A jumping mechanism can be an efficient mode of motion for small robots to overcome large obstacles on the ground and rough terrain. In this paper, we present a 7 g prototype of locust-inspired jumping mechanism that uses springs, wire, reduction gears, and a motor as the actuation components. The leg structure and muscles of a locust or grasshopper were mimicked using springs and wire, springs for passive extensor muscles, and a wire as a flexor muscle. A small motor was used to slowly charge the spring through a lever and gear system, and a cam with a special profile was used as a clicking mechanism for quick release of elastic energy stored in the springs to create a sudden kick for a quick jump. Performance analysis and experiments were conducted for comparison and performance estimation of the jumping mechanism prototype. Our prototype could produce standing jumps over obstacles that were about 14 times its own size (approximate to 71 cm) and a jumping distance of 20 times its own size (approximate to 100 cm).

The realization of a high-speed running robot is one of the most challenging problems in developing legged robots. The excellent performance of cheetahs provides inspiration for the control and mechanical design of such robots. This paper presents a three-dimensional model of a cheetah that predicts the locomotory behaviors of a running cheetah. Applying biological knowledge of the neural mechanism, we control the muscle flexion and extension during the stance phase, and control the positions of the joints in the flight phase via a PD controller to minimize complexity. The proposed control strategy is shown to achieve similar locomotion of a real cheetah. The simulation realizes good biological properties, such as the leg retraction, ground reaction force, and spring-like leg behavior. The stable bounding results show the promise of the controller in high-speed locomotion. The model can reach 2.7 m•s−1 as the highest speed, and can accelerate from 0 to 1.5 m•s−1 in one stride cycle. A mechanical structure based on this simulation is designed to demonstrate the control approach, and the most recently developed hindlimb controlled by the proposed controller is presented in swinging-leg experiments and jump-force experiments.

Most hovering insects flap their wings in a horizontal plane, called ‘normal hovering’. But some of the best hoverers, e.g. true hoverflies, hover with an inclined stroke plane. In the present paper, the longitudinal dynamic flight stability of a model hoverfly in inclined-stroke-plane hovering was studied. Computational fluid dynamics was used to compute the aerodynamic derivatives and the eigenvalue and eigenvector analysis was used to solve the equations of motion. The primary findings are as follows. (1) For inclined-stroke-plane hovering, the same three natural modes of motion as those for normal hovering were identified: one unstable oscillatory mode, one stable fast subsidence mode, and one stable slow subsidence mode. The unstable oscillatory mode and the fast subsidence mode mainly have horizontal translation and pitch rotation, and the slow subsidence mode mainly has vertical translation. (2) Because of the existence of the unstable oscillatory mode, inclined-stroke-plane hovering flight is not stable. (3) Although there are large differences in stroke plane and body orientations between the inclined-stroke-plane hovering and normal hovering, the relative position between the mean center of pressure and center of mass for these two cases is not very different, resulting in similar stability derivatives, hence similar dynamic stability properties for these two types of hovering.

Aerodynamic characteristics of the beetle, Trypoxylus dichotomus, which has a pair of elytra (forewings) and flexible hind wings, are investigated. Visualization experiments were conducted for various flight conditions of a beetle, Trypoxylus dichotomus: free, tethered, hovering, forward and climbing flights. Leading edge, trailing edge and tip vortices on both wings were observed clearly. The leading edge vortex was stable and remained on the top surface of the elytron for a wide interval during the downstroke of free forward flight. Hence, the elytron may have a considerable role in lift force generation of the beetle. In addition, we reveal a suction phenomenon between the gaps of the hind wing and the elytron in upstroke that may improve the positive lift force on the hind wing. We also found the reverse clap-fling mechanism of the T. dichotomus beetle in hovering flight. The hind wings touch together at the beginning of the upstroke.  The vortex generation, shedding and interaction give a better understanding of the detailed aerodynamic mechanism of beetle flight.

Microrobots is playing more and more important roles for medical applications, such as targeting tumoral lesions for therapeutic purposes, Minimally Invasive Surgery (MIS) and highly localized drug delivery. However, energy efficient propulsion system poses significant challenges for the implementation of such mobile robots. Flagellated chemotactic bacteria can be used as an effective integrated propulsion system for microrobots. In this paper, we proposed a new type of propulsion method that is inspired by the motility mechanism of flagellated chemotactic bacteria in different pH gradients. The pH gradient field was established in solution through electrolysis method. The distribution of the pH values in solution was measured with pH indicator and analyzed with image processing technology, and the mechanism by which the pH values changed was also discussed. The swimming speed and direction of the bacteria were studied experimentally. Through analyzing the key parameters, such as stabilization time and electrode voltage, the optimal design of propulsion mechanism based on bacteria motion in the pH gradient field was proven.

