Development of Eco-friendly Etching and Laser Micromachining Process for Transparent Ceramics

최경곤 인하대학교 대학원 2025 국내박사

Transparent ceramics are advanced materials that possess the optical clarity of glass while maintaining the mechanical durability typical of ceramics. Their unique characteristics arise from a controlled microstructure and highly engineered processing techniques that minimize light-scattering defects. Therefore, these materials find applications in cutting-edge fields, including aerospace, laser systems, and protective technologies, due to their unparalleled combination of strength and transparency. Additionally, transparent ceramics are increasingly considered for use as substrates in semiconductor devices due to their unique characteristics. As the interest in utilizing transparent ceramics as substrates grows, so does the emphasis on advancing fabrication processes for their development. Micromachining technology is one of the essential techniques for manipulating transparent ceramics such as Y2O3 or glass, enabling the creation of complex, high-precision microstructures that integrate mechanical, electrical, and fluidic components on a single substrate. The micromachining processes are highly versatile and compatible with a variety of materials. The precision of micromachining allows for the creation of devices with complicated geometries and high aspect ratios (ARs) to enhance the functionality. Despite its many advantages, micromachining for transparent ceramics faces challenges. Additionally, the high expense of fabrication equipment and the advanced integrating multiple processes into a single production flow can hinder large-scale manufacturing. Therefore, development of micromachining for transparent ceramics still requires additional research. One issue is the micromachining technique using laser. Transparent ceramics face limitations in micromachining due to the challenges posed by their inherent properties. After sintering, the surface of untreated ceramics typically exhibits high roughness and slight concave or convex irregularities. These surface imperfections make precise processing difficult and can sometimes lead to the formation of cracks during machining. This issue highlights the need for advanced micromachining techniques and post-processing methods to achieve the required precision and surface quality while minimizing the risk of damage. Another issue is etching technique. Conventional ceramics, especially glass etching has relied on hydrofluoric acid, which presents several problems, including being harmful to human health, causing pollution, corroding materials, and producing a low aspect ratio due to its isotropic nature. Therefore, alternative etching techniques that enable the fabrication of high ARs are needed. In this study, we investigated the development of eco- friendly etching and laser micromachining processes for transparent ceramics. Specifically, we focused on micromachining techniques, including laser micromachining and selective laser-induced etching (SLE). A singulation process window for Y2O3 was proposed using a pico-second laser. The results demonstrated a low heat-affected zone (HAZ), absence of cracks, and minimal surface roughness. Furthermore, SLE techniques were applied to fabricate through glass vias (TGVs) and microfluidic channels using an alkaline etching solution. This eco-friendly approach enabled the fabrication of morphologies with high ARs. The findings indicated that while NaOH exhibited a higher etch rate compared to KOH, it resulted in increased surface roughness. Additionally, a process window was suggested for fabricating three-dimensional (3D) glass microfluidic channels with high aspect ratios using a femto-second laser ablation process. A high aspect ratio microfluidic channel was successfully fabricated at 14 μJ and 300 kHz. Lastly, we developed a gas sensor by depositing palladium (Pd) on zinc oxide (ZnO) nanoparticles, utilizing glass substrates and TGV structures to create a bidirectional hydrogen detection sensor. This research provides foundational insights into H2 sensor applications leveraging glass substrates. This thesis represents a critical advancement in micromachining technology for transparent ceramics, offering the precision and scalability required to develop miniature, multifunctional devices. Considering the growing demand for transparent ceramics, including glass substrates, this study underscores the importance of laser micromachining and eco- friendly etching techniques. These methods are poised to unlock innovative opportunities across diverse fields, thereby contributing to the development of next-generation technologies.

