Dry adhesives inspired from climbing animals, such as geckos and spiders, rely on van der Waals forces to attach to the opposing surface. Biological fibrillar dry adhesives have a hierarchical structure closely resembling a tree: the surface of the skin on the animal’s feet is covered in arrays of slender micro-fibrils, each of which supports arrays of fibrils in submicron dimensions. These nano-meter size fibrils can conform closely to the opposing surfaces to induce van der Waals interaction. Bioinspired dry adhesives have been developed in research laboratories for more than a decade. To mimic the biological fibrillar adhesives, fibrillar structures have been prepared using a variety of materials and geometrical arrangements. In this review article, the mechanism and selected fabrication methods of fibrillar adhesives are summarized for future reference in adhesive development. Robotic applications of these bioinspired adhesives are also introduced in this article. Various successful appli-cations of bioinspired fibrillar adhesives can shed light on developing smart adhesives for use in automation.

Biomimetics is an established field in research and industry. Current approaches focus on the use of biological principles in product development, while large potentials have also been identified for transferring organisational principles from nature to production organisation. This study gives a comprehensive overview of existing literature and illustrates that only fragmented research is being conducted at present. In order to enable systematic translation into methods that are available to practitioners, a framework is developed which allows the body of literature to be structured and potential fields not being researched at present to be identified. It also points out that some biological principles receive more attention in research approaches and practical implementation in production organisation than others. Furthermore, correlations between biological principles and principles in production are identified that there have already been successful translations of biomimetic approaches to production or-ganisation. On the other hand, it suggests that there are numerous promising approaches only described in an initial paper that need further research before they can be implemented in practice.

Oilseed rape, widely cultivated all over the world, plays an important role for our daily life due to its high nutritional and economic values. In this paper, for the first time we discuss the surface wettability of oilseed rapes with special surface struc-tures. It is found that the fresh rape flowers are superhydrophobic with a low Adhesion Force (AF), showing the self-cleaning properties similar to lotus leaves. In contrast, the fresh rape leaves also exhibit hydrophobicity but a high AF, which resemble rose petals. Furthermore, we study the effect of storage time on the wetting properties of rape leaves. The high hydrophobicity of rape leaves gradually switches to hydrophilicity. Meanwhile, the AF intensely increases after placement at room temperature for 10 days. This research offers a profound inspiration to artificially fabricate biomimetic materials with high hydrophobicity and different adhesion characterizations.

This study describes the dynamic behaviour of droplets of biological liquids on hydrophobic surfaces under electrostatic actuation, to devise sample handling in lab-on-chip diagnostic tools. Bovine Serum Albumin (BSA) is taken as a representative biomolecule, since it is often used in adsorption studies. Green Fluorescence Protein (GFP) is also considered, given its natural fluorescence. Several effects such as sample concentration and pH are discussed. The results show negligible effects of proteins concentration in electrowetting, although increased concentrations endorse passive adsorption mechanisms, which alter the local wettability of the substrates precluding droplet motion. Bioinspired surfaces promote the largest spreading diameter, which is beneficial for droplet motion. However, surface roughness promotes energy dissipation limiting the receding droplet motion. Hence, the most effective approach is altering the surface chemistry. The coating is applied to a surface with a mean roughness smaller than 20 nm and does not alter significantly the topography, thus leading to the so-called smooth superhydrophobic surface. This coating also reduces passive proteins adsorption, as confirmed by Confocal Microscopy (CM), which is beneficial for droplet motion. Evaluating absorption spectra of protein solutions evidences an increase in protein concentration ascribed to droplet evaporation as confirmed by theoretical analysis and time resolved infrared visualization.

Hovering ability is one of the most desired features in Flapping-Wing Micro Air Vehicles (FW-MAVs). This paper presents a hybrid design of flapping wing and fixed wing, which combines two flapping wings and two fixed wings to take advantage of the double wing clap-and-fling effect for high thrust production, and utilizes the fixed wings as the stabilizing surfaces for inherently stable hovering flight. Force measurement shows that the effect of wing clap-and-fling significantly enhances the cycle-averaged vertical thrust up to 44.82% at 12.4 Hz. The effect of ventral wing clap-and-fling due to presence of fixed wings produces about 11% increase of thrust-to-power ratio, and the insect-inspired FW-MAV can produce enough cycle-averaged vertical thrust of 14.76 g for lift-off at 10 Hz, and 24 g at maximum frequency of 12.4 Hz. Power measurement indicates that the power consumed for aerodynamic forces and wing inertia, and power loss due to gearbox friction and mechanism inertia was about 80% and 20% of the total input power, respectively. The proposed insect-inspired FW-MAV could endure three-minute flight, and demonstrate a good flight performance in terms of vertical take-off, hovering, and control with an onboard 3.7 V-70 mAh LiPo battery and control system.

