Being inspired by the “seismonastic reaction” of Mimosa pudica, an asymmetric swelling system was constructed to induce the controllable directional deformation of filter paper. In this work, multifunctional biomimetic Janus paper was facilely fabricated via depositing poly(vinylidene fluoride) (PVDF) on one side of Qualitative Filter Paper (QFP), the permeation of polymer solutions within filter paper was well controlled during fabrication. The wetting and swelling behavior of the prepared Janus paper were detected. The Janus paper showed controllable swelling-induced deformations in water. Both the degree and orientation of the deformation were fully investigated. On the one hand, the degree of deformation depends on the gradient wettability and hygroscopicity of the Janus paper, on the other hand, the orientation of deformation is related to the storage and release of stress. Additionally, the steady deformation during swelling endows the Janus paper with novel shape memory property both under idling and loading conditions. The Janus paper was also applied to achieve reversible energy conversion from the swelling potential energy to mechanical potential energy.

Although laser ablation is considered as a facile technique to fabricate bio-inspired super-hydrophobic surfaces, the issue is that the initial laser treated metallic surfaces show super-hydrophilic property. It will take a long period to reach super-hydrophobic state under ambient air. It is reported that these super-hydrophobic surfaces could be easily damaged by thermal heating effect or interaction with other liquids, causing uncontrolled loss of super-hydrophobicity. In this study, a stable super-hydrophobic aluminum surface was rapidly fab-ricated via the hybrid laser ablation and surface chemical modification of (heptadecafluoro-1, 1, 2, 2-tetradecyl) triethoxysilane (AC-FAS). Surface morphology and chemistry were systematically investigated to explore the generation mechanism of super-hydrophobicity. The water contact angle of the treated surfaces can reach up to 160.6? ± 1.5? with rolling angle of 3.0? ± 1.0?, exhibiting perfect self-cleaning capability, long-term stability, and excellent chemical stability in acidic as well as alkaline solutions. The potentiodynamic polarization tests implied that the super-hydrophobic surfaces showed better anti-corrosion performance. This hybrid laser ablation and surface chemical modification are very time-saving and low-cost, which offers a rapid way for quantity production of super-hydrophobic surface on aluminum material.

In this work, a simple and economic route was presented to fabricate an anti-icing superhydrophobic surface with nanocone structures, which were constructed only by one-step facile method of hydrothermal treatment with zinc acetate on the aluminum substrate. After modifying with fluoroalkylsilane (FAS-17), the nanocone structures with the appropriate size could induce the high superhydrophobicity with the water contact angle reaching 160.2? ± 0.4? and the sliding angle only being 1? ± 0.5?. Under the dynamic environments, the impact droplets could rapidly bounced off the surface with the shorter contact time of ~10.6 ms, and it was mainly attributing to lower capillary adhesive force (water adhesion force of 4.1 μN) induced by the open system of nanocone structures. Furthermore, the superhydrophobic nanocone surfaces were verified to be a promising anti-icing/icephobic materials, on which the water droplets needed to spend the time of ~517 s to complete the entire freezing process at ?10 ?C, displaying the increased ~50 times of icing-delay performance comparing with untreated substrate. Even if ice finally was formed on the superhydrophobic nanocone surfaces, it could be easily removed away with lower ice adhesion of ~45 kPa. The repeatable measurement of ice adhesion strength on the same place of the superhydrophobic surface is still far less than the surface ice adhesion of smooth substrate, exhibiting better stability.

Magnetically driven super-hydrophobic materials were prepared by Fe3O4 nanoparticles and stearic acid, which were deposited on the surface of polyurethane sponges. The presence of the Fe3O4 nanoparticles makes the sponge have the magnetic, and the micro-nano hierarchical structure and hydrophobic functional groups lead to the sponge have excellent superhydrophobicity. The as-prepared sponge exhibited excellent absorption capacities for various oils and organic solvents ranging from 23.8 times to 86.7 times of its own weight. Moreover, the oil separation capacities still keep a high value after 50 cycles of squeezing the saturated absorbed as-prepared sponge. All of these satisfactory properties make the as-prepared sponge as a candidate of ideal absorbents for oily industrial wastewater and oil spills in oceans.

Tactile and slip sensors have gained tremendous attention for their promising applications in the fields of smart robotics, implantable medical devices and minimally invasive surgery. Inspired by the structure-enhanced sensing mechanisms of human fingertips and tree frog toes, we developed a tactile and slip sensor by combining biomimetic surface microstructures with highly sensitive P(VDF-TrFE) nano-fiber sensors on a flexible polyimide substrate. As the surface microstructures could mediate the micro-vibration induced by slip motion, the frequencies of output signals revealed a strong correlation with the periods of microstructures. In addition, we proposed a method to discriminate touch force from slip motion using the criterion of standard deviation of time delay from the output signals of neighboring sensor elements.

