Microfluidic Separation of Colloidal Particles and Soft X-ray Spectromicroscopy Characterization Studies on Photonic Crystals

Abstract

The colloidal system is significantly used in various research fields such as optics, catalysis, sensors, and energy storage devices, because of their unique optical and physical properties induced by the size or shape as well as assembled structures of colloids. Therefore, it is an issue to develop methods for specific sorting and structural characterization of assembled colloidal particles. This thesis is for studying about separation and detection of colloidal particles. In the first part (chapter 2 - 3), a novel pinched flow fractionation device with tilted sidewalls and cross-flow vertical focusing channels (t-PFF-v) was designed and fabricated to improve size-based and shape-based separation abilities. As a result, using the t-PFF-v device, 2 and 4 µm polystyrene (PS) particles were well separated with 9.5-fold enhanced separation resolution (R2,4) compared with a conventional normal PFF device (n-PFF). Moreover, disc-shaped PS particles (thickness of ~ 2 μm, diameter of ~ 5.0 μm) were separated from the suspension of disc-shaped and spherical PS particles (diameter of 2 μm). Bio-colloids (red blood cells (RBCs) and platelets (PLTs)) having similar minor dimensions but different shapes were also separated with RPLTs, RBCs of 1.28, which is improved 2.6-fold compared with n-PFF device. In the second part (chapter 4 - 6), imaging capability of synchrotron based X-ray microscopy (XRM) was researched for the local structural characterization of multi-domain photonic crystals (PCs) composed with PS particles. Various local structures as well as internal defects were directly identified without any additional sample preparations such as cross-sectioning, metallic coating, and fluorescent labelling by full field transmission X-ray microscopy (TXM). Moreover, as comparing images observed by scanning transmission (STXM) and optical microscopy (OM), the domain of PCs with different structures and colors were directly identified. Therefore, it was possible to investigate structural colors in the local domains such as face centered cubic (FCC) of different orientations (FCC (111) and FCC (100)), and hexagonal close-packed structure (HCP (0001)) of unary and binary PCs. In the last chapter, the newest XRM technique, ptychography was introduced. Ptychography of diffractive imaging has been developed at CLS, SM (10ID-1) beamline for transcending the limitation of spatial resolution originated by the X-ray optics. Spherical 40 nm Au nanoparticles (NPs) were observed with below 10 nm spatial resolution by ptychography. |콜로이드 시스템은 입자의 크기, 형태 및 조립된 구조에 따라 유발되는 그 특유의 광학적, 물리적 성질 때문에 광학, 촉매, 센서, 전지 등 광범위한 연구분야에서 사용되고 있다. 따라서 콜로이드 입자의 정밀한 분리와 광결정 같은 콜로이드 구조체의 정확한 구조 분석은 상기 응용에 앞서 필수적으로 수행되어야 한다. 본 학위 연구는 미세유체칩을 이용하여 콜로이드 입자를 크기 및 형태별로 분리하고, 연 X-ray 현미경을 이용하여 콜로이드 입자로 조립된 광결정의 구조를 분석하기 위하여 수행되었다. 첫 번째 파트 (제 2 - 3 장)에서는 콜로이드 입자를 크기와 형태별로 정밀하게 분리 하기 위하여 기울어진 벽면과 수직적 정렬 채널이 특징인 새로운 미세유체칩 (t-PFF-v)을 디자인하였고, 이를 입자분리에 적용하였다. 그 결과 2 와 4 μm polystyrene (PS) 입자를 기존보다 9.5 배 향상된 분리능으로 분리할 수 있었다. 또한, 이를 이용하여 기존 미세유체칩으로는 분리할 수 없었던 원반형태와 구형태 PS 입자가 혼재된 시료에서 각 다른 형태의 입자를 분리하였고, 이를 생체시료로 확대·적용하여 두께와 지름이 비슷한 크기인 적혈구와 혈소판을 기존 보다 2.6 배 향상된 분해능으로 분리하였다. 두번째 파트 (제 4 - 6 장)에서는 기존 현미경법의 단점을 보완할 수 있는 방사광 기반 연 X-ray 현미경을 이용하여 여러 구조가 혼재한 광결정의 구조분석을 수행하였다. 연 X-ray 투과현미경 (Full field transmission X-ray microscopy, TXM)을 이용함으로써, 기존 현미경법에 필수적이었던 형광 표지, 금속 박막 코팅, 시료 절단 등의 시료 전처리 과정 없이 다양한 광결정 구조 및 내부 결정 결함 구조를 신속하고, 직접적으로 관측 하였다. 또한 단일 혹은 이종 콜로이드 입자로 구성된 광결정의 구조 및 광학 특성을 주사 투과 X-ray 현미경 (Scanning transmission X-ray microscopy, STXM)과 광학 현미경 (Optical microscopy, OM)을 이용하여 분석함으로써, 광결정 내 분포한 면심입방 (FCC (111), FCC (100)) 및 육방 밀집 구조 (HCP (0001))를 파악하고, 그 색깔을 확인 하여 광결정의 구조와 색깔의 상관관계를 직접적으로 제시할 수 있었다. 마지막 장에서는 광학 부품으로 기인하는 공간분해능의 한계를 뛰어넘을 수 있는 ptychography 영상 기법을 소개하였다. STXM 구성을 활용하여 ptychography를 적용할 수 있는 현미경법을 구축하고, 이를 이용하여 40 nm 금나노입자를 10 nm 이하의 공간분해능으로 관측하였다.; The colloidal system is significantly used in various research fields such as optics, catalysis, sensors, and energy storage devices, because of their unique optical and physical properties induced by the size or shape as well as assembled structures of colloids. Therefore, it is an issue to develop methods for specific sorting and structural characterization of assembled colloidal particles. This thesis is for studying about separation and detection of colloidal particles. In the first part (chapter 2 - 3), a novel pinched flow fractionation device with tilted sidewalls and cross-flow vertical focusing channels (t-PFF-v) was designed and fabricated to improve size-based and shape-based separation abilities. As a result, using the t-PFF-v device, 2 and 4 µm polystyrene (PS) particles were well separated with 9.5-fold enhanced separation resolution (R2,4) compared with a conventional normal PFF device (n-PFF). Moreover, disc-shaped PS particles (thickness of ~ 2 μm, diameter of ~ 5.0 μm) were separated from the suspension of disc-shaped and spherical PS particles (diameter of 2 μm). Bio-colloids (red blood cells (RBCs) and platelets (PLTs)) having similar minor dimensions but different shapes were also separated with RPLTs, RBCs of 1.28, which is improved 2.6-fold compared with n-PFF device. In the second part (chapter 4 - 6), imaging capability of synchrotron based X-ray microscopy (XRM) was researched for the local structural characterization of multi-domain photonic crystals (PCs) composed with PS particles. Various local structures as well as internal defects were directly identified without any additional sample preparations such as cross-sectioning, metallic coating, and fluorescent labelling by full field transmission X-ray microscopy (TXM). Moreover, as comparing images observed by scanning transmission (STXM) and optical microscopy (OM), the domain of PCs with different structures and colors were directly identified. Therefore, it was possible to investigate structural colors in the local domains such as face centered cubic (FCC) of different orientations (FCC (111) and FCC (100)), and hexagonal close-packed structure (HCP (0001)) of unary and binary PCs. In the last chapter, the newest XRM technique, ptychography was introduced. Ptychography of diffractive imaging has been developed at CLS, SM (10ID-1) beamline for transcending the limitation of spatial resolution originated by the X-ray optics. Spherical 40 nm Au nanoparticles (NPs) were observed with below 10 nm spatial resolution by ptychography.