Patent Application
20090284101
There is an increasing demand in the field of sensors, actuators or data communications for autonomous microsystems which are independent of an external power supply and which guarantee wireless and maintenance-free operation. Usual autonomous Microsystems are typically based on the use of solar energy and feature solar cells for converting the solar energy into electrical energy. Because these systems are dependent on the sun or on other suitable light sources however their area of application is greatly restricted. In addition difficulties arise with these types of system with increasing miniaturization and for integration into known CMOS technology. One device known to the applicant for converting mechanical energy into electrical energy is based on electrostatic induction and employs an electret to obtain energy. An electret film is arranged at a first electrode which is provided with an electrical charge, with the first electrode being connected to a ground potential. A second electrode is arranged at a distance from the first electrode and connected via a load circuit to ground potential. The electret film is arranged between first and second electrodes. A movement of the second electrode in a direction parallel to the main surface of the first electrode causes the overlapped surface of first and second electrode and thereby the charge induced in the first electrode to change. This leads to a flow of current from the second electrode to the ground potential. The disadvantage with this arrangement is that the first electrode or the electret film respectively must first of all be provided with an electrical charge.
One potential object is thus to create an improved arrangement for converting mechanical energy into electrical energy and a method for operation of said arrangement.
The inventors propose a device for converting mechanical energy into electrical energy. The device comprises a first electrode made from a first material, which has a first work function for charge carriers and a second electrode made from a second material, which has a second work function for charge carriers, with the second work function differing from the first work function. The first electrode and the second electrode are connected electrically-conductively to each other via a first load circuit. The fact that the second electrode is arranged relative to the first electrode with a variable spacing enables an oscillating current to be impressed in a simple manner in the load circuit by imparting an oscillation to the device. The first electrode can comprise a material which is selected from a group consisting of platinum, titanium and palladium.
In one embodiment the first electrode is arranged in a recess of a surface of a first area of a first substrate part. The device can furthermore comprise a second substrate part which features a first and a second surface, with the first and the second surface of the second substrate part facing away from each other and the first surface of the second substrate part being arranged on the surface of the first substrate part. The second substrate part features a first area and a second area, with the second area of the second substrate part being coupled to a second area of the first substrate part, the first surface of the first area of the second substrate part faces towards the first electrode and the second electrode is formed by the first area of the second substrate part. A cavity is embodied between the first area of the second substrate part and the second area of the second substrate part. The cavity embodied between the first area of the second substrate part and the second area of the second substrate means that the first area of the second substrate part is not rigidly coupled to the second area of the second substrate part, while the second area of the second substrate part is coupled rigidly to the second area of the first substrate part. Advantageously the coupling strength of the second area of the second substrate part can be tailored to the first area of the second substrate part by suitable selection of the dimensioning of the cavity to a frequency of an imparted oscillation to the device such that a current impressed into the load circuit is maximized.
In an embodiment of the present invention the device furthermore features a third substrate part which features a first and a second surface, with the first and the second surface of the third substrate part facing away from each other. The first surface of the third substrate part is arranged on the second surface of the second substrate part. A third electrode made from a material with a third work function, with the third work function differing from the second work function, is embodied in a recess of a first area of the first surface of the third substrate part. The second area of the second substrate part is coupled to a second area of the third substrate part. The second surface of the first area of the second substrate part faces towards the third electrode and is spaced away from the third electrode. The second electrode and the third electrode are connected to each other via a second load circuit electrically-conductively. The advantage of the proposed device is that when an oscillation is imparted to the device an oscillating current is impressed into the first load circuit and into the second load circuit respectively.
The first substrate part comprises a second material, with the second material able to be selected from a group consisting of silicon and silicon oxide. The second substrate part comprises a third material, with the third material able to be selected from a group consisting of silicon and silicon oxide. The third substrate part comprises a fourth material, with the fourth material able to be selected from a group consisting of silicon and silicon oxide. The selection of the materials for first, second and third substrate part advantageously allows the integration of the device into components based on silicon technology.
The third electrode comprises a fifth material. The fifth material can be selected from a group consisting of platinum, titanium and palladium.
The inventors also propose a device having a second substrate part, which features a first and a second surface, with the first and the second surface of the second substrate part facing away from each other and the first surface of the second substrate part being arranged on the surface of the first substrate part. The second substrate part features a first and a second area. The second electrode is embodied on the first surface of the first area of the second substrate part. The second area of the second substrate part is coupled to a second area of the first substrate part. The second electrode faces towards the first electrode. A cavity is embodied between the first area of the second substrate part and a second area of the second substrate part. The advantage of the device is that the choice of material of the second electrode can be made independently of the choice of material of the second substrate part. This allows the difference of the work functions between first and second electrode to be increased.
