Sharif Digital Repository

To have a complete model of a thunniform Fish-Robot, models of both body and tail are required. The dynamic model of the body is developed according to the parameters of a thunniform Fish-Robot built in MIT University, while, as the main part of this paper, the dynamic model of the tail is developed using fuzzy logic. Using experimental data and table look-up scheme, a fuzzy black box is introduced that gives the value of thrust force generated for any value of the Fish-Robot's input parameters: frequency of tail oscillation, amplitude of tail oscillation and speed of the Fish-Robot. In the second part, a trajectory fuzzy controller is designed for the Fish-Robot. The output of trajectory... 

Bioinspired materials can mimic the stem cell environment and modulate stem cell differentiation and proliferation. In this study, biomimetic micro/nanoenvironments were fabricated by cell-imprinted substrates based on mature human keratinocyte morphological templates. The data obtained from atomic force microscopy and field emission scanning electron microscopy revealed that the keratinocyte-cell-imprinted poly(dimethylsiloxane) casting procedure could imitate the surface morphology of the plasma membrane, ranging from the nanoscale to the macroscale, which may provide the required topographical cell fingerprints to induce differentiation. Gene expression levels of the genes analyzed... 

The present work studied bioactive coatings on the surface of ceramic biomaterials. Zirconia toughened alumina (ZTA) composites containing 15 mol.-%. Partially stabilised zirconia was prepared after 1 h sintering at 1550°C. Apatite layers were then coated onto the surfaces of composites by the biomimetic method using 1·5-2 multiply concentrations of simulated body fluid (SBF). Before treatment in SBFs, a sodium silicate layer was employed as nucleating agent to induce the formation of a calcium phosphate layer. The effect of immersion time on the morphology of the precipitate was monitored with a scanning electron microscope. X dot maps revealed that there is a relationship between... 

Mechanical alloying and sintering were used to fabricate nanostructured Ti6Al4V scaffolds of highly controllable pore geometry and fully interconnected porous network. Elemental powders were milled for different periods of time (10, 20, 30, 40 and 60 h), mixed with 40-60 vol.-% of 200-400 μm cuboidal NaCl, compacted at 500-600 MPa and sintered according to single or double stage heat treatment regimes at 790 and 950°C under vacuum. After sintering, the samples were soaked in distilled water to washout the NaCl. Foamy microstructures were obtained showing well shaped biopores and fragmentary embedded micropores. The shape of initial NaCl was copied into the biopores which had highly... 

Hydroxyapatite (HA) is the most substantial mineral constituent of a bone which has been extensively used in medicine as implantable materials, owing to its good biocompatibility, bioactivity high osteoconductive, and/or osteoinductive properties. Nevertheless, its mechanical property is not utmost appropriate for a bone substitution. Therefore, a composite consist of HA and a biodegradable polymer is usually prepared to generate an apt bone scaffold. In the present work polycaprolactone (PCL), a newly remarkable biocompatible and biodegradable polymer, was employed as a matrix and hydroxyapatite nanoparticles were used as a reinforcement element of the composite. HA/PCL nanocomposites were... 

This research presents virtual prototyping and performance evaluation of a series elastic torque actuator developed for augmenting lower extremity exoskeletal systems employing biomechanical framework. For this purpose, experimental kinematical data of the lower extremity were collected for walking and backpack load carrying. Forward dynamics simulation of the movements under investigation is performed in a biomechanical framework consisting of a musculoskeletal model with ten degrees-of-freedom actuated by eighteen Hill-type musculotendon actuators per leg to perform the muscle functional analysis. Muscle torque analysis results employed for optimal design and selection of components in the... 

Nanocrystalline hydroxyapatite (nHA) of 50 nm average diameter and length to diameter ratio of >3 was synthesized by biomimetic method. Non-isothermal sintering improved densification behavior and mechanical properties of apatite to 0.88 maximum fractional density, 70MPa bending strength, 148MPa compressive strength and 2.53GPa microhardness at sintering temperature of 1250°C. Higher sintering temperatures resulted in the decomposition of the apatite and in-situ biphasic calcium phosphate HAP/TCP formation. This process lowered apatite densification and weakened mechanical properties of the sintered specimen. Transmission electron microscopy (TEM), x-ray diffraction (XRD) and field emission... 

