Unidirectional liquid transport without any need of external energy has drawn worldwide attention for its potential applications in various fields such as microfluidics, biomedicine and mechanical engineering. In nature, numerous creatures have evolved such extraordinary unidirectional liquid transport ability, such as spider silk, Sarracenia’s trichomes, and Nepenthes alata’s peristome, etc. This review summarizes the current progresses of natural unidirectional liquid transport on 1-Dimensional (1D) linear structure and 2-Dimensional (2D) surface structure. The driving force of unidirectional liquid transport which is determined by unique structure exist distinct differences in physics. The fundamental understanding of 1D and 2D unidirectional liquid transport especially about hierarchical structural characteristics and their transport mechanism were concentrated, and various bioinspired fabrication methods are also introduced. The applications of bioinspired directional liquid transport are demonstrated especially in fields of microfluidics, biomedical devices and anti-icing surfaces. With newly developed smart materials, various liquid transport regulation strategies are also summarized for the control of transport speed, direction guiding, etc. Finally, we provide new insights and future perspectives of the directional transport materials.

The development of water purification device using solar energy has received tremendous attention. Despite extensive progress, traditional photothermal conversion usually has a high cost and high environmental impact. To overcome this problem, we develop a low cost, durable and environmentally friendly solar evaporator. This bi-layered evaporator is constructed with a thermal insulating polyvinylidene fluoride (PVDF) membrane as a bottom supporting layer and plasmonic silver nanoparticles decorated micro-sized hybrid flower (Ag/MF) as a top light-to-heat conversion layer. Compared with the sample with a flat silver film, the two-tier Ag/MF has a plasmonic enrichment property and high efficiency in converting the solar light to heat as each flower can generate a microscale hotspot by enriching the absorbed solar light. On the other hand, the PVDF membrane on the bottom with porous structure not only improves the mechanical stability of the entire structure, but also maintains a stable water supply from the bulk water to the evaporation interface by capillarity and minimizes the thermal conduction. The combination of excellent water evaporation ability, simple operation, and low cost of the production process imparts this type of plasmonic enhanced solar-driven interfacial water evaporator with promising prospects for potable water purification for point-of-use applications.

Superhydrophobic coatings with high flexibility and mechanical durability can well address many practical application problems. To this end, we proposed and fabricated a kind of bio-based superhydrophobic (multi-walled carbon nanotubes) CNT@PU (polyurethane) coatings. It was demonstrated that the CNT@PU coatings with 64% soft segment content possessed the preferable bonding strength (5B) with metal substrates. The multi-walled carbon nanotubes, as additive materials, were used to construct the microscopic structures of the coating surfaces, which made polyurethane surface superhydrophobic (water contact angle being 156.9?, and water sliding angle being 
4.3?). Furthermore, the high bonding strength between CNT and coating matrix led to robust mechanical durability of superhydrophobic CNT@PU coatings, and the coatings remained superhydrophobicity after 10 cycles of abrasion under 100 g load pressure. Also, the superhydrophobic coatings could well resist 5 cycles of tape-peeling action, and presented outstanding flexibility. The superhydrophobic CNT@PU coatings with high flexibility and mechanical durability could be applied to various substrates suggesting their big potential in future real-world application. 

Although superhydrophobic materials have attracted much research interest in anti-icing, some controversy still exists. In this research, we report a cost-effective method used to verify the contribution of area fraction to ice adhesion strength. We tried to partially-embed silica nanoparticles into microscale fabrics of a commercial polyamide mesh. Then, the area fraction could be determined by altering the mesh size. Generally, the ice adhesion strength decreases as the area fraction decreases. An ice adhesion strength of ~1.9 kPa and a delayed freezing time of ~1048 s can be obtained. We attribute the low ice adhesion strength to the combination of superhydrophobicity and stress concentration. The superhydrophobicity prohibits the water from penetrating into the voids of the meshes, and the small actual contact area leads to stress concentration which promotes interfacial crack propagation. Moreover, our superhydrophobic mesh simultaneously exhibits a micro-nano hierarchical structure and a partially-embedded structure. Therefore, the as-prepared superhydrophobic mesh retained the icephobicity after 20 icing/deicing cycles, and maintained its superhydrophobicity even after 60 sandpaper-abrasion cycles and a 220 ?C thermal treatment.

