Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2001-04-07
2003-12-09
Vo, Anh T.N. (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S900000
Reexamination Certificate
active
06659598
ABSTRACT:
BACKGROUND OF THE INVENTION
In general, the present invention relates to the fabrication of tiny conductive devices sized on the order of the microcircuits, and even smaller, that operate as active elements on printed circuit boards, or any other such support structure, of varying sizes (including microchip-sized to the level of so-called molecular electronics where one or a small collection of molecules is capable of operating as an active electronic element). The fabrication of extremely small reliable components and complex circuits, although difficult, is very important to the ongoing development and distribution of miniaturized computerized contraptions ranging from analytical instruments and testing equipment (whether simple or complex) such as sensors, voltmeters, data collection equipment, and so on, to consumer devices such as notebook computers, multifunctional palm-sized computers, watch-sized computerized cellular communication devices, etc.
More particularly, the invention relates to a new apparatus that incorporates a unique method for dispersing a plurality of elongated nano-sized elements within a carrier-fluid to assemble any of a number of different tiny conductive devices built to replace a wide variety of conventional devices or built to the specifications of new conductive devices; such devices to include: diodes (used as light emitters and sensors, switches, etc.), transistors, on-tube junctions, capacitors, inductors, resistors, oscillators, MEMS (MicroElectroMechanical System) technology elements/devices—tiny mirrors, sensors, light reflectors, switches, microactuators, read/write heads, etc.
The apparatus includes a nozzle or orifice through which the elongated nano-elements within the carrier-fluid are directed such that they pass through an electromagnetic (EM) field and toward a first charge-receptive area of a support surface. This charge-receptive area has been given a charge to attract at least an end-portion of one of the nano-elements. The amount of charge held by the charge-receptive area being targeted depends upon the charge imparted to one or both ends of the nano-element upon passing through the EM field. A second charge-receptive area having a charge to attract either a second end-portion of the first nano-element or an end-portion of a second nano-element is preferably included; this second area in proximity to the first charge-receptive area, multiple charge-receptive areas may be patterned as needed.
If the carrier-fluid is in liquid form, the liquid is chosen so that preferably a substantial amount of it evaporates once the nano-element has attached to the charge-receptive area being targeted. If the carrier-fluid is in gas form, to minimize unwanted turbulence of the gas being discharged from the nozzle in an effort to better control flow and direction of nano-elements toward, as well as attachment thereof to a respective the charge-receptive area, preferably the area around the nozzle and charge-receptive area being targeted is under vacuum (i.e., the pressure around the charge-receptive area being targeted is less than the surrounding area) or the nano-elements within carrier-fluid are dispersed and directed toward target charge-receptive areas under high pressure.
I. Technical Background/History of Nanotubes
Carbon nanotubes belong to a small family of carbon compounds known as fullerenes. These tube-like structures may have single walls or multiple walls, generally each nanotube wall is essentially one carbon atom thick. They have been described as tiny strips of graphite sheet rolled into tubes and capped with half a fullerene at each end. Nanotubes may be multiwalled (made up of several concentric hollow cylinders of carbon atoms nested inside each other) or single-walled with an outer diameter on the order of 1 nanometer (a billionth of a meter) and length varies from several microns to 100
+
microns depending upon, among other things, fabrication method used to form the nanotubes. Nanotubes are very strong, stable (chemically inert), lightweight, and can withstand repeated bending, buckling, and twisting-plus they are efficient heat transfer agents. Atoms in a nanotube arrange themselves in hexagonal rings like chicken wire.
Graphite is a semimetal: Whereas most other electrical conductors can be classified as either a metal or a semiconductor, graphite is balanced in the transitional zone between the two. This is due to the unique properties of the building material of graphite, namely, carbon. Under intense pressure, carbon atoms form bonds with four neighboring carbons, creating the pyramidal arrangement of diamond. When carbon forgoes that fourth bond and links up with only three neighbors, it creates the hexagonal rings in graphite's structure. This arrangement leaves graphite with a host of unpaired electrons, which effectively ‘float’ above or below the plane of carbon rings. These floating electrons are more or less free to buzz around graphite's surface, which makes it a good electrical conductor. It is, however, these unattached bonds that leaves carbon atoms at the border of a graphite sheet susceptible to reaction with something nearby. This characteristic is what allows a heated (1200 degrees Celsius, or so) graphite sheet to curl back against itself, inter-knit together, and form a tiny cylindrical graphite element now commonly referred to as a nanotube.
In a graphite sheet, one particular electron state (called the Fermi Point) gives graphite almost all of its conductivity; none of the electrons in other states are free to move about. Statistically, only a fraction (estimated at one-third) of graphite walled nanotubes of any collection will act as truly metallic nanowires, while the remaining two-thirds will operate like semiconductors. Meaning that these nanotubes do not conduct current easily without an additional boost of energy (by way of a burst of light or sufficient voltage) to knock electrons from valence states into conducting states along the nanotube. The amount of energy needed depends on the separation between the two levels and is the so-called band gap of a semiconductor. It is this band gap that makes semiconductors useful in circuits. Carbon nanotubes do not all have the same band gap, because for every circumference there is a unique set of allowed valences and conduction states. The smaller-diameter nanotubes have very few states that are spaced far apart in energy. As the diameter increases, more and more states are allowed and the spacing between them shrinks. In this way, different-sized nanotubes can have band gaps as low as zero (similar to a metal), or as high as the band gap of silicon, and almost anywhere in between-making it readily tuned. It is predicted that multiwalled nanotubes have even more complex behavior, as each layer in the tube has its own, individual geometry.
In connection with describing a computer-designed model of nanotube gears that have benzene groups arrayed around the nanotube to act as cogs whereby, as a nanocylinder rolls, its tiny teeth turn the nanotube like a microscopic drive shaft, SCIENCE magazine author Robert F. Service admits that fabrication remains an issue (“Superstrong Nanotubes Show They Are Smart, Too”, Aug. 14, 1998, Vol. 281, see pg. 942): “[n]anogears are likely to remain simulations for some time, however, as there's no obvious way to build them.” As reported in the December 2000 issue of Scientific American (“Nanotubes for Electronics”, Philip Collins and Phaedon Avouris, see pg. 66) the authors explain their labor-intensive method of forming a FET: “We should emphasize, however, that so far our circuits have all been made one at a time and with great effort. The exact recipe for attaching a nanotube to metal electrodes varies among different research groups, but it requires combining traditional lithography for the electrodes and higher-resolution tools such as atomic force microscopes to locate and even position the nanotubes.” Thus, current fabrication methods fall short of being feasible in large-scale nan
Dickey Elizabeth
Grimes Craig A.
Macheledt Bales LLP
University of Kentucky Research Foundation
Vo Anh T.N.
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