Gliding is an important flight mode for insects because it saves energy during long distance flight without wing flapping. In this study, we investigated the influence of locust wing corrugation on the aerodynamic performance in gliding mode at low Reynolds number. Numerical simulations using two-dimensional Navier-Stokes equations are applied to study the gliding flight, which reveals the interaction between forewing and hindwing. The lift of the corrugated airfoil in a locust wing decreases from the wing root to the tip. Simulation results show that the pressure drags on the forewing and hindwing increase with an increase in wing thickness; while the lift-drag ratio of the airfoil is marginally affected by the corrugation on the airfoil. Geometric parameters analysis of the locust wing is also carried out, which includes the corrugation height, the corrugation placement and the shapes of leading and trailing edges.

This paper provides a parametric study to obtain the optimal wing rotation angle for the generation of maximum transla-tional force in an insect-mimicking Flapping-Wing Micro Air Vehicle (FWMAV) during hovering. The blade element theory and momentum theory were combined to obtain the equation from which the translational aerodynamic force could be esti-mated. This equation was converted into a non-dimensional form, so that the effect of normalized parameters on the thrust coefficient could be analyzed. The research showed that the thrust coefficient for a given wing section depends on two factors, the rotation angle of the wing section and the ratio of the chord to the travel distance of the wing section in one flapping cycle. For each ratio that we investigated, we could arrive at an optimal rotation angle corresponding to a maximum thrust coefficient. This study may be able to provide guidance for the FWMAV design.

In this paper an experiment of human locomotion was carried out using a motion capture system to extract the human gait features. The modifiable key gait parameters affecting the dominant performance of biped robot walking were obtained from the extracted human gait features. Based on the modifiable key gait parameters and the Allowable Zero Moment Point (ZMP) Variation Region (AZR), we proposed an effective Bio-inspired Gait Planning (BGP) and control scheme for biped robot to-wards a given travel distance D. First, we construct an on-line Bio-inspired Gait Synthesis algorithm (BGSN) to generate a complete walking gait motion using the modifiable key gait parameters. Second, a Bio-inspired Gait Parameters Optimization algorithm (BGPO) is established to minimize the energy consumption of all actuators and guarantee biped robot walking with certain walking stability margin. Third, the necessary controllers for biped robot were introduced in briefly. Simulation and experiment results demonstrated the effectiveness of the proposed method, and the gait control system was implemented on DRC-XT humanoid robot.

Passive dynamics is always one of research emphases of the legged robots. Studies have proved that cheetah robot could achieve stably passive bounding motion under proper initial conditions in the ideal case. However, the actual robot must have energy dissipation because of friction and collision compared with the theoretical model. This paper aims to propose a control method that can drive the cheetah robot running in passive bounding gait. First, a sagittal-plane model with a rigid torso and two compliant legs is introduced to capture the dynamics of robot bounding. Numerical return map studies of the bounding model reveal that there exists a large variety of passively cyclic bounding motions (fixed points). Based on the distribution law of fixed points, an open-loop control method including touchdown angle control strategy and leg length control strategy is put forward. At last, prototype of the cheetah robot is designed and manufactured, and locomotion experiment are carried out. The experi-ment results show that the cheetah robot can achieve a stable bounding motion at different speeds with the proposed control method.

In this paper, a miniaturized segment robot using solenoids is developed to mimic the plane locomotion of earthworms. The bioinspired robot is composed of five segmented bodies, and one segment has two solenoid actuators. This robot can move linearly and it can also turn due to the pair of solenoid actuators that facilitate the earthworm-like peristaltic locomotion. We have designed a miniaturized solenoid with a permanent magnet plunger in order to increase the total electromagnetic force. A theoretical analysis is performed to predict the linear and turning motions of each segment, and the optimal profiles of input signals are obtained for fast locomotion. Experiments are then conducted to determine the linear and turning motions of the segment robot. It takes about 0.5 s for the five segments to complete one cycle of the peristaltic locomotion. In experiments, the segment robot is shown to have the linear and angular velocities of 27.2 mm•s−1 (0.13 body-length per second) and 2 degrees per second, respectively.

