11 research outputs found
IMECE2002-33859 MANUFACTURING OF ELECTRICALLY CONDUCTIVE MICROSTRUCTURES BY DROPWISE PRINTING AND LASER CURING OF NANOPARTICLE-SUSPENSIONS
ABSTRACT A novel method for the manufacturing of electric microconductors for semiconductor and other devices is presented. The method brings together three technologies: controlled (on demand) printing, laser curing, and the employment of nanoparticles of matter, possessing markedly different properties (here, melting point) than their bulk counterparts. A suspension of gold particles in toluene solvent is employed to print electrically conducting line patterns utilizing a modified on demand ink jet printing process. To this end, microdroplets of 80-100 µm diameters are deposited on a moving substrate such that the droplets form continuous lines. Focused laser irradiation is utilized in order to evaporate the solvent, melt the metal nanoparticles in the suspension, and sinter the suspended particles to form continuous, electrically conducting gold microlines on a substrate. The ultra fine particles in the suspension have a diameter size range of 2 -5 nm. Due to curvature effects of such small particles, the melting point is markedly lower (400°C) than that of bulk gold (1063°C). Thermodynamic aspects of the effect of particle size on the melting and evaporation temperatures of gold and toluene, respectively, are discussed in the paper. The structure and line width of the cured line as a function of the laser irradiation power and stage velocity are reported in detail. Preliminary measurements of the electrical conductivity are represented
Pattern formation during the evaporation of a colloidal nanoliter drop: a numerical and experimental study
An efficient way to precisely pattern particles on solid surfaces is to
dispense and evaporate colloidal drops, as for bioassays. The dried deposits
often exhibit complex structures exemplified by the coffee ring pattern, where
most particles have accumulated at the periphery of the deposit. In this work,
the formation of deposits during the drying of nanoliter colloidal drops on a
flat substrate is investigated numerically and experimentally. A finite-element
numerical model is developed that solves the Navier-Stokes, heat and mass
transport equations in a Lagrangian framework. The diffusion of vapor in the
atmosphere is solved numerically, providing an exact boundary condition for the
evaporative flux at the droplet-air interface. Laplace stresses and thermal
Marangoni stresses are accounted for. The particle concentration is tracked by
solving a continuum advection-diffusion equation. Wetting line motion and the
interaction of the free surface of the drop with the growing deposit are
modeled based on criteria on wetting angles. Numerical results for evaporation
times and flow field are in very good agreement with published experimental and
theoretical results. We also performed transient visualization experiments of
water and isopropanol drops loaded with polystyrene microsphere evaporating on
respectively glass and polydimethylsiloxane substrates. Measured evaporation
times, deposit shape and sizes, and flow fields are in very good agreement with
the numerical results. Different flow patterns caused by the competition of
Marangoni loops and radial flow are shown to determine the deposit shape to be
either a ring-like pattern or a homogeneous bump
Synthesis, structure, electrochemistry and magnetism of cobalt-, nickel- and zinc-containing [M-4(OH)(3)(H2O)(2)(alpha-SiW10O36.5)(2)](13-) (M = Co2+, Ni2+, and Zn2+)
Interaction of the trilacunary 9-tungstosilicate [A-alpha-SiW9O34](10-) with cobalt(ii), nickel(ii) and zinc(ii) ions in pH 9 aqueous medium at room temperature led to the formation of the respective M-4-containing heteropolytungstates [M-4(OH)(3)(H2O)(2)(alpha-SiW10O36.5)(2)](13-) (M = Co2+ (1), Ni2+ (2), and Zn2+ (3)). Polyanions 1-3 were characterized in the solid state by single-crystal XRD, FT-IR spectroscopy, and thermogravimetric and elemental analyses. Electrochemical studies showed that the Co2+ ions in 1 can be oxidized to Co3+ and the CVs of the W-VI centers of the polyanions feature well-defined and chemically reversible reduction waves. Magnetic measurements on 1 and 2 showed paramagnetism with complex ferromagnetic and antiferromagnetic interactions. A model was presented for extracting the exchange constants for the magnetic exchange interaction