In one embodiment the device furthermore comprises a third substrate part which features a first and a second surface, with the first and the second surface of the third substrate part facing away from each other. The first surface of the third substrate part is arranged on the second surface of the second substrate part. Embodied on the second surface of the first area of the second substrate part is a third electrode made from a material with a third work function. A fourth electrode made from a material with a fourth work function is embodied in a recess of the first surface of a first area of the third substrate part. The fourth work function is different from the third work function. The second area of the second substrate part is coupled to a second area of the third substrate part. The fourth electrode faces towards the third electrode and is spaced from the third electrode. The third electrode and the fourth electrode are connected electrically-conductively to each other via a second load circuit.
The first substrate part is preferably embodied from a second material, with the second material being selected from a group consisting of silicon and silicon oxide. The second substrate part preferably comprises a third material, with the third material able to be selected from a group consisting of silicon and silicon oxide. The third substrate part preferably comprises a fourth material, with the fourth material able to be selected from a group consisting of silicon and silicon oxide. The second electrode is preferably embodied from a fifth material, with the fifth material being selected from a group consisting of platinum, titanium and palladium. The third electrode preferably comprises a sixth material, with the sixth material being selected from a group consisting of platinum, titanium and palladium. The fourth electrode preferably comprises a seventh material, with the seventh material being selected from a group consisting of platinum, titanium and palladium.
The inventors further propose a device with the first electrode being arranged on a first area of a substrate and a first isolating layer being arranged between the first electrode and the substrate. The second electrode is arranged on a second area of the substrate and spaced from the substrate. The second electrode is coupled to the substrate via a flexible mechanical connection. The first electrode is rigidly connected to the substrate. The fact that the second electrode is connected via a flexible mechanical connection to the substrate enables an oscillating current to be impressed in a simple manner in the load circuit by imparting an oscillation to the device.
In one embodiment the device furthermore comprises a third electrode arranged on a third area of the substrate, which is embodied from a material with a third work function, with the third work function differing from the second work function and with a second isolating layer being arranged between the third electrode and the substrate. The second electrode and the third electrode are connected electrically-conductively to each other via a second load circuit. Preferably the first electrode and the third electrode are embodied from silicon. The second electrode preferably comprises a material which is selected from a group consisting of platinum, titanium and palladium.
These and other objects and advantages of the present invention will become more apparent and more readily appreciated from the following description of the preferred embodiments, taken in conjunction with the accompanying drawings of which:
Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout.
If a mechanical oscillation is now imparted to the external system with an oscillation frequency, the first electrode executes a mechanical movement with the oscillation frequency. Because of the flexible coupling of the second electrode 2 to the external system the second electrode 2, after a certain settling time, also executes a mechanical movement with the oscillation frequency. Depending on the strength of the flexible coupling the phase of the oscillation of the second electrode 2 is however displaced by a phase angle in relation to the oscillation of the first electrode 1. A result of the phase shift between the oscillation of the first electrode 1 and the oscillation of the second electrode 2 a change over time of the distance between first electrode 1 and second electrode 2 and thereby a change over time of the capacitance of the capacitor formed from first electrode 1 and second electrode 2 occurs.
Preferably the mass of the second electrode 2 and the coupling strength of the second electrode 2 to the external system are selected such that the inherent frequency of the system formed from second electrode 2 and the flexible coupling corresponds to the oscillation frequency imparted. This means that the change in distance between first 1 and second electrode 2 occurs periodically and the amount of current induced by the changes over time of the distance between first electrode 1 and second electrode 2 averaged over time is maximized. The external system can for example be a motor which vibrates and thus creates the mechanical movement with the oscillation frequency. The current occurring at the first load circuit 3 can also be fed to an accumulator or another form of storage for electrical energy. The voltage present at the load circuit 3 can be tapped off via a device for tapping off a voltage 4.
The arrangement is especially advantageous since the capacitor, through the different work functions of first electrode 1 and second electrode 2, features an integrated biasing voltage, with the application of charges to one of the two electrodes being omitted before the device for converting mechanical energy into electrical energy is put into service.
