Synthesis of Metallic Nanowires Using Integrated DNA Molecules as Templates

The DNA double helix is inherently a nanoscale wire-like object, possessing a 2 nm diameter as well as a remarkable capability for molecular recognition and the interaction with other chemical compounds, thus making it an attractive material for biologically driven assembly of artificial nanostructures. In this work methods for the construction of functional electronic networks from single DNA molecules are presented. For this, (i) the generation of patterns of distinct interconnects between micro-fabricated contact pads are explored by stretching end-specifically thiol-functionalized, single-tethered DNA molecules using hydrodynamic flow as well as an electric field-induced thermal flow. (ii) These networks then serve as a template for a selective in-situ photoinduced nucleation and growth of platinum clusters of 4 nm diameter along the DNA molecules. In the synthesis exclusively platinum ions from an aqueous platinum nitrate solution bonded electrostatically to the backbone of the immobilized DNA can be reduced upon irradiation with UV light, while background metallization is inhibited. Furthermore, the metallization scheme is applied to DNA nanotubes and another photochemical deposition process is used to tune the interparticle gap space in a discontinuous platinum cluster chain to form conducting nanowires. The "process toolbox'' presented in this work offers a versatile alternative for the hierarchical patterning and incorporation of biotemplated nanomaterials into micro-/nanofabrication schemes.Ein doppelhelikaler DNA-Strang besitzt mit seinem hohen Aspektverhältnis von Natur aus Ähnlichkeit mit einem Kabel. Zusammen mit seinen einzigartigen Selbstassemblierungseigenschaften sowie der Fähigkeit, mit einer Vielzahl von chemischen Stoffen eine Verbindung einzugehen, macht dies ihn zu einem aussichtsreichen Baumaterial für den Aufbau von künstlichen Nanostrukturen. In dieser Arbeit werden deshalb verschiedene Methoden für den Bau von elektronischen Schaltkreisen aus einzelnen DNA-Strängen demonstriert. Dazu wird (i) die Herstellung von Verdrahtungsmustern zwischen lithographisch gefertigten Kontaktstrukturen untersucht. Endständig mit Thiolgruppen funktionalisierte DNA-Moleküle, die an nur einem Ende mit der Oberfläche verknüpft sind, werden mittels Strömung oder eines elektrothermisch induzierten Flusses zwischen Elektroden gespannt. (ii) Diese Netzwerke dienen im Weiteren als Vorlage für ein selektives, lichtinduziertes Wachstum von Platinpartikeln mit Durchmessern von 4 nm lokal entlang der DNA-Moleküle. Dabei werden unter UV-Bestrahlung nur solche Platinionen reduziert, die aus einer Platinnitrat-Lösung elektrostatisch an die immobilisierte DNA angebunden haben. Partikelwachstum in der umgebenden Lösung wird weitgehend verhindert. Darüber hinaus wird dieses Verfahren auch auf DNA-Nanoröhren angewendet und ein weiterer photochemischer Abscheideprozess eingesetzt, um unterbrochene Clusterkettern zusammenzuwachsen, mit dem Ziel, elektrisch leitfähige Nanodrähte zu erhalten. Die vorgestellten Verfahren stellen eine vielseitige Alternative zu herkömmlichen, hierarchischen Fabrikationsschemen der Mikro- und Nanotechnologie dar

Trapping of nanoparticles with dielectrophoretic nano-probes.

Dielectrophoresis (DEP) is an electrokinetic force capable of attracting or repelling neutrally charged particles due to a non-uniform electric field [1, 2]. Positive dielectrophoresis attracts particles in the region of the highest electric field gradient; negative dielectrophoresis repels particles from the region of the highest electric field gradient. The dielectrophoretic force is directly proportional to the square of the electric field gradient, as well as the cube of the radius of the particles involved. As particles decrease in size, the gradient of the electric field must increase rapidly in order to capture or repel the particles. The intense electric field gradients were produced using fabricated silver gallium (Ag2Ga) nano-probes electrodes in conjunction with indium tin oxide (ITO) coated microscope cover slips, which served as the opposite electrode. The silver gallium nano-probes ranged from approximately 100-500 nm in diameter and were typically positioned less than 40 ?m above the ITO cover slips. Positive and negative dielectrophoretic forces were able to dominate the other electrokinetic forces acting on sub-micron particles, which were suspended in deionized water and aqueous potassium chloride, using the nano-probes and ITO cover slips as electrodes. Colloidal quantum dots of gold, as small as 5 nm in diameter, were captured using positive DEP forces, as were sub-micron fluorescent polystyrene particles. Negative DEP forces repelled sub-micron fluorescent polystyrene particles suspended in a low conductivity solution

Trapping of 27 bp - 8 kbp DNA and immobilization of thiol-modified DNA using dielectrophoresis

