Application of “bioactive materials”, as a modified version of biomaterials, can optimize the response of the biological system due to their surface reactivity and formation of strong interactions with the adjacent tissue upon implantation. However, choosing an appropriate bioactive material that suits to the application and provides the desired mechanical, physical, chemical and biological functionality, as well as understanding the aspects of biological reaction to the biomaterial, in particular immune response, it plays a key role in successful integration of the implant. In this review, we will discuss different bioactive materials including bioactive ceramics, polymers and composites and their applications in drug delivery and scaffold preparation in order to provide an adequate introduction to the recent studies. Considering the necessity of regulation of implant fate for higher biocompatibility, the comprehensive overview to the immune response will be reviewed with the focus on representing the cell-biomaterial interactions and more importantly, the inflammatory responses. Ultimately, we will also discuss about different approaches namely as immunomodulation to elicit the desired physiochemical properties and mimicking native cellular response using bioactive compounds, functionalizing the implant surface with active molecules and alteration of the surface morphology. With better understanding of bioactive materials and their interactions with body, more novel biomaterials representing desired properties can be designed.

This paper introduces the design and fabrication of a crawling soft robot controlled by a Shape Memory Alloy (SMA) wire. The robotic smart structure was inspired by the inchworm’s abdominal contractions during locomotion. The SMA wires were embedded longitudinally in the robotic body to imitate the inchworm’s longitudinal muscle fibers that are used to control the inchworm’s abdominal contractions. A ratchet structure was used to imitate the inchworm’s feet and provided friction with the ground during moving. Based on the resistor self-feedback of the SMA wire, we proposed an adaptive control strategy to avoid overheating. Experiments were conducted to evaluate the robotic locomotive performance for crawling, avoiding an obstacle, and the effect of the adaptive control strategy. The maximum speed of the robot was 48 mm?min?1, and the SMA wire’s temperature was kept below 69 ?C to prevent overheating. Those results show that this robot is with the ability to adapt to different environments.

This paper presents the design and manufacture process of a wheel-less, modular snake robot with series elastic actuators to reliably measure motor torque signal and investigate the effectiveness of active stiffness control for achieving adaptive snake-like locomotion. A polyurethane based elastic element to be attached between the motor and the links at each joint was designed and manufactured using water jet cutter, which makes the final design easier to develop and more cost-effective, compared to existing snake robots with torque measurement capabilities. The reliability of such torque measurement mechanism was examined using simulated dynamical model of pedal wave motion, which proves the efficacy of the design. A distributed control system was also designed, which with the help of an admittance controller, enables active control of the joint stiffness to achieve adaptive snake robot pedal wave locomotion to climb over obstacles, which unlike existing methods does not require prior information about the location of the obstacle. The effectiveness of the proposed controller in comparison to open-loop control strategy was verified by the number of experiments. The results show the capability of the robot to successfully climb over obstacles with the height of more than 55% of the diameter of the snake robot modules.

This paper explores the design of leg morphology in a six-legged robot. Inspired by nature, where animals have different leg morphology, we examined how the difference in leg morphology influences behaviors of the robot. To this end, a systematic search was conducted by scanning over the parameter space consisting of default angles of leg joints of the six-legged robot, with two main objectives: to maximize the kinematic flexibility and walking performance of the robot. Results show that (1) to have a high kinematic flexibility with both the torso and swing legs, the femur segment should tilt downwards by 5? – 10? and the tibia segment should be vertically downwards or with a slight inward tilt; (2) to achieve relatively energy-efficient and steady walking, the tibia segment should be approximately vertically downwards, with the femur segment tilting upwards to lower the torso height. The results of this study suggest that behaviors of legged robots can be passively enhanced by careful mechanical design choices, thereby leading to more competent legged machines.