Femto-second 레이저를 이용한 금형재료 미세가공

윤 지욱 경북대학교 대학원 2009 국내석사

Nevertheless laser machining have several problems, such as heat transfer, it become popular for many fields of research and industry in the world. Especially femtosecond laser is widely using for many laser applications because of its characteristic of minimizing the heat transfer to the near area which can be a problem for machining process. In order to examine the potentiality of laser micromachining on mold material, we tested by femtosecond laser on the STAVAX which is well known for mold material for plastic injection process. We tested on the STAVAX using different pulse energy and different pulse numbers(single, 1, 5, 10, 25, 50, 100 pulses). The damage threshold and morphological change on the surface were examined using the SEM. The single pulse induced-damage threshold was measured 3.97TW/cm². In case of the multiple pulse-induced ablation, the damage threshold decreased with the number of pulses. We were able to observe the multiple pulse-induced ripple structure on the surface. The ripple structure is characterized as the repetitive lines with a 400nm pitch and the orientation is governed by the polarization of incident laser beam. We were also able to micromachine the grating lines with different pitch and different polarization angle. The ripple pattern angle which depends on the polarization angle was observed, as we expected. We observed the gap of undamaged area was not stable which polarization angle was 45, 0 degree. With this test result, we decided the grating fabrication with 90 degree polarization angle which is stable about the gap of unprocessed area. We fabricated diffraction grating which we designed alphabet letter "N". Fabricated area was 2mm x 2mm and we analyzed the diffraction grating using He-Ne laser.

Glass microstructuring with near-infrared laser induced backside wet etching using phosphoric acid

권귀감 서울대학교 대학원 2021 국내박사

This dissertation examined the laser-induced backside wet etching process that used a phosphoric acid-added absorbent. Glass materials have high strength, corrosion resistance, non-conductivity, and bio compatibility properties that are difficult to find in other transparent materials; however, these material properties make glass a hard-to-cut material in terms of processing. Various attempts have been made to increase the utilization of glass through industrial-friendly processing techniques such as mechanical cutting—conventional processing method—chemical etching, and carbon dioxide laser micromachining. Nevertheless, industry-friendly techniques still have target shape limitations due to process characteristics and glass’s material properties. To solve these problems, various processes, such as femtosecond pulse laser machining, electrochemical discharge machining, and deep reactive ion etching, have been widely studied and applied. Such processes can be used to manufacture various glass microstructure geometries. Research into glass processing has studied various techniques, but only a few studies have examined industrial techniques for processing complex shapes. In this dissertation, the processable geometry of glass produced through an industry-friendly process was extended using a LIBWE process and a near-infrared laser. Previous studies of laser-induced backside wet etching using near-infrared lasers found that fracturing occurred due to excessive heat absorption. This crack generation could be suppressed by the passive layer created by the reaction between phosphoric acid and glass. By suppressing the breakage of the glass, it was possible to process high-aspect-ratio glass microstructures with no tapering. Also, a scan path optimization method for laser-induced backside wet etching was developed to process not only one-dimensional channel shapes, but also a variety of glass microstructures that were difficult to manufacture using conventional laser-induced backside wet etching and industrial-friendly techniques. Based on this crack suppression and scan path optimization method, glass microstructures for various glass applications, such as microfluidic devices, UV-imprint molds, and glass components, were machined to validate the proposed techniques for actual glass applications. 본 논문에서는 인산이 첨가된 흡광용액을 사용한 레이저 후면 식각공정과 이를 활용한 다양한 형상의 유리 미세형상 가공 대해 연구하였다. 유리는 광학적으로 투명한 특성을 가지면서 다른 투명한 재료에는 없는 고강도, 내식성, 비전도성, 생물친화성 등의 특성을 가지고 있어 다양한 분야에서 활용되고 있으며, 미래에도 그 활용성이 높은 재료이다. 하지만 이러한 재료적 안정성이 가공 측면에서 유리를 난삭재로 만들어 다양한 미세 형상의 제작을 어렵게 하였다. 다양한 공정 연구를 통해 유리의 미세 가공 및 그 활용범위를 넓히는 시도가 진행중이다. 전통적인 가공방식인 절삭가공부터 화학적 식각, 이산화탄소 레이저 미세가공 등 산업 친화적인 가공기술들을 통해 유리의 활용도를 높이고자 하는 다양한 시도들이 진행중이지만 공정 자체의 한계로 인해 목표로 하는 형상이 제한되는 문제가 있다. 이러한 문제를 해결하기 위해 다양한 공정들이 새로이 개발되고 활용되고 있으며, 대표적으로 펨토초 펄스 레이저 가공, 전해방전가공, 건식 식각 등이 있다. 이러한 공정들의 높은 공정 자유도를 통해 다양한 유리 미세형상 제작이 가능하여, 다방면으로 공정의 최적화 및 활용방안이 연구되고 있다. 이렇게 다양한 공정을 통해 유리의 가공연구가 진행되고 있으나 산업적으로 적용 가능한 기술을 활용하면서도 목표로 하는 복잡한 형상이 가공 가능한 기술에 대해서는 연구가 부족한 상황이다. 본 논문에서는 산업적으로 다양하게 활용되고 있는 근적외선 레이저를 활용한 레이저 후면 식각공정을 통해 가공 가능한 유리의 형상을 확장하고, 그 원리를 탐구하였다. 일반적인 근적외선 레이저를 활용한 레이저 후면 식각 공정의 경우 흡광용액으로 활용하는 황산구리 용액이 열분해에 의해 산화구리가 되고, 이러한 산화 구리의 과도한 증착으로 인해 파단이 발생하는 것을 밝혀져 있다. 본 논문에서 인산을 첨가하였을 때 산화구리의 증착이 방해되어 파단의 발생이 억제되는 것을 확인하였으며, 유리의 파단을 억제함으로써 레이저의 자유도를 활용한 다양한 형상의 가공이 가능하였다. 또한 임의의 점과 선 경로의 최적화 방안을 도입하여 일차원적인 채널 형상뿐만 아니라 기존의 레이저 후면 식각공정이나 산업 친화적인 장비로 제작이 어려웠던 다양한 유리 미세 구조물의 가공을 진행하였고, 실제 연구나 산업에서 활용될 수 있는 형상을 가공하였다.