Controlling the shape of surface nanostructures is fundamental for various potential applications for examples, in water harvesting systems, liquid transportation or oil/water separation membranes. In this paper, the creation of porous surface structures is made by a process called templateless electropolymerization, in which water (H2O) is oxidized/reduced to form gas (O2/H2) bubbles onto the surfaces and acting as soft template for the polymer growth. Keeping the monomer (thieno[3,4-b]thiophene) and the substituent (pyrene) constant, we demonstrate how a flexible PEG spacer can affect the structure shape. When the PEG spacer increases, the structures change from nanotubes (1D growth) to nanoribbons (2D) and after to hollow nanospheres (3D), which also affects the wetting properties.

This paper presents a new and safe method of fabricating super-hydrophobic surface on NiTi Shape Memory Alloy (SMA), which aims to further improve the corrosion resistance performance and biocompatibility of NiTi SMA. The super-hydrophobic surfaces with Water Contact Angle (WCA) of 155.4? ± 0.9? and Water Sliding Angle (WSA) of 4.4? ± 1.1? were obtained by the hybrid of laser irradiation and polydimethylsiloxane (PDMS) modification. The forming mechanism was systematically revealed via Scanning Electron Microscopy (SEM) and X-ray Photoelectron Spectroscopy (XPS). The anti-corrosion of samples was investigated in Simulated Body Fluid (SBF) via the potentiodynamic polarization (PDP) and Electrochemical Impedance Spectroscopy (EIS) tests. PDMS super-hydrophobic coatings showed superior anti-corrosion performance. The Ni ions release experiment was also conducted and the corresponding result demonstrated that the super-hydrophobic samples effectively inhibited the release of Ni ions both in electrolyte and SBF. Besides, biocompatibility was further analyzed, indicating that the prepared super-hydrophobic surfaces present a huge potential advantage in biocompatibility.

Solid particle erosion on the material surfaces is a very common phenomenon in the industrial field, which greatly affects the efficiency, service life, and even poses a great threat to life safety. However, current research on erosion resistance is not only inefficient, but also limited to the improvement of hardness and toughness of materials. Inspired by typical scorpion (Parabuthus transvaalicus), biomimetic functional samples with exquisite anti-erosion structures were manufactured. Macroscopic morphology and structure of the biological prototype were analyzed and measured. According to above analysis, combined with response surface methodology, a set of biomimetic samples with different structural parameters were fabricated by using 3D printing technology. The anti-erosion performance of these biomimetic samples was investigated using a blasting jet machine. Based on the results of blasting jet test, as well as regression analysis and fitting, the optimal structural parameters were obtained. In addition to the static test conditions, the optimal biomimetic sample was also eroded in rotating condition and showed excellent erosion resistance property. The presence of bump and groove structures, on the one hand, reduced the eroded area of biomimetic sample surface. On the other hand, they made the airflow turbulent and consequently reduced the impact energy of solid particles, which significantly improved the erosion resistance of biomimetic materials. This study provides a new strategy to improve the service life of components easily affected by erosion in the aviation, energy and military fields.

Skin acts as protective barrier against a number of factors such as dust, opportunistic microbial and viral infections, regulates body temperature and waste discharge. Fibroblast cell population plays an important role in development of skin architecture. A scaffold having capability to support and enhance fibroblast growth is a viable option for wound dressing material which can shorten the time for wound to heal. In this work, Silk Fibroin (SF) and Xanthan (Xa) were blended in three ratios 80 SF: 20 Xa (SFX82), 60 SF: 40 Xa (SFX64), and 50 SF: 50 Xa (SFX55) to create SF/Xa scaffold. Miscibility and other physicochemical properties of SF/Xa scaffold are functions of blending ratios and blend with the ratio 80 SF: 20 Xa has the highest miscibility. Thermal properties of SF/Xa blends are a function of miscibility with SFX82 having superior thermal properties of all fabricated scaffolds. The porosity of SF/Xa scaffolds is in the range of 67% to 50%, with pore size of 58.1 μm – 45.5 μm, water uptake capacity of 92% – 86%, and surface roughness of 49.95 nm – 385 nm. SFX82 shows highest growth rate of L929 fibroblast cells indicating its superiority over other scaffolds for providing biological cues for the growth and proliferation of fibroblastic cells in natural environment. SFX82 scaffold is found to be most suitable for fibroblastic cells thereby enhancing the tissue regeneration at wound site.

