Wall climbing robots can be used to undertake missions in many unstructured environments. However, current wall climbing robots have mobility difficulties such as in the turning or accelarating. One of the main reasons for the limitations is the poor flexibility of the spines. Soft robotic technology can actively enable structure deformation and stiffness varations, which provides a solution for the design of active flexible spines. This research utilizes pneumatic soft actuators to design a flexible spine with the abilities of actively bending and twisting by each joint. Using bending and torsion moment equilibriums, respectively, from air pressure to material deformations, the bending and twisting models for a single actuator with respect to different pressure are obtained. The theoretical models are verified by finite-element method simulations and experimental tests. In addition, the bending and twisiting motions of single joint and whole spine are analytically modeled. The results show that the bionic spine can perform desired deformations in accordance with the applied pressure on specified chambers. The variations of the stiffness are also numerically assessed. Finally, the effectiveness of the bionic flexible spine for actively producing sequenced motions as biological spine is experimentally validated. This work demonstrated that the peneumatic spine is potential to improve the spine flexibility of wall climbing robot.

Total shoulder arthroplasty is a standard restorative procedure practiced by orthopedists to diagnose shoulder arthritis in which a prosthesis replaces the whole joint or a part of the joint. It is often challenging for doctors to identify the exact model and manufacturer of the prosthesis when it is unknown. This paper proposes a transfer learning-based class imbalance-aware prosthesis detection method to detect the implant’s manufacturer automatically from shoulder X-ray images. The framework of the method proposes a novel training approach and a new set of batch-normalization, dropout, and fully convolutional layers in the head network. It employs cyclical learning rates and weighting-based loss calculation mechanism. These modifcations aid in faster convergence, avoid local-minima stagnation, and remove the training bias caused by imbalanced dataset. The proposed method is evaluated using seven well-known pre-trained models of VGGNet, ResNet, and DenseNet families. Experimentation is performed on a shoulder implant benchmark dataset consisting of 597 shoulder X-ray images. The proposed method improves the classifcation performance of all pre-trained models by 10–12%. The DenseNet-201-based variant has achieved the highest classifcation accuracy of 89.5%, which is 10% higher than existing methods. Further, to validate and generalize the proposed method, the existing baseline dataset is supplemented to six classes, including samples of two more implant manufacturers. Experimental results have shown average accuracy of 86.7% for the extended dataset and show the preeminence of the proposed method.

While sharkskin surface roughness in terms of denticle morphology has been hypothesized but remains yet controversial to be ca-pable of achieving turbulent flow control and drag reduction, sharkskin-inspired “riblets” have been reported to be an effective biomimetic design. Here we address an integrated study of biomimetic riblets inspired by sharkskin denticles by combining 3D digitizing and mod-eling of “fresh” denticles and computational fluid dynamic modeling of turbulent flows on a rough surface with staggered denticles and hound-tooth-patterned grooves. Realistic microstructures of denticles in five shark species of Galapagos, great white, whitetip reef, blacktip reef, and hammerhead sharks were first measured and digitized in three fold: (1) 2D imaging of lubricated sharkskin in a wet state by means of a “nano-suit” technique with a Field-Emission Scanning Electron Microscope (FE-SEM); (2) 3D structures of sharkskin denticles with a micro-focus X-ray CT; and (3) single denticles of the five shark species in a 3D manner with 3D-CAD. The denticles at mid-body location in the five species were observed to have a structure of five non-uniform-ridges (herein termed “non-uniform grooves”) with Angles Of Inclination (AOI) ranging over 20? – 32?. Hydrodynamics associated with the unique five-ridge denticles were then in-vestigated through modeling turbulent flow past a denticle-staggered skin surface. We further constructed a biomimetic riblet model inspired by the non-uniform grooves and investigated the hydrodynamic effects of height-to-spacing ratios of mid-ridge and side-ridges. Our results indicate that the morphological non-uniformity in sharkskin denticles likely plays a critical role in passively controlling local turbulent flow and point to the potential of denticle-inspired biomimetic riblets for turbulent-flow control in aquatic vehicles as well as other fluid machinery.