In order to enhance the dynamic motion capability of the bionic quadruped robot, a flying trot gait control method based on full-scale virtual model and optimal plantar force distribution is proposed. A stable flying trot gait is accomplished by mapping the robot torso motion to the foot trajectory. The force distribution calculated by the torso virtual model is converted into a quadratic optimization problem and solved in real time by the open source library Gurobi. The transition between the trot gait and the flying trot gait is achieved by co-ordinating leg motion phases. The results of the dynamic simulation verify that the proposed method can realize the 3D stable flying trot gait. Compared against the trot gait, the flying trot gait can improve the speed of the quadruped robot. Combine the trot gait and the flying trot gait, the quadruped robot can move efficiently and adapt to complex terrains.

The aim of this study is to propose the output controller to solve the execution of the gait sequence for Gecko Bio-inspired Robotic Devices (GBRDs). The Twisting Controller (TC) serves as basis of the tracking trajectory designed algorithm. The TC uses both the tracking error and its estimated derivative, which is calculated by a set of distributed Super-Twisting Algorithms (STAs). Each STA is implemented as a robust and exact differentiator. The output-based controller structure corresponds to a sort of decentralized form for robotic devices. Consequently, each articulation is controlled by an independent TC. A set of proposed references trajectories reproduce the gait cycle of a Real Gecko-Lizard (RG-L). The reference trajectories are proposed as the superposition of sigmoid functions ful-filling the conditions of the Bezzier polynomials. Numerical simulations evaluate the GBRD movement enforced by the suggested controller in the horizontal as well as the vertical gaits. An own 3D printed GBRD is the experimental platform aimed to test the distributed controller. Two controlled vacuum pumps are used to adhere the GBRD to the wall surfaces. A set of experimental validations confirm the robustness and the reliability of the proposed controller when its performance is compared with classical output feedback controllers.

In this paper, we propose a novel study for gesture identification using surface electromyography (sEMG) signal, and the raw sEMG signal and the sEMG envelope signal are collected by the sensor at the same time. An efficient method of gesture identification based on the combination of two signals using supervised learning and univariate feature selection is implemented. In previous research techniques, researchers tend to use the raw sEMG signal and extract several constant features for classification, which inevitably causes a result of ignoring individual differences. Our experiment shows that both the optimal feature set and redundant feature set are not same for different subjects. In order to address this problem, we extract all the common features from two signals, up to 76 features, most of which has been established as the common EMG-based gesture index. In addition, extracting too many features in an application can reduce operational efficiency, so we apply for feature selection to get the optimal feature set and decrease the number of extracting feature. As a result, the combination of two signals is better than using a single signal. The feature selection can be used to select optimal feature set from all features to achieve the best classification performance for each subject. The experimental results demonstrate that the proposed method achieves the performance with the highest accuracy of 95% for identifying up to nine gestures only using two sensors. Finally, we develop a real-time intelligent sEMG-driven bionic hand system by using the proposed method.

The back pain is the most common injury in human activities where heavy objects must be lifted or must be suspended for a long time. A weight lifting exoskeleton also known as force augmentation exoskeleton is designed to reduce the strain on the back and the limbs and reduce the risk to suffer injuries. On the other hand, different kinds of controllers have been implemented to achieve whit this goal, for example, a conventional PD Control, PD Control with Gravity Compensation, PD Control with Adaptive Desired Gravity Compensation and PD Control with Robust Compensator. This paper aims to evaluate and compare the performance from the previously cited controllers used to reduce the strain in the back, through the implementation of each controller in a three Degrees Of Freedom (DOF) exoskeleton powered by pneumatic muscle actuators; some numerical simulations as well as experimental trials have been conducted and three different performance indices were used in order to determine the effectiveness of each one with respect to the simple PD controller when the mass to be lifted is unknown.