Microstructures and corrosion of TiNbTaZrMo (Ti20Nb20Ta20Zr20Mo20) High-Entropy Alloy (HEA) were investigated in the Simulated Body Fluid (SBF). Microstructure of this alloy was investigated by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) techniques. Our observations confirmed the presence of two bcc phases as the major matrix as well as another minor phase in the microstructure of the alloy. Concentration of some elements, such as tantalum, niobium, and molybdenum in the dendritic branches and the presence of zirconium and titanium in the inter-dendritic branches were clearly evidenced by Energy Dispersive X-ray (EDX) analysis. Given importance of corrosion of implant alloys in the human’s body, electrochemical impedance and cyclic polarization tests were performed on the alloy in SBF. Through the corrosion tests, corrosion potential, current, and resistance were obtained as Ecorr = ?0.42 V, icorr = 0.34 μAcm?2, and Rp = 27.44 k ohmcm2, respectively. The results revealed that the rate of corrosion in TiNbTaZrMo HEA is about 26 times better than that of Ti6Al4V alloy. Also, both alloys had no pitting corrosion in the SBF solution.

Effective Selective Laser Melting (SLM) molding methods for femur implant design and molding can improve femur implant surgery success rates and enhance patients quality of life. In this study, an individualized femur implant and individualized biological fixed-type femur implant were designed using the parametric modeling method. The implants were then directly manufactured via SLM molding technology as the forming process was carefully analyzed. The results indicate that the proposed implant allows for favorable conjunction of the reconstructed implant model with the surrounding bone tissues under the premise of a relatively small amount of bone-cutting. The proposed implant also shows even pore distribution, good overall connectivity, relatively high bearing capacity, favorable overlapping between supports, and strong inter-pore connectivity. Only a small amount of powder adheres onto the surface and can be directly used after simple sand blasting and polishing. The comprehensive analyses of femur implant modeling and molding methods given in this paper may provide a sound foundation for the design and direct manufacture of individualized femur implants in the future.

To improve the flexural properties of Beetle Elytron Plates (BEPs) and clarify the effect of the transition arcs (chamfers) between the skins and the trabeculae, the chamfers were set in BEPs, and then the influence of the chamfer on BEPs’ mechanical properties was investigated via experimentation and the Finite Element Method simulation (FEM). The results indicate that the influence of the chamfer on the flexural properties and ductility was most obvious in the Trabecular Beetle Elytron Plates (TBEPs), less obvious in the Honeycomb Plates (HPs) and basically no effect was observed on End-trabecular Beetle Elytron Plates (EBEPs). The chamfer can improve the mechanical stability of EBEPs. As the chamfer diameter increased in the BEPs, the length of the residual trabecular root on the skin increased when failure occurred in the TBEPs. The crack position in the honeycomb walls of the HPs gradually shifted from the skin to the center. The EBEPs continued to exhibit oblique cracks. From the perspective of the force characteristics of these BEPs, combined with numerical simulation, the influence mechanism of the chamfer on their flexural properties was investigated.

The objective of this study is to develop a bio robot with a high degree of biomechanical fidelity to the human musculoskeletal system in order to investigate the biomechanical principles underlying human walking. The robot was designed to possess identical biomechanical characteristics to the human body in terms of body segment properties, joint configurations and 3D musculoskeletal geometries. These design parameters were acquired based on the medical images, 3D musculoskeletal model and gait measurements of a healthy human subject. To satisfy all the design criteria simultaneously, metal 3D printing was used to construct the whole-body humanoid robot. Flexible artificial muscles were fabricated in accordance with the predefined 3D musculoskeletal geometries. A series of physical tests were conducted to demonstrate the capacity of the robot platform. The fabricated robot shows equivalent mechanical characteristics to the human body as originally designed. The results of the physical tests by systematically changing environmental conditions and body structures have successfully demonstrated the capability of the robot platform to investigate the structure-function interplay in the human musculoskeletal system and also its interaction with the environment during walking. This robot might provide a valuable and powerful physical platform towards studying human musculoskeletal biomechanics by generating new hypotheses and revealing new insights into human locomotion science.

