Multifunctional Tool for Expanding AFM-Based Applications

A multifunctional tool which expands the application field of atomic force microscope-based surface modification is presented. The AFM-probe can be used for surface modification and in-situ characterization at the same time, due to a special configuration with two cantilevers. Various applications from different fields are presented, which were carried out with one and the same tool: in-situ characterization of wear generated with and without local lubrication (tribology), fountain-pen lithography in which material is deposited or removed (physical chemistry), and electrochemical metal deposition (electrochemistry)

Microfabrication of a cantilever probe

Tese de mestrado integrado, Engenharia Física, Universidade de Lisboa, Faculdade de Ciências, 2020In this dissertation, microcantilevers are designed and fabricated. The cantilevers were dimensioned to be used in Atomic Force Microscopy in static and dynamic mode. Structures with different geometries were analysed, namely rectangular cantilevers, arrow-ended cantilevers, cantilevers with a hollow section and with different tips at the end. This work aims to obtain a cantilever with both a hollow section and a tip allowing it to be used in AFM and as a nanoparticle dispenser. Various approaches and materials were tested during the fabrication to obtain the desired features. The tips were successfully fabricated and characterized independently of the cantilever. The hollow section was not fully characterised, but it was possible to observe that the channel was closed. Silicon nitride cantilevers were successfully fabricated, however, due to the anomalous chip format, these could not be tested in a sample.Nesta dissertação foram desenhados e fabricados microcantilevers. Os cantilevers foram dimensionados para serem utilizados em Microscopia de Força Atómica nos modos estático e dinâmico. Estes foram analisados assumindo diferentes geometrias nomeadamente cantilevers retangulares, cantilevers com uma extremidade triangular, cantilevers com uma seção oca e com diferentes pontas no final. Este trabalho tem como objetivo obter um cantilever com uma seção oca e uma ponta permitindo que seja utilizado no AFM e como dispensador de nanopartículas. Várias abordagens e materiais foram testados durante a fabricação para obter as propriedades desejadas. Inicialmente foi medida a taxa de erosão no plano (100) do silício para uma solução de KOH de 85 % (m/m), que resultou em (0;44 ± 0;01) μm/min e (1;70 ± 0;01) μm/min para uma temperatura de 60 ºC e 80 ºC respetivamente. Inicialmente foi testado um procedimento para obter um cantilever de silício com e sem ponta. Foi possível obter um cantilever simples, fixado ao substrato, com uma espessura de 10 μm. Porém, a litografia para definir a ponta no topo deste cantilever não ficou bem definida, possivelmente devido ao facto de o laser não focar nos planos separados de 10 μm ou pelo fotoresiste não apresentar uma boa uniformidade ao longo da amostra, devido à espessura dos cantilevers. De modo a averiguar esta impossibilidade de definir a ponta no topo da estrutura foi testado um cantilever de silício com 1 μm de espessura. A etapa de litografia definiu com sucesso uma ponta no cantilever, no entanto, o contorno da estrutura tornou-se irregular ao longo processo de erosão por KOH para definir a ponta. Estes cantilevers de silício foram protegidos com uma camada de crómio e ouro, e titânio e ouro que não resistiram, para além de 1 hora, à erosão de KOH. Este procedimento foi efetuado numa amostra com um lado polido e outro não polido. O chip foi definido no lado não polido por ser de dimensões macroscópicas, onde o contorno não precisava ter alta resolução. No entanto, o Si3N4 que definiu a estrutura, após 2 horas de erosão com KOH, foi totalmente erodido deixando o chip desprotegido. Por esta razão, procedeu-se para a utilização de amostras com ambas as faces polidas para a fabricação de cantilevers de Si3N4. O procedimento para obter os cantilevers de Si3N4 é muito semelhante ao de silício. Na etapa em que a amostra é erodida com KOH, o Si3N4 usado para proteger as estruturas acabou por ser erodido após 2 horas. De modo a obter cantilevers suspensos procedeu-se a um método que não requeria tanto tempo de erosão com KOH. Estes foram obtidos com sucesso, porém, devido ao formato do chip estes não podem ser utilizados em microscopia de força atómica por não permitirem simultaneamente a interação com uma amostra e com o laser no topo do cantilever. Independentemente do fabrico dos cantilevers, as pontas foram fabricadas e caracterizadas com sucesso junto com os seus parâmetros de fabricação. Duas pontas foram obtidas: uma cónica e outra piramidal. Estas pontas formam-se a partir da erosão anisotrópica do silício no quadrado de Si3N4 impresso, esta erosão foi medida e tem um valor de etchdia = (0;76 ± 0;02) μm/min ao formar uma ponta cónica com um ângulo de αcon = (65 ± 15)º. Para a ponta piramidal foi medida uma taxa de erosão para o plano (111) do silício de etch111 = (0;21 ± 0;02) μm/min. Relativamente aos canais ocos foi possível observar que os canais se encontravam selados após o passo de PECVD e que estes não colapsaram após 1 hora de erosão com KOH. As propriedades físicas dos cantiléveres fabricados não foram medidas devido às dimensões do chip não corresponderem às do suporte de AFM. Estes foram excitados na plataforma da amostra do AFM, porém os atuadores piezoelétricos desta não tinham amplitude suficiente para os cantiléveres oscilarem. Foram obtidos valores de frequência de ressonância para diferentes geometrias de cantilevers pelo método de elementos finitos, no entanto estes não puderam ser validados com resultados experimentais. Com esta caracterização, seria possível deduzir √E=ρ para o Si3N4 depositado, para que futuros cantiléveres possam ser melhor dimensionados