Maximal local loads in animal joints are necessary to design bio-inspired mechanical joints. Many studies presented methods to determine joint reaction forces in humans and animals. However, many of these methods are invasive, and no work has been published yet about the joint reaction forces in the horse forelimb during jumping. Non-invasive methods to measure the kinematics and ground reaction force of a horse forelimb were used in this work. A musculoskeletal model of horse forelimb was built with mechanical methods for the estimation of joint reaction forces. The entire forelimb was reconstructed by scanning real bones geometry with a 3D optical scanner and modeling all the muscles on a Computer Assisted Design (CAD) software. The model dynamics were simulated with OpenSim in order to estimate the joint loading. This study allows knowing an order of magnitude of the loads at the joints at jumping in order to determine latter the maximal joint contact loading values that will be a key at designing bio-inspired joints for mechanical assemblies.

In this study, we developed a powder extruder system that can extrude and deposit powder mixtures to overcome the reported limitations of conventional dual-pore scaffold manufacturing methods. To evaluate the extrusion and deposition capability of the powder extruder system, 3D tissue-engineering scaffolds with dual-pore characteristics were fabricated with a PCL/PEO/NaCl (polycaprolactone/polyethylene oxide/sodium chloride) powder mixture. In addition, to evaluate the fabricated scaffolds, their compressive modulus, morphology, and in-vitro cell activity were assessed. Consequently, it was confirmed that the proposed powder extruder system can fabricate dual-pore scaffolds with well-interconnected pores as well as arbitrary 3D shapes shown by the fabrication of a 3D femur-shape scaffold similar to the femur model. The results of the cell proliferation and Cell Counting Kit-8 (CCK-8) assays, DNA content analysis and viability assays confirm that the dual-pore scaffold fabricated by the powder extruder system improves cell attachment, proliferation, and viability.

Bionic devices are an integral part of human life, and continuous innovations in their design and functions with the help of nanotechnology has revolutionized the area of neuroscience and technology. Bio-interfaces play a key role in bionic devices such as neural implants for efficient transfer of the signal to smart prosthetics. We report here on the design of a new microelectrode, comprising Carbon Nanofiber (CNF) and a biopolymer, namely carboxymethyl xyloglucan (CMX) hydrogel inside the CNF, which enhances the current density across the interface. Microelectrode was prepared by in-situ cross-linking of CMX inside CNF, with optimized CMX: CNF ratio, resulting in continuous ionic channels confined within the hollow core of CNF. Electron microscopy images of microelectrodes illustrate the formation of CMX hydrogel network inside the CNF hollow core without wrapping its surface. The presence of hydrogel in the CNF was confirmed by Scanning Electron Microscope (SEM) and Transmission Electron Microscopy (TEM). The electrochemical studies indicate the enhancement in charge density as well as the active surface area of the microelectrodes due to the presence of CMX hydrogel network. These microelectrodes have great potential as neural interfaces for designing smart prosthetics with voluntary control.

Seashells, commonly referred to as nature’s armors against predatory attacks, have been serving as the inspirations for designing strong and tough engineering materials. Previous studies on conch shells have been focused on the shell body parts. The conch spines which are evenly distributed at the tail of conch shell are generally accepted as the decoration, enabling conch shells as art pieces. Here we report a new finding that nature uses curved reinforcements, different from the straight ones in conch body parts, to construct conch spines which exhibit 30% increase in fracture strength compared to conch shell body parts. The curved lamellae not only endow conch spines with pyramid-shape but also add extra shielding to the shells. Under equilibrium state, the curved lamellar configuration withholds 3 times higher loading than the straight one. Our finding uncovered nature’s wisdom in constructing seashells and provides an additional design guideline for utilizing curved reinforcements to achieve multifunctionalities and superior mechanical prowess.

With the development of water purification technologies, the usage of superhydrophobic meshes is increased but the fabrication of durable and cost effective superhydrophobic meshes is still challenging. Here, the formation of hierarchical copper fractals on stainless steel meshes and their superhydrophobicity without any physical or chemical modification were studied. In addition, the improvement of superhydrophobicity of surfaces during storing in a glass bottle for a long time (> one year) is reported. The structures were prepared using electrodeposition method applying cyclic voltammetry and square pulse deposition approaches on stainless steel meshes with 50 ?m, 100 ?m and 200 ?m pore sizes. The prepared layers are a composition of copper with varying amounts of cuprite (Cu2O) depending on deposition method and mesh pore size. As-prepared cyclic voltammetry layer on 100 ?m mesh showed the parahydrophobicity with the contact angle of 154? but a large sliding angle. The one-year stored samples in the glass bottle showed superhydrophobicity with the contact angles larger than 150? and sliding angles in the range of 4? – 20?. The observed improvement of superhydrophobicity is a great success in the realm of industrial water purification, while most other proposed samples by the others have problems related to the durability of superhydrophobicity. 