As the basis of flight behavior, the initiation process of insect flight is accompanied by a transition from crawling mode to flight mode, and is clearly important and complex. Insects take flight from a vertical surface, which is more difficult than takeoff from a horizontal plane, but greatly expands the space of activity and provides us with an excellent bionic model. In this study, the entire process of a butterfly alighting from a vertical surface was captured by a high-speed camera system, and the movements of its body and wings were accurately measured for the first time. After analyzing the movement of the center of mass, it was found that before initiation, the acceleration perpendicular to the wall was much greater than the acceleration parallel to the wall, reflecting the positive effects of the legs during the initiation process. However, the angular velocity of the body showed that this process was unstable, and was further destabilized as the flight speed increased. Comparing the angles between the body and the vertical direction before and after leaving the wall, a significant change in body posture was found, evidencing the action of aerodynamic forces on the body. The movement of the wings was further analyzed to obtain the laws of the three Euler angles, thus revealing the locomotory mechanism of the butterfly taking off from the vertical surface. 

All 18 extant species of penguin are strongly countershaded, having dark dorsal and light ventral coloration. In this paper, the thermal effects of this body color in penguins are investigated through analytical and observational analyses. First, a thermal analysis that takes into account the environmental characteristics of penguins’ habitats, fluxes, and morphology is used to analytically calculate penguin dorsal surface temperature. Next, a turbulent analytical solution for a heated boundary layer over a flat plate is applied to show that the dark color on the top of the penguins’ bodies is very effective at skin drag reduction. To verify this result, a 2D model penguin is computationally analyzed at different temperatures, confirming in principle underwater skin drag reduction through color-based surface warming with efficiency savings of up to 30%. Finally, to study how color-based increases in body surface temperatures are maintained through foraging dives, thermal cameras are used to measure the surface temperature of captive penguins before and after dives. This study shows conceptually that dark dorsal coloration in penguins could have a significant influence on in-water drag.

There are significant advantages to investigate underwater attachments, which would be valuable in providing inspirations and design strategies for multi-functional surfaces and underwater robots. Here, an abalone-inspired sucker integrating an elastic body and a membrane structure is proposed and fabricated filled with rigid quartz particles to adjust the backing stiffness of the contact like abalone. The membrane is used to conform and contact surfaces well, the center area of which can be pulled in exposed to a negative pressure differential, to create a suction cavity. The pulling experiments indicate that the sucker can adhere to three-dimensional surfaces with both suction and adhesion mechanisms in both dry and liquid environments. The switching between soft/hard contact states leads to the change of adhesive strength over 30 times. Furthermore, we provide theoretical analysis on how the sucker work well in both dry and liquid environments. Finally, the developed sucker can easily lift up smooth planar objects and 3D objects, and can grip objects both smaller and larger than the size of the sucker, which have a difficulty for conventional suckers or friction-based grippers. The potential application of the sucker in flexible transfer robot is demonstrated on various surfaces and environments, paving the way for further bio-inspired adhesive designs for both dry and wet scenarios.

Dynastes tityus (D. tityus) is a typical beetle whose elytra are light and strong. The primary function of elytra is to protect beetle’s hindwings. In this paper, D. tityus elytra were selected as the biological prototype for the investigation to obtain bio-inspirations for the design and development of light materials with high ratio of strength to mass. Firstly, the microstructure investigation and quasi-static nanoindentation tests have been carried out on the ten samples of the selected elytra of D. tityus to reveal their mechanical properties and microstructures. Secondly, based on the findings from the microstructure investigation and nanoindentation tests, three models of bio-inspired materials have been proposed for further study to gain the deep understanding of the relationships between the special me-chanical characteristics and microstructures. Then Finite Element Analysis (FEA) simulations have been performed on the three models for harvesting the bio-inspirations for the initial design of light materials. Finally, through comparative analysis of the findings from the microstructure investigation, the nanoindentation tests and the simulations, some meaningful bio-inspirations have been reaped for the future optimization of the design and development of light materials with high ratio of strength to mass.

In the present work, polyester composites reinforced with a newly identified Cyperus pangorei fiber (CPF) were developed by compression moulding technique. The effects of varying fiber content and fiber length on the mechanical properties of the Cyperus pangorei fiber reinforced polyester composites (CPFCs) such as tensile, flexural, and impact properties were studied. Mechanical strength of the CPFCs increased with fiber length up to 40 mm beyond which a reverse trend was observed. Based on the test results, it was con-cluded that the critical fiber length and the optimum fiber weight percentage were 40 mm and 40 wt% respectively. The maximum increase of 164% and 117% were found for the tensile and flexural strength of the composite with 40 mm fiber length and 40 wt% fiber content, respectively. On the other hand, a 64% increase in impact strength was noticed for the optimum case. The increasing contact surface between the fiber and the polyester matrix in optimum condition can restrict the probability of fiber pullout and in turn can make the composite carry more load. The chemical structure of CPF was also analyzed using Fourier-Transform Infrared Spectroscopy (FTIR) spectrum. The morphological analysis of fractured samples was performed using Scanning Electron Microscopy (SEM) to understand the interfacial bonding between CPFs and polyester matrix. The optimal composite can be a suitable alternative in the field of structural applications in construction and automobile industries.

