정렬된 은나노와이어와 PDMS 복합재를 이용한 고감도 유연 스트레인 센서

최재혁 부산대학교 대학원 2020 국내석사

본 연구에서는 은나노와이어를 정렬한 후 Polydimethylsiloxane (PDMS)로 전사하여 스트레인 센서를 제작한 정렬방향에 따라 스트레인 센서가 보이는 성능을 비교하였다. 정렬된 은나노와이어가 함입된 유연 스트레인 센서는 정렬방향과 같은 종방향으로 제작한 스트레인 센서와 정렬방향과 수직인 횡방향으로 제작된 스트레인 센서 두 종류 (종방향, 횡방향)로 제작 후 특성을 평가하였다. 제안된 종방향 스트레인 센서의 경우 25%의 인장상태에서 최대 GF=89.99의 감도를 보였다. 이는 횡방향 스트레인 센서가 보인 25%의 인장상태에서의 GF=12.71의 감도에 비해 7.08배 높은 수치이며, 이를 통해 은나노와이어의 정렬방향이 제작되는 유연 스트레인 센서의 민감도에 영향을 끼치는 것을 확인하였다. 횡방향 스트레인 센서 (ε>60%)의 경우 웨어러블 디바이스에서 요구하는 인장범위 (ε>50%)를 충족하여 적용 가능성을 보였다. 제작된 스트레인 센서들은 온도를 조절한 딥코팅 공정을 이용하여 값이 싸고 대면적화가 용이하며 상업화에 장점을 가지고 있다. 이러한 특징들은 유연 스트레인 센서 외의 다양한 유연소자에도 적용이 가능할 것으로 기대된다

무동력 유수 분리를 위한 친유소수성 마이크로 메쉬의 제작과 특성 평가

이민철 부산대학교 2013 국내석사

The separation of water from oil that is collected in oil spill recovery operation is a continuing and necessary requirement during every stage of the effort. In order to separate oil from oil spill, hydrophobic and oleophilic micro-nano technology is new way to do oil skimming. A hydrophobic and oleophilic mesh is one way for oil skimming. In this study, hydrophobic and oleophilic mesh was obtained by plasma polymerized fluorocarbon coating (PPFC) and Ni-Cu electrodeposition on nikel mesh and oil skimmer using a hydrophobic and oleophilic mesh is proposed to collect oil from oil spill on the sea. In order to evaluate the hydrophobic and oleophilic properties of the mesh, nonstructure and micro-nano structure on mesh are fabricated and C.A (contact angle) and oleostatic pressure was measured. The hydrophobic and oleophilic properties of micro-nano structure on mesh is higher than non-structure on mesh. However, oleostatic pressure of meshs is similar. The oil-water separation system is designed that oleopilic substrate is contact with the back of mesh. It is possible that mesh with high oleostatic pressure and hydrostatic separates oil from oil spill. In order to evaluate oil-water separation system, rate of collecting oil was measured. Rate of collecting oil using non-structure mesh is higher than that using micro-nano structure mesh. It is because that adhesion force of micronano structure is major cause of oil flow slowly on surface of mesh. Through the results, using bare or nano surface of mesh is more efficient than using micro surface of mesh in oil-water separation system and it is expected that higher open area ratio would show better performance of oil-water separation.

순환전압전류법을 이용한 생물막 형성량 측정용 전기화학센서의 제작 및 측정

황병준 부산대학교 2013 국내석사

Microorganisms stick to each other on a solid surface in aqueous solution. These adherent cells shape thin layer called biofilm. Biofilms have been found to be in a wide variety of microbial infections in the body. And also biofilms can lead to considerable corrosion problems in industries. So detecting formation of biofilms on the surface of medical appliance, water pipe and industrial utility is highly important to prevent the problem caused by biofilms. This study investigated the change of acetate ion in the biofilms and determined quantitative relationship between biofilms and current at redox potential of acetate ion. Acetate ion is a composition of biofilm and aerobic bacterial metabolite. We designed 3-electrochemical cell and cultured Pseudomonas aeruginosa to form biofilm. Cyclic voltammetry, frequently used for analyzing electrochemical reaction, is used to measure current change. Potassium chloride aqueous solution used as an electrolyte due to standard electro potential. Potassium ion and chloride ion have higher standard electrode potential than acetate ion. So controlling the potential range can induce the redox of acetate ion. The change in current was observed 2, 4, 6, 8, 12 and 24 hours of biofilm formation. As a result the current changed in proportion of biofilm formation. This phenomenon was due to ionic imbalance by electrochemical reaction of acetate ion and water. Previous electrochemical measurements techniques of biofilms such as measure of MIC(Microbial Influenced Corrosion) and observing current change by the decrease of electrode surface area caused by biofilms are hard to distinguish biofilms and external factors. Measurement of acetate ion in the biofilms relatively has less effect of external factors. And it was shown the possibility that can be used to detect biofilm formation for preventing damage caused by biofilm.

