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Journal of Bionic Engineering

ISSN 1672-6529

CN 22-1355/TB

Editor-in-Chief : Luquan Ren Published by Science Press and Springer

Table of Content
10 May 2022, Volume 19 Issue 3

Target-oriented Passive Localization Techniques Inspired by Terrestrial Arthropods: A Review

Fu Liu, Yueqiao Wang, Yufeng Zhao, Meihe Liu, Tao Hou & Zhiwu Han
Journal of Bionic Engineering. 2022, 19 (3):  571-589.  DOI: 10.1007/s42235-022-00157-5
Abstract ( 251 )  
For centuries, researchers have been fascinated by how simple-minded arthropods pick up definite cues and locate a potential target in an instant. Contrary to the active echolocation of classical creatures, arthropods exhibit passive characteristics. They use spatially separated sensilla to cooperatively pinpoint target-generated signal sources such as sound, light, ground vibration, air disturbance, and thermal radiation. The paper introduces the localization mechanisms of typical terrestrial arthropods with diverse survival habits. Focusing on these special mechanisms, a series of theoretical models and advanced bionic equipment have been reviewed, and some key challenges and future directions are proposed. We believe that intensive study on arthropods can promote innovative development of miniaturized, low power-dissipation, and high-performance localization equipment, thereby enhancing and expanding current localization techniques.
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Bionic MEMS for Touching and Hearing Sensations: Recent Progress, Challenges, and Solutions

Chang Ge & Edmond Cretu
Journal of Bionic Engineering. 2022, 19 (3):  590-615.  DOI: 10.1007/s42235-022-00159-3
Abstract ( 177 )  
This paper reviews the recent progress on bionic microelectromechanical systems (MEMS) used for touching and hearing sensations, focusing on the following three types of devices: MEMS tactile sensors, MEMS directional microphones, and MEMS vector hydrophones. After reviewing the electromechanical coupling principles, design, and performance of these MEMS devices, the authors conclude that it is vital for future research efforts in bionic MEMS to focus more on microfabrication technologies. The development of robust microfabrication flows is the basis to implement hybrid electromechanical coupling principles based on novel functional materials. High-quality polymeric micromachining technologies can also significantly enhance the potential of existing bionic MEMS designs for more practical applications.
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Bionics-based Optimization of Step-climbing Gait in a Novel Mini-RHex Robot

Xingguo Song, Jiajun Pan, Xiaolong Zhang, Chunjun Chen & Danshan Huang
Journal of Bionic Engineering. 2022, 19 (3):  616-628.  DOI: 10.1007/s42235-022-00160-w
Abstract ( 173 )  
Hex-style robots can perform manifold moving gaits in different applications, but they have always faced a challenge of climbing up high obstacles. In this paper, the bionics-based gait optimization in an RHex-style robot is proposed for climbing steps at different heights, which even enables the robot to climb up the step with 4.2 times of the leg length. First, a thoracic flexion is designed in the robot, and an algorithm of adjusting body inclination is proposed to perform the rising stage after placing front legs on top of step, which can be applied in different RHex-style robots with different sizes. Especially, when the thoracic flexion is implemented, the robot can climb the higher step with the proposed algorithm. Second, to climbing the higher steps, a claw-shape legs-based algorithm is proposed for robot reaching the higher step and climbing it up. During the vital rising stage, when the front legs of the robot have reached the top of the step, the robot can bend the front body downward with its thoracic flexion like a cockroach, and then lift the front and middle legs alternately to move COM up and forward onto the step. The simulation analysis is utilized to verify the feasibility of the proposed algorithms. Finally, the step-climbing experiments at different heights are performed in our robot to compare with the existing works. The results of simulations and experiments show the superiority of the proposed algorithms for the improved robot due to climbing up the higher steps.
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Nonlinear Modeling and Analysis of a Novel Robot Fish with Compliant Fluidic Actuator as a Tail