Motivated by optimal combination of paired wings configuration and stroke-plane inclination in biological flapping flights that can achieve high aerodynamic performance, we propose a biomimetic rotor-configuration design to explore optimal aerodynamic performance in multirotor drones. While aerodynamic interactions among propellers in multirotor Unmanned Aerial Vehicles (UAVs) play a crucial role in lift force production and Figure of Merit (FM) efficiency, the rotor-configuration effect remains poorly understood. Here we address a Computational Fluid Dynamics (CFD)-based study on optimal aerodynamic performance of the rotor-configuration in hovering quadrotor drones with a specific focus on the aerodynamic effects of tip distance, height difference and tilt angle of propellers. Our results indicate that the tip distance-induced interactions can most alter lift force production and hence lead to remarked improvement in FM, and the height difference also plays a key role in improving aerodynamic performance, while the tilt angle effect is less important. Furthermore, we carried out an extensive analysis to explore the optimal aerodynamic performance of the rotor-configuration over a broad parameter space, by combining the CFD-based simulations and a novel surrogate model. We find that a rotor-configuration with a large tip distance and some height difference with zero tilt angle is capable of optimizing both lift force production and FM, which could offer a novel optimal design as well as maneuver strategy for multirotor UAVs.

Biobased smart packaging is been the most interesting research field. In this study, pH-sensitive films based on anthocyanin molecules from red cabbage and sepiolite mineral nano-clay as functional additives were studied. The films were fabricated by casting method of blend polymer Chitosan/Poly (Vinyl Alcohol) at two fillers loading (5wt.% and 10wt.%). The structural, morphological, thermal, optical, hygroscopic, and mechanical properties as well as the pH sensitivity of films were investigated. The thermal properties confirm that the amount of the anthocyanin in sepiolite was around 6.4%. The tensile strength and the young’s modulus of produced composites at 10wt.% sepiolite–anthocyanin content was increased to 8.90 MPa and 163 MPa, respectively. The maximum water absorption that the films may absorb was 12.3%. pH sensitivity analysis showed that the Smart films change the color by changing the pH level, from pink at pH lower than 6 to yellow at pH higher than 6. Thus, the developed pH-sensitive films show band gaps in visible light that make them useful for monitoring milk spoilage.

In the field of robotics to enhance the interaction with humans in real-time and in the bioengineering field to develop prosthetic devices, the need for artificial skin is in high demand. In this work, the hydrogen-bonded complex network structure of the Pectin/PEG composite has been designed, resulting in the free-standing film functioning as a temperature-sensing device. With the gelation technique and the addition of PEG, the film’s flexibility and conductivity were enhanced. The fabricated device worked at a low voltage of 1 V supply with high throughput. With different dimensions, three devices were fabricated, and the maximum-induced ionic current was 34 μA?±?5%. The device has an average sensitivity of 1.3–2.7 μA/°C over the range of 30 °C to 42 °C. The device's fastest response time to sense the temperature change was 2 s?±?5%. The present device exhibits good stability for a long duration of time. These pectin/PEG films can be used as biomimetic skin to improve the efficiency in sensing the temperature.

This paper proposes a modified version of the Dwarf Mongoose Optimization Algorithm (IDMO) for constrained engineering design problems. This optimization technique modifies the base algorithm (DMO) in three simple but effective ways. First, the alpha selection in IDMO differs from the DMO, where evaluating the probability value of each fitness is just a computational overhead and contributes nothing to the quality of the alpha or other group members. The fittest dwarf mongoose is selected as the alpha, and a new operator ω is introduced, which controls the alpha movement, thereby enhancing the exploration ability and exploitability of the IDMO. Second, the scout group movements are modified by randomization to introduce diversity in the search process and explore unvisited areas. Finally, the babysitter's exchange criterium is modified such that once the criterium is met, the babysitters that are exchanged interact with the dwarf mongoose exchanging them to gain information about food sources and sleeping mounds, which could result in better-fitted mongooses instead of initializing them afresh as done in DMO, then the counter is reset to zero. The proposed IDMO was used to solve the classical and CEC 2020 benchmark functions and 12 continuous/discrete engineering optimization problems. The performance of the IDMO, using different performance metrics and statistical analysis, is compared with the DMO and eight other existing algorithms. In most cases, the results show that solutions achieved by the IDMO are better than those obtained by the existing algorithms

