Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and...
Reexamination Certificate
2000-07-28
2003-08-26
Kalafut, Stephen (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Reexamination Certificate
active
06610440
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to electrical power sources and more particularly to microscopic batteries some forms of which are integrated or integratable with and providing internal power to MEMS and integrated microcircuits, either on a retrofit or original manufacture basis. MEMS (microelectromechanical systems) involve the fabrication and use of miniature devices which comprise microscopic moving parts (such as motors, relays, pumps, sensors, accelerometers, etc.). MEMS devices can be combined with integrated circuits, and can perform numerous functions.
BACKGROUND OF THE INVENTION
Integrated circuits, including microelectronic circuits, have been used extensively, and have the advantage of small size and low production costs particularly when produced on a large scale. A class of integrated circuits that are of particular interest comprise microelectronic circuits having at least one MEMS device. MEMS may comprise complex engineering systems comprising microscopic mechanical elements, such as motors, pumps, relays, sensors, accelerometers and other components, which are powered by electrical energy. MEMS devices make possible controlled physical movement of tiny parts within miniature circuits.
MEMS devices have the potential to revolutionize computational technology. The concept of MEMS fabrication provides the promise of low cost comparable to the cost effectiveness in producing integrated electronic circuitry. MEMS can include sensing and actuating components. In defense systems, MEMS are expected to revolutionize the gathering, evaluation, and communication of militarily-significant information. “MEMS will create new military capabilities, make high-end functionality affordable to low-end military systems, and extend the operational performance and lifetimes of existing weapons platforms.” (Department of Defense [DOD], 1995).
The great strength of MEMS as a technology fundamentally depends on: 1) the ability of MEMS to obtain increased functionality in a single, integrated system; 2) the low-cost, high-volume nature of MEMS fabrication; and 3) the overall reduction in size and mass of sensor/actuator systems. Heretofore, MEMS technology has typically focused on the need to fabricate MEMS and electronic devices that meet these three goals, but has failed to address the difficult problem of electrical energy availability and management. The overall goals of many MEMS applications has not and will not be met unless one or more appropriate MEMS power sources are developed.
While power and energy availability and management are problems for all integrated circuits, they are acute problems for MEMS. Many MEMS devices require periodic power pulses. Conventional wisdom has required and still requires that electrical power be supplied from relatively large, heavy external sources. Moving electrical current into an integrated circuit from such an external power source is difficult, and results in high power losses, particularly for a MEMS circuit where high capacities are required. Additionally, present MEMS devices must be continuously connected to the external power source. Thus, autonomous (self-contained), portable or remote operation of MEMS devices (such as MEMS sensors) is difficult if not impossible to achieve using an external fixed power source. It is reported that the 1994 market for MEMS was $500M. The projections of potential future market, based on expected growth of existing markets and expansion into anticipated markets within a decade, are that the production of MEMS will approach $3 billion per year.
A large fraction of MEMS production presently occurs in two areas, sensors and accelerometers ($200M/year). These two markets are expanding very rapidly at present. In addition, other types of MEMS applications are rapidly emerging. Presently, none of these devices are using integrated batteries, because none exist, nor have they previously been invented and developed.
One analysis of the MEMS sensor and accelerometers applications is that nearly 100% of the sensor market, and approximately 30% of the accelerometer market, would use microscopic batteries, if they were available. On this basis, it is estimated that a market for microscopic batteries in these two fields would be $50M/year, if such a product existed. Other significant markets would also come into place if a microscopic battery could be provided, such that within a decade microscopic batteries, would have a market of over $100M/year.
While the storage of energy in miniature, rechargeable devices for MEMS application is contrary to the state-of-the-art, a long term unsatisfied need for such has existed. If miniature energy sources were inventively created, significant advantages would be obtained, which are not presently available. First, more autonomous MEMS devices could be produced because the present dependency on continuous supply of power from an external source would be overcome. Second, significant improvement in energy efficiency would result. The supply of electrical energy would be at low power, stored temporarily, and then released at higher power levels in close proximity to the point of use, thus reducing overall power losses. Third, the cost of the MEMS system its integrated power supply would be lowered by reducing the complexity of electrical connections. Presently, it is difficult if not impossible to effectively store energy locally within a MEM system. Miniature capacitors have unacceptable useful discharge times (and hence unacceptable energy storage capacity). Fourth, cells can selectively be arrayed in series and in parallel to achieve different (and variable) combinations of operating voltage and capacity.
Further, unitary simultaneous formation, for example, of a microcircuit, one or more MEMS devices and a microscopic battery would provide a substantial advantage.
Presently, batteries for MEMS devices are unsatisfactory external power sources, which undesirably contributing to both the overall weight and volume of the MEMS device, and have other disadvantages. There are two primary reasons for this. The first primary reason is the size of the batteries. The smallest commercial batteries are the button-shaped energy cells used in watches, calculators and hearing aids. These are huge when compared with the MEMS to which such an external battery heretofore has supplies power. The second primary reason is that the need for energy supply in MEMS is at a relatively high power level. High power is often needed to produce mechanical movement in MEMS devices. Commercially available batteries typically maximize the amount of energy they store, as opposed to providing high power release of stored energy. Consequently, conventional external batteries must be overly large in order to supply the power levels required by the circuit.
A further limitation of present commercially available external batteries for MEMS is that no small batteries are rechargeable batteries. Rechargeability is mandated by many MEMS applications.
Table 1, below, compares the characteristics of several power source solutions with respect to size, weight, capacity, and assembly difficulty. Table 2, below, is a partial list of potential DOD applications for MEMS taken from the text “Microelectromechanical Systems: A DOD Dual Use Technology Industrial Assessment” (DOD, 1995), together with an indication of the power source requirements for the majority of applications in the given area. As stated above, a significant portion of MEMS production presently occurs in two areas, sensors and accelerometers. Military applications for remote sensors and accelerometers include: safing and arming of fuses; friend or foe identification; embedded sensors for system integrity monitoring; communications systems monitoring, such as with satellites; low power mobile displays; flexible sensing surfaces; and numerous others.
Many of the application areas in Table 2 will require an integrated or integrable microscopic battery power. In general, systems that require mobile, autonomous, extensively-int
Harb John N.
LaFollette Rodney M.
Salmon Linton G.
Alejandro R
Bipolar Technologies, Inc
Foster Lynn G.
Kalafut Stephen
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