Metals are indispensable engineered materials for day-to-day life. Researches focused on metallic surfaces with superlyophobicity
(superhydrophobicity, superoleophobicity, underwater superoleophobicity and slippery characteristic) have attracted much attention
recently. Nature is a magician that gives each organic life a unique advantage. Researchers have created a large number of biomimetic
superlyophobic metallic surfaces through various approaches. These biomimetic superlyophobic metallic surfaces exhibit advantages in
many applications, such as self-cleaning, corrosion resistance, anti-icing, and drag reduction. In this review, the specific fabrication and
applications of biomimetic superlyophobic metallic surfaces were reported. The remaining challenges and future outlook of biomimetic
superlyophobic metallic surfaces were preliminarily analyzed. It is hoped that the review will be essential for broadening the scope of
potential applications of metals and providing a powerful reference for future research on metal-based advanced functional materials.

Inspired by cicada wings, a flexible film with self-cleaning and broadband antireflection properties was fabricated with a rapid,
straightforward and cost-effective method. The cicada wing was selected as the original template, and a polymethyl methacrylate (PMMA)
negative replica was obtained by evaporation solvent process. The original template was directly peeled off. Subsequently, the polydimethylsiloxane
(PDMS) was spread in the as-prepared PMMA negative replica. After curing and peeling processes, the PDMS positive
replica was manufactured successfully. The morphologies and performances of cicada wings were perfectly inherited by the PDMS positive
replica. What is more, the excellent optical property of cicada wing was investigated experimentally and theoretically. Compared with
flat PDMS film, the average reflectivity of structural PDMS film was reduced from 9% to 3.5% in the wavelength range of 500 nm –
900 nm. These excellent antireflection properties of bio-inspired antireflection film can be attributed to the nanostructures which achieve a
gradient refractive index between air and the materials, and the mechanism of the antireflection properties was revealed via effective
medium theory. Besides, the bio-inspired broadband antireflective film exhibited superhydrophobic property after the surface treatment (a
152.1? water contact angle), and it also displayed satisfactory flexibility. This work provided a universal method to fabricate the exquisite
biological structures, realizing the transfer of structure and function. Moreover, the multifunctional antireflection film exhibited the potential
value for applications in optical communications, flexible display screens, and anti-dazzle glasses. 

Various bio-inspired dry adhesive materials have been investigated. In this work, lithography and silicon deep etching method were
used to fabricate bio-inspired micro-pillar dry adhesive materials of which the parameters, such as side length, Height to Side length
Aspect Ratio (HSAR), and inter-pillar Distance to Side length Aspect Ratio (DSAR) were comprehensively studied to obtain a dry adhesive
with high adhesion. An orthogonal array method was designed and a series of fabrication experiments were conducted to identify
optimum parameters, which resulted in a high normal adhesion of 2.98 N?cm?2 and a shear adhesion of 9.59 N?cm?2. An adhesion and
desorption device was further designed on basis of the optimum dry adhesive, which enables an Unmanned Aerial Vehicle (UAV) to
successfully adhere on and detach from a ceiling. This would allow an UAV to stay aloft for prolonged time, which could be invaluable to
many applications, such as energy conservation and aerial detection.

This paper describes a flexible pressure sensor based on polypyrrole(PPy)-Cotton composites, in which PPy is grown on cellulose
fibers of cotton pads via an in situ vapor growth method, which is beneficial to the homogeneity of the composites. The resulting devices
exhibits rapid response and recovery speed, the response and recovery times are 220 ms and 240 ms, respectively. The optimal PPy-Cotton Pads (PCPs) sensor shows low detection limit, which is about 50 Pa. At the same time, it exhibits excellent durability in the measurement of repeated loading-unloading pressure over 1000 cycles. The resultant sensor can be attached on different positions of body and applied to recording physiological signals, such as wrist pulse, vocal cord vibration, respiration and eyes blinking. Finally, a 4 × 4 pressure sensor array shows that the PCPs sensor has capability in pressure distribution detection and represents great potential in the fields of wearable electronics and biomedical devices.