Properties of air-silica structured optical waveguide : from ray to electromagnetic optics regime

박민규 Graduate School, Yonsei University 2013 국내박사

Air-silica structured optical waveguides have three different characteristics from conventional silica-structured optical waveguides: High contrast of refractive index, Free-space propagation with no phase delay, and available of arbitrary structures in periodic patterns. In order to analyze air-silica structured optical waveguides exactly, scale of air structure and optical waveguides with respect to wavelength is important. If the scale is larger than wavelength, its governing theory is characterized by ray optics regime. When the structural size is almost same as wavelength, it is explained by wave optics regime. And if the size is smaller than wavelength, optical waveguide can be fully described by Maxwell's equation of electromagnetic optics regime. In this dissertation, air-silica structured optical waveguides and their applications were fully analyzed by exact theories under each optics regime and precisely demonstrated by experiments. In ray optics regime, a novel tapered dielectric waveguide solar concentrator was proposed for compound semiconductor solar cells utilizing optical fiber preform. The concentrator in millimeter scale is enormously bigger than wavelength and its optical mechanism was analyzed by non-imaging optics. Light collecting capability was numerically simulated by ray-tracing method and experimentally demonstrated for feasibility and potential assessments. Utilizing tapered shape of an optical fiber preform with a step-index profile, low loss guidance was enhanced and the limitation in the acceptance angle of solar radiation was alleviated by an order of magnitude. Using a solar simulator the device performances were experimentally investigated and discussed in terms of the photocurrent improvements. Total acceptance angle exceeding ± 6° was experimentally achieved sustaining a high solar flux. In wave optics regime, a compact intrinsic fiber Mach?Zehnder interferometer (MZI) was proposed and experimentally demonstrated by incorporating a micro air-cavity ablated by femtosecond laser irradiation. A short cavity of length ~10 um along the single-mode fiber core provided two optical paths: one propagating through the air and the other guided along the ring-shaped silica cladding. Its exact optical behavior was analyzed by beam-propagation method and a spectral analysis confirmed MZI in a good agreement with experimental results. Temperature-dependent spectral shifts were also measured and analyzed. In electromagnetic optics regime, two different photonic crystal fibers were utilized to study optical properties. One is a new type of birefringent index guiding photonic crystal fiber (PCF) with two hollow GeO2-doped silica ring defects imbedded in a hexagonal hole arrays. Air-holes of photonic crystal are smaller than wavelength, and rigorous finite element method (FEM) using the perfectly matched layer (PML) was applied to calculate complex propagation constant and analyze optical transmission characteristics. Birefringence was flexibly controlled independent of chromatic dispersion, and improvement in confinement loss was achieved by optimizing hollow ring defect parameters. Another is characterizing optical nonlinearity of a Ge-doped core photonic crystal fiber (PCF) in the spectral domain, C-band, by using a cross-phase modulation (XPM) method with a pulsed pump laser and a continuous wave signal laser. A nonlinear phase shift accumulated along the PCF was directly measured in the spectral domain by a high-resolution optical spectrum analyzer. The proposed technique was validated for a conventional step-index high nonlinear optical fiber with a known nonlinear parameter, to confirm its potential in efficiently characterizing the optical nonlinearity of an arbitrary PCF overcoming dispersion and insertion loss penalties.