This paper presents the design and analysis of an osmosis-based artificial muscle inspired by the leaf movements of Mimosa pudica. M. pudica’s leaves quickly contract using osmosis pressure in the pulvinus when they are stimulated. We analyzed and simulated an osmosis system to identify the factors for fast osmosis reactions and designed a prototype artificial muscle based on the results. The osmosis phenomenon was mathematically modeled, analyzed, and verified through several experiments. The analysis shows that fast osmosis responses require a large diffusion coefficient with a high-flux membrane or small ratio of the cross-sectional area to the volume of the osmosis system. We designed a micro-scale system to achieve the required ratio. The contraction and relaxation of the artificial muscle are realized by changes of the local concentration of potassium ions, which can be aggregated by a controllable electric field. As a result, the artificial muscle shows controllable behavior with fast reactions.

In this paper, the effects of tube feet pores on the mechanical properties of Sea Urchin Skeleton (SUS) have been studied. The pore structure of drop-like Tripnenstes gratilla (a sea urchin) skeleton is characterized by Scanning Electron Microscopy (SEM). Based upon the data, the finite element method has been employed to analyze the Maximum Tensile Stress (MTS) of SUS models with different pore positions, accompanied by compressive tests on SUS-like ceramics. Results indicate that for a drop-like SUS, the MTS keeps a linear relationship with the maximum load applied on the SUS. More importantly, the mechanical performances of some perforated SUSs are better than their non-perforated counterparts due to their lower MTS values, e.g. the maximum load can thus be increased by 35% when the pore is perforated at ?10?. The strengthening is attributed to the introduced pore that causes the redistribution of stress and partly reduces the stress intensity on the original MTS position. By contrast, the pore only increases the MTS value of a spherical shell under isostatic pressure or unidirectional pressing. This is a strong hint that the drop-like shape of SUS has evolved to work with the tube feet pores to better protect their bodies.

Recently, micro-vibrational perception mechanisms of nocturnal arthropods such as scorpions and spiders are attracting increasingly more attention and research. The relevant micro-vibrational receptors are exquisite, in terms of their comprehensive performance such as sensitivity, stability, high anti-interference, and ultralow-power consumption. In this work, we find the Basitarsal Compound Slit Sensilla (BCSS) of scorpion (Heterometrus petersii) are composed of the crack-shaped slits as mechanosensory structure and can efficiently detect substrate-borne vibrational signal in complex natural environment. The study on microstructures and mechanical properties of tissue phases constituting the BCSS reveals that the strategy of tessellation is used to make crack-shaped slit amplify the tiny mechanical signal. In addition, the magnitude-frequency characteristics of electrophysiological signals caused by vibration stimulation with different fre-quencies indicate that the scorpion is sensitive to micro-vibrational signals at a certain frequency range. Meanwhile, the vibrational per-ception mechanism based on geometrical amplification and resonance is proposed to explain how scorpions detect the tiny biotic vibra-tional signal efficiently in noise environment. This finding not only promotes our further understanding of ultra-sensitive mechanism of the vibrational receptors, but also provides biological inspiration for the next generation of mechanosensor for a broad range of applica-tions.

This study is aimed at exploring the prediction of the various hand gestures based on Force Myography (FMG) signals generated through piezoelectric sensors banded around the forearm. In the study, the muscles extension and contraction during specific movements were mapped, interpreted, and a control algorithm has been established to allow predefined grips and individual finger movements. Decision Tree Learning (DTL) and Support Vector Machine (SVM) have been used for classification and model recognition. Both of these estimated models generated an averaged accuracy of more than 80.0%, for predicting grasping, pinching, left flexion, and wrist rotation. As the classification showed a distinct feature in the signal, a real-time control system based on the threshold value has been implemented in a prosthetic hand. The hand motion has also been recorded through Virtual Motion Glove (VMD) to establish dynamic relationship between the FMG data and the different hand gestures. The classification of the hand gestures based on FMG signal will provide a useful foundation for future research in the interfacing and utilization of medical devices.

