Non-contact Mesoscale Manipulation Using Laser Induced Convection Flows

Abstract — Laser induced convection flows is a new and promising method to achieve better manipulation of mesoscale objects (above 1 µm and below 500 µm) in a liquid medium. The temperature gradient created by laser absorption generates natural and thermocapillary (or Marangoni) convection flows. These flows are used to perform the manipulation itself. In this paper, we demonstrate for the first time that large and heavy particles can be dragged using the Marangoni convection flows. Experiments based on these phenomena show that fast and accurate underwater micromanipulation of particles up to 280 µm is possible using only a convergent 1 480 nm laser beam. I

Liquid-Liquid Interface Can Promote Micro-Scale Thermal Marangoni Convection in Liquid Binary Mixtures

Liquid-liquid phase separation, a physical transition in which a homogeneous solution spontaneously demixes into two coexisting liquid phases, has been a key topic in the thermodynamics of two-component systems and may find applications in separation, drug delivery, and protein crystallization. Here we applied a microscale temperature gradient using optothermal heating of a gold nanoparticle to overcome the experimental difficulties inherent in homogeneous heating: we aimed at highlighting precise structural development by avoiding randomly nucleating/growing microdomains. In response to laser illumination, a single gold nanoparticle immersed in a binary mixture of aqueous 2,6-dimethylpiridine (lutidine) and N-isopropylpropionamide (NiPPA) was clearly sensitive to the phase transition of the surrounding liquid as demonstrated by light scattering signals, spectral red-shifts and bright-spot images. The local phase separation encapsulating the gold nanoparticle resulted in immediate formation and growth of an organic-rich droplet which was confirmed by Raman spectroscopy. Remarkably, the droplet was stable under a non-equilibrium steady-state heating condition because of strong thermal confinement. Microdroplet growth was ascribed to thermocapillary flow induced by a newly formed liquid-liquid interface around the hot gold nanoparticle. Based upon a tracer experiment and numerical simulation, it is deduced that the transport of solute to the high temperature area is driven by this thermocapillary flow. This study enhances our understanding of phase separation in binary mixtures induced by microscale temperature confinement

Thermophysical Phenomena in Metal Additive Manufacturing by Selective Laser Melting: Fundamentals, Modeling, Simulation and Experimentation

Among the many additive manufacturing (AM) processes for metallic materials, selective laser melting (SLM) is arguably the most versatile in terms of its potential to realize complex geometries along with tailored microstructure. However, the complexity of the SLM process, and the need for predictive relation of powder and process parameters to the part properties, demands further development of computational and experimental methods. This review addresses the fundamental physical phenomena of SLM, with a special emphasis on the associated thermal behavior. Simulation and experimental methods are discussed according to three primary categories. First, macroscopic approaches aim to answer questions at the component level and consider for example the determination of residual stresses or dimensional distortion effects prevalent in SLM. Second, mesoscopic approaches focus on the detection of defects such as excessive surface roughness, residual porosity or inclusions that occur at the mesoscopic length scale of individual powder particles. Third, microscopic approaches investigate the metallurgical microstructure evolution resulting from the high temperature gradients and extreme heating and cooling rates induced by the SLM process. Consideration of physical phenomena on all of these three length scales is mandatory to establish the understanding needed to realize high part quality in many applications, and to fully exploit the potential of SLM and related metal AM processes

A microgripper for single cell manipulation

This thesis presents the development of an electrothermally actuated microgripper for the manipulation of cells and other biological particles. The microgripper has been fabricated using a combination of surface and bulk micromachining techniques in a three mask process. All of the fabrication details have been chosen to enable a tri-layer, polymer (SU8) - metal (Au) - polymer (SU8), membrane to be released from the substrate stress free and without the need for sacrificial layers. An actuator design, which completely eliminates the parasitic resistance of the cold arm, is presented. When compared to standard U-shaped actuators, it improves the thermal efficiency threefold. This enables larger displacements at lower voltages and temperatures. The microgripper is demonstrated in three different configurations: normally open mode, normally closed mode, and normally open/closed mode. It has-been modelled using two coupled analytical models - electrothermal and thermomechanical - which have been custom developed for this application. Unlike previously reported models, the electrothermal model presented here includes the heat exchange between hot and cold arms of the actuators that are separated by a small air gap. A detailed electrothermomechanical characterisation of selected devices has permitted the validation of the models (also performed using finite element analysis) and the assessment of device performance. The device testing includes electrical, deflection, and temperature measurements using infrared (IR) thermography, its use in polymeric actuators reported here for the first time. Successful manipulation experiments have been conducted in both air and liquid environments. Manipulation of live cells (mice oocytes) in a standard biomanipulation station has validated the microgripper as a complementary and unique tool for the single cell experiments that are to be conducted by future generations of biologists in the areas of human reproduction and stem cell research