Femtosecond laser based high-performance micro-hole drilling on metal with vibration assistance and AgNW/CNT hybrid film patterning

윤지욱 과학기술연합대학원 대학교 2015 국내박사

In this dissertation, development of laser micromachining process for industrial applications and those experimental results are described. First, based on interaction mechanism between femtosecond pulse and material, theoretical background of femtosecond laser micromachining process is introduced. Second, two different researches using femtosecond laser are described in the paper as title of femtosecond laser micro hole drilling integrated with vibration module, patterning technique for silver nanowire (AgNW) / carbon nanotube (CNT) hybrid conductive film. First, femtosecond laser micromachining integrated with vibration module for micro hole drilling has been studied. Thickness of 30 ㎛ Invar alloy is drilled to investigate on angle control of hole taper by changing parameters including amplitude of vibration module and laser pulse energy. Wavelength of 795 nm, pulse width of 90 fs femtosecond laser system integrated with vibration module, so called the hybrid laser system, is used for the experiment. Displacement of focusing position is generated by moving the objective lens vertically by vibration module. The displacement value is range from 0 to 16 ㎛ by following the amplitude parameter, and the test is conducted without changing parameters except displacement of the focused beam. Comparison between shape of the ablated hole with vibration module and without is reported and discussed about possible mechanisms. Various micro machined holes with different taper angle results are observed, and holes with different taper angle are resulted. Second, femtosecond laser micromachining for patterning silver nanowire (AgNW) / carbon nanotube (CNT) hybrid conductive film have studied. A femtosecond laser which specifications of 1027nm wavelength and 380fs pulse width is used for the experiment. Ablation test for the AgNW/CNT film is performed at laser fluence values ranging from 9.7 mJ/cm2 to 70.8 mJ/cm2, and the threshold of the film is found at 13.6 mJ/cm2. By increasing laser flunce, diameter of crater is sharply increased until fluence reaches at 65.2 mJ/cm2, and damage to the glass substrate is observed when fluence is over than 67.9 mJ/cm2. Fluence value for line pattering is determined as fluence value of 67.9 mJ/cm2 which is not influenced value to glass substrate. From the measurement result of the patterned line, the irregularly ablated area is easily observed near the completely ablated region. To pattern line without residual at the irradiated area, quasi flat-top beam profile is employed instead of the conventional Gaussian’s. The measurement result of the patterned line shows dramatically decreased uneven area when the quasi flat-top energy distribution is used.

Development of the automatic real-time focus control system for use in laser micromachining