Behzad Janizadeh Haji & Mahdi Bamdad
Journal of Bionic Engineering. 2022, 19 (3):  629-642.  DOI: 10.1007/s42235-022-00166-4
Abstract ( 149 )  
Compliant mobile robotics is a developing bioinspired concept of propulsion for locomotion. This paper studies the modeling and analysis of a compliant tail-propelled fish-like robot. This biomimetic design uses a fluid-filled network of channels embedded into the soft body to actuate the compliant tail and generate thrust. This study analyzes the nonlinear dynamics of Fish Tail Fluidic Actuator (FTFA). The fluidic expansion under pressure creates a bending moment in the tail. It is demonstrated that the tail response follows the theoretical formulation extracted from the accurate modeling. In this modeling, tail is assumed as a continuous Euler–Bernoulli beam considering large deflection and nonlinear strain. Then, the implementation of Hamilton's principle and the method of calculation lead to the motion equations. The assumed mode method is used to achieve the mathematical model in the multi-mode system that is more similar to the soft continuous system. We investigate the tendencies of the tail amplitude, swimming speed, and Strouhal number when the input driving frequency changes. The simulation results disclose that high swimming efficiency can be obtained at the multi-order resonances; meanwhile, the compliant fish robot is pushed at the corresponding frequency illustrating nonlinear behavior.
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Task Planning and Collaboration of Jellyfish-inspired Multiple Spherical Underwater Robots

Ruochen An, Shuxiang Guo, Yuanhua Yu, Chunying Li & Tendeng Awa
Journal of Bionic Engineering. 2022, 19 (3):  643-656.  DOI: 10.1007/s42235-022-00164-6
Abstract ( 134 )  
Task planning and collaboration of multiple robots have broad application prospects and value in the field of robotics. To improve the performance and working efficiency of our Spherical Underwater Robot (SUR), we propose a multi-robot control strategy that can realize the task planning and collaboration of multiple robots. To complete real-time information sharing of multiple robots, we first build an acoustic communication system with excellent communication performance under low noise ratio conditions. Then, the task planning and collaboration control strategy adjust the SURs so that they maintain their positions in the desired formation when the formation moves. Multiple SURs can move along desired trajectories in the expected formation. The control strategy of each SUR uses only its information and limited information of its neighboring SURs. Finally, based on theoretical analysis and experiments, we evaluate the validity and reliability of the proposed strategy. In comparison to the traditional leader–follower method, it is not necessary to designate a leader and its followers explicitly in our system; thus, important advantages, such as fault tolerance, are achieved.
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Task-oriented Hierarchical Control of Modular Soft Robots with External Vision Guidance

Xin Sui, Tianjiao Zheng, Jian Qi, Zhiyuan Yang, Ning Zhao, Jie Zhao, Hegao Cai & Yanhe Zhu
Journal of Bionic Engineering. 2022, 19 (3):  657-667.  DOI: 10.1007/s42235-022-00170-8
Abstract ( 126 )  
General, high-precision theoretical modeling method is not well developed in the field of soft robotics, which holds back motion control and practical application of soft robots. The concept of modularization brings novel structure, novel locomotion patterns as well as novel control method for soft robots. This paper presents the concept of hierarchical control method for modular soft robot system and a H-configuration pneumatic modular soft robot is designed as the control object. The H-configuration modular soft robot is composed of two basic motion units that take worm-like locomotion principle. The locomotion principle of the basic motion unit is analyzed and the actuation sequence is optimized by evolution strategy in VOXCAD simulation software. The differential drive method is applied to the H-configuration modular soft robot with multi motion modes and vision sensor is used to control the motion mode of the robot. The H-configuration modular soft robot and the basic motion unit are assembled by a cubic soft module made of silicone rubber. Also, connection mechanism is designed to ensure that the soft modules can be assembled in any direction and posture. Experiments are conducted to verify the effect of the hierarchical control method of the modular soft robots.
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Printable Kirigami-inspired Flexible and Soft Anthropomorphic Robotic Hand

Yunhol Chan, Zion Tsz-Ho Tse & Hongliang Ren
Journal of Bionic Engineering. 2022, 19 (3):  668-677.  DOI: 10.1007/s42235-022-00182-4
Abstract ( 115 )  
We present a kirigami-inspired design scheme for a robotic hand by 3D printable folds and cuts. The unique contribution is the printable flexible hand, which provides flexibility and maneuverability that is unavailable in rigid robotic systems. The integration of sensors in the robotic system enables force adjustment for robotic systems applicable in the future. The experimental results have shown that this design can perform everyday tasks through grasping and pinching different items. The fingers can bend from 40 to 100 degrees. Furthermore, the direct printable kirigami cuts and folds from soft elastic printable materials have significant potential for prosthetic devices. The printable kirigami design framework opens the possibility for future developments and modifications in numerous robotic applications.
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Design and Control of a Quasi-direct Drive Actuated Knee Exoskeleton