The second substrate part 6 features a cavity 7 between a first area of the second substrate part 6 and the second area of the second substrate part 6. The cavity 7 can for example be embodied by etching. The dimensions of the cavity 7, especially in the direction perpendicular to the first surface of the second substrate part 6 define the coupling strength between the first area of the second substrate part 6 and the second area of the second substrate part 6. But the dimension of the cavity 7 in the direction parallel to the first surface of the second substrate part 6 also has an influence on the coupling strength between the first area of the second substrate part 6 and the second area of the second substrate part If the dimension of the cavity 7 perpendicular to the first surface of the second substrate part 6 for example amounts to almost the thickness of the second substrate part 6, then the coupling strength between the first and the second area of the second substrate part 6 is small. The dimensions of the cavity 7 can be different in different areas between the first area and the second area of the second substrate part 6. For example first and second area of the second substrate part 6 can be not connected to one another in some areas of the second substrate part 6, or the first and second area of the second substrate part 6 can only be connected to each other in the vicinity of the first of the second surface of the second substrate part 6 respectively. As an alternative the first and second area of the second substrate part 6 can also only be connected through a material of the second substrate part 6 arranged between first and second surface of the second substrate part 6.
The first area of the second substrate part 6 represents a second electrode 2 of a capacitor which is formed by the first 1 and the second electrode 2. The first electrode 1 and the second electrode 2 are arranged in a perpendicular direction to the first surface of the second substrate part 6 spaced from each other, and the second electrode is formed from a material having a second work function which differs from the first work function. The first electrode and the second electrode are connected electrically-conductively to each other via a first load circuit.
Arranged on the second surface of the second substrate part 6 is a first surface of a third substrate part 9. Embodied in a first area of the first surface of the third substrate part 9 is a third electrode 8 made from a material which has a third work function which is different from the second work function. The second electrode 2 and the third electrode 8 form two electrodes of a second capacitor. The third electrode can for example contain platinum, titanium, palladium or another material. The third electrode 8 is arranged at a distance from the second electrode 2 in a direction perpendicular to the first surface of the third substrate part 9. A second area of the third substrate part 9 is coupled to the second area of the second substrate part 6, with the second area of the second substrate part 6 preferably being rigidly coupled to the second area of the third substrate part 9. The rigid coupling can be undertaken by a wafer bonding method for example. The second electrode and the third electrode are connected electrically-conductively to each other via a second load circuit 10.
If a mechanical oscillation is imparted to the overall system formed from the first 5, second 6 and third substrate part 9 with an oscillating frequency which has a component perpendicular to the first surface of the second substrate part 6, then the second electrode 2 after a certain settling phase as a consequence of the flexible coupling of the first area of the second substrate part 6 to the second area of the second substrate part 6 and as a consequence of the inertia of the mass of the second electrode 2, likewise executes a periodic movement with the oscillation frequency. Depending on the strength of the coupling between the first area and the second area of the second substrate part 6 the phase of the oscillation of the second electrode 2 is however displaced by a phase angle compared to the oscillation of the first electrode 1.
If the strength of the coupling between the first area and the second area of the second substrate part 6 and the mass of the first area of the second substrate part is selected such that the inherent frequency of the system formed from them corresponds to the oscillation frequency imparted to the overall system, the distance between second electrode 2 and first or third electrode 8 respectively changes periodically and induces a current flow between second 2 and first 1 or second 2 and third electrode respectively. The voltage present at the load circuit 3 can be tapped off via a first device for tapping off a voltage 4. The voltage present at the load circuit 10 can be tapped off via a second device for tapping off a voltage 19.
The second substrate part 6 features a cavity 7 between a first and the second area of the second substrate part 6. The cavity 7 can for example be embodied by etching.
A second electrode 2 is embodied in the first area of the first surface of the second substrate part 6. The first electrode 1 and the second electrode 2 represent the two electrodes of a first capacitor of the device.
The first electrode 1 and the second electrode 2 are arranged in a perpendicular direction to the first surface of the second substrate part 6 at a distance from each other, and the second electrode 2 is formed from a material having a second work function which differs from the first work function. The first electrode 1 and the second electrode 2 are connected electrically-conductively to each other via a first load circuit 3.
Embodied on the second surface of the second substrate part 6 in the first area is a third electrode 8 made from a material with a third work function.
A first surface of a third substrate part 9 is arranged on the second surface of the second substrate part 6.
In a recess of a first area of the first surface of the third substrate part 9 is a fourth electrode 12 embodied from a material, which has a fourth work function which differs from the third work function. The third electrode 8 and the fourth electrode 12 form two electrodes of a second capacitor of the device. The fourth electrode 12 is arranged at a distance from the third electrode 8 in a direction perpendicular to the first surface of the third substrate part 9. A second area of the third substrate part 9 is coupled to the second area of the second substrate part 6, with the second area of the second substrate part 6 preferably being rigidly coupled to the second area of the third substrate part 9. The rigid coupling can be undertaken by a wafer bonding method for example. The third electrode 8 and the fourth electrode are connected electrically-conductively to each other via a second load circuit 10.