CAO XUAN BINH UNIVERSITY OF SCIENCE AND TECHNOLOGY 2018 국내박사

레이저 가공기를 위한 실시간 레이저 포커스 컨트롤 시스템 개발 극초단파 레이저를 이용한 미세 가공이 점점 더 중요해 지고 있다. 극초단파 레이저를 이용한 미세 가공은 나노 광학, 나노 포토닉스, 플라즈모닉스, 나노 전자 등의 많은 분야에서 적극 사용되어 지고 있다. 이런 여러가지 극초단파 레이저의 장점에도 불구하고, 레이저 가공에서는 시편과 포커스의 위치에 따라서 많은 가공 성능이 달라진다. 시편과 레이저 포커스 위치가 적절하지 않을 때 가공 품질의 저하를 야기 시킬 수 있다. 시편과 레이저 포커스의 위치가 정확히 위치 되었들 때 가장 작은 빔의 사이즈를 구현 할 수 있고, 결국 가장 작은 선폭의 미세 패터닝이 가능하다. 본 연구에서는 레이저 미세 가공기를 위한 새로운 포커스 컨트롤 시스템을 제안하였다. 기존 방시의 포커스 컨트롤 시스템의 경우에는 가공 전에 시편의 3차원 정보를 측정하고 나서, 이 3차원 데이터를 이용해서 포커스 렌즈를 움직이게 하였다. 이 방법은 가공 시간이 늘어나고 , 가공 정밀도에 한계를 가지고 있었다. 따라서 본 논문에서는 새로운 방식의 포커스 컨트롤 시스템을 개발하였다. 레이저 가공시간을 단축하기 위해 측정과 동시에 가공이 이루어질 수 있는 실시간 포커스 컨드롤 시스템을 개발하였다. 본 논문에서는 새로운 방식의 레이저 포커스 컨트롤 시스템의 광학적 설계 와 이를 실제 구현하여 레이저 미세 가공기에 적용하여 실험하였다. 실험을 통해서 광학적 설계와 레이저 미세가공기에 적용하여 나온 실험값이 동일함을 증명하였다. 따라서 본 논문에서 제작된 레이저 포커스 파인더는 실제 레이저 미세 가공기에 실질적으로 사용 될 수 있을 것이다. Currently, ultrafast laser fabrication has become more and more important in academic research and engineering. With the ability of fabricating nano-scale 3D patterns with high resolution, laser fabrication has a huge number of applications in both science and industry, such as nano-optics, nano-photonics, plasmonics, nano-electronics, and nano-magnetism. Nevertheless, because of its ultrafast working, laser fabrication has a restriction in terms of the focusing condition. A bad focusing condition can lead to the permanent damage of the target sample, a decrease of resolution, a reduced sensitivity of optic and electronic nano-devices, and low reproducibility. Accurately adjusting the target sample at the laser focus, at which the highest optical fluence and smallest beam-spot size are acquired, is extremely meaningful. Therefore, an accurate, versatile, and fast focus detection system is prerequisite for increasing the productivity as well as precision of laser processing. Here, our research focuses on the new technique of detection of focal position for high-precision laser processing. The quality of micro-patterns fabricated by high-intensity laser is decided by the accuracy of focusing process and the surfaces of target sample with unpredictable roughness is difficult to be located at focus during laser fabrication. The conventional methods pose their limitations because they could not detect the focal position on a rough surface as well as could not perform both focus detection and laser fabrication simultaneously. Moreover, the inaccuracy in detection focal position can lead to the permanent damage of target sample and thus decrease the quality and productivity of laser processing. As a result, the proposed research is shown to outweigh these disadvantages. The new methods are demonstrated to detect the focal position on a target sample with rough morphology as the same time with laser fabrication and achieve high precision, high versatility, and low price. In this thesis, the details in experiment to check the performance of focus determination system are also meticulously presented. The research analyzes the efficiency and accuracy of methods based on theoretical models of geometrical optics as well as experimental results of practical optical systems. The unification between theory and experiment is properly acquired. The methods are expected to be widely applied in both industry and technology in the near future.