Optofluidic System for Microlens and Plasmonic Applications

학위논문 (박사)-- 서울대학교 대학원 : 공과대학 재료공학부, 2019. 2. 윤재륜.광유체역학은 광학과 미세유체역학을 기반으로 한 학문으로써 각 분야의 장점 및 특징을 유기적으로 활용해 광학요소 및 유체시스템을 보다 유연하게 구성할 수 있는 장점을 가지고 있다. 즉, 미세유체시스템을 이용해 광학기능을 하는 요소를 다양하게 구현하거나 광학시스템과 결합된 미세유체시스템 내에서 극소량의 유체 및 유체 기반 샘플을 조작하고 처리하는 것을 가능하게 한다. 예를 들어, 변형이 가능한 유체는 마이크로 렌즈, 도파관 등과 같은 광학 시스템을 쉽게 재구성할 수 있게 하는 장점을 가지고 있는데, 이는 단순히 서로 다른 성질을 가진 유체 물질로 변경하거나 또는 유체의 계면 모양을 변형시킴으로써 가능하다. 한편, 광학 시스템에 연결된 미세유체 시스템은 극소량의 샘플만을 이용해 효율적인 분석을 할 수 있게 하는 편리한 기반을 제공한다. 이러한 관점에서 광유체역학 활용을 위한 연구가 활발히 진행되고 있고, 이 시스템을 이용한 다양한 광학 요소 구성, 생물학적 분석, 에너지 하베스팅, 화학적 센싱 등의 응용들이 많이 제안되었다. 본 논문의 2장에서는 기체-액체 계면의 형태를 수력학적으로 조절함으로써 광유체역학 기반 다초점 마이크로 렌즈를 구현하였다. 또한 렌즈의 특성을 결정하는 기체-액체 계면 형성과 관련된 물리적 현상을 수치해석 및 이론적 분석을 통해 조사하였다. 안정된 다상 계면을 형성시키기 위해 관련 이론을 이해하는 것은 본 연구에서 제안하는 마이크로 렌즈 구축에 있어서 매우 중요한 요소였다. 결론적으로 기체-액체 계면에서의 비선형적 표면장력효과가 렌즈 모양에 많은 영향을 미치는 것을 알 수 있었고, 이 표면장력 효과는 렌즈를 구성하기 위해 사용한 유체의 성질에 의해 결정되었다. 뿐만 아니라 제안된 마이크로 렌즈는 기체와 액체 계면에 기반하고 있으므로, 이 두 유체의 큰 굴절률 차이를 활용해 액체-액체 기반 마이크로 렌즈와 비교하여 상대적으로 짧은 초점 거리를 형성시킬 수 있다는 장점을 지니고 있다. 이와 같이 짧은 초점 거리를 형성하는 마이크로 렌즈는 앞으로 나아가 더욱 소형화된 광유체역학 시스템을 구현하는데 있어 기여를 할 수 있을 것으로 기대된다. 3장에서는 금속-유전물질로 이루어진 하이브리드 플라즈모닉 기판을 설계하고 제작함으로써 향상된 플라즈모닉 집게를 제안하였다. 실험적으로는 폴리스타이렌 입자와 E.coli 세포를 잡고 조작해보았다. 이 시스템에서 플라즈모닉 집게의 성능을 향상시키기 위해 국소표면플라즈몬공명현상 (LSPR)을 활용하였는데, 이는 국소 표면의 근접장의 에너지를 증폭시키기 위한 도구로서 많은 관심을 받고 있는 광학적 현상이다. 본 연구에서는 이 LSPR현상에 의해 유도된 열발생 효과를 이용해 효율적으로 입자 및 세포를 잡는 미세 광유체 시스템을 구현하였다. 또한 궁극적으로 이 시스템의 효율을 높인 하이브리드 플라즈모닉 구조체의 시너지 효과를 분석 및 입증하기 위해 수치해석 및 실험적 분석을 진행했다. 하이브리드 구조체 도입은 금나노 입자의 LSPR 현상을 더 강화시키기 위한 것이었고, 단순히 아연 산화물 나노막대기와 결합된 금나노 입자 구조체를 제작함으로써 향상된 결과를 얻을 수 있었다. 결론적으로, 아연산화물 나노막대기가 입사된 빛보다 더 증폭된 빛을 표면에 부착된 금 나노입자에 전달하는 역할을 하였고 그 결과로 플라즈모닉 집게의 성능을 월등히 증가시켜주었다. 이와 같이 향상된 플라즈모닉 기판 제안과 그 배경에 대한 심도 깊은 분석은 앞으로 광유체 시스템에 기반한 효율적인 생화학적 분석 플랫폼을 구축하는데 있어서 많은 도움을 줄 수 있을 것으로 예상된다. 4장에서는 플라즈모닉 현상에 의해 향상된 빛 에너지 하베스팅 시스템을 구현하였는데, 이를 위해 하이브리드 플라즈모닉 광전극을 본 연구에서 구현한 바이오 기반 광전지 시스템의 음극으로 활용하였다. 해당 시스템에서 태양 에너지 전환은 Synechocystis sp. 세포의 광합성 현상과 하이브리드 플라즈모닉 음극 (ZnONRs/AuNPs) 구조체의 광여기, 광산란 그리고 플라즈모닉 현상에 기초한다. 또한 본 시스템은 전기 생산을 위해 매우 소량의 세포 용액 (수마이크로 리터)을 필요로 한다. 뿐만 아니라 사용된 플라즈모닉 음극은 광원의 넓은 스펙트럼 영역에서 빛 에너지 하베스팅을 가능하게 하는데, 이는 플라즈모닉 구조체가 LSPR에 의해 유도된 현상으로 인해 자체적으로 전자를 생성할 뿐만 아니라 세포의 광합성 활동을 훨씬 더 향상시켜주는 것으로부터 기여된다. 결과적으로 플라즈모닉 현상에 의해 향상된 바이오 기반 광전지 시스템을 이용했을 때 획기적인 파워 향상을 얻을 수 있었으며, 음극으로 단순히 ITO glass를 사용한 시스템과 비교했을 때 약 17.3 배에 해당하는 파워를 얻었다. 이러한 관점에서 본 연구에서 제안된 플라즈모닉 음극 플랫폼은 앞으로 광유체 시스템에 기반한 효율적인 에너지 하베스팅 시스템을 구현하는데 있어 기여할 수 있을 것으로 기대된다.Optofluidics is an interdisciplinary research of optics and microfluidics, which enables flexible optical functions by using microfluidic system or enables manipulation of small amounts of fluids (or sample solution) by using optics. Therefore, on the one hand, deformable fluids make it possible to easily reconfigure the optical system