Ishak Ertugrul

Temperature is very important in the fabrication of products developed for different applications, considering the widespread use of additive manufacturing (AM) technology. Thermal properties seriously affect the mechanical properties of products. In this study, the effect of printing nozzle temperature changes on the dimensional and mechanical properties of samples fabricated with acrylonitrile butadiene styrene (ABS) material was investigated. This material can be preferred over foam material for drone and model aircraft areas due to its low density. A total of thirty-six tensile test samples (ISO527–type1A) were fabricated with fused filament fabrication (FFF), one of the AM methods, and their dimensional properties (length, width, thickness, and mass) were determined. During the fabrication process, the nozzle temperature of the 3D (three-dimensional) printer was increased from 220 °C to 270 °C in 10 °C increments. All samples were subjected to tensile testing, and stress–strain values were measured. Analysis of variance (ANOVA) was applied to examine the effect of nozzle temperature change on the findings obtained as a result of the experimental study. The printing nozzle temperature significantly affected both the mechanical strength and dimensional properties of the samples. The samples showed lower viscosity and less hardness at higher nozzle temperatures. The mass and density of the samples decreased with increasing temperature. The tensile strength value decreased by 41.52%.

As a result of the developments in additive manufacturing (AM) technology, 3D printing is transforming from a method used only in rapid prototyping to a technique used to produce large-scale equipment. This study presents the fabrication and experimental studies of a 3D-printed strain sensor that can be used directly in soft applications. Photopolymer-based conductive and flexible ultraviolet (UV) resin materials are used in the fabrication of the sensor. A Stereolithography (SLA)-based printer is preferred for 3D fabrication. The bottom base of the sensor, which consists of two parts, is produced from flexible UV resin, while the channels that should be conductive are produced from conductive UV resin. In total, a strain sensor with a thickness of 2 mm was produced. Experimental studies were carried out under loading and unloading conditions to observe the hysteresis effect of the sensor. The results showed a close linear relationship between the strain sensor and the measured resistance value. In addition, tensile test specimens were produced to observe the behavior of conductive and non-conductive materials. The tensile strength values obtained from the test results will provide information about the sensor placement. In addition, the flexible structure of the strain sensor will ensure its usability in many soft applications.

Process control covers the analysis, design, and application of control systems to achieve specific objectives in process safety, production capacity, and product quality. Control of any system is significant, especially in chemical process systems. For this, it is necessary to use a control that can meet the system's demands and work harmoniously. In this study, a system that can be adapted to the chemical process industry has been designed and modelled in the COMSOL program. The concentration level and velocity behaviour of the same type of fluid applied from two channels over this model were kept at the desired level with the Proportional Integral Derivative (PID) control algorithm. The flow rate of the fluids can be changed with the controller to achieve the desired concentration. As a result of the simulation with different PID coefficients, the best response was obtained when the high proportional gain coefficient was applied. It has been determined that the best response of the process in both concentration and velocity data is achieved when kp= –1 m4/(mol·s). A high overshoot and steady-state error occurred at low proportional gain values in the system response.

Soft pneumatic grippers (SPGs) contribute significantly to the development of soft robotic devices and help enable different and complex hardware designs for soft robots. Apart from the many advantages, the lack of position feedback of soft grippers presents a problem for position control. This study aims to examine this problem with the SPG, which is fabricated using additive manufacturing technology. The soft gripper is fabricated in two parts using the molding technique. The structure of the gripper consists of molded silicone (room-temperature-vulcanizing [room-temperature-vulcanizing]-3015) and polyethylene terephthalate (PET) film consisting of chambers. These sections are an active chamber consisting of 10 airtight sections that can be operated with compressed air and a passive chamber covered with PET film. During the bending of the SPG, the PET film inside the passive chamber begins to be compressed by the compressed air, resulting in a higher load-holding capacity of the gripper. In addition, the position of the feedback module made of flex sensor is integrated during fabrication. Various experiments were carried out to evaluate the performance of the SPG. Finite element analysis of the gripper was performed with COMSOL to compare the accuracy of real-time experiments. With the experimental studies’ results, the SPG’s motion characteristics, the relationship between the bending angle and the pressure, and the position-tracking performance were analyzed. Experimental results of the SPG were found to be in good agreement with the simulation results. The experimental results determined that the SPG showed successful trajectory tracking performance with the proportional-integral-derivative control algorithm. The root mean square value for the controller is calculated as 0.1245°.

This study aims to perform optimizatione to achieve the best diffusion control between the channels by designing and analysing a microfluidic-based micromixer. The design and analysis of the micromixer were made with the COMSOL Multiphysics program. Some input and output parameters must be defined for diffusion control of the micromixer. Among these parameters, inputs are the diffusion coefficient and inlet flow rate, while outputs are velocity, pressure, and concentration. Each input parameter in the microfluidic chip affects the output of the system. To make the diffusion control in the most optimum way, the data were obtained by making much analysis. The data obtained from this program was also provided with the Fuzzy Logic method to optimize the microfluidic chip. The diffusion coefficient value (5E-11m²/s) should be given to the channels to achieve the optimum diffusion between the micromixer channels, if the inlet flow rate value (15E-15m³/s) is the output value of the system, the velocity is 0.09mm/s. The pressure is 2Pa, and the concentration is 0.45mol/m³. These values are the optimum values obtained from the analysis without damaging the liquids microfluidic channels supplied to the micromixers inlet.