Worker honeybee pierces animal or human skin with its ultra-sharp stinger and injects venom to defend itself. The insertion behavior is a painless transdermal drug delivery process. In this study, Apis cerana cerana worker honeybee was chosen as the research object. The geometry and structure of the stinger were observed by the Scanning Electron Microscope (SEM). High-speed video imaging technique was adopted to observe the stinger insertion and pull behavior of honeybee. The skin insertion, pull-out, in-plane buckling and out-of-plane bending forces of honeybee stinger were tested by a self-developed mechanical loading equipment. Results showed that the honeybee stinger pierces directly into skin without frequent vibration. The pull-out force (average 136.04 mN) was two orders of magnitude higher than the penetration force (average 1.34mN). Compared with the penetration force, the in-plane buckling force (average 6.72 mN) was in the same order of magnitude. The result of out-of-plane bending test showed that the stinger was elastic and it could recover after bending. The excellent geometry and structure of honeybee stinger will provide an inspiration for the further improved design of microneedle-based transdermal drug delivery system.

The paper deals with the mechanical vibrational motion of vibrissae during natural exploratory behaviour of mammals. The theoretical analysis is based on a mechanical model of a cylindrical beam with circular natural configuration under an applied periodic force at the tip, which corresponds to the surface roughness of an investigated object. The equation of motion of the beam is studied using the Euler-Bernoulli beam theory and asymptotic methods of mechanics. It is shown that from the me-chanical point of view the phenomenon of parametric resonance of the vibrissa is possible. It means that the amplitude of forced vibrations of a vibrissa increases exponentially with time, if it is stimulated within a specific resonance frequency range, which depends on biomechanical parameters of the vibrissa. The most intense parametric resonance occurs, when the excitation fre-quency is close to the doubled natural frequency of free vibrations. Thus, it may be used to distinguish and amplify specific periodic components of a complex roughness profile during texture discrimination.

A series of bionic grooves based on bird wing, such as cluster spiral groove, multi-array spiral groove and flow-split spiral groove, are introduced to improve the film stiffness and sealing properties of dry gas seal. A theoretical model solved with Finite Difference Method (FMD) is developed to study the static sealing performance, such as film stiffness and leakage rate of these bionic groove dry gas seals. Then, a performance comparative study between the bionic groove dry gas seals and common spiral groove dry gas seal with different groove geometry parameters such as groove depth ratio, spiral angle and micro groove number under different average linear velocity at seal ring face and seal pressure is carried out. The closing force, film thickness and leakage rate of dry gas seals with bionic grooves and common spiral groove are measured experimentally. Results show that cluster spiral groove and multi-array spiral groove dry gas seals have superiority in the film stiffness and stiffness-leakage ratio compared with common spiral groove under the condition of high-speed and low-pressure, while flow-split spiral groove dry gas seal has no obvious advantages of performance. Film stiffness of cluster spiral groove dry gas seal and stiffness-leakage ratio of multi-array spiral groove dry gas are 20% and 50% larger than that of common spiral groove dry gas seal, respectively, which are verified by the experimental results.

The fore claws of the nymph of Cryptotympana atrata have excellent ability to cut and dig soil. Inspired by this, we de-signed a biomimetic stubble cutter to reduce the cutting resistance. Reverse engineering and 3D print technology were applied to design the biomimetic stubble cutter. Two types of biomimetic corn stubble cutters with different tooth heights (5 mm and 2.5 mm) were designed. The cutting ability of biomimetic corn stubble cutters was compared to the conventional design by the quadratic regression orthogonal test. Tooth height, dip angle of cutting edge, and cutting velocity were chosen as orthogonal test factors. The biomimetic stubble cutters show lower cutting resistance than the conventional one. Cutting velocity exerts the least effect on cutting resistance, followed by tooth height and dip angle of cutting edge.  Optimal combination with the least cutting resistance is tooth height of 2.5 mm and dip angle of cutting edge of 40? while the cutting resistance does not vary remarkably with cutting velocity.  Test results indicate the serrated structure design as a principal factor for cutting resistance reduction. The biomimetic stubble cutter design, inspired by the soil-cutting mechanism of Cryptotympana atrata nymph, remarkably im-proves the performance of stubble cutter.

This study proposes a new topology optimization solution providing designers with choices for feasible stiffener layouts inside large-scale containers of garbage trucks. Firstly, the mathematical expressions of loading conditions inside garbage containers are derived. Then, a growth-based layout optimization framework is built, taking inspiration from the morphology of plant ramifications. The principles of the highly effective but individual design rules of existent leaf venation layout problems are explored and transferred into analytical laws. Based on this, an evolutionary algorithm is developed to simulate the load-adapted growth of stiffener layouts, which provides an approximately homogeneous stress distribution along the surface of self-optimizing structures. Unlike the conventional methods, the new approach needs neither the densest ground structure nor the modification of the existing finite element programs, it is fast, easy to apply and nearly constraint free. Finally, a case study is provided showing how a large-scale container structure can be designed by this extremely intelligent CAD approach.