Geometrical instruments – Distance measuring – Scale reading position sensor
Reexamination Certificate
1999-09-24
2001-09-11
Gutierrez, Diego (Department: 2859)
Geometrical instruments
Distance measuring
Scale reading position sensor
C200S061410, C073S865100
Reexamination Certificate
active
06286226
ABSTRACT:
RELATED APPLICATIONS
This application is related to U.S. patent application Ser. No. 09/426,457, titled “Article Comprising Vertically Nano-Interconnected Circuit Devices and Method for Making the Same,” filed by inventors Brown and Jin, and U.S. patent application Ser. No. 09/426,453, titled “In-situ Nano-interconnected Circuit Devices and Method for Making the Same,” also filed by inventors Brown and Jin, both of which are assigned to the present assignee and incorporated herein by reference.
FIELD OF THE INVENTION
This invention relates to a tactile sensor device using nanowires and more particularly, to a high-resolution tactile sensor comprising vertically aligned nanowires. The invention has many applications including use in touch-sensitive controllers in computer-related and robotic products.
BACKGROUND OF THE INVENTION
Sensors are used in a variety of modem devices and transducers. Tactile sensors are useful in a wide variety of applications for robotics and computer hardware. In robotics, tactile sensors provide useful information about the state of contact between a robot hand and an object in prehension. Sensors can indicate the presence or shape of an object, its location in the hand, and the force of contact. However, most robotic sensors are based on a pressure sensor design and can measure only compressive force without regard to shear movement. Shear sensors would be useful, for example, in detecting the movement of a grasped object.
Most controls for computer-related products are pressure-sensitive devices such as keys. Controllers such as the computer “mouse” or the computer “joy-stick” respond to movement in two dimensions but are relatively complex to manufacture and subject to mechanical failure. Accordingly, there exists a need for simple, compact tactile shear sensors for robotic and computer applications. High resolution tactile sensors are useful for accurate control devices such as for high-density, miniature computer products, for highly sensitive robotic skin sensing, or for touch-sensitive virtual reality devices such as control gloves worn by a remote operator or the fingers of a robot used for surgical operation of patients.
Nano-scale wires such as carbon nanotubes with a very small size scale, on the order of 1-100 nanometers in diameter and 0.1-100 &mgr;m in length, have received considerable attention in recent years. See Liu et al., Science, Vol. 280, p. 1253 (1998); Ren et al., Science, Vol. 282, p. 1105 (1998); Li et al., Science, Vol. 274, p. 1701 (1996); Frank et al., Science, Vol. 280, p. 1744 (1998); J. Tans et al., Nature, Vol. 36, p. 474 (1997); Fan et al., Science, Vol. 283, p. 512 (1999); Collins et al., Science, Vol. 278, p. 100 (1997); Kong et al., Nature, Vol. 395, p. 878 (1998); and Ebbesen et al., Nature, Vol. 382, p. 54 (1996).
Carbon nanotubes exhibit unique atomic arrangements, nano-scale structures and interesting physical properties such as one-dimensional electrical behavior, quantum conductance, and ballistic transport characteristics. The ballistic transport in carbon nanotubes, as reported by Frank et al, allows the passage of huge electrical currents in electronic circuits, with the magnitude of current density comparable to or better than those in some superconductors. Carbon nanotubes are one of the smallest dimensioned nanowire materials with generally high aspect ratio and small diameter of ~1 nm in the case of single-wall nanotubes and less than ~50 nm in the case of multi-wall nanotubes. See Rinzler et al, Appled Physics, Vol. A67, p. 29 (1998); Kiang et al, J. Physical Chem., Vol. 98, p. 6612 (1994), and Kiang et al, Physical Review Letters, Vol. 81, p. 1869 (1998).
High-quality single-walled carbon nanotubes are typically grown as randomly oriented, needle-like or spaghetti-like, tangled nanotubes by laser ablation or arc techniques (a chemical purification process is usually needed for arc-generated carbon nanotubes to remove non-nanotube materials such as graphitic or amorphous phase, catalyst metals, etc). Chemical vapor deposition (CVD) methods such as used by Ren et al., Fan et al., and Li et al tend to produce multiwall nanotubes attached to a substrate, often with a semi-aligned or an aligned, parallel growth perpendicular to the substrate. As described in these articles, catalytic decomposition of hydrocarbon-containing precursors such as ethylene, methane, or benzene produces carbon nanotubes when the reaction parameters such as temperature, time, precursor concentration, flow rate, are optimized. Nucleation layers such as a thin coating of Ni, Co, Fe, etc. are often intentionally added to the substrate surface to nucleate a multiplicity of isolated nanotubes. Carbon nanotubes can also be nucleated and grown on a substrate without using such a metal nucleating layer, e.g., by using a hydrocarbon-containing precursor mixed with a chemical component (such as ferrocene) which contains one or more of these catalytic metal atoms. During the chemical vapor decomposition, these metal atoms serve to nucleate the nanotubes on the substrate surface. See Cheng et al., Chem. Physics letters, Vol. 289, p. 602 (1998).
The as-grown single-wall nanotubes (SWNT) such as commonly synthesized by laser ablation or arc method, have a spaghetti-like configuration and often are tangled with each other. The multi-wall nanotubes (MWNT), such as commonly made by chemical vapor deposition, are easier to prepare in an aligned and parallel configuration. However, these as-grown nanotubes such as reported by Ren et al. and Li, et al. differ in height or length. Applicants have discovered a high-resolution tactile sensor may be fabricated with nanowires vertically attached to a sensor substrate such that, upon tactile contact, the nanowires make physical and electrical contacts between them such that presence of tactile shear or compression contact can be determined by electrical interrogation. For reliable tactile sensors as disclosed in this invention, the nanowires should be substantially vertically aligned and of equal length, such that prior methods of making SWNT and MWNT are generally unsuitable for the inventive high-resolution tactile sensors.
SUMMARY OF THE INVENTION
Summarily described, the invention embraces a tactile sensor device for detecting the position and movement activity of an object. The sensor device includes a circuit substrate; an array of contact pads on the circuit substrate, and a set of nanowires attached to each of the contact pads. The contact pads may be isolated or formed from a matrix of interconnecting strips of material, and each one of the contact pads defining the array is, in the absence of tactile activation, electrically isolated from adjacent contact pads defining the array. Each set of nanowires comprises at least one and preferably a plurality of nanowires that are advantageously substantially-vertically aligned and substantially equal in length. With this configuration, when an object contacts at least one of the plurality of sets of nanowires, it causes at least one set of nanowires to bend and make contact along a portion of the length thereof with at least another set of nanowires. The position and movement activity of the object can be sensed by electrically interrogating the contact pads to determine whether a connection has been made between sets of nanowires.
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Agere Systems Guardian Corp.
Gutierrez Diego
Lowenstein & Sandler PC
Smith R. Alexander
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