Bird feathers sustain bending and vibrations during flight. Such unwanted vibrations could potentially cause noise and flight instabilities. Damping could alter the system response, resulting in improving quiet flight, stability, and controllability. Vanes of feathers are known to be indispensable for supporting the aerodynamic function of the wings. The relationship between the hierarchical structures of vanes and the mechanical properties of the feather has been previously studied. However, still little is known about their relationship with feathers’ damping properties. Here, the role of vanes in feathers’ damping properties was quantified. The vibrations of the feathers with vanes and the bare shaft without vanes after step deflections in the plane of the vanes and perpendicular to it were measured using high-speed video recording. The presence of several main natural vibration modes was observed in the feathers with vanes. After trimming vanes, more vibration modes were observed, the fundamental frequencies increased by 51–70%, and the damping ratio decreased by 38–60%. Therefore, we suggest that vanes largely increase feather damping properties. Damping mechanisms based on the morphology of feather vanes are discussed. The aerodynamic damping is connected with the planar vane surface, the structural damping is related to the interlocking between barbules and barbs, and the material damping is caused by the foamy medulla inside barbs.

The wheel-legged biped robot is a typical ground-based mobile robot that can combine the high velocity and high efciency pertaining to wheeled motion and the strong, obstacle-crossing performance associated with legged motion. These robots have gradually exhibited satisfactory application potential in various harsh scenarios such as rubble rescue, military operations, and wilderness exploration. Wheel-legged biped robots are divided into four categories according to the open–close chain structure forms and operation task modes, and the latest technology research status is summarized in this paper. The hardware control system, control method, and application are analyzed, and the dynamic balance control for the two-wheel, biomimetic jumping control for the legs and whole-body control for integrating the wheels and legs are analyzed. In summary, it is observed that the current research exhibits problems, such as the insufcient application of novel materials and a rigid–fexible coupling design; the limited application of the advanced, intelligent control methods; the inadequate understanding of the bionic jumping mechanisms in robot legs; and the insufcient coordination ability of the multi-modal motion, which do not exhibit practical application for the wheel-legged biped robots. Finally, this study discusses the key research directions and development trends for the wheel-legged biped robots.

Biological water striders have advantages such as fexible movement, low disturbance to the water surface, and low noise. Researchers have developed a large number of biomimetic water strider robots based on their movement mechanism, which have broad application prospects in water quality testing, water surface reconnaissance, and search. This article mainly reviews the research progress of biomimetic water strider robots. First, the biological and kinematic characteristics of water striders are outlined, and some mechanical parameters of biological water striders are summarized. The basic equations of water strider movement are then described. Next, an overview is given of the past and current work on skating and jumping movements of biomimetic water strider robots based on surface tension and water pressure dominance. Based on the current research status of biomimetic water strider robots, the shortcomings of current research on biomimetic water striders are summarized, and the future development of biomimetic water strider robots is discussed. This article provides new insights for the design of biomimetic water strider robots.

Cartilage regeneration and repair are considered clinical challenges since cartilage has limited capability for reconstruction. Although tissue-engineered materials have the ability to repair cartilage, they have weak mechanical characteristics and cannot resist long-term overload. On the other hand, surgery to replace the joint is frequently done to treat signifcant cartilage deterioration these days. However, the materials that are being used for replacement have high friction coefcients, lack shock absorption functions, and lack cushioning. Further research on natural articular cartilage structure and function may lead to bionic hydrogels, which have suitable physicochemical and biological characteristics (e.g., tribological and mechanical properties and the ability to support loadbearing capability), but need improvements. Based on their tribological and mechanical characteristics, the current review highlights the most recent advancements of bionic hydrogels used for articular cartilage, highlighting both the feld's recent progress and its potential for future research. For this reason, frstly, some important property improvement methods of bionic hydrogels are discussed and then, the recent fndings of various research on the making of those bionic materials are provided and compared. It seems that by using some modifcations such as product design, surface treatments, animal tests, controlling the isoelectric point of hydrogels, and computer simulation, the intended mechanical and tribological characteristics of natural articular cartilage may be attained by the bionic hydrogels.