Yi Long & Yajun Peng
Journal of Bionic Engineering. 2022, 19 (3):  678-687.  DOI: 10.1007/s42235-022-00168-2
Abstract ( 354 )  
This paper describes the design and control of a portable and lightweight knee exoskeleton for people with knee dysfunction. The knee exoskeleton is designed based on our custom quasi-direct drive actuation composed of a DC motor unit and a transmission mechanism encompassing three gears. An online gait generation method based on gait step calculation and direct measurement using Inertial Measurement Unit (IMU) sensors is proposed to provide continuous assistance during walking. Based on the generated gait trajectory online, Active Disturbance Rejection Control (ADRC) incorporating the feedforward compensation approach is proposed to help the human leg move in consideration of external disturbances. The developed knee exoskeleton has been employed successfully to assist impaired users with knee dysfunction to walk in a health recovery center. The experimental results indicate that the online gait generation method and the proposed control method are suitable for the knee exoskeleton. The maximum value of the target knee angular position is approximately 50° and the mean of the control torque for the knee joint is located in the interval of [? 2 Nm, 4 Nm]. The developed knee exoskeleton has the potential to regain normal gait to improve strength and endurance during walking in their activities of daily life.
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Development and Evaluation of a Wearable Lower Limb Rehabilitation Robot

Wanting Li, Keping Liu, Chunxu Li, Zhongbo Sun, Shui Liu & Jian Gu
Journal of Bionic Engineering. 2022, 19 (3):  688-699.  DOI: 10.1007/s42235-022-00172-6
Abstract ( 147 )  
This paper introduces a rigid-flexible coupling wearable exoskeleton robot for lower limb, which is designed in light of gait biomechanics and beneficial for low limb movement disorders by implementing gait training. The rationality of the proposed mechanism is shown with the implementation of the dynamic simulation through MSC ADAMS. For the purposes of lightweight, the exoskeleton mechanism is optimized through finite element analysis. It can be concluded from performance evaluation experiment, the mechanism has certain advantages over existing exoskeleton robots, namely, comfortable, lightweight, low cost, which can be utilized for rehabilitation training in medical institutions or as a daily-walking ancillary equipment for patients.
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Comparing EMG Pattern Recognition with and Without Hand and Wrist Movements

Lizhi Pan, Kai Liu, Kun Zhu & Jianmin Li
Journal of Bionic Engineering. 2022, 19 (3):  700-708.  DOI: 10.1007/s42235-022-00171-7
Abstract ( 106 )  
Electromyography (EMG) pattern recognition has been widely employed for prosthesis control. Several studies demonstrated that amputees had poorer performances of EMG pattern recognition when compared to able-bodied individuals. Several factors, such as the muscle weakness and atrophy of residual limbs, the length of residual limbs, and the decrease of the affected side's motor cortex, had been studied to improve the performance of amputees. However, there was no study on the factor that the absence of joint movements for amputees. This study aimed to investigate whether the hand and wrist joint movements had effects on the EMG pattern recognition. Ten able-bodied subjects were tested for 11 hand and wrist gestures with two different gesture modalities: hand and wrist joints unconstrained (HAWJU) and constrained (HAWJC). Time-domain (TD) features and Linear Discriminant Analysis (LDA) were employed to compare the classification performance of the two modalities. Compared to HAWJU, HAWJC significantly reduced the average Classification Accuracy (CA) across all subjects from 95.53 to 85.52%. The experimental results demonstrated that the hand and wrist joint movements had significant effects on EMG pattern recognition. The outcomes provided a new perspective to study the factors affecting EMG pattern recognition.
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The Effect of Concave Size on the Aerodynamics of a Maglev Train