A flexible Artificial Lateral Line (ALL) sensor is presented in this paper, featuring a barium titanate/polyvinylidene
fluoride?trifluoroethylene [BTO/P(VDF?TrFE)] nanofiber mat, a hydrogel cupula, and a constriction structure in the canal.. The excellent
piezoelectric performance of the BTO/P(VDF-TrFE) nanofiber, superior to that of a pristine P(VDF-TrFE) nanofiber, helps improve the
sensitivity of the ALL sensor. The hydrogel cupula imitating the cupula in a fish lateral line system enhances the ALL sensitivity through a
material-induced drag enhancement mechanism. The constriction mimics the diminution structure found in fish canal lateral line systems,
endowing the canal ALL sensor with enhanced sensitivity through a structure-induced drag enhancement mechanism. The contributions of
the hydrogel cupula and constriction structure in offering an enhanced sensing performance are studied experimentally, in comparison with
conventional ALL sensors. The constriction structure in the canal helps modify the frequency response of the canal ALL sensor, i.e.,
attenuating low frequencies while amplifying high frequencies. The proposed biomimetic flow sensor is expected to aid in the development
of smart skins for underwater robotics applications.

Magnesium (Mg), is widely used for the bone repair in oral and orthopedic application due to excellent bioactivity, degradation and
biocompatibility. However, the range of application is greatly limited because of the rapid degradation of Mg metal in the body. Surface
modification is an effective method to enhance the corrosion resistance and reduce the degradation rate of Mg metal. In the present study,
pure Mg metal (P-Mg) was subjected to alkali-heat treatment (AT-Mg) or anodic oxidation-heat treatment (AO-HT-Mg). Both AT-Mg and
AO-HT-Mg had a layer of MgO on their surfaces after treatment. Then the effects of MgO coating on corrosion resistance, bioactivity,
Mesenchymal Stem Cells’ (MSCs) proliferation, adhesion and osteogenic differentiation, and the bone repair capability of Mg metal were
investigated. We found both AT-Mg and AO-HT-Mg had stronger corrosion resistance than P-Mg. MSCs on both AT-Mg and AO-HT-Mg
had higher expression of proteins and genes of ALP, OCN, Col-I and Runx2 than those on P-Mg. They also showed better bone repair
property than P-Mg in vivo. In general, MgO layer formed by anodic oxidation-heat treatment had better resistance and biocompatibility
than that produced by alkali-heat treatment. This study indicated the MgO coating not only improved the corrosion resistance of Mg metal,
but also promoted the osteogenic differentiation of MSCs and bone regeneration. 

Nano-ceramic particles can serve as reinforcing agents for metallic materials to improve their mechanical properties. However, it is
important to ensure chemical compatibility between the matrix and particles. In the present study, magnesium composites with and without nano-hydroxyapatite (nHA) particles were fabricated for bone reconstruction applications. Two different techniques were used, Conventional Sintering (CS) of powder compacts and Spark Plasma Sintering (SPS) of pre-compacted powder. Results showed that a
10 wt% addition of nHA particles to magnesium, followed by SPS improved the compression strength by 27%. CS did not lead to any
significant improvement compared to SPS processing. X-ray diffraction data after CS revealed the formation of unfavorable phases due to
chemical reactions between nHA particles and the magnesium matrix, while these phases were absent after SPS processing. The mechanical properties of the specimens fabricated by CS were much inferior to those processed using SPS. The shorter processing time
associated with SPS leaded to reduced interaction between nHA particles and the Mg-matrix, compared to CS.

Improving the strength of bone cement is one of the critical goals in cement designing to maintain their integrity and stabilize connection
between the cement and their surrounding tissue during the time that the cement has been replaced by matured bone tissue. To this
aim, the authors decided to evaluate setting behavior and compressive strength of Magnesium Phosphate Cement (MPC) by adding carboxylated Single-Walled Carbon Nanotubes (c-SWCNTs) and assess the biocompatibility of the composite cement. MPC containing 0
wt% to 0.5 wt% of c-SWCNTs at the Powder to Liquid Ratio (PLR) of 1 g·mL?1 to 2 g·mL?1 were produced. Adding c-SWCNTs to MPC
postponed the setting time of the cement at the beginning of the cementation process and preserved the reaction with a high rate for a
longer time. In addition, the compressive strength of MPC was enhanced to 28 MPa by adding 0.2 wt% c-SWCNTs because of producing
cement with compact and uniform microstructure. In addition, cell behavior on MPC with/without c-SWCNTs indicated no cytotoxic
effect alongside a suitable adhesion and proliferation of them. 