Natural composites, formed through biomineralization, have highly ordered structures which have been aptly explored for functional applications. Though the role of organic phases has been well understood in biomineralization, not enough attention has been paid to the role of bio-membranes which are often found encapsulating the chamber in which mineralization occurs. We have used the natural protein and semi-permeable membrane of chicken eggs to grow different materials such as ceramics, semi-metals and metals to understand the role of bio-membranes in biomineralization. We here report the successful biomimetic synthesis of calcite, cadmium sulphide, and silver having homogeneous morphologies. We have found that the membrane operates like a tuned gateway, playing a significant role in controlling the morphology of the inorganic crystals formed during biomineralization.

Based on the research of a biological olfactory system, a novel chaotic neural network model - K set model has been es-tablished. This chaotic neural network not only simulates the real brain activity of an olfactory system, but also presents a novel chaotic concept for signal processing and pattern recognition. The characteristics of the K set models are investigated and show that a KIII model can be used for image pattern classification.

Locomotion ability, efficiency and reliability are key targets for a good robot. The linkage mechanism for robot locomotion is a discontinuous-constraint metamorphic mechanism. Here we set up equations to present the discontinuous-constraint, point out that driving and controlling are the key points to improve the performance and efficiency of the linkage mechanism. Inspired by controlling strategy of the motor nervous system in peripheral vertebrae to the locomotion, we draw off motor control and drive strategy.

Using eucollagen solutions from ox hide, we cast collagen films to assess the influence of calcium and silica on the re-constitution of the fibrous structure of collagen. The tensile strength and the breaking elongation of the reconstituted collagen films were measured and analysed. Significant differences were observed between reconstituted collagen films with and without calcium and silica. The breaking elongation of the films obtained in the presence of silica was significantly greater, and the degradation was lower than other films of reconstituted collagen. Collagen and chitosan do not exist together as blends in nature, but the specific properties of each may be used to produce in biomimetic way man-made blends with biomedical applications, that confer unique structural, mechanical (detail) and in-vivo properties.

Biomimetic leg designs often appear to be arbitrarily chosen. To make a more objective choice regarding biomimetic leg configuration for small canine-inspired robots, we compare one hind leg to the same leg arranged in a different orientation, and show that the less biomimetic leg provides better performance. This differently-oriented leg design, which we call “trans-verse-mirrored” was more efficient and faster, both in simulation and experiment even though both leg configurations used the same passive and active components, rest angles, and monoarticular knee spring.  In experiments the normal configuration had a maximum speed of 0.33 m•s−1 and a specific resistance of 5.1. Conversely, the less biomimetic transverse-mirrored configura-tion had a maximum speed of 0.4 m•s−1 and specific resistance of 3.9. Therefore the transverse-mirrored leg’s best performance yields a 21% increase in speed and 24% decrease in specific resistance when compared to the best performance achieved in the normal biomimetic leg. The major underlying reason is that the knee spring engages more readily in the transverse-mirrored configuration, resulting in this faster and more efficient locomotion. The conclusion is that simply copying from nature does not lead to optimal performance and that insight into the role played by passive design components on natural locomotory dynamics is important.

A microclimatic layer of the green façade is proven to have specific temperature and flow conditions on the building en-velope. Lower temperatures and wind velocities, and higher relative humidity in the microclimatic layer are the characteristics of vertical greenery systems, which cause lower energy consumption for the cooling and heating of buildings. Despite innova-tive architectural solutions, there are some drawbacks to applying vertical greenery on building envelopes. In this study, a bionic façade that mimics the positive effects and eliminates the disadvantages of green façades is presented. The bionic façade consists of bionic leaves, which are made of photovoltaic cells and evaporative matrices. A real scale experiment was carried out in the summer to evaluate the potential of the cooling efficiency of the microclimatic layer and a new photovoltaic cooling technique. The results show a good agreement of the thermal performance between the bionic and the green façade and up to 20.8 K lower surface temperatures of photovoltaic cells, which increase the daily electricity yield by 6.6%.

The knowledge of wing orientation and deformation during flapping flight is necessary for a complete aerodynamic analysis, but to date those kinematic features have not been simultaneously quantified for free-flying insects. A projected comb-fringe (PCF) method has been developed for measuring spanwise camber changes on free-flying dragonflies and on beating-flying dragonflies through the course of a wingbeat, which bases on projecting a fringe pattern over the whole measurement area and then measuring the wing deformation from the distorted fringe pattern. Experimental results demonstrate substantial camber changes both along the wingspan and through the course of a wingbeat. The ratio of camber deformation to chord length for hind wing is up to 0.11 at 75% spanwise with a flapping angle of -0.66 degree for a free-flying dragonfly.

