effect, which was confirmed by dynamic-mechanical analysis (Payne effect).