To have a complete model of a thunniform Fish-Robot, models of both body and tail are required. The dynamic model of the body is developed according to the parameters of a thunniform Fish-Robot built in MIT University, while, as the main part of this paper, the dynamic model of the tail is developed using fuzzy logic. Using experimental data and table look-up scheme, a fuzzy black box is introduced that gives the value of thrust force generated for any value of the Fish-Robot's input parameters: frequency of tail oscillation, amplitude of tail oscillation and speed of the Fish-Robot. In the second part, a trajectory fuzzy controller is designed for the Fish-Robot. The output of trajectory... 

The formation of biomimetic bone-like apatite layers throughout the biopolymer-based hydrogel scaffold is an attractive approach in bone tissue engineering. Here, the starch scaffold was prepared using a combination of particulate leaching and freeze-drying techniques. The fabricated structures were then modified by citric acid to investigate the formation of bone-like apatite layer on the porous citrate-based scaffold after soaking in simulated body fluid (SBF). The Fourier Transform Infrared (FTIR) spectra and X-ray diffraction (XRD) patterns revealed that the B-type carbonated apatite has successfully deposited on the scaffold after immersing in SBF for 28 days. Indeed, high chemical... 

In certain types of biomimetic surgery systems, micro robots inspired by Paramecium are designed to swim in a capillary tube for gaining access to internal organs with minimal invasion. Gaining insight into the mechanics of Paramecium swimming in a capillary tube is vital for optimizing the design of such systems. There are two approaches to modeling the physics of micro swimming. In the envelope approach, which is widely accepted by researchers, Paramecium is approximated as a sphere, self-propelled by tangential and normal surface distortions. However, not only is this approach incapable of considering the specific geometry of Paramecium, but it also neglects short range hydrodynamic... 

Development of predictive multi-organ models before implementing costly clinical trials is central for screening the toxicity, efficacy, and side effects of new therapeutic agents. Despite significant efforts that have been recently made to develop biomimetic in vitro tissue models, the clinical application of such platforms is still far from reality. Recent advances in physiologically-based pharmacokinetic and pharmacodynamic (PBPK-PD) modeling, micro- and nanotechnology, and in silico modeling have enabled single- and multi-organ platforms for investigation of new chemical agents and tissue-tissue interactions. This review provides an overview of the principles of designing... 

Gimbal transmissions are non-linear direct transmissions and can be used in robotic arms replacing the traditional revolute joints. To investigate manipulability of robotic manipulators, the classical criterion of Manipulability Ellipsoid has been formulated. Thus by keeping a constant norm for robot joint torques vector, the effects of replacing some traditional revolute joints in robotic arms with Gimbal transmissions, have been analyzed. The results show that the magnitude of the maximum force applicable when employing Gimbal transmission can be considerably larger. Also, the joint angles in which this maximum occurs, can be adjusted, thanks to the behavior of Gimbal transmission. Two... 

This paper presents a new approach based on Artificial Potential Fields (APF) which provides real-time and very effective methodology for practical motion planners in unknown dynamic environments. The Maxwell's equations are exploited to define Artificial Magnetoquasistatic Fields (AMF) as an extension of APF, which provides a predictive, intelligent, and natural behavior in contrast with other approaches. The essential aim of the AMF is dealing with moving obstacles, as well as static ones. The main idea is to consider an electrical current in the direction of each moving obstacle which induces magnetic field around it. These moving obstacles could be arbitrary in shape, size, and number.... 