실리콘 압저항형 고충격 가속도센서의 제작과 성능평가

배공명 부산대학교 2014 국내박사

Since the development of a piezoresistive silicon accelerometer by L. M. Roylance and J. B. Angell in 1979, micromachined silicon accelerometers have been used in many devices including automobiles, portable electronics, biomedical, and military. In order to measure incident acceleration, a variety of micromachined silicon accelerometer technologies have been adopted (e.g., capacitive, piezoresistive, piezoelectric, resonant, optical). Among these, the capacitive and piezoresistive detection devices have been widely used and successfully commercialized. The capacitive detection method is generally used in those situations (including automobiles and portable electronics) which require a relatively low-level acceleration (~1,000 g). On the other hand, the piezoresistive detection method is preferred for high-level acceleration (> 1,000 g) of which applications include vehicle crash analysis and bomb fuses. In this paper, a high-shock (2,000 g) accelerometer is presented, with suspended piezoresistive sensing bridges and four hinges. Unlike cantilever-type accelerometers that have suspended piezoresistors, the mass of the proposed accelerometer is connected with four hinges. An optimal design process has been conducted to obtain the structural sizes, and numerical simulation has been carried out on the model-design using commercial software. The silicon accelerometer chips are fabricated using silicon micro-electro-mechanical system (MEMS) fabrication techniques, and the chips are packaged with ceramic boards. Their performance has been evaluated regarding sensitivity, linearity, and over-shock survivability. A sensitivity of 25.5 μV/g has been measured from the fabricated accelerometer with a nonlinearity of 0.2% in an acceleration range within 2,000 g. The real-time response of the fabricated accelerometers accurately follows the reference accelerometer. The newly fabricated accelerometer has survived an over-shock condition of 4,667 g. The proposed accelerometer can be directly applied to a wide variety of applications where there is a need to measure high-level acceleration, including vehicle crash analysis and bomb fuses.

판스프링을 구비한 압저항형 고충격 실리콘 가속도 센서

이재민 부산대학교 대학원 2015 국내박사

Since the cantilever-type silicon accelerometer was introduced by L.M. Roylance and J.B. Angell in 1979, micromachined accelerometers have been used in various industry fields. There are several methods for sensing the acceleration of such micromachined accelerometers, including capacitive, piezoresistive, piezoelectric, resonant, and optical methods. Among these, the most commercially used methods are capacitive, piezoresistive, and piezoelectric detection. Among them, the piezoresistive detection method measures high-shock over thousands of g without additional circuit or packaging in the most stable way. The measurement of high-shock over thousands of g is highly significant in various fields such as vehicle collision test, building blast test, oil drilling, and manufacturing bomb fuses. Thus, research on the manufacture and application of high-shock piezoresistive accelerometer have been actively conducted. In this paper, a high-shock (2,000 g) accelerometer with a plate spring is presented. The acceleration sensor comprised of the presented plate spring has merits of relatively simple manufacturing process and possibility of precisely controlling the dimension of the spring. In addition, the sensor has high structural stability because it is manufactured in a form where the plate spring surrounds the mass body of the sensor. Detailed design of the dimensions of the presented acceleration sensor was determined through an optimum design process using commercial software. Furthermore, the presented acceleration sensor was manufactured through a micro-machining process based on semiconductor process technology. The performance of the presented acceleration sensor was evaluated by measuring the sensitivity, cross-sensitivity, and over-shock survivability of the sensor. When a shock of 2,000 g was applied, the sensitivity of the manufactured acceleration sensor was 34.6 μV/g. When a shock within 2,000 g was applied, the crosssensitivity of the acceleration sensor was measured to be 2.5% or below. The presented acceleration sensor exhibited a stability to the extent that it was not destroyed even under a shock of over 6,000 g, which was three times the sensing range, and the crosssensitivity was 15% or below the measured sensitivity. The presented acceleration sensor is expected to be applied in various fields where measurements of high-shock over thousands of g are required.