This paper presents the design, modeling, integration, and application of 3D printed high power hexapole magnetic tweezers for 3D
micromanipulation applications. Six sharp-tipped magnetic poles were configured with electromagnetic coils and mounted on 3D printed
magnetic yokes to form a tilted Cartesian coordinate system for actuation. A closed loop control algorithm was developed to automatically
manipulate external power supplies connected to the magnetic tweezers, by using 3D positional information obtained from real-time
image processing techniques. When compared against other designs of magnetic tweezers, our system has a larger working space and can generate higher magnetic field strengths. This allows for more diverse applications regarding small scale manipulation, including cell
manipulation and cell therapy. Experiments and analytics explained in this paper demonstrate the closed-loop manipulation of microswimmers can provide a magnetic force as high as 800 pN while maintaining a positional error below 4 μm in 3D and 1.6 μm in 2D. Using the desired location as the control input, the microswimmers investigated were able to achieve arbitrary 2D and 3D trajectories. We also show that the implemented hexapole magnetic tweezers have adequate power to control microswimmers in Newtonian fluid environments. The system will later be optimized and deployed to control microswimmers in non-Newtonian fluid environments. 

This paper presents an innovative design for a biomimetic whale shark-like underwater glider aiming at the combination of high
maneuverability and long duration. As a hybrid of the underwater glider and the robotic fish, its pectoral fins and tail can serve as not only
the external control surfaces for attitude regulation during gliding but also the propellers for agile fish-like swimming mode. To verify the
gliding capability of the whale shark-like glider and prepare for future dynamic analysis, the hydrodynamic coefficients, including drag,
lift, sliding force, and corresponding moments are estimated through computational fluid dynamics method. In addition, the hydrodynamic
analyses of the proposed glider and an equivalent conventional glider during steady gliding motion are executed for comparison. Extended
experiments are performed to verify the downward gliding performance. The results reveal that the whale shark-like glider has less drag
as well as higher lift-to-drag ratio and a markable gliding capability in practice. It may offer important inspiration for improving the gliding
efficiency and performance of an underwater glider in biomimetic shape design. 

A foot positioning compensator is developed in this paper for a full-body humanoid to retrieve its balance during continuous walking.
An online Foot Position Compensator (FPC) is designed to improve the robustness of biped walking, which can modify predefined step
position and step duration online with sensory feedback. Foot placement parameters are learned by the FPC based on the Policy Gradient
Reinforcement Learning (PGRL) method. Moreover, the FPC assists the humanoid robot in rejecting external disturbances and recovering
the walking position by re-planning the trajectories of walking pattern and the Center of Mass (CoM). An upper body pose control strategy
is also presented to further enhance the performance of humanoid robots to overcome strong external disturbances. The advantages of this proposed method are that it neither requires prior information about the walking terrain conditions, nor relies on range sensor information for surface topology measurement. The effectiveness of the proposed method is verified via Webots simulation and real experiments on a full-body humanoid NAO robot.

This paper reports the effect of the Center of Gravity (CG) position on lateral flight dynamic stability of hovering KUBeetle, a tailless
FW-MAV, providing further insights on the effects of asymmetries in body mass distribution and wing kinematics. For the current study,
the standard linearized equations of motion were applied as in the previous work on longitudinal dynamic stability. The stability derivatives
were acquired using the computational fluid dynamic methods via the commercial software of ANSYS Fluent. There exists a stable
region for CG between 2.6% and 3.5% of the mean chord below the wing pivot point, in which the lateral motion of hovering KUBeetle is
passively stable. For CG below the stable region, because of an unstable oscillatory mode, the lateral motion of the FW-MAV is unstable
but can be stabilized using rolling rate feedback. For CG above the stable region, because of a divergence mode, the system remains
unstable even with the rolling rate feedback. Comparison with other works on an FW-MAV based on a quasi-steady aerodynamic model
and on insect showed similar characteristics for flapping flight. It is also interesting to note that the asymmetries in body mass and wing
kinematics can enlarge the stable region of the system by a non-zero Ixz which approaches the root square of x z I I , a negative LrNp, and a positive Ixz(Ir+Np). Combining the current result with that of the previous work on longitudinal motion, the most beneficial region of the
CG for full 6-DOF flight dynamic stability of hovering KUBeetle was suggested.

The two-dimensional (2D) inclined stroke plane kinematics of insect wing is studied for various stroke plane angles using the Immersed
Boundary (IB) solver. The numerical results revealed the dominant lift enhancement mechanisms for this class of flows. The
generated dipole was analyzed to find the maximum velocity, inclination and spread. The analysis of these dipole characteristics for the
different stroke plane angles exposed the alternate method to study the vertical force variation with the stroke plane angles. Lift enhancement mechanisms and dipole characteristics complement the high vertical force coefficient for the stroke plane angle of 60? commonly used by dragonflies during hover. The location of the dipole identified a region of influence around the wing and demonstrated the role of the dipole jet in multi-body dynamics and wall effects.