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It is the aim to develop optimization techniques to separate platelets from Red Blood Cells (RBCs) after designing and analyzing a microfluidic chip in this study. RBCs and platelets are present in the blood, but some healthcare applications require either platelets or RBCs. Therefore, it is necessary to separate platelets from RBCs. In this study, the design and analysis of the microfluidic chip were carried out with the Comsol Multiphysics program. Since the separation of platelets and RBCs in the blood flowing from a channel is provided by the Dielectrophoretic (DEP) force technique, the DEP force feature was given importance in the design of microfluidic channels. Much data was obtained while designing and analyzing processes. It has been observed that the voltage applied to the microfluidic channel and the inlet velocity of the blood affect the fluidic velocity and pressure along the microfluidic channel. It was also understood that the separation of platelets from RBCs depends on input data. Input and output data were analyzed in the Comsol Multiphysics program, and the optimization of the microfluidic chip was realized with the Matlab-Fuzzy Logic program. In order for the platelets to be separated from the RBCs, the optimum voltage to be applied to the microfluidic chip should be in the range of 4–6 V and the inlet velocity of the blood in the range of 800–900 μm s⁻¹. When these input values are given, the maximum pressure affecting the microfluidic outlet channel is 10–12 Pa, and the maximum velocity is in the range of 1.25–1.5 mm s⁻¹. These results are the optimum values required to separate platelets from RBCs.

In this study, it is aimed to perform a COMSOL analysis of the inertial measurement unit (IMU), which is a sensor based on a microelectromechanical system (MEMS) in an inertial navigation system (INS). Autonomous vehicles are the types of vehicles that can go on the move without the intervention of the driver by detecting the road, traffic flow, and environment without the need of a driver, thanks to its automatic control systems, software algorithms, and intelligent sensor structures. Autonomous vehicles can detect objects around them using technologies and techniques such as radio detection and ranging (RADAR), light imaging detection and ranging (LIDAR), Global Positioning System (GPS), INS, ultrasonic sensors, camera systems, and computer vision. After providing information about the use of IMU sensors in autonomous vehicles, the finite element analysis of the gyroscope sensor by the COMSOL program was performed in this study.

3D printing has lately received considerable critical attention for the fast fabrication of 3D structures to be utilized in various industrial applications. This study aimed to fabricate a micro beam with digital light processing (DLP) based 3D printing technology. Compound technology and essential coefficients of the 3D printing operation were applied. To observe the success of the DLP method, it was compared with another fabrication method, called projection micro-stereolithography (PμSL). Evaluation experiments showed that the 3D printer could print materials with smaller than 86.7 µm dimension properties. The micro beam that moves in one direction (y-axis) was designed using the determined criteria. Though the same design was used for the DLP and PμSL methods, the supporting structures were not manufactured with PμSL. The micro beam was fabricated by removing the supports from the original design in PμSL. Though 3 μm diameter supports could be produced with the DLP, it was not possible to fabricate them with PμSL. Besides, DLP was found to be better than PμSL for the fabrication of complex, non-symmetric support structures. The presented results in this study demonstrate the efficiency of 3D printing technology and the simplicity of manufacturing a micro beam using the DLP method with speed and high sensitivity.

Mikro-elektro-mekanik (MEMS) rezonatörler uzun zamandır sensör tasarımı için kullanılmaktadır ve artık günümüzde güç elektroniği alanında osilatörler olarak giderek önem kazanmaktadır. Bu çalışmada, bir mikro mekanik filtrenin parçası olarak tasarlanan bir yüzey mikro işlenmiş MEMS rezonatörü ayrıntılı olarak analiz edilmiştir. Geliştirilen model, uygulanan 100 V DC gerilim ile rezonatörün analizini gerçekleştirir. Mikro rezonatör içerisinden geçen akım, termal genleşme ile ısı enerjisini dağıtmaktadır. Bu genleşme, rezonatör içerisinden geçen akım ve yayılan sıcaklığa bağlı olarak değişmektedir. COMSOL yazılımı kullanılarak 400 μm uzunluğunda ve 50 μm kalınlığında dikdörtgen bir kiriş olarak tasarlanan rezonatör için polikristalin silikon, demir, alüminyum, gümüş ve altın malzeme ataması yapılarak gerekli analizler yapılmıştır. Giriş potansiyeli rezonatörün hava boşluğu merkezinden uygulanarak y ekseninde meydana gelen deformasyonlar ölçülmüştür. En yüksek deformasyon 0.062 µm ile alüminyum malzemede ortaya çıkarken; en düşük deformasyon 0.029 µm ile polikristalin silikon malzemede ölçülmüştür. Demir, gümüş ve altın malzemelerinde ise sırasıyla 0.030 µm, 0.052 µm ve 0.059 µm deformasyon verileri ölçülmüştür. Sonuç olarak, mikro rezonatör tasarımında kullanılan alüminyumun diğer metalik rezonatörler ile kıyaslandığı zaman önerilen geometri için önemli miktarda deformasyon verdiği gözlemlenmiştir.