MEMS 기술을 이용한 엑스선 영상 센서용 섬광체 패널의 제작 및 특성평가

배공명 부산대학교 2008 국내석사

The use of X-rays for diagnosis increases in medical practice. The conventional analog-typed X-ray film detectors are rapidly substituted for the digital ones. The introduction of picture archiving and communication systems (PACS) increases demanding digital radiography in many hospital. Digital radiography offers the potential of improved image quality as well as providing opportunities for advances in medical imaging management. In this study, we have fabricated scintillator panel which convert X-ray into light. Due to the cross-talk in scintillator, the spatial resolution was still limited. The pixel-structured scintillator is fabricated by MEMS technology. The pixel-structured scintillator have been designed and fabricated and the difference of the spatial resolution according to the pixel size has been evaluated. The material of pixel-structured scintillator used silicon and polyethylene. The pixel-structured scintillator of silicon was fabricated by photolithography and deep reactive ion etching (DRIE) process. The pixel-structured scintillator of polyethylene was fabricated by hot embossing. The terbium doped gadolinium oxysulfide (Gd2O2S:Tb) that can be processed at room temperature has been used as a scintillator material. To evaluate their image quality, this study acquired CC (characteristic curve), MTF (modulation transfer function) and DQE (detective quantum efficiency). This study verifies that the pixel-structured scintillator is effective against the over-spreading of the converted visible light. However, the sensitivity of fabricated scintillator panel is much lower than sensitivity of commercial screen. NNPS and DQE were also much lower than them of commercial screen. Therefore, the next study is needed to find out the method of the sensitivity improvement of scintillator panel.

Wearable High-sensitivity Flexible Pressure Sensor Made Using Silicon Elastomer Containing Carbon Nanotubes

정영 부산대학교 대학원 2017 국내석사

본 논문에서는 탄소나노튜브(CNT)가 함유된 실리콘(PDMS) 탄성체를 이용하여 낮은 압력범위에서 매우 높은 감도를 가진 신개념 유연 압력센서 어레이를 제안한다. 제안한 유연 압력센서는 실리콘을 기본 물질로 사용하기 때문에 매우 유연하고, 저비용으로 대면적 제작이 용이하다. 높은 감도와 유연성을 가지므로 웨어러블용 촉각센서에 적합하다. 제작된 센서는 250 ㎩ 이내의 압력범위에서 1.39 ㎪-1 의 높은 감도와 0.05 s 이내의 빠른 응답시간을 보였다. 10,000회 이상의 연속 구동 후에도 초기 감도를 그대로 유지하여 매우 뛰어난 내구성을 보였다. 제작된 센서 어레이를 이용하여 패턴 인식 및 인공피부로의 적용 가능성을 검증하였다. 또한, 유연 압력센서의 측면에도 감지부를 장착하여 수직한 방향(z축)에서 가해지는 압력뿐만 아니라 측면(x, y축)에서 가해지는 압력을 측정할 수 있는 3축 압력감지센서를 제작하였다. 인공손가락을 이용한 가압 시험 결과, 3축에 가해지는 압력을 정확히 측정할 수 있음을 증명하였다.