Shuang Meng, Dan Zhou & Changda Tan
Journal of Bionic Engineering. 2022, 19 (3):  709-723.  DOI: 10.1007/s42235-022-00158-4
Abstract ( 106 )  
Inspired by shark’s skin in nature, a non-smooth surface could be an ideal model for changing the flow characteristics of fluids on the object surface. To analyze the effect of a non-smooth surface with concaves on the maglev train aerodynamic performances and to investigate how the concave size affects the aerodynamic forces and flow structure of a maglev train, four 1/10th scaled maglev train models are simulated using an Improved Delayed Detached Eddy Simulation (IDDES) method. The numerical strategy used in this study is verified by comparison with the wind tunnel test results, and the comparison shows that the difference was in a reasonable range. The results demonstrate that the concaves could effectively reduce the tail car pressure drag, thus reducing the total drag, and that the smaller the concave size was, the better the drag reduction effect would be. The change in the lift with the concave size was more significant than that of the drag, and the tail car lift of R1 (0.0012H), R2 (0.0024H), and R3 (0.0036H) train models was 30.1%, 43.0%, and 44.5% less than that of the prototype, respectively. In addition, different flow topologies of the wake are analyzed. The width and height of the vortex core of the counter-rotating vortices tended to decrease with the concave size. Thus, from the point of view of ensuring the operating safety of a maglev train, a non-smooth surface with small-size concaves is recommended.
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Foldable Units and Wing Expansion of the Oakleaf Butterfly During Eclosion

Jinwen Zhang, Xiaoming Chen, Qin Lu, Jinguo Liu, Xiaofei Ling, Weiwei Wang, Pengfei Liu & Hang Chen
Journal of Bionic Engineering. 2022, 19 (3):  724-736.  DOI: 10.1007/s42235-022-00178-0
Abstract ( 141 )  
Eclosion is a rapid process of morphological changes in insects, especially for the wings of butterflies. The orange oakleaf butterfly (Kallima inachus) transits from pupae to adults with a 9.3 fold instant increase in the surface area of their wings. To explore the mechanism for the rapid morphological changes in butterfly wings, we analyzed changes in microstructures in the wings of K. inachus. We found that there were lots of micron-sized foldable units in the wings at the pupal stage. The foldable units could provide as much as 31.35 times of increase in wing surface area. During eclosion, foldable units were flattened sequentially and resulted in a rapid increase in wing surface areas. The unfolding process was regulated by the structures and layouts of wing veins. Based on our observation, foldable units play important roles in both deformation and stretching of wings. The foldable units of microstructures may provide mimics for simulating entities of large-deformational bionic structures with practical application.
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Current Status and Outlook of Porous Zn-based Scaffolds for Bone Applications: A Review

Abdul Hakim Md Yusop, Mokhamad Fakhrul Ulum, Ahmed Al Sakkaf & Hadi Nur
Journal of Bionic Engineering. 2022, 19 (3):  737-751.  DOI: 10.1007/s42235-022-00152-w
Abstract ( 164 )  
Over the past 5 years, many works have been performed to reveal the potentials of Zinc (Zn)-based materials as temporary bone scaffolds with the expectation that their emergence could address some of the main concerns associated with magnesium- and iron-based materials. Thanks to the emerging Additive Manufacturing (AM) technology, it facilitates the optimization of the design and production of topological porous Zn-based materials suited for bone scaffolds. Since the studies on the porous Zn-based scaffolds are on the rise, we provide the most current progress in the development of porous Zn-based scaffolds for bone applications. The impacts of recently developed topological design from the AM as well as the advanced dynamic-flow corrosion on their corrosion, mechanical properties, and in vitro biocompatibility are also presented. Plus, we identify a number of research gaps and the challenges encountered in adopting porous Zn-based scaffolds for orthopedic applications and suggest some promising areas for future research.
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Polymer Modified Banana Pseudo Stem-based Interfacial Solar-driven Evaporation System

Vivek Chandran, Sujith Lal & Sudip K. Batabyal
Journal of Bionic Engineering. 2022, 19 (3):  752-760.  DOI: 10.1007/s42235-021-00149-x
Abstract ( 106 )  
Interfacial solar-driven evaporation technique is an environmental friendly and cost-effective advanced approach for water purification using solar energy. Free energy sources are effectively utilized using the structural design of evaporators and functional materials. In this work, we have fabricated a solar-driven interfacial evaporation device with Banana Pseudo Stem (BPS) and a photothermal layer made up of PVA PDMS Carbon (PPC) is attached to it. High evaporation rate of 2.03 kg m?2 h?1 is achieved by the system under 1 sun illumination. Heat localization on interfacial surface, reflectance of photothermal layer, presence of micro-fluidic channels in BPS were studied using IR imaging, UV-DRS and SEM characterization techniques, respectively. Effective localization of interfacial temperature around 53 °C and very low reflectance of photothermal layer substantiates high photothermal conversion efficiency of the device. The complete purification of water containing high concentration of Rhodamine-B dye using BPS is a novel and simple approach for water purification. This is an eco-friendly, cost-efficient novel approach in fabrication of interfacial solar-driven evaporation system with high evaporation rate for purification of water containing high concentration of organic dye.
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Plant vs. Animal Prototype for Designing Bio-inspired PEMFC Flow Fields: Corn Veins or Murray’s Law?