such as microlens, waveguides, etc. by simply replacing the liquid material or deforming the fluid interface. On the other hand, the microfluidic system coupled to optical components can provide beneficial platform for handling and analyzing only small amounts of interesting fluid samples at microscale. In this regard, optofluidics is being rapidly developed in various applications such as optical component construction, biological analysis, energy harvesting, chemical sensing, etc. In Chapter 2, a tunable optofluidic microlens is demostrated by using a hydrodynamically controllable gas-liquid interface. The relevant physics governing the interface formation are exploited through numerical and theoretical analyses as well. Understanding the physics is important to fabricate the stable multiphasic interface which determines the performance of the lens. We show that non-linear surface tension effect at the gas- liquid interface significantly affects the lens shape and is dependent on the values of fluid parameters. Since our in-plane microlens is based on the gas-liuquid multiphase, a relatively short focal lenth can be obtained due to the intrinsically large distinction of the refractive indices across the gas-liquid interface. This short focal length would then contribute to realization of more miniatureized optofluidic system for a lab on a chip application. In chapter 3, an enhanced plasmonic tweezer is suggested by designing and fabricating the metal-dielectric hybrid plasmonic substrate for trapping polystyrene particles or E.coli cells. Localized surface plasmon resonance (LSPR) is an emerging optical phenomenon as a promising tool for near-field energy enhancement. Therefore we utilize the LSPR-induced heating effect for fabricating an efficient microscale trapping system. The synergistic effects of the hybrid plasmonic structure are explored through numerical and experimental analyses. In order to more intensify the LSPR-induced plasmonic effects, we simply introduce the hybrid structure which consists of zinc oxide nanorods (ZnONRs) and gold nanoparticles (AuNPs). We show that ZnONRs transfer the amplified light energy to AuNPs at the interfaces between the ZnONRs and the AuNPs via leaky wave guide modes. Thus, the ZnONRs enhance the LSPR of the AuNPs as well as the trapping performance outstandingly. Our hybrid plasmonic substrate and in-depth analyses would contribute to the construction of an effective optofluidic biological analysis platform through the efficient trapping/manipulation of the fluid-based sample. In chapter 4, a plasmon-enhanced light harvesting system is developed by introducing a hybrid plasmonic photoelectrode as a photoanode of our bio-photovoltaic system. The solar energy conversion is based on the photosynthesis of cells (Synechocystis sp.) and the photoexcitation, scattering