Dielectrophoretic trapping of six different DNA fragments, sizes varying from the 27 to 8416 bp, has been studied using confocal microscopy. The effect of the DNA length and the size of the constriction between nanoscale fingertip electrodes on the trapping efficiency have been investigated. Using finite element method simulations in conjunction with the analysis of the experimental data, the polarizabilities of the different size DNA fragments have been calculated for different frequencies. Also the immobilization of trapped hexanethiol- and DTPA-modified 140 nm long DNA to the end of gold nanoelectrodes was experimentally quantified and the observations were supported by density functional theory calculations.Comment: 17 pages (1 column version), 8 figure

The Response of an Ellipsoidal Colloid Particle in an AC Field

The quest for new smart materials with engineered properties and desired functionalities has driven scientists into the domain of nanotechnology over the past 30 years. Particles with anisotropic properties as a result of their geometry, chemical patterning or surface functionality have been envisioned as building blocks for advanced materials. By tuning the anisotropic interactions engendered by anisotropic particles, one potentially could manipulate the dynamic pathways for assembly.The work described in this thesis considers the response of an ellipsoidal colloid particle to a nearby AC electrode polarized at ~0.1 – 4 kV/m and ~0.1 – 3 kHz. The ellipsoidal particle, which had a surface sulfate functional group, was dispersed in 10^-6M NaCl. The particle experienced typical electric-field induced responses, including electro-rotation and electro-orientation at low frequency - 100Hz - with an electric field intensity of 2500V/m. For instance, the particle (lying) was observed to frequently try to align its longer axis parallel to the electric field. We quantified the ellipsoid’s response by tracking its position and orientation with and without an electric field. The translational diffusion coefficient without and with electric field was calculated to be in the range of (7.625 – 39.2750) × 10^-3µm2/s and (0.725 – 305.525) × 10^-3µm2/s respectively. Surprisingly, the ellipsoid was also observed to propel in the direction normal to the electric field, which we believe to be a first for such a system. We proposed that the propulsion is a result of broken symmetry in the electrohydrodynamic (EHD) flow due to non-symmetric ellipsoid shape of our particle

Design of a dielectrophoretic cell loading device

In recent years there has been an increasing interest in studying individual cells, and structures that physically entrap one or few cells have been developed for this purpose, but the approaches to load cells into these structures leave a lot to be desired. This dissertation discusses the design of a device that loads cells suspended in a solution into microvials using a combination of dielectrophoresis and fluid flow, which offers significant advantages over previous loading approaches. The basic concept is to use fluid flow and dielectrophoretic forces to position a given cell above a given vial, within an array of similar vials, and then bringing the cell into the vial. The loading of several cells flowing in a channel into a vial in a matter of seconds is demonstrated. The design of the loading device spurred the development of novel topics in the area of dielectrophoresis. The structures into which cells are loaded produce "parasitic cages". The effect of multiple electric fields and at multiple frequencies had to be explored to eliminate the parasitic cages, and new theory was developed to describe the phenomenon in a straight forward and convenient way. The design process of dielectrophoretic structures known as flow through sorters was simplified significantly using a method that relies on non dimensional analysis and a figure of merit. These topics investigated have broader applications than just loading cells into vials. The dissertation demonstrates technologies and design and fabrication methods key to the cell loading design. The dissertation ends by describing the design of a device that can be implemented to load cells into vials on integrated circuit chips and outlining this device's expected characteristics and performance based on the theory and methods presented through the dissertation

DESIGN AND EVALUATION OF A CONTINUOUS-FLOW DIELECTROPHORESIS DEVICE TO ELIMINATE PATHOGENS FROM TAP WATER

M.S. Thesis. University of Hawaiʻi at Mānoa 2018

Microfluidics and Nanofluidics Handbook

The Microfluidics and Nanofluidics Handbook: Two-Volume Set comprehensively captures the cross-disciplinary breadth of the fields of micro- and nanofluidics, which encompass the biological sciences, chemistry, physics and engineering applications. To fill the knowledge gap between engineering and the basic sciences, the editors pulled together key individuals, well known in their respective areas, to author chapters that help graduate students, scientists, and practicing engineers understand the overall area of microfluidics and nanofluidics. Topics covered include Finite Volume Method for Numerical Simulation Lattice Boltzmann Method and Its Applications in Microfluidics Microparticle and Nanoparticle Manipulation Methane Solubility Enhancement in Water Confined to Nanoscale Pores Volume Two: Fabrication, Implementation, and Applications focuses on topics related to experimental and numerical methods. It also covers fabrication and applications in a variety of areas, from aerospace to biological systems. Reflecting the inherent nature of microfluidics and nanofluidics, the book includes as much interdisciplinary knowledge as possible. It provides the fundamental science background for newcomers and advanced techniques and concepts for experienced researchers and professionals