For a successful repair and reconstruction of bladder tissue, fabrication of scaffolds with proper biochemical and biomechanical characteristics is necessary. Decellularized bladder tissue has been proposed in previous studies as a gold standard material for scaffold fabrication. However, weak mechanical properties of such a load-bearing tissue has remained a challenge. Incorporation of both biological and synthetic materials has been known as an effective strategy for improving mechanical and biological properties of the scaffolds. In the present work, a simple process was developed to fabricate hybrid hydrogel scaffolds with a biomimetic architecture from the natural urinary bladder... 

Designing meta-materials and cellular solids with biomimetic structures has received increasing attention in the past few years partially due to advances in additive manufacturing techniques that have enabled the fabrication of advanced materials with arbitrarily complex microarchitectures and novel functionalities. To impact on this trend, it is essential to develop our understanding about the role of microstructure on mechanical responses of these structures. Although a large literature exists on the general subject, the role of microstructure on the post-yield instability is not yet adequately documented. This research introduces a numerical approach to study the post-yield instability in... 

This paper presents a new mechanism with unique and prominent features for a helical swimmer robot. "Double Helices Propulsion Mechanism" consists of two parallel helices with a single axis rotating in the same direction. The outer helix acts as the main propulsion component, and the inner helix, which is made of a Shape Memory Alloy (SMA), controls the forward velocity during swimming. This mechanism, by varying the geometrical parameters of its helical tail, can change the forward velocity of the helical swimmer robot that is required by its predefined missions. In order to study the effects of geometric parameters on the forward velocity in the single helical swimmer, a hydrodynamic model... 

An Iron(lV)-oxo heme(+·) complex (Compound I, Cpd I) is the proposed active species of heme enzymes such as the cytochromes P450 and Is elusive; therefore, biomimetic studies on active site mimics give valuable Insight Into the fundamental properties of heme active species. In this work we present density functional theory (DFT) calculations on substrate hydroxylatlon by a Compound I mimic [FeIV=O(Por+̇)Cl] and its one-electron reduced form [FeIV=O(Por)Cl]-. Thus, recent experimental studies showed that [FeIV =O(Por)Cl]- is able to react with substrates via hydride transfer reactions [Jeong, Y. J.; Kang, Y.; Han, A.-R.; Lee, Y.-M.; Kotani, H.; Fukuzumi, S.; Nam, W. Angew. Chem., Int. Ed.... 

The catalytic activity of highvalent iron-oxo active species of heme enzymes is known to be dependent on the nature of the axial ligand trans to the iron-oxo group. In a similar fashion, experimental studies on iron-oxo porphyrin biomimetic systems have shown a significant axial ligand effect on ethylbenzene hydroxylation, with an axial acetonitrile ligand leading to phenyl hydroxylation products and an axial chloride anion giving predominantly benzyl hydroxylation products. To elucidate the fundamental factors that distinguish this regioselectivity reversal in iron-oxo porphyrin catalysis, we have performed a series of density functional theory calculations on the hydroxylation of... 

Background: Researchers are trying to study the mechanism of neural stem cells (NSCs) differentiation to oligodendrocyte-like cells (OLCs) as well as to enhance the selective differentiation of NSCs to oligodendrocytes. However, the limitation in nerve tissue acces-sibility to isolate the NSCs as well as their differentiation toward oligodendrocytes is still challenging. Purpose: In the present study, a hybrid polycaprolactone (PCL)-gelatin nanofiber scaffold mimicking the native extracellular matrix and axon morphology to direct the differentiation of bone marrow-derived NSCs to OLCs was introduced. Materials and Methods: In order to achieve a sustained release of T3, this factor was... 

ILS-based reservoir is a bio-inspired computational model consisting of spiking neurons which has been designed to process spatiotemporal patterns appropriately. In ILS-based reservoir, the neurons are located in an ionic environment and the connections are provided by ionic density. By using ionic diffusion as a processing operation, this model is able to consider the effects of both the preceding and current stimuli properly. Since character recognition is an important task in various applications, this paper focuses on the classification of handwritten digits using ILS-based reservoir. For this purpose, a neuromorphic handwritten digit dataset called N-MNIST dataset is used as a...