가열판을 이용한 딥코팅 방식의 은나노와이어 정렬

최창준 부산대학교 대학원 2017 국내석사

우수한 성능의 투명전극을 만들기 위해 은나노와이어들(AgNWs)을 정렬하는 연구가 활발하다. 많은 방법들 중, 딥코팅 방법은 제작과 코팅 특성의 제어가 쉬우며 대면적화가 용이하다는 장점이 있다. 이에 따라, 딥코팅을 이용하여 나노와이어들을 정렬하려는 시도가 이어져왔다. 현재까지 진행되어온 딥코팅 연구는 주로 저속영역(V<1 mm/s)에서 수행되었다. 그러나, 이 영역(regime)에서는 stick-slip effect가 발생하여 균일한 코팅이 어렵다. 또한 속도가 너무 느려 양산에 응용하기 어렵다는 단점이 있다. 본 연구에서는 은나노와이어들을 정렬하기 위한 새로운 방법으로 가열판을 이용하는 공정을 제안한다. 이 방법을 통해 우리 연구진은 80 ℃, 20 mm/s의 조건에서도 은나노와이어들이 높은 정렬도를 갖음을 확인하였다. 은나노와이어들의 정렬도는 기판온도(substrate temperature)와 후퇴속도(withdrawal velocity)에 의해 평가 되었다. 결론적으로, 은나노와이어들의 정렬도는 온도가 높을수록 더 빠른 후퇴속도(withdrawal velocity)에서도 유지됨을 확인할 수 있었다. 이것은 증발률 증가에 따른 전단력의 증가 때문이다. 선행연구에 따르면, 후퇴속도가 증가할수록 코팅두께(coating thickness)가 증가하게 된다. 그러나 본 연구에서는 기판온도가 증가함에 따라 증발률이 증가하게 된다. 따라서 코팅두께가 얇아지게 되고,은나노와이어 분산액 내부의 전단력이 강해지게 된다. 따라서 강한 전단력을 받은 은나노와이어들이 정렬되게 되는 것이다. 이를 증명하기 위해 딥코팅 직후 가열판 위에 남아있는 은나노와이어 분산액의 면적을 추적해보았다. 이 실험을 통해 증발률의 증가가 은나노와이어들을 정렬시킨다는 것을 추론할 수 있었다. 또한 증발률의 증가로 인해 은나노와이어들이 더 잘 퍼질 수 있음을 확인하였다. Researches have been actively undertaken to align the silver nanowires (AgNWs) to create an excellent transparent electrode. Among several methods, dip coating method has numerous advantages that it is easy to manufacture and control its coating properties, and easy to make large-area. Thus, the attempts to align nanowires by using dip coating method have been continued. Ongoing researches on dip coating methods are predominantly conducted in slow velocity range (V < 1 mm/s). However, it is difficult to achieve a uniform coating in this regime due to the stick-slip effect. Moreover, its withdrawal velocity is too slow to apply for a mass production. In this study, we propose a new method of aligning the AgNWs by using the heating plate. Through this method, we confirmed that AgNWs can have high degree of alignment at 80 ℃, 20 mm/s. The degree of alignment of the AgNWs was evaluated by experiments performed with the substrate temperature and withdrawal velocity. In conclusion, the degree of alignment was able to be maintained in higher withdrawal velocity when the heating plate temperature rises. This is due to the increase of shear force with an increasing evaporation rate. According to previous studies, the coating thickness increases as withdrawal speed increases. However, this study shows when the substrate temperature rises, the evaporation rate increases. Therefore, the thickness of coating decreases and the shear force inside the AgNWs dispersion becomes stronger. As a result, the AgNWs having strong shear force can be aligned. To prove this, we traced the area of the AgNWs dispersion remaining on the heating plate after dip coating. Through this experiment, we infer that the increase of evaporation rate leads to the alignment of AgNWs. Additionally, it was confirmed that the AgNWs can be more dispersed due to the increase of the evaporation rate.