A Body and/or Caudal Fin (BCF) fish modulate its body stiffness by mechanisms consisting of antagonistic muscles. The mecha-nisms can be considered as Redundant Planar Rotational Parallel Mechanisms (RPRPM) with antagonistic flexible elements. For a typical RPRPM, its stiffness consists of the adjustable stiffness resulting from internal forces and the inherent stiffness caused by inherent com-pliances of flexible elements. In order to decouple the adjustable stiffness from the inherent stiffness and expand the range of stiffness variation, a variable-stiffness decoupled mechanism based on the Mechanically Adjustable Compliance and Controllable Equilibrium Position Actuator (MACCEPA) is presented and used to construct a soft robotic fish with large stiffness variation. According to the analysis of the evolution from RPRPM to MACCEPA, it can be found that MACCEPA is just a special type of RPRPM with only an adjustable stiffness. In addition, MACCEPA existed before RPRPM mechanism. The prototype of the soft robotic fish with variable-
stiffness decoupled mechanisms is built to explore the relationships between the body stiffness and the swimming performance. It is validated experimentally that the stiffness variation multiple of the robotic fish is raised, the swimming performance of the robotic fish is improved when the stiffness is modulated to match the driving frequency.

A physical model for a micro air vehicle with Flapping Rotary Wings (FRW) is investigated by measuring the wing kine-matics in trim conditions and computing the corresponding aerodynamic force using computational fluid dynamics. In order to capture the motion image and reconstruct the positions and orientations of the wing, the photogrammetric method is adopted and a method for automated recognition of the marked points is developed. The characteristics of the realistic wing kinematics are presented. The results show that the non-dimensional rotating speed is a linear function of non-dimensional flapping frequency regardless of the initial angles of attack. Moreover, the effects of wing kinematics on aerodynamic force production and the underlying mechanism are analyzed. The results show that the wing passive pitching caused by elastic deformation can sig-nificantly enhance lift production. The Strouhal number of the FRW is much higher than that of general flapping wings, indi-cating the stronger unsteadiness of flows in FRW.

This paper presents a control approach for bounding gait of quadruped robots by applying the concept of Virtual Constraints (VCs). A VC is a relative motion relation between two related joints imposed to the robots in terms of a specified gait, which can drive the robot to run with desired gait. To determine VCs for highly dynamic bounding gait, the limit cycle motions of the passive dynamic model of bounding gait are analyzed. The leg length and hip/shoulder angle trajectories corresponding to the limit cycles are parameterized by leg angles using 4 th-order polynomials. In order to track the calculated periodic motions, the polynomials are imposed on the robot as virtual motion constraints by a high-level state machine controller. A bounding speed feedback strategy is introduced to stabilize the robot running speed and enhance the stability. The control approach was applied to a newly designed lightweight bioinspired quadruped robot, AgiDog. The experimental results demonstrate that the robot can bound at a frequency up to 5 Hz and bound at a maximum speed of 1.2 m•s−1 in sagittal plane with a Froude number approximating to 1.

Plant can take water from soil up to several metres high. However, the mechanism of how water rises against gravity is still controversially discussed despite a few mechanisms have been proposed. Also, there still lacks of a critical transportation model because of the diversity and complex xylem structure of plants.
This paper mainly focuses on the water transport process within xylem and a mathematical model is presented. With a simplified micro channel from xylem structure and the calculation using the model of water migration in xylem, this paper identified the relationship between various forces and water migration velocity. The velocity of water migration within the plant stem is considered as detail as possible using all major forces involved, and a full mathmetical model is proposed to calculate and predict the velocity of water migration in plants.
Using details of a specific plant, the velocity of water migration in the plant can be calculated, and then compared to the experimental result from Magnetic Resonance Imaging (MRI). The two results match perfectly to each other, indicating the accuracy of the mathematical model, thus the mathematical model should have brighter future in further applications.