A new type of propeller that is optimized for low Reynolds numbers is required to propel a small object in a medium where the flow is dominated by viscous rather than inertial forces. A propeller in the shape of a bacterial flagellum seems an appropriate choice for driving a small object. Accordingly, in this study, we visualized the velocity field induced by a spring-like propeller inspired by the Escherichia coli flagellum, using a macroscopic model and applying stereoscopic particle image velocimetry. We also experimentally evaluated the effect of pitch and rotational speed on the performance of this flagellar propeller. Silicone oil, which has a kinematic viscosity 100,000 times that of water, was used as the working fluid to generate a low Reynolds number for the macroscopic model. Thrust, torque, and velocity were measured as functions of pitch and rotational speed, and the efficiency of the propeller was calculated from the measured results. We found that the flagellar propeller reached a maximum efficiency when the pitch angle was approximately 53?. Compared to pitch, rotational speed had a relatively small effect on the efficiency, and the pitch altered the flow pattern behind the rotating propeller.

The turtle shell is an amazing structure optimized through the long-term evolution by nature. This paper reports the mechanical response of the shell (Red-ear turtle) to static and dynamic loads, respectively. It is found that the turtle shell under a compressive load yields the maximum vertical displacement at the rear end, but the vertical displacement at the front end is only half of that at the rear end. The maximum horizontal displacement of the shell also occurs at the rear end. It is believed that such a deformation pattern is helpful for protecting the turtle’s internal organs and its head. The principal stress directions in the inside surface of the shell under a compressive load are almost the same as those of the biofiber distribution in the inside surface, which results in the strong bending resistance of the turtle shell.

A computer-aided design model for a fixed partial denture was constructed and used in a finite element analysis to study the overall load sharing mechanism between the fixed partial denture and oral structures while the denture base rested on the alveolar ridge. To investigate the consequences of non-contact conditions, three additional models were generated incorporating a uniform clearance of 0.125 mm, 0.25 mm, and 0.5 mm, respectively. A 100 N static load located at the free end of the pros-thesis was applied while the distal portion of the jaw was set fixed. The results show that whilst releasing the ridge almost entirely, the presence of the clearance drastically increased the load on the splinting teeth. A pull-out force on the canine tooth of about 44 N was computed, accompanied by a mesio-distal moment of about 500 N?cm. The combination of which was similar to the tooth extraction maneuver performed by the dentist. In contrast, the second premolar was found to bear a push-in force of almost 115 N. The first molar, though barely solicited in the contact condition, became substantially loaded in non-contact conditions, which validates the choice of sacrificing three teeth to support the denture.

Plantar Region of Interest (ROI) detection is important for the early diagnosis and treatment of morphologic defects of the foot and foot bionic research. Conventional methods have employed complex procedures and expensive instruments which prohibit their widespread use in healthcare. In this paper an automatic plantar ROIs detection method using a customized low-cost pressure acquisition device is proposed. Plantar pressure data and 3D motion capture data were collected from 28 subjects (14 healthy subjects and 14 subjects with hallux valgus). The maximal inter-frame difference during the stance phase was calculated. Consequently, the ROIs were defined by the first-order difference in combination with prior anatomic knowledge. The anatomic locations were determined by the maximal inter-frame difference and second maximal inter-frame difference, which nearly coincided. Our system can achieve average recognition accuracies of 92.90%, 89.30%, 89.30%, 92.90%, 92.90%, and 89.30% for plantar ROIs hallux and metatarsi I–V, respectively, as compared with the annotations using the 3D motion capture system. The maximal difference of metatarsus heads II-V, and the impulse of the medial and lateral heel features made a significant contribution to the classification of hallux valgus and healthy subjects with ? 80% sensitivity and specificity. Furthermore, the plantar pressure acquisition system is portable and convenient to use, thus can be used in home- or community-based healthcare applications.