Biomarker Sensors and Method for Multi-Color Imaging and Processing of Single-Molecule Life Signatures

The invention is a device including array of active regions for use in reacting one or more species in at least two of the active regions in a sequential process, e.g., sequential reactions. The device has a transparent substrate member, which has a surface region and a silane material overlying the surface region. A first active region overlies a first portion of the silane material. The first region has a first dimension of less than 1 micron in size and has first molecules capable of binding to the first portion of the silane material. A second active region overlies a second portion of the silane material. The second region has a second dimension of less than 1 micron in size, second molecules capable of binding to the second portion of the active region, and a spatial distance separates the first active region and the second active region

Nanoscale dispensing of single ultrasmall droplets

Nanoscale dispensing (NADIS) is a novel technique to deposit material at micrometric and submicrometric dimensions. It has great flexibility in feature shape and choice of deposited material. Due to its expected low cost and short turn-around time, it has the potential to be an interesting tool complementary to standard lithographic processes. Furthermore, NADIS has a great potential in the creation of high-density microarrays used in proteomics or genomics. The key feature of NADIS is the deposition of a liquid through an aperture created in a scanning force microscopy probe tip. The liquid is loaded into the hollow back of the pyramidal probe tip. Upon contact, liquid is transferred from the tip to the substrate surface. The transfer of liquid occurs without any external pressure. The control of the NADIS probe displacement is achieved using a standard atomic force microscope. Two different approaches to fabricate tips with apertures were investigated. The first approach relies on opening the tip during the microfabrication of the probe, whereas the second approach implies a modification of commercially available probes by focused ion beam milling. Both kinds of probes have shown their ability to perform successfully the dispensing of droplets. Nanoscale dispensing has been demonstrated for deposition of ultrasmall single droplets with volumes down toattoliters in a controlled way and with high lateral accuracy. The smallest droplet spacing that has been achieved was less than 500 nm. The size of the droplets and the possible droplet density are largely dependent on the aperture diameter and on the surface wettability. Nanoparticles and fluorescent molecules were also dispensed. In such cases, the liquid is used as a transport medium for the substances to be deposited. By moving the NADIS probe during contact on the substrate, it was possible to write features such as lines with sizes that can be as small as 400 nm. Some theoretical aspects are discussed, in particularly the capillary forces associated with axisymmetric liquid menisci. Experimentally measured capillary forces during the dispensing are compared with theoretically determined values