This paper presents a novel Central Pattern Generator (CPG) based rolling gait generation in a small-sized spherical robot and its nonlinear control mechanism. A rhythmic rolling pattern mimicking Pleurotya caterpillar is produced for the spherical robot locomotion. A synergetically combined feedforward-feedback control strategy is proposed. The feedforward component is generated from centrally connected network of CPGs in conjunction with nonlinear robot dynamics. Two nonlinear feedback control methods namely integral (first order) Sliding Mode Control (SMC) and High (or second) Order Sliding Mode Control (HOSMC) are proposed to regulate robot stability and gait robustness in the presence of matched parameter uncertainties and bounded external disturbances. Design, implementation and experimental evaluation of both roll gait control strategies for the spherical robot are done on smooth (indoor) and irregular (outdoor) ground surfaces. The performance of robot control is quantified by measuring the roll angle stability, phase plane convergence and wheel velocities. Experimental results show that proposed novel strategy is efficient in producing a stable rolling gait and robust control of a spherical robot on two different types of surfaces. It further shows that proposed high HOSMC strategy is more efficient in robust rolling gait control of a spherical robot compared to an integral first-order SMC on two different ground conditions.

Flap-bounding, a form of intermittent flight, is often exhibited by small birds over their entire range of flight speeds. Its purpose is unclear during low to medium speed (2 m•s−1 – 8 m•s−1) flight: aerodynamic models suggest continuous flapping would require less power output and lower cost of transport. To explore its functional significance at low speeds, we measured body trajectory and kinematics of wings and tail of two zebra finches (Taeniopygia guttata) during flights between two perches in a laboratory. The flights consisted of three phases: initial, descending and ascending. Zebra finch first accelerated using continuous flapping, then descended, featuring intermittent bounds. The flight was completed by ascending using nearly-continuous flapping. When exiting bounds in descending phase, they achieved higher velocity than that of pre-bound forward by swinging their body forward similar to pendular motion with conserved me-chanical energy. We recorded takeoffs of three black-capped chickadees (Poecile atricapillus) in the wild and also found similar kine-matics. Our modeling of power output indicated finch achieved higher velocity (13%) with lower cost of transport (9%) when descending, compared with continuous flapping in previously studied pigeons. Flap-bounding could be useful for unmanned aerial vehicle design by mimicking descending flight to achieve rapid take-off and transition to forward flight.

This paper presents a new Center of Gravity (COG) trajectory planning algorithm for a quadruped robot with redundant Degrees of Freedom (DOFs). Each leg has 7 DOFs, which allow the robot to exploit its kinematic redundancy for various locomotion and manipu-lation tasks. Also, the robot can suitably adapt to different environment (e.g., passing through a narrow gap) by simply changing the body posture. However, the robot has significant COG movement during the leg swinging phase due to the heavy leg weights; the weight of all the four legs takes up 80% of the robot’s total weight. To achieve stable walking in the presence of undesired COG movements, a new COG trajectory planning algorithm was proposed by using a combined Jacobian of COG and centroid of a support polygon including a foot contact constraint. Additionally, the inverse kinematics of each leg was solved by modified improved Jacobian pseudoinverse (mIJP) algorithm. The mIJP algorithm could generate desired trajectories for the joints even when the robot’s leg is in a singular posture. Owing to these proposed methods, the robot was able to perform various modes of locomotion both in simulations and experiments with improved stability.

The effect of asymmetric heaving motion on the aerodynamic performance of a two-dimensional flapping foil near a wall is studied numerically. The foil executes the heaving and pitching motion simultaneously. When the heaving motion is symmetric, the mean thrust coefficient monotonically increases with the decrease in mean distance between foil and wall. Meanwhile, the mean lift coefficient first increases and then decreases sharply. In addition, the negative mean lift coefficient appears when the foil is very close to the wall. After the introduction of asymmetric heaving motion, the influence of wall effect on the force behavior becomes complicated. The mean thrust coefficient is enhanced when the duration of upstroke is reduced. Moreover, more and more enhancement can be achieved when the foil approaches the wall gradually. On the other hand, the positive mean lift coefficient can be observed when the duration of downstroke is shortened. By checking the flow patterns around the foil, it is shown that the interaction between the vortex shed from the foil and the wall can greatly modify the pressure distribution along the foil surface. The results obtained here might be utilized to optimize the kinematics of the Micro Aerial Vehicles (MAVs) flying near a solid wall.