The shortfin mako shark (Isurus oxyrinchus) is one of the fastest marine fishes, reaching speeds of up to 70 km?h?1. Their speed is related to the skin surface design composed of dermal denticles. Denticles vary in size and shape according to placement on the body and minimize turbulence around the body. The objective of this study is to analyze the interaction between seawater flow and denticles on the dorsal fin. High-resolution microscopy (scanning electron microscopy and confocal microscopy) were used to measure defined parts of the dermal denticles. These measurements, along with ratios based on length-to-width define three morphologies (rounded, semi-rounded, long) that were 3D reconstructed. Computational fluid dynamics simulated fluid passage over reconstructed denticles and describe hydrodynamic efficiency under different conditions. An increase in angle of inclination produced a relevant increase in the drag coefficient, especially for high velocity inlets. The lowest drag coefficient values were found in long and semi-rounded, followed by rounded morphologies. The hydrodynamic behavior of shark skin demonstrates a relation to the morphological characteristics of dermal denticles on the dorsal fin. It is concluded that the best hydroefficiency relies on the rounded morphology and may serve to design hydrodynamically efficient surfaces or manmade assemblies.

The building industry is one of the main contributors to worldwide resource consumption and anthropogenic climate change. Therefore, sustainable solutions in construction are particularly urgent. Inspired by the success principles of living nature, biologists and engineers present here an interdisciplinary work: The sustainability assessment of a bio-inspired material technology called graded concrete, which was developed at ILEK. Gradient structural materials can be found in plants on different hierarchical levels, providing a multitude of creative solutions for technology. Graded concrete applies this biological concept of structural optimization to the interior structure of concrete com-ponents to minimize material and resource expenditure. To evaluate the sustainability of this innovation, a newly developed quantitative Bio-inspired Sustainability Assessment (BiSA) method is applied. It focuses on the relationship of environmental, social and economic functions and the corresponding burdens quantified basing on life cycle assessment. The BiSA of graded concrete slabs shows significant improvements over conventional concrete for the applied use case. While an overall reduction of environmental burdens by 13% is expected, economic burdens can be reduced by up to 40% and social burdens by 35.7%. The assessment of the graded concrete technology identifies its potential with regard to sustainable construction. The presented work provides a blueprint for the interdisciplinary, integrative work on sustainable, bio-inspired innovations. It shows that the synergies of bio-inspiration and BiSA within technical product development can be fruitful. 

The main objective of this investigation is to valorize a Moroccan crop residue (Sabra fibers, Agave Americana L.) and to compare with Alfa fibers (Stipa tenacissima L.) as reinforcement in an elastomeric matrix in term of the relaxation properties, mechanical and rheological properties. The preparation and properties of these two natural fibers embedded in Styrene-Butadiene Rubber (SBR) are presented with and without the addition of Styrene-Ethylene-Butadiene-Styrene grafted with Maleic Anhydride (SEBS-g-MA) as a coupling agent. Five different series (SBR, SBR/Alfa, SBR/Alfa/SEBS, SBR/Sabra and SBR/Sabra/SEBS) were compounded by extrusion and compression molding. As a result, the addition of the coupling agent in the elastomeric matrix improves the relaxation properties, mechanical and rheological properties. Moreover, Sabra fibers show the good results compared to Alfa fibers. Finally, the Zener model was used to determine the rheological time response of the composites. A good agreement between the experimental data and the model was observed (R2 = 0.99).