Sharif Digital Repository

Nowadays, with the increasing need to design and manufacture parts with dimensions less than 1 millimeter in various fields such as medicine, drug delivery, microfluidics, precision casting, and many other areas, methods for manufacturing such parts have gained significant attention. Numerous studies have been conducted to develop 3D printing methods for manufacturing increasingly smaller parts, with optical 3D printing research being at the forefront. In this regard, researchers have enabled the achievement of smaller parts by developing in three areas: increasing the resolution of the light source, changing the resin compositions, and improving the accuracy and correction of image pixels.... 

The ability to fabricate scaffolds that closely resemble the structural characteristics of natural bone remains one of the major challenges in bone tissue engineering. Moreover, developing materials for scaffold fabrication that can accelerate the regeneration process is another important issue. A hybrid scaffold was developed in this study using Melt electrowriting (MEW) and fused deposition modeling (FDM) techniques to mimic the hierarchical architecture of natural bone, consisting of cancellous and cortical regions. The cancellous region was fabricated via MEW using polycaprolactone (PCL), while the cortical region was produced through FDM employing polyvinylidene fluoride (PVDF). The two... 

Metamaterials, due to their unique structure-dependent properties, exhibit characteristics beyond those of natural materials. One of the design methods for these materials is topology optimization. This research presents a novel topology optimization approach that directly employs convolutional neural networks (CNNs) to determine material distribution within the design domain. The input features of the neural network are physically meaningful attributes that have a direct correlation with the objective function, applied constraints, and optimal structure. This characteristic accelerates the optimization process and enhances the accuracy of the results. The network architecture is inspired by... 

The creation of materials with properties at the human satisfaction and beyond what is found in nature has long been the subject of various studies. One of the structures that have received a lot of attention recently is metamaterial. Metamaterials are engineered and purposefully designed materials that, due to this aspect, show unique properties that are not usually found in nature. These unique properties are mainly due to their designed microstructure, which exhibits properties beyond the base material from which they are made. The pentamod metamaterials are among these materials with uncommon properties. A pentamod metamaterial is a three-dimensional structure with a specific... 

In recent years, 3D printing technology has found widespread applications in various industries such as aerospace, medical, and the production of complex parts. Among different 3D printing technologies, coaxial printing has been developed to overcome the limitations of single-material printing and enables the combination of multiple materials to create new properties that are a combination of the individual properties of the materials used. These advantages include the creation of conductive fibers, shock-absorbing structures, and hollow structures. Research indicates that the successful production of coaxial structures mainly depends on three key factors, the compatibility of core/shell... 

Millions of people due to factors such as osteoporosis, aging, sports incidents, and accidents face complications from bone fracture injuries every year. Nitinol shape memory alloy and Gyroid metamaterial have attracted researchers to use them as suitable replacements to fill empty areas of broken bones. In this research, numerical modeling and additive manufacturing were used to take advantage of the special properties of both nitinol and gyroid structures. In the modeling section, finite element modeling of the superelastic effect and the one-way shape memory effect of sheet and solid gyroids in cubic and cylindrical geometries with different porosities were done. As a result of the... 

Tactile sensors are essential for providing critical feedback in applications requiring precise and dexterous control. Capacitive tactile sensors, which are the most common type of tactile sensors, typically employ incompressible dielectrics made of fully filled solid, liquid, or gas, and face limitations that hinder their practical use, such as low sensitivity, slow recovery times, and limited measurable pressure range. While previous studies have shown that structural dielectrics can significantly mitigate these drawbacks, the employed structures were limited by manufacturing constraints. This paper presents the development of multiple novel tactile sensors featuring 3D-printed lattice... 

In this thesis, the behavior of an auxetic metamaterial has been studied with the aim of investigating and deriving the appropriate yield surface and criteria for it. For this purpose, first by studying the available literature, the appropriate antielastic structure was selected for the research and then its 3D model was created using design softwares. Then the optimal simulation method was selected and its results were validated using the experimental results found in other articles. After ensuring the validation of the numerical results, obtaining the appropriate yield level for the structure was considered. For this purpose, three yielding relations of Von Mises, Hill and Tsia-Wu were... 

Today, with the development of micro-technology in chemical reactions, the use of appropriate systems for the separation and purification of synthesized chemicals seems to be necessary. In this study, the continuous synthesis of bromide-lithium exchange reaction and the separation of organic and aqueous phase products in micro systems was investigated.The method used to construct micro-separator and micro reactor, a laser engraving technique, and thermal bonding of glass to glass.In the first step, the factors affecting the separation of organic and aqueous phase in the capillary micro-separator, such as the width of the capillary, the length of the capillary, the number of capillaries and...