Loss of function of large tissues is an urgent clinical problem. Although the artificial microfluidic network fabricated in large tis-sue-engineered constructs has great promise, it is still difficult to develop an efficient vessel-like design to meet the requirements of the biomimetic vascular network for tissue engineering applications. In this study, we used a facile approach to fabricate a branched and multi-level vessel-like network in a large muscle scaffolds by combining stereolithography (SL) technology and enzymatic crosslinking mechanism. The morphology of microchannel cross-sections was characterized using micro-computed tomography. The square cross-sections were gradually changed to a seamless circular microfluidic network, which is similar to the natural blood vessel. In the different micro-channels, the velocity greatly affected the attachment and spread of Human Umbilical Vein Endothelial Cell (HUVEC)-Green Fluorescent Protein (GFP). Our study demonstrated that the branched and multi-level microchannel network simulates biomimetic microenvironments to promote endothelialization. The gelatin scaffolds in the circular vessel-like networks will likely support myoblast and surrounding tissue for clinical use.

The dragonfly has excellent flying capacity and its wings are typical 2-dimensional composite materials in micro-scale or nano-scale. The nanomechanical behavior of dragonfly membranous wings was investigated with a nanoindenter. It was shown that the maxima of the reduced modulus and nanohardness of the in-vivo and fresh dragonfly wings are about at position of 0.7L, where L is the wing length. It was found that the reduced modulus and nanohardness of radius of the wings of dragonfly are large. The reduced modulus and nanohardness of Costa, Radius and Postal veins of the in-vivo dragonfly wings are larger than those of the fresh ones. The deformation, stress and strain under the uniform load were analyzed with finite element simulation software ANSYS. The deformation is little and the distribution trend of the strain is probably in agreement with that of the stress. It is shown that the main veins have better stabilities and load-bearing capacities. The understanding of dragonfly wings’ nanomechanical properties would provide some references for improving some properties of 2-dimentional composite materials through the biomimetic designs. The realization of nanomechanical properties of dragonfly wings will provide inspirations for designing some new structures and materials of mechanical parts.

The ultrasonic scalpel has a number of excellent properties; however, its use in in vivo surgery is limited since the scalpel is not flexible enough. Changing the mechanism of ultrasonic vibration can allow the ultrasonic scalpel to bend. This paper reveals the mecha-nism of vibration generation of leaf-cutting ants, which is based on the microstructural and mechanical properties of special organs that produce the vibrations. Microstructural characteristics of cross-sections of the vibratory organ of Atta cephalotes were observed using scanning electron microscopy. It was found that the scraper perfectly matches the file plate dorsoventrally; however, the file teeth cannot catch the scraper. An exploration of the kinematics of the file-scraper device was subsequently carried out to reveal a face-to-face contact mode, facilitating a gentler engagement process. For the first time, the mechanism of vibration generation of leaf-cutting ants was inves-tigated using a laser micrometer and high-speed camera. Results reveal the file-scraper device significantly amplifies the input frequency by 125 times, and magnification depends mainly on the tooth spacing and speed of engagement. Finally, nanoindentation tests were performed on file and scraper samples. The results show that they have similar mechanical properties, which greatly reduces friction and wear. This paper may provide theoretical guidance for the development of bionic vibration generators.

This paper presents an Enhanced Moth-Flame Optimization (EMFO) technique based on Cultural Learning (CL) and Gaussian Mutation (GM). The mechanism of CL and the operator of GM are incorporated to the original algorithm of Moth-Flame Optimization (MFO). CL plays an important role in the inheritance of historical experiences and stimulates moths to obtain information from flames more effectively, which helps MFO enhance its searching ability. Furthermore, in order to overcome the disadvantage of trapping into local optima, the operator of GM is introduced to MFO. This operator acts on the best flame in order to generate several variant ones, which can increase the diversity. The proposed algorithm of EMFO has been comprehensively evaluated on 13 benchmark functions, in comparison with MFO. Simulation results verify that EMFO shows a significant improvement on MFO, in terms of solution quality and algorithmic reliability.

This paper proposes a hand exoskeleton system for evaluating hand functions. To evaluate hand functions, the hand exoskeleton system must be able to pull each finger joint, measure the finger joint angle and exerted force on the finger simultaneously. The proposed device uses serially connected 4-bar linkage structures, which have two embedded actuators with encoders and two loadcells per finger, to move each phalanx independently and measure the finger joint angles. A modular design was used for the exoskeleton, to facilitate the removal of unnecessary modules in different experiments and improve convenience. Silicon was used on the surface of the worn part to reduce the skin irritation that results from prolonged usage. This part was also designed to be compatible with various finger thicknesses. Using the proposed hand exoskeleton system, finger independence, multi-finger synergy, and finger joint stiffness were determined in five healthy subjects. The finger movement and force data collected in the experiments were used for analyzing three hand functions based on the physical and physiological phenomena.