시편 단면 분석을 위한 펨토초 레이저 가공에서 입사각이 측벽 각도에 미치는 영향

김재경 부산대학교 대학원 2024 국내석사

고장 분석 (failure analysis)은 제품 결함의 원인 탐색 및 제거를 위해 시행되는 분석 방법으로 전기적으로 내부 결함의 위치를 파악한 후, 파괴 분석 방법을 통해 직접적으로 결함을 관찰하여 발생 원인을 파악하고 해결하여 제품의 신뢰성 및 수율을 높이는 중요한 분석 방법이다. 최근 기술의 발전으로 3D IC, flexible electronics 등 대면적 고장 분석의 중요성이 커지고 있다. 하지만 파괴 분석 장비로 가장 많이 활용되는 FIB의 낮은 가공 성능으로 인해 대면적 분석이 불가능하다. 이를 해결하기 위해 아르곤 이온 가공 및 플라즈마 이온원을 사용하는 PFIB가 개발되었으나, 여전히 수백 μm 의 넓은 영역의 가공에 어려움이 있을 뿐만 아니라, 높은 장비 사용 비용으로 인한 한계가 존재한다. 이를 해결하기 위해 FIB 가공 전에 레이저 가공을 수행하는 방법이 제시되었다. 하지만 가우시안 형상의 에너지 분포와 초점 흐려짐 등에 의해 가공면은 계곡 형상을 띄며, 이는 이온빔 가공량의 증가로 이어지게 된다. 이러한 문제를 해결하기 위해 빔 형상 변경, 가공 변수 제어 등과 같은 방법이 연구되었으나, 측벽 각도 제어량이 한정적이고 실제 적용이 어렵다는 한계가 존재한다. 일부 연구에서는 빔 입사각(angle of incident, AOI)을 달리하여 표면 특성 및 가공 형상을 제어할 수 있음이 알려져 있다. 본 연구에서는 이온빔 가공량 최소화를 위해 빔 입사각을 달리하여 가공 영역의 형상이 수직에 가깝게 되도록 빔 입사각의 최적화를 목표로 한다. 이를 위해 빔 입사각을 적용하기 전, 가파른 측벽을 위해 laser fluence, overlap ratio 등 가공 변수의 최적화를 통해 측벽 각도 62.1˚를 지닌 형상을 제작하였다. 그 후, AOI에 따른 가공 형상의 변화를 관찰하여 AOI = 8˚에서 87.5˚의 각도를 지니는 측벽을 제작하였으며 스캔 전략 최적화를 통해 측벽에 curtaining effect의 발생을 억제하고 조도를 최적화하여 측벽의 품질을 개선하였다. 레이저 가공에 의해 발생한 결함을 제거하고 수직벽 제작을 위한 FIB 가공량을 판단하고자 라만 분광법과 energy dispersive X-ray spectrometry (EDS) 분석을 진행하였다. 라만 분광법을 통해 약 1 μm 깊이의 잔류응력 발생을 확인하였고, EDS 분석을 통해 1 μm 미만의 산화를 관측하였다. 87.5 도의 측벽 각도를 지닌 100 μm 높이의 벽을 수직으로 만들기 위해 약 5 μm의 가공이 필요하며, 이를 활용하여 이온빔 가공에 걸리는 시간을 확인하였다. 너비 300 μm와 높이 100 μm 영역 가공에 레이저 가공 유무에 따른 FIB 가공 시간을 비교하였다. AOI 적용 없이 레이저 가공만 진행하는 경우 약 162 시간이 소요되는 것으로 계산된 반면, AOI를 적용하여레이저 가공을 수행한 경우 약 34 시간이 소요되어 약 79%의 가공 시간 감소를 확인하였다. Advanced technologies such as 3D integrated circuit (IC), flexible electronics are being applied to achieve better product performance. However, the complexity of circuits and increased thickness raises the difficulty of failure analysis (FA). FA can improve product reliability and yield by identifying and eliminating the causes of product defects. The use of FIB in FA is hindered by low processing performance, making large-area analysis of 3D ICs impossible. To address this issue, Argon ion processing and plasma ion source FIB (PFIB) have been developed. However, the high cost of the PFIB and the large area (over hundreds of micrometers) hindered the FA process. Therefore, studies to reduce the processing time with laser processing before FIB processing have been proposed. However, because of the Gaussian-shaped energy distribution and defocusing on the specimen surface, the processing surface takes on a V-shape. This problem leads to an increase in the amount of FIB processing. Efforts have been made to address this issue by optimizing the process parameters and changing the beam shape. Several studies have suggested that changes in the angle of incident (AOI) of the beam can control the surface properties and geometry. However, there are still challenges in sidewall angle control, and practical applications are difficult to apply. Laser processing has a faster removal rate than FIB but creates damage around the processed area. therefore, the process parameters must be optimized to restrict the damaged area. In this paper, the laser process parameters and AOI of laser processing have been optimized to obtain a vertical-like wall. Laser induced damage areas were investigated by Raman spectroscopy and EDS analysis. Based on these analyses, both residual stress and oxidization occurred below 1 μm thickness. The FIB milling time was calculated by considering the defect thickness and the time required to transform a vertical-like wall into a vertical wall. It was calculated that making a vertical wall for FA specimen fabricated without AOI would take about 162 hours, while processing with specimen fabricated with AOI=8 would take about 34 hours. It has been confirmed that 79% of the processing time is reduced by applying a laser to the processing before FIB milling.