and plasmonic effects of the hybrid plasmonic photoanode (ZnONRs/AuNPs) under the irradiation. The system contains only small amount of cell solution for the current production. Moreover, the plasmonic photoanode enables the efficient light harvesting in broadband of the light source by not only generating electrons itself but also stimulating the photosynthetic activity of the cells through the LSPR-induced effects. An anomalous power improvement about 17.3-fold can be obtained from the plasmon-enhanced bio-photovoltaic system, compared to the control system of which photoanode is the bare ITO glass. In this respect, our plasmonic photoanode platform would give an inspiration for fabricating an efficient energy harvesting system based on the optofluidic device.Chapter 1. Introduction 1 1.1. Optofluidics . 1 1.2. Research background . 3 1.2.1. Microfluidics 3 1.2.2. Plasmonics 5 1.2.3. Localized surface plasmon resonance (LSPR). 7 1.3. Objectives of present work. 11 1.4. References . 12 Chapter 2. Tunable Multiphase Microlens. 14 2.1. Introduction . 14 2.2. Experimental section 19 2.2.1. Design and fabrication of the optofluidic chip. 19 2.2.2. Materials 19 2.2.3. Experimental set-up . 21 2.3. Numerical analysis. 22 2.4. Theoretical analysis 23 2.5. Results and discussion 25 2.5.1. Lens shape 25 2.5.2. Non-linear surface tension effect on the lens shape. 25 2.5.3. Characteristics of the tunable microlens 30 2.6. Summary 38 2.7. References . 39 Chapter 3. Enhanced Plasmonic Tweezer 41 3.1. Introduction . 41 3.2. Experimental section 44 3.2.1. Preparation of plasmonic substrate 44 3.2.2. Experimental set-up . 45 3.2.3. Temperature measurement . 45 3.2.4. Particle trapping experiment 46 3.3. Numerical analysis. 50 3.4. Results and discussion 53 3.4.1. Prediction and analysis of synergistic effects 53 3.4.2. Characterization of plasmonic substrate 58 3.4.3. Plasmonic heating 58 3.4.4. Enhanced particle trapping performance . 64 3.4.5. Verification of synergistic effects. 65 3.4.6. Analysis of trapping forces 70 3.5. Summary 75 3.6. References . 76 Chapter 4. Plasmon-enhanced Light Harvesting System 79 4.1. Introduction . 79 4.2. Experimental Section . 84 4.2.1. Preparation of plasmonic anodes . 84 4.2.2. Preparation of cell solution and MEA 84 4.2.3. Device assembly 85 4.2.4. Electrochemical characterization . 85 4.2.5. Angle-dependent light scattering measurement . 86 4.3. Numerical analysis. 91 4.4. Results and discussion 93 4.4.1. Characterization of plasmonic anodes 93 4.4.2. Living solar cell performance 98 4.4.3. Working mechanism of plasmon-enhanced living solar cell 101 4.4.4. Broadband multiplex living solar cell 103 4.4.5. Far-field scattering effect . 105 4.4.5.1. Structural effect . 105 4.4.5.2. Size effect of AuNPs . 111 4.5. Summary 114 4.6. References . 115 Korean Abstract 118Docto