A major advantage of animal aggregations concerns cooperative antipredator strategies. Schooling behavior emerges earlier in many
fish species, especially in those cannibalizing their offspring. Experience is fundamental for developing schooling behavior. However, the
cognitive ability of naive newborn fish to aggregate remains unclear. Herein, Poecilia reticulata, was selected as model organism to
investigate how combinations of biomimetic robotic agents and adult conspecific olfactory cues affect collective responses in newborns.
The role of white and brown backgrounds in evoking aggregations was also assessed. Olfactory cues were sufficient for triggering aggregations
in P. reticulata newborns, although robotic agents had a higher influence on the group coalescence. The combination of robotic
agents and olfactory cues increased schooling behavior duration. Notably, schooling was longer in the escape compartment when robotic
agents were presented, except for the combination of the male-mimicking robotic fish plus adult guppy olfactory cues, with longer
schooling behavior in the exploring compartment. Regardless of the tested cues, newborn fish aggregated preferentially on the brown areas
of the arena. Overall, this research provides novel insights on the early collective cognitive ability of newborn fish, paving the way to the
use of biomimetic robots in behavioral ecology experiments, as substitutes for real predators.

Areca catechu, is a species of palm belonging to the family of Arecaceae/Palmae, grows vertically, to the height of 10 m to 20 m, the
stem is straight, solitary and slender, 10 cm to 15 cm in diameter, with marks of annulated scars of fallen leaf sheaths. Areca fibres are
predominantly extracted not only from the fruit as areca husk, but also from leaf stalks and fronds. In this review paper, areca fibre is
compared with those of other representative species of the Arecaceae/Palmae family, such as the coconut tree and the palm tree, in terms of physical and mechanical properties. This review article also discusses the physical, mechanical and thermal properties of areca fibre and its composites. The review of known published data reveals that, while areca fibre has the potential to be used as an alternative reinforcement in polymer composites. Besides, it has been also noticed that some other species from the family of Arecaceae/Palmae have not been explored as natural fibre reinforcement in polymer composites either, thus revealing further options of natural alternative reinforcement to be investigated with regard to their potential to be used in fibre based composites for the automotive, aerospace, and construction industries.

Potential use of condensate generated by cooling the steam obtained during high-frequency/vacuum drying step of hardwood lumber
was investigated. The liquid condensates were obtained from oak, beech and walnut wood. This liquid condensate was then used as a
replacement for deionized water in the synthesis of Urea-Formaldehyde (UF) resin (5 wt% of total resin) using a laboratory scale reactor.
Medium Density Fibreboards (MDFs) were produced using control and modified resins. Emissions of Volatile Organic Compounds
(VOCs) from the MDFs were determined by Micro Chamber method. The bonding properties of the MDFs were determined according to
European standards. The main VOC emissions from MDFs produced using UF resin containing the condensate were a-Pinene, b-Pinene,
careen, and acetic acid, which were lower than those of the control MDF, except for the acetic acid emission of MDF with oak condensate.
In the tree species, the beech wood condensate gave the lowest VOC emissions (732 μg·m?3) from the MDFs, followed by the MDFs containing walnut wood condensate (852 μg·m?3), oak wood condensate (998 μg·m?3), and control MDF (3529 μg·m?3), respectively.However, the internal bond strength of MDFs containing the condensate was negatively impacted by the condensate (0.70 N·mm?2 to 0.54 N·mm?2 depending on the tree species). The results showed that the liquid wood-drying condensate which generally released to the ground could be efficiently used as an alternative to expensive VOCs scavenger used in the production of UF resin bonded MDF. This may be one of the most efficient uses of the condensate in high value-added materials. 

Aerial transportation and manipulation have attracted increasing attention in the unmanned aerial vehicle field, and visual servoing methodology is widely used to achieve the autonomous aerial grasping of a target object. However, the existing marker-based solutions pose a challenge to the practical application of target grasping owing to the difficulty in attaching markers on targets. To address this problem, this study proposes a novel image-based visual servoing controller based on natural features instead of artificial markers. The natural features are extracted from the target images and further processed to provide servoing feature points. A six degree-of-freedom (6-DoF) aerial manipulator system is proposed with differential kinematics deduced to achieve aerial grasping. Furthermore, a controller is designed when the target object is outside a manipulator’s workspace by utilizing both the degrees-of-freedom of unmanned aerial vehicle and manipulator joints. Thereafter, a weight matrix is used as basis to develop a multi-tasking visual servoing framework to integrate the controllers inside and outside the manipulator’s workspace. Lastly, experimental results are provided to verify the effectiveness of the proposed approach.