Development and applications of inkjet printed conducting polymer micro-rings

A drying sessile drop moves the solute particles to the periphery where they get deposited in the form of a ring. This phenomenon is prevalent even with micro drops falling at high velocity from a piezo-actuator based inkjet printer. In polymer microelectronic field, this phenomenon is a major challenge for fabricating devices using inkjet printing. We exploited this problem and applied it for various novel applications in the field of polymer microelectronics. Various dispensing techniques and temperature variations for micro-drop printing were used for modifying the micro-drops in such a way that the periphery of the micro-ring holds most of the solute as compared to inner base layer. Reactive ion etching (RIE) was used for removing the inner base layer in order to make the micro-rings completely hollow from the center. These micro-rings were applied in the fabrication of polymer light emitting diode, humidity sensor and vertical channel field effect transistor. High resolution polymer light emitting diode array (\u3e200 pixels/inch) was fabricated by inkjet printing of micro-ring and each micro-ring acts as a single pixel. These micro-rings were applied as a platform for layer-by-layer (LbL) nano-assembly of poly-3,4-ethylenedioxythiophene:poly-styrenesulfonate (PEDOT:PSS) for the fabrication of humidity sensor. Enhanced sensitivity of the humidity sensor was obtained when the inkjet printed micro-rings are combined with LbL assembled PEDOT:PSS films. During the fabrication of vertical channel field effect transistors, inkjet printed PEDOT:PSS micro-rings were used as source and the inner spacers between the adjacent micro-rings were used to make channel. These micro-rings can also find other applications in the field of biological sciences. These micro-rings can be used as cell culture plates and as scaffolds for cell and/or tissue growth