정밀 레이저 가공 기술을 이용한 초소수성 표면 형상 제어 및 특성 연구

이창준 전남대학교 2023 국내석사

In the study, cone-shaped periodic micro and nano-structures were upbuilt on a silica surface with femtosecond and picosesecond laser, and there were 10 µm intervals in rising the period of micro-structures between cone shape patterns. The test was conducted from 140 µm to 600 µm with 10 µm interval uprising.I analyzed the contact angle and image of the super-hydrophobic surface. To measure the contact angle, the cone(aspect-ratio 1 : 1.27) shape model with micro-protrusion structure similar to the surface of the lotus leaf was built. To analyse the differences in the contact angles between the cone shapes and heights of the micro-protrusion, different samples with aspect-ratio 2.00, 1.67, 1.27, 1.00, 0.67, 0.34 shapes were made through laser micro-machining technology. A cone shape was a optimum condition for immitating the natural loyus leaves. Samples of PDMS with various shapes and mixed micro/nano-structures were built with a PDMS mold insert. The largest contact angle among data was 170.42°. And that result value is similarity to the contact angle of the lotus leaf. This mold insert is advantageous for cost reduction and industrialization because the molding processing time is fast with laser equipment and it can be used repeatedly. 본 연구에서는 펨토초와 피코초 레이저를 이용하여 연꽃잎 표면의 원뿔형 돌기(마이크로/나노) 구조를 모사하는 연구를 진행하였다. 실리카 표면에 레이저 가공으로 폭과 높이, 종횡비 비율을 조절하여 구조를 제작하였으며, PDMS (Polydimethylsiloxane) 금형을 통해 구현된 표면의 특성을 비교 분석하였다. 첫 번째 실험은 원뿔형 돌기 구조의 주기 간격만 조절하여 최대 접촉각을 가지는 구조의 주기를 확인하였으며, 두 번째 실험을 통해 확인된 최적의 주기 구조의 종횡비 비율을 변경하여 특성을 비교하였다. 실험을 통해 170 µm 주기, 종횡비 1.27에서 가장 높은 접촉각(170.42°)을 가지는 초소수 특성을 확인하였다. 세 번째 실험에서는 금형의 반복 사용에 따른 접촉각 변화를 확인하였으며, 170 µm 주기, 종횡비 1.27의 비율의 구조를 사용하였다. 총 10회 반복 실험을 진행하였으며, 접촉각을 측정한 결과 반복 사용이 증가할수록 접촉각이 점차 감소하였지만(170° → 156°), 10회 반복에도 초소수성 특성이 유지되는 것을 확인하였다. PDMS 금형을 통해 원뿔형 돌기 구조 제작을 통해 다른 물질을 코팅하지 않고도 170°의 높은 초소수성 특성을 보였으며, 원뿔형 돌기 구조의 주기와 비율에 따라서 초소수성 특성이 변화함을 실험을 통해서 확인하였다.

저에너지 펨토초 레이저를 이용한 탄소나노튜브 필름의 미세가공 및 응용

백인형 아주대학교 일반대학원 2009 국내석사

Microfluidic Platforms for Multiplexed Functional Testing of Intact Tumor Tissues

Rodriguez Arizpe, Adan David University of Washington ProQuest Dissertations & 2021 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

Despite advances in targeted therapies, cancer treatment continues to face significant challenges as it moves toward the goal of rationally chosen personalized therapy. There is a great need for functional testing platforms that use human, intact tumor tissue to predict patient outcomes to cancer therapy. The successful development of such platforms would advance both drug development and identification of optimal treatments for a given patient (i.e., precision oncology). However, current approaches that solely use patient-derived cells from dissociated tissue typically lack most of the tumor microenvironment (TME) and are not rapid enough to guide patient-specific therapy decisions. Furthermore, the response of each individual to a given treatment can vary widely across the population. This report outlines the progress we have made in developing two digitally fabricated microfluidic platforms that utilize intact patient-derived tumor tissue to solve critical challenges related to the advancement of personalized therapy. The first chapter outlines an introduction to digital manufacturing and laser micromachining through CO2 laser ablation and compatible bonding techniques for microfluidic applications. The second chapter summarizes the development of a digitally fabricated microfluidic platform (Oncoslice) that allows for selective spatiotemporal exposure of organotypic slice cultures to dozens of drug conditions. The chapter includes published demonstrations of successful microfluidic delivery of small-molecule cancer drug panels to glioblastoma (GBM) xenograft slices and GBM and colorectal cancer patient tumor slices. Furthermore, it includes preliminary results that spear our future aims to utilize the platform to evaluate combination immunotherapies and their interaction with the TME. Finally, the third chapter summarizes our most recent advances in developing a microfluidic platform that enables drug treatment, exogenous T cell therapy, and high-content analysis using hundreds to thousands of similarly sized, precision-sliced cuboidal micro-tissues (“cuboids”) produced from a single tumor sample. The chapter incorporates published results related to cuboid sectioning and characterization (i.e., size, viability, TME), microfluidic platform prototype development and functionality, and pilot drug delivery experiments.