Wenxuan Fan, Taotao Zhao, Ke Jiang, Lei Sun, Saisai Jia, Qianqian Wu, Guolong Lu & Zhenning Liu
Journal of Bionic Engineering. 2022, 19 (3):  761-776.  DOI: 10.1007/s42235-022-00174-4
Abstract ( 121 )  
Designing bio-inspired flow fields holds great potential in improving the performance of Proton Exchange Membrane Fuel Cell (PEMFC). Two kinds of biological prototypes are widely used: plant prototype and animal prototype. It remains a question which one of these prototypes is more appropriate for the scenario of PEMFC. Here, a comparative study was conducted to compare bionic flow fields based on animal and plant prototypes. First, a Corn Leaf Vein Mathematical Model (CLMM) was established by extracting structural parameters from corn leaves of two growth stages. Then the obtained CLMM and well-known Murray’s law were employed to design bionic flow fields corresponding to the plant and animal prototypes, respectively, which have been subsequently compared by numerical investigations. The results demonstrate that the flow field guided by Murray’s law outperforms the counterpart based on the structural parameters of CLMM in terms of PEMFC net output power, mass transport, water management and pressure drop, suggesting that animal circulation system is more suitable to the bionic flow field design of PEMFC than plant leaf veins. The work may also offer valuable insights into the design of other flow fields related to electrochemical energy conversion.
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Optical and Nanomechanical Characteristics of Multilayer Structure Derived from Color-changing Beetle Popillia Indgigonacea Motsch

Wei Wu & Jiyu Sun
Journal of Bionic Engineering. 2022, 19 (3):  777-787.  DOI: 10.1007/s42235-022-00154-8
Abstract ( 85 )  
The architecture of multilayer acting in colorful appearance has been widely reported. In spite of this, it is interesting that dense multilayer in epicuticle for Popillia indgigonacea Motsch elytra not only helps presenting angle dependence color-changing, but also showing higher reduced modulus (Er) and hardness (H) to protect soft abdomen below. The optical and nanomechanical properties of elytron were investigated by structural observation, optical experiments, nanoindentation and coupled bionic model simulations. The peak reflectance gradually varies from 588 nm to 510 nm with color change from orange and yellow to green when the incidence angle switches from 0° to 60°, which is attributed to the regulated variation from refractive spectra between the layers in different angle. In addition, the relatively higher Er and H of elytron epicuticle and endocuticle could play a role in resisting force with its multilayer. To identify the multifunctional characteristics of multilayer, optical and mechanical simulations were conducted based on coupled bionic models, and a strong consistence between the experiments and simulations is obtained. The multilayer could resist force with lowest strain and stress, and the structural thickness is the most necessary factors that could adjust the colors in color-changing process.
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Green Plant Leaf-inspired Smart Camouflage Fabrics for Visible Light and Near-infrared Stealth

Qixin Lu, Min Li, Anli Tian & Shaohai Fu
Journal of Bionic Engineering. 2022, 19 (3):  788-798.  DOI: 10.1007/s42235-022-00156-6
Abstract ( 116 )  
Due to Visible light and Near-Infrared (Vis–NIR) stealth play an important role in the commercial, military, and scientific fields, camouflage materials related to it attracted increasing attention in decades. Green plant leaves, as the most extensive background materials on the earth, were widely simulated in the camouflage materials. However, difficult full-spectrum simulation (380–2500 nm), low-similarity simulation and the complex preparation have been great challenges for Vis–NIR Camouflage Materials (Vis–NIR-CMs). Herein, basing on the color-matching principle, two novel Vis–NIR-CMs including Dark Green Materials and Light Green Materials (DGM and LGM) were facilely fabricated by simple printing organic disperse dyes including C.I. Disperse Blue 291, C.I. Disperse Yellow 114, and C.I. Disperse Orange 30 (B-291, Y-114 and O-30), and titanium dioxide (TiO2) on the viscose fabrics. Based on the excellent red edge property of B-291 and high scattering ability of TiO2, DGM and LGM exhibited generally high spectral correlation coefficients rm (>?0.95) with green plant leaves. Moreover, with the great color performance, excellent objects covering performance, low areal density (<?146.3 g cm?2), high tensile strength (>?7.7 MPa), high softness (>?81.27), high air permeability (>?45.848 mm s?1), DGM and LGM showed good simulation performance and wearing comfort to satisfy the application needs. This work presents a high-similarity Vis–NIR-CMs as a reference for full-spectrum camouflage materials, as well as low-cost and efficient preparation method is beneficial to the development of camouflage field.
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Bending Resistance and Anisotropy of Basalt Fibers Laminate Composite with Bionic Helical Structure