Stability is of great significance in the theoretical framework of biped locomotion. Real-time control and walking patterns planning are on the premise that the robot works in the stable condition. In this paper, we address the crucial issue of the locomotion stability based on the modified Poincare return map and the hybrid automata. Not akin to the traditional stability criteria, i.e., the Zero Moment Point (ZMP) and the Center of Mass (CoM), the modified Poincare return map is more appropriate for both dynamic walking and non-periodic walking. Moreover, a novel high-level reinforcement learning methodology, so-called active PI2 CMA-ES, is proposed in this paper to plan the exoskeleton locomotion. The proposed learning methodology demonstrates that the locomotion of the exoskeleton is asymp-totically stable according to the modified Poincare return map criterion. Finally, the proposed learning methodology is tested by the Lower Extremity Augmentation Device (LEAD) and its effectiveness is verified by the experiments.

Since the commencement of climbing robots, the moving ability of climbing robots has continuously lagged far behind that of climbing animal. A primary cause is the insufficient understanding of how animals govern their climbing locomotion. To reveal the mechanism of vertical locomotion and enhance the performance of climbing robots, we have measured the reaction forces acting on climbing geckos and recorded the locomotor behaviors synchronously. The coordinates of reference points were regressed to analyze kinematic feature factors. Meanwhile, the data of reaction forces were further processed by fast Fourier transform and wavelet transform to acquire time-frequency domain characteristics. The results show a good agreement between the reaction forces and the locomotor be-haviors in time-frequency domain; the main locomotor frequency of trunk in fore-aft direction is twice that in lateral direction; the ex-cellent adhesion system of geckos enables them to climbing up vertical substrate with not only a very tiny impact in time scale but also not easily identifiable characteristics in frequency-domain. Above research will help deepen our understanding of the climbing locomotion, and provide a more precise prototype for the design of gecko-like robot.

The influence of Center of Gravity (CG) location on longitudinal dynamic stability of hovering KUBeetle, a tailless Flapping-Wing Micro Air Vehicle (FW-MAV), is reported in this paper. The rigid-body approximation was assumed, allowing application of the standard equations of motion used for fixed-wing aircraft. For each considered location of CG, stability derivatives were obtained using the computational fluid dynamics method via the commercial software of ANSYS Fluent. The dynamic stability was studied using technique of eigenvalue analysis. There exists a narrow stable region for CG between 23% – 24% of mean chord above the wing pivot point, where the longitudinal hovering of KUBeetle is passively stable. When CG is located below the stable region, the analysis identifies two subsidence modes and one unstable oscillatory mode, which makes the hovering of KUBeetle unstable. However, it can be stabilized using pitching rate feedback. When CG is located above the stable region, the system yields one stable oscillatory mode, one subsidence mode, and one divergence mode. Because of the divergence mode, the system remains unstable even with the angular rate feedback. These results share similar characteristics to another FW-MAV and insects. This study may provide a reference for FW-MAV developers.

A conceptual design of bionic Autonomous Underwater Glider (AUG) is introduced, with a pair of flapping wings. The immersed boundary method is employed and Navier–Stokes equations are solved to investigate the propulsive performance of the bionic AUG with Aspect Ratios (ARs) of the flapping wings varying from 0.36 to 5. The propulsive efficiency of the whole AUG is newly defined, in contrast to the definition of single flapping wing. The numerical results show that the thrust of flapping wings increases due to the wing-fuselage interaction. The thrust coefficient of the flapping wings increases as the AR increases. The propulsive efficiency of the AUG increases first and then decreases as the AR increases. There is an optimum AR leading to the highest propulsive efficiency, which is different from the result of the single wing case. To balance the advancing speed and gliding endurance, the AR of the flapping wing is recommended to be set as the optimum value of around 0.60. The vortex structures in the wake of the AUG with different ARs are also presented and compared.

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.

This paper focuses on the study of the effect of modification of Oil Palm Empty Fruit Bunch (OPEFB) and sugarcane bagasse (SCB) biomass as potential reinforcement for composites panel and thermal insulation. Both fibres were treated with three types of chemicals: 2% silane, 4% H2O2 and 4% H2O2-2% silane for 3 h. The influence of modified fibres content in composites was examined by structural changes using image analyser, Fourier transform infrared (FTIR), Scanning Electron Microscopy (SEM), tensile, interfacial shear strength (IFSS) and thermal characteristic. The diameter of both fibres was reduced after treatment and showed decreasing of lignin and hemi-cellulose in fibre. Tensile strength has been increased by 2% silane treatment for both fibres and 4% H2O2 treatment displays higher result for IFSS. Thermal properties of treated SCB fibre with silane display higher residual content and better thermal stability. SEM charac-terization showed that 2% silane treatment removed silica bodies of OPEFB fibre while 4% H2O2 treatment uniformly filled porosity of SCB fibre. Finally, results revealed that treated OPEFB fibre is enough to improve compatibility and mechanical properties, while treated SCB fibre was effective in thermal stability for fabrication of composite materials.