We wish to draw the attention to a potential deficiency in the biocompatibility of polystyrene cell culture dishes which is caused by a softening of the material under relevant culture conditions. The finding confirms the central hypothesis of our previous model study. In it we assumed a local increase in pH at the interface between the hydrophilic polymer and liquid. The finding is of considerable biological interest. Polystyrene tissue culture dishes are now in use for 50 years. To the best of our knowledge their biocompatibility has never been challenged. Here we report the first experimental proof that exposure to water softens the surface of polystyrene Petri dishes. We expect that our results will stimulate the development of a new generation of cell culture devices, including Petri dishes and culture flasks, and the establishment of improved biomimetic settings for tissue engineering and stem cell research. New non-swelling biomaterials or nanocoatings designed to reduce the swelling of polymer culture dishes could improve cell performance. The need for further study is clear.

With the rapid development of semiconductor technology and the increasing proliferation of emission sources, digital circuits are frequently used in harsh and hostile electromagnetic environments. Electrostatic Discharge (ESD) interferences are gradually gaining prominence, resulting in performance degradations, malfunctions and disturbances in component and/or system level applications. Conventional solutions to such problems are shielding, filtering and grounding. This paper proposes a novel Evolvable Digital Circuit (EDC) for intrinsic immunity. The key idea is motivated by the noise-robustness and fault-tolerance of the biological system. First, the architecture of the EDC is designed based on the cell structure. Then, ESD immunity tests are carried out on the most fragile element of the EDC in operation. Based on the results, fault models are also presented to simulate different functional disturbances. Finally, the immunity of the EDC is evaluated while it is exposed to a variety of simulated environments. The results which demonstrate a graceful immunity to ESD interference are presented.

Cuttlebone signifies a special class of ultra-lightweight cellular natural material possessing unique chemical, mechanical and structural properties, which have drawn considerable attention in the literature. The aim of this paper is to better understand the mechanical and biological roles of cuttlebone. First, the existing literature concerning the characterisation and potential applications inspired by this remarkable biomaterial is critiqued. Second, the finite element-based homogenisation method is used to verify that morphological variations within individual cuttlebone samples have minimal impact on the effective mechanical properties. This finding agrees with existing literature, which suggests that cuttlebone strength is dictated by the cuttlefish habitation depth. Subsequently, this homogenisation approach is further developed to characterise the effective mechanical bulk modulus and biofluidic permeability that cuttlebone provides, thereby quantifying its mechanical and transporting functionalities to inspire bionic design of structures and materials for more extensive applications. Finally, a brief rationale for the need to design a biomimetic material inspired by the cuttlebone microstructure is provided, based on the preceding investigation.

Biological structural fixed joints exhibit unique attributes, including highly optimized fiber paths which minimize stress concentrations. In addition, since the joints consist of continuous, uncut fiber architectures, the joints enable the organism to transport information and chemicals from one part of the body to the other. To the contrary, sections of man-made composite material structures are often joined using bolted or bonded joints, which involve low strength and high stress concentrations. These methods are also expensive to achieve. Additional functions such as fluid transport, electrical signal delivery, and thermal conductivity across the joints typically require parasitic tubes, wires, and attachment clips. By using the biomimetic methods, we seek to overcome the limitations which are present in the conventional methods.
In the present work, biomimetic co-cured composite sandwich T-joints were constructed using unidirectional glass fiber, epoxy resin, and structural foam. The joints were fabricated using the wet lay-up vacuum bag resin infusion method. Foam sandwich T-joints with multiple continuous fiber architectures and sandwich foam thickness were prepared. The designs were tested in quasi-static bending using a mechanical load frame. The significant weight savings using the biomimetic approaches is discussed, as well as a comparison of failure modes versus architecture is described.

In order to fabricate a biomimetic skin for an octopus inspired robot, a new process was developed based on mechanical properties measured from real octopus skin. Various knitted nylon textiles were tested and the one of 10-denier nylon was chosen as reinforcement. A combination of Ecoflex 0030 and 0010 silicone rubbers was used as matrix of the composite to obtain the right stiffness for the skin-analogue system. The open mould fabrication process developed allows air bubble to escape easily and the artificial skin produced was thin and waterproof. Material properties of the biomimetic skin were characterised using static tensile and instrumented scissors cutting tests. The Young’s moduli of the artificial skin are 0.08 MPa and 0.13 MPa in the longitudinal and transverse directions, which are much lower than those of the octopus skin. The strength and fracture toughness of the artificial skin, on the other hand are higher than those of real octopus skins. Conically-shaped skin prototypes to be used to cover the robotic arm unit were manufactured and tested. The biomimetic skin prototype was stiff enough to maintain it conical shape when filled with water. The driving force for elongation was reduced significantly compared with previous prototypes.