Binjie Zhang, Qigang Han, Hanlin Qin, Junqiu Zhang, Shichao Niu, Zhiwu Han & Luquan Ren
Journal of Bionic Engineering. 2022, 19 (3):  799-815.  DOI: 10.1007/s42235-022-00155-7
Abstract ( 125 )  
The appendages of mantis shrimp often bear bending loads from different directions during the in the process of preying on prey with its grazing limb. Hence, it has excellent bending resistance and isotropy to confront complex and changeable external load. The outstanding performance owes to the helical Bouligand structure with a certain interlayer corner, which is also widely found in other natural materials. Hence, the bio-inspired materials with basalt fiber are fabricated with outstanding bending resistance, isotropy and toughness. The research shows laminates with 18° interlayer corners exhibit relatively excellent bending resistance and isotropy, and the laminate with 11.25° interlayer corner has best toughness. Compared with traditional composites, average bending strength along different loading direction of bio-inspired materials increased by 28%, and anisotropy decreased by 86%. Besides, the maximum toughness of laminates can increase to 1.7 times of the original. Following the introduction of interlayer corners, the bio-inspired composite tends to be isotropic. To explore the reason for the change of the isotropic performance caused by diverse interlayer corners, the Finite Element Analysis based on classical laminate theory and Tsai–Wu and Tsai–Hill failure criterion. Besides, further experiments and observations are conducted to explore possible reasons. In conclusion, following the introduction of interlayer corners, the bio-inspired composites tend to be isotropic. This bio-inspired composites are expected to be applied to various complex modern engineering fields, such as vehicle, rail transit and aerospace.
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Experimental Investigation on Saline Water Purification Using Reverse Osmosis by a Novus Biomimetic Membrane

Yasin Edmam Iman, Nadim Ahmed, Sayed Abul Monsur Anachh & Kazi Abu Manjur
Journal of Bionic Engineering. 2022, 19 (3):  816-836.  DOI: 10.1007/s42235-022-00167-3
Abstract ( 129 )  
A substantial amount of Earth’s water is inadequate for human consumption while local demand is outstripping traditional supplies in many world regions; thereby, brackish and seawater treatment has become a prerequisite. This investigation suggested a complete design of an RO-based desalination filter with a multilayer biomimetic membrane. The study demonstrated a comprehensive method for experimentally fabricating a proprietary biomaterial-based multilayer nano-porous membrane. This analysis revealed that Silk Nano-Fibril (SNF) and Hydroxyapatite (HAP) extracted from Bombyx Mori silkworm cocoons may be utilized to manufacture highly methodical multilayer membranes by incorporating protein-self-assembly and in-situ-bio-mineralization. Membrane’s aquaporin layer containing lipid-bilayers has rapid water permeability and high efficacy at eliminating salt ions and contaminants. The 4 μm thick SNF/HAP membrane showed a considerable decrease in salinity, with a salt rejection of 93.33%. The proposed membrane had a saline water permeability of 6.58 LMH/bar, almost 61.09% higher than conventional TFC membranes. Hydrophobic barrier and spiral-wrapped filter architecture of the membrane enable low fouling and self-cleaning properties. The schematic filter design and biomimetic fabrication of the SNF/HAP membrane have formulated a conceptual framework that might direct to the broad-scale, low-cost RO water purification filters, increasing the efficiency of water desalination and boosting the effectiveness of water treatment technologies to reduce potable water scarcity.
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pH-indicative Films Based on Chitosan–PVA/Sepiolite and Anthocyanin from Red Cabbage: Application in Milk Packaging

Marya Raji, Laila El Foujji, Mohamed El Mehdi Mekhzoum, Mounir El Achaby, Hamid Essabir, Rachid Bouhfid & Abou el kacem Qaiss
Journal of Bionic Engineering. 2022, 19 (3):  837-857.  DOI: 10.1007/s42235-022-00161-9
Abstract ( 161 )  
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.
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