다구치 방법을 이용한 비아 홀의 균일한 도금 공정의 최적화

김선경 부산대학교 대학원 2017 국내석사

A Through Silicon Via (TSV) is a 3D packaging technology that can satisfy consumer needs for miniaturization, low power consumption, high circuit density, and smart functions. TSV is a vertical electrical connection (via) passing completely through a silicon wafer or die. The wiring length is quite reduced, compared with the previous wire bonding method, and such problems as restriction of I/O count, loss of current, and signal delay can be solved. Compared with a 2D packaging method, electric performance is much higher, and thus TSV technology is applied to various parts: hybrid memory cube (HMC), MEMS sensor, and CMOS image sensor (CIS). The filling process using copper electroplating among the TSV processes accounts for 40% of the total cost. The filling process is focused on minimizing process time and cost and filling via without any defect. Recently, studies on condition optimization and filling mechanism are carried out. Especially, studies on condition optimization concerned with experimental factors affecting a plating process to fill via without any defect. The copper electroplating is a physicochemical process, and void or seam occurs, due to different rates of electrodeposition at the entrance and floor part of via, which causes a serious product reliability problem. To solve such a problem, there are studies using chemical methods and physical methods. Studies on organic additives added to basic plating solutions and chlorine ion were carried out using chemical methods. Various studies on periodic pulse current application and solution’s stirring were undertaken using physical methods. Most previous studies reported conditions to produce successful results by selecting and controlling specific experimental factors. However, an electroplating process affects results through interactions of many factors without classification of chemical and physical methods. Therefore, there is a need to draw an optimum condition in consideration of the factors affecting an experiment in a comprehensive manner. This study conducted the experimental factors affecting an experiment using a Taguchi method. By using the Taguchi method, this study aimed to find the optimum condition of factors at the aspect ratios 1, 2, and 3 through diverse considerations of the experimental factors with minimum experiment. This study analyzed the effects of experimental factors on the plating process quantitatively and investigated each factor’s contribution. One of the most important objectives of this study is to select an optimum condition affecting the selected factor’s filling via holes with aspect ratios 1, 2, and 3 without any defect.

추가 질량체를 이용한 초소형 충격 스위치

박병건 부산대학교 2018 국내석사

With the fourth industrial revolution, interests and demands of sensors have increased significantly. As one of frequently used sensors, accelerometers enable to detect acceleration or impact in various applications such as automobiles, buildings and defense/security. While accelerometers have been widely used, inertial switches are also emerging in the same area owing to their lower power consumption and very low probability of malfunctioning due to electromagnetic interference, compared to accelerometers. Especially, MEMS-based inertial switches have been under intense development for high sensitivity and precision measurements, due to their very small size at micro-scales. In this study, we aim to develop an inertial switch which has uniform detection ability for omni-directional impact along with the establishment of simple fabrication protocols, compared to the existing recipes so far. Both theoretical and experimental investigations were done to design an inertial switch. A system for evaluating the performance of the inertial switch was set up and the performance tests were conducted to obtain the threshold impact which can be detected using the fabricated device. The fabricated device turned to the state "ON" at 670 g in the vertical direction, and had a much faster response time of 0.3 ms. than the conventional devices. Furthermore, we could reduce blind angles through rotational motion, which can finally lead to the uniform detection of impact. 산업 구조의 변화와 함께 센서의 관심과 수요가 증대됨에 따라, 이에 대한 연구가 지속적으로 이루어지고 있다. 가속도 센서는 가속도 혹은 충격을 감지하기 위한 소자로 에어백과 같은 자동차 산업과 군수산업 등 다양한 환경에서 사용된다. 이와 유사한 분야에서 사용되는 충격 스위치는 전력 소모가 적은 장점뿐만 아니라 전자기 간섭으로 인한 오작동 발생율이 적고, MEMS 기반의 충격 스위치는 작은 크기를 가진다. 본 연구에서는 기존 연구에 비해 단순한 공정을 통해 다양한 방향의 충격에 대해 균일한 감지능력을 가지는 충격 스위치의 제작을 목표로 하였다. 다층 니켈 도금에 있어서 니켈-니켈 간의 접착력을 증대시키기 위한 공정을 진행하였다. 충격 스위치를 평가하기위한 시스템을 구축하고 제작된 소자에 충격을 인가하는 테스트를 진행하였다. 제안하는 충격 스위치는 3.02.20.55 ㎣의 초소형인 크기를 가진다. 제작된 소자는 수직 방향 670 g에서 신호가 발생하였으며, 이는 800 g로 해석한 결과보다 감소된 수치이다. 제작 오차로 인하여 소자의 질량이 증가하고, 전극 간격이 감소하여 이와 같은 결과를 얻은 것으로 추정된다. 또한 670 g의 가속도에서 0.3 ㎳의 응답속도를 보였다. 본 연구를 통해서 높은 무게중심을 가지는 충격 스위치가 기존 연구에 비해 빠른 응답 특성을 가지고 회전 운동을 통해 blind angle을 감소시켜 균일한 감지를 할 수 있는 가능성을 보였다.