This paper presents a study on bioinspired closed-loop Central Pattern Generator (CPG) based control of a robot fish for obstacle avoidance and direction tracking. The biomimetic robot fish is made of a rigid head with a pair of pectoral fins, a wire-driven active body covered with soft skin, and a compliant tail. The CPG model consists of four input parameters: the flapping amplitude, the flapping angular velocity, the flapping offset, and the time ratio between the beat phase and the restore phase in flapping. The robot fish is equipped with three infrared sensors mounted on the left, front and right of the robot fish, as well as an inertial measurement unit, from which the surrounding obstacles and moving direction can be sensed. Based on these sensor signals, the closed-loop CPG-based control can drive the robot fish to avoid obstacles and to track designated directions. Four sets of experiments are presented, including avoiding a static obstacle, avoiding a moving obstacle, tracking a designated direction and tracking a designated direction with an obstacle in the path. The experiment results indicated that the presented control strategy worked well and the robot fish can accomplish the obstacle avoidance and direction tracking effectively.

Animal robots have outstanding advantages over traditional robots in their own energy supplies, orientation, and natural concealment, delivering significant value in the theories and applications of neural science, national security, and other fields. Presently, many animal robots have been fabricated, but researches about the applications of avian robots are still lacking. In this study, we constructed a Pigeon Robot System (PRS), optimized the electric stimulation parameters, assessed the electric stimulus of navigation, and evaluated the navigation efficiency in the field. Biphasic pulse constant current pattern was adapted, and the optimal stimulus parameters of 4 nuclei tested were of amplitude 0.3 mA, 5 pulse trains, frequency 25 Hz, 5 pulses, and a 25% duty cycle. Effective ratio of left and right steering behavior response to electric stimulus dorsointermedius ventralis anterior nuclei was 67% and 83%, respectively (mean value 75%). Electrical stimulation efficiency was 0.34 – 0.68 and path efficiency was 0.72 – 0.85 among pigeon robot individuals in the open field. Neither electrical stimulation efficiency nor path efficiency differed significantly (P > 0.05), suggesting that the navigational PRS performance was not biased in either direction. PRS can achieve continuous navigation along simple pathways and provide the necessary application infrastructure and technical reference for the development of animal robot navigation technology.

The Flapping Rotary Wing (FRW) is a micro air vehicle wing layout coupling flapping, pitching, and rotating motions. It can gain benefits in high lift from a fast passive rotating motion, which is tightly related to the passive pitching motion directly caused by wing flexible deformation. Therefore, flexible deformation is crucial for the wing kinematics and aerodynamic performance of an FRW. In this paper, we explored the effect of flexibility on wing kinematics and aerodynamics on the basis of a mechanical FRW model. A photogrammetric method was adopted to capture motion images according to which wing orientations and deformations were reconstructed. Corresponding aerodynamic force was computed using computational fluid dynamic method, and wing kinematics and deformations were used as simulation inputs. The experimental measurements presented the real orientation and deformation pattern of a real FRW. The wing passive deformation of a high-intensity FRW was found to be mainly caused by inertial force, and a linear positive spanwise twist was observed in the FRW. The effects of wing deformation on aerodynamic force production and the underlying mechanism were addressed. Results showed that lift augment, rotating moment enhancement, and power efficiency improvement can be achieved when a wing becomes flexible. Wing spanwise twist mainly accounts for these changes in aerodynamics, and increment in spanwise twist could further contributes to aerodynamic improvement.

The potential of electromagnetic fields (EMFs) for disease treatment and health enhancement has been actively pursued over the recent decades. This review first provides a general introduction about natural EMFs and related biological effects. Then the recent progress on the EMF treatment of some common diseases (such as cancer, diabetes, wound healing and neurological diseases, etc.) has been carefully reviewed and summarized. Yet, the blindness on the selection of therapeutic EMF parameters still hinders the broad application of EMF therapy. Moreover, the unclear mechanism of EMF function and poor reproducibility of experimental results also remain big challenges in the field of bioelectromagnetics. Bionics is a useful methodology that gains inspiration from nature to serve human life and industry. We have discussed the feasibility of applying bionic approach on the selection of therapeutic EMFs, which is based on the findings of natural EMFs. Finally, we advocate that the detailed information of EMFs and biological samples should be thoroughly recorded in future research and reported in publications. In addition, the publication of studies with negative results should also be allowed.