DEVELOPTMENT OF HYDROGEL-SOLID HYBRIDS FOR ELECTRO-MICROFLUIDICS AND SINGLE CELL ANALYSIS

학위논문 (박사) -- 서울대학교 대학원 : 공과대학 협동과정 바이오엔지니어링전공, 2020. 8. 권성훈.Agarose and other noncovalent hydrogels have good biocompatibility but their applications were restricted since they tend to have low interfacial bonding strength with other polymers or solids. Previously introduced noncovalent hydrogel-to-solid fixation strategies relied heavily on mechanical clamping which is a temporary approach and difficult to apply to kinetic parts or morphologically non-trivial adhesions. Here, we introduce a facile method that increased interfacial bonding strength of agarose hydrogel against solids via an interface-toughening hydrogel. The method showed applicability to several other noncovlanet hydrogels as well, including gelatin, alginate, agar, and chitosan. The bonding method requires no mechanical clamping, liquid glue or bulk modification of the noncovalent hydrogels polymer backbone. It is also compatible with forming micropatterns within the bonding interface. With this new bonding technique, we were able to fabricate various noncovalent hydrogel-solid integrated structures with novel functionalities for in vitro assay, soft robotics and biologically inspired systems.아가로스를 비롯한 noncovalent 하이드로겔들은 biocompatibility가 좋은 반면에 다른 고체 표면과의 접착력이 약해 그 활용성이 낮은 편이었다. 기존의 noncovalent 하이드로겔 접착 방법은 주로 기계적 고정방법에 많이 의존했는데 이는 일시적인 접착일 뿐이고, 동적 부품이나 복잡한 표면에는 적용이 어려웠다. 본 논문에선 접착면 toughness 증강을 도모하는, 그리고 활용성, 범용성이 좋은 하이드로겔 접착방법을 제시한다. 본 접착방법은 gelatin, alginate, agar, 그리고 chitosan등의 noncovalent hydrogel에 대해 적용 가능하다는 것을 보여줬다. 본 방법은 기계적 고정이 전혀 필요 없고, 액상 접착제나 하이드로겔 polymer backbone 수정을 요구하지 않는다. 또한 접착표면상에 미세구조들을 유지할 수 있다. 이 접착방법을 사용해서 전기미세유체, 단일세포전사체분석 등의 활용 예시들을 보여줬다. 본 접착방법은 이 외에도 in vitro 어세이, 소프트 로보틱스, 생체모방 등의 분야에 활용 가능할 것으로 예상한다.Chapter 1 １ Chapter 2 ６ 2.1 Fabrication of hybrid hydrogel films ７ 2.2 Fabrication of hybrid hydrogel and noncovalent hydrogel double layer structure ８ 2.3 Performing various hydrogel-to-hybrid gel bonding ８ 2.4 Agarose hydrogel to tough hydrogel bonding procedure. ９ 2.5 Preparing solids and elastomers to bond with hybrid gels. １０ Chapter 3 １１ 3.1 FTIR measurement of imine bond formation １２ 3.1.1 Sample preparation for FTIR measurement １２ 3.1.2 FTIR Measurement result １２ 3.2 13C-NMR chemical shift measurement １５ 3.2.1 Sample preparation for NMR measurement １５ 3.2.2 NMR measurement result １６ 3.3 SEM/EDS measurement of monomer diffusion layer １９ 3.3.1 Sample preparation for SEM measurement １９ 3.3.2 SEM measurement result １９ 3.3.3 EDS measurement result ２１ Chapter 4 ２５ 4.1 Bonding strength measurement ２６ 4.1.1 The effect of monomer concentration ２６ 4.1.2 The effect of agarose chain aldehyde modification ３０ 4.1.3 The effect of monomer diffusion ３１ 4.1.4 Fracture energy analysis ３３ 4.2 Noncovalent hydrogel to solid bonding ３５ 4.2.1 Noncovalent hydrogel to solid surface bonding ３５ 4.2.2 Noncovalent hydrogel to elastomer surface bonding ３７ 4.2.3 Noncovalent hydrogel to tough hydrogel bonding ４１ Chapter 5 ４５ 5.1 Zig-free hydrogel microfluidic system ４６ 5.2 Electrophoretic oligonucleotide retrieval system ５２ 5.3 Discussion ５７ Chapter 6 ５９ 6.1 Introduction of the field and the proposed approach ６０ 6.2 Device design ６２ 6.2.1 Optimization of cell assembly protocol ６６ 6.2.2 Optimization of electrophoretic mRNA capture protocol ７０ 6.2.3 Crosslinking mRNA capturing probe onto magnetic microparticles ７４ 6.2.4 Optimizing RT-PCR protocol for single cell or small number of cells using mouth pipetting ７５ 6.2.5 Critical limitation of the approach ８０ Chapter 7 ８１ 7.1 Single cell electrophoresis protocol optimization ８２ 7.1.1 Optimization of barcoded mRNA-capturing microparticle synthesis ８２ 7.1.2 Optimization of cell assembly and bead assembly ８７ 7.1.3 Optimization of electrophoretic mRNA capture protocol ９３ 7.2 Single cell RNA retrieval demonstration ９６ 7.2.1 Single cell mRNA retrieval test ９６ 7.2.2 Bead harvest and RT-PCR １０５ 7.2.3 Validation using Sanger sequencing １０７ 7.2.4 Discussion １１０ Chapter 8 : Summary １１５ Bibliography １１７ Abstract(국문초록) １２０Docto

An Automated System for Chromosome Analysis

The design, construction, and testing of a complete system to produce karyotypes and chromosome measurement data from human blood samples, and to provide a basis for statistical analysis of quantitative chromosome measurement data are described

The motion, stability and breakup of a stretching liquid bridge with a receding contact line

The complex behavior of drop deposition on a hydrophobic surface is considered by looking at a model problem in which the evolution of a constant-volume liquid bridge is studied as the bridge is stretched. The bridge is pinned with a fixed diameter at the upper contact point, but the contact line at the lower attachment point is free to move on a smooth substrate. Experiments indicate that initially, as the bridge is stretched, the lower contact line slowly retreats inwards. However at a critical radius, the bridge becomes unstable, and the contact line accelerates dramatically, moving inwards very quickly. The bridge subsequently pinches off, and a small droplet is left on the substrate. A quasi-static analysis, using the Young-Laplace equation, is used to accurately predict the shape of the bridge during the initial bridge evolution, including the initial onset of the slow contact line retraction. A stability analysis is used to predict the onset of pinch-off, and a one-dimensional dynamical equation, coupled with a Tanner-law for the dynamic contact angle, is used to model the rapid pinch-off behavior. Excellent agreement between numerical predictions and experiments is found throughout the bridge evolution, and the importance of the dynamic contact line model is demonstrated.Comment: 37 pages, 12 figure