Research and technology, fiscal year 1986, Marshall Space Flight Center

The Marshall Space Flight Center is continuing its vigorous efforts in space-related research and technology. Extensive activities in advanced studies have led to the approval of the Orbital Maneuvering Vehicle as a new start. Significant progress was made in definition studies of liquid rocket engine systems for future space transportation needs and the conceptualization of advanced laucnch vehicles. The space systems definition studies have brought the Advanced X-ray Astrophysics Facility and Gravity Probe-B to a high degree of maturity. Both are ready for project implementation. Also discussed include significant advances in low gravity sciences, solar terrestrial physics, high energy astrophysics, atmospheric sciences, propulsion systems, and on the critical element of the Space Shuttle Main Engine in particular. The goals of improving the productivity of high-cost repetitive operations on reusable transportation systems, and extending the useful life of such systems are examined. The research and technology highlighted provides a foundation for progress on the Hubble Space Telescope, the Space Station, all elements of the Space Transportation System, and the many other projects assigned to this Center

Mesoporous Coatings with Simultaneous Light‐Triggered Transition of Water Imbibition and Droplet Coalescence

A systematic study of gating water infiltration and condensation into ceramic nanopores by carefully adjusting the wetting properties of mesoporous films using photoactive spiropyran is presented. Contact angle measurements from the side reveal significant changes in wettability after irradiation due to spiropyran/merocyanine-isomerization, which induce a wetting transition from dry to wet pores. The change in wettability allows the control of water imbibition in the nanopores and is reflected by the formation of an imbibition ring around a droplet. Furthermore, the photoresponsive wettability is able to overcome pinning effects and cause a movement of a droplet contact line, facilitating droplet coalescence, as recorded by high-speed imaging. The absorbed light not only effectuates droplet merging but also causes flows inside the drop due to heat absorption by the spiropyran, which results in gradients in the surface tension. IR imaging and particle tracking is used to investigate the heat absorption and temperature-induced flows, respectively. These flows can be used to manipulate, for example, molecular movement inside water and deposition inside solid mesoporous materials and are therefore of great importance for nanofluidic devices as well as for future water management concepts, which include filtering by imbibition and collection by droplet coalescence. © 2021 The Authors. Advanced Materials Interfaces published by Wiley-VCH Gmb

Oscillatory flow reactors (OFRs) for continuous manufacturing and crystallization

Continuous crystallization is an attractive approach for the delivery of consistent particles with specified critical quality attributes (CQAs), which are attracting increased interest for the manufacture of high value materials, including fine chemicals and pharmaceuticals. Oscillatory flow reactors (OFRs) offer a suitable platform to deliver consistent operating conditions under plug-flow operation while maintaining a controlled steady state. This review provides a brief overview of OFR technology before outlining the operating principles and summarizing applications, emphasizing the use for controlled continuous crystallization. While significant progress has been made to date, areas for further development are highlighted that will enhance the range of applications and ease of implementation of OFR technology. These depend on specific applications but include scale down, materials of construction suitable for chemical compatibility, encrustation mitigation, the enhancement of robust operation via automation, process analytical technology (PAT), and real-time feedback control

NASA/MSFC FY-82 atmospheric processes research review

The NASA/MSFC FY-82 Atmospheric Processes Research Program was reviewed. The review covered research tasks in the areas of upper atmosphere, global weather, and severe storms and local weather. Also included was research on aviation safety environmental hazards. The research project summaries, in narrative outline form, supplied by the individual investigators together with the agenda and other information about the review are presented