First electrode 1, second electrode 2, third electrode 8 and fourth electrode 12 are preferably embodied from platinum, titanium or palladium.
A second electrode 2 is embodied on a second area of the substrate 13, with the second electrode 2 being arranged at a distance from the substrate 13 and a cavity (not shown in
A third electrode 8 is embodied on a third area of the substrate 13, with a second isolating layer 15 (not shown in
The first electrode 1 is embodied as a comb-like structure. Extending from the partial area of the first electrode 1 are teeth 20 in a first direction (y). Between the teeth 20 of the first electrode 1 and the substrate 13 is embodied a cavity (not shown in
The second electrode 2 has a double comb-shaped structure, with first teeth 18 extending from a partial area of the second electrode 2 along a second direction opposite to the first direction (y) and second teeth 25 extending from the partial area of the second electrode 2 in a first direction (y).
The teeth 20 of the first electrode 1 and the first teeth 18 of the second electrode 2 are arranged to intermesh and are spaced from each other.
The second electrode 2 is coupled via at least one flexible electrically-conductively connecting element 17 to the substrate 13. A first 17-1 and a second electrically-conductive flexible connecting element 17-2 are arranged in the vicinity of sides of the second electrode 2 facing away from each other. The first 17-1 and the second electrically-conductive flexible connecting element 17-2 are arranged spaced from the substrate and extend in the first direction (y).
Opposite ends 21-1, 21-2 of the first electrically-conductive, flexible connection element 17-1 are coupled to the substrate 13 by a first conductive structured layer 22 in a fourth area of the substrate 13 and spaced from the substrate 13 by a third isolating layer 16 (not shown in
Opposite ends 24-1, 24-2 of the second electrically-conductive, flexible connection element 17-2 are coupled to the substrate 13 by a second conductive structured layer 23 in a fifth area of the substrate 13 and spaced from the substrate 13 by a fourth isolating layer 11 (not shown in
The third electrode 8 is embodied as a comb-like structure, with teeth 26 of the third electrode 8 extending from the partial area of the third electrode 8 in the second direction. Between the teeth 26 of the third electrode 8 and the substrate 13 is embodied a cavity (not shown in
The first electrode 1 and the second electrode 2 are connected electrically-conductively to each other via a first load circuit 3. The second electrode 2 and the third electrode 8 are connected to each other electrically-conductively via a second load circuit 10. The first electrode 1 and the third electrode 8 are preferably embodied from silicon. The second electrode 2 preferably contains, platinum, titanium, palladium or another suitable electrode material.
If a mechanical oscillation is supplied to the system formed from substrate 13, first electrode 1, second electrode 2 and third electrode 8 with an oscillating frequency which features a component perpendicular to the first direction (y) and parallel to a surface of the substrate 13, the second electrode 2 after a certain settling time as a consequence of the flexible coupling 17 to the substrate 13 and as a consequence of the inertia of the mass of the second electrode 2, likewise carries out a periodic movement with the supplied oscillation frequency. Depending on the strength of the coupling between the second electrode 2 and the substrate 13 the phase of the oscillation of the second electrode 2 is shifted however by a phase angle in relation to the oscillation of the first electrode 1 and of the third electrode 8.
If the strength of the coupling between the second electrode 2 and the substrate 13 and the mass of the first area of the second substrate part is selected such that the inherent frequency of the system formed therefrom corresponds to the oscillating frequency supplied to the system, the distance between second electrode 2 and first 1, or third electrode 8 respectively changes periodically and induces a current flow between second 2 and first 1 or second 2 and third electrode 8 respectively. The voltage present at the first load circuit can be tapped off using a first device for tapping a voltage 4. The voltage present at the second load circuit 10 can be tapped off via a second device for tapping off a voltage 19.
The invention has been described in detail with particular reference to preferred embodiments thereof and examples, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention covered by the claims which may include the phrase “at least one of A, B and C” as an alternative expression that means one or more of A, B and C may be used, contrary to the holding in Superguide v. DIRECTV, 69 USPQ2d 1865 (Fed. Cir. 2004).
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2005-037-876.5 | Aug 2005 | DE | national |
This application is based on and hereby claims priority to German Application No. 10 2005 037 876.5 filed on Aug. 10, 2005 and PCT Application No. PCT/EP2006/064746 filed on Jul. 27, 2006, the contents of which are hereby incorporated by reference.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2006/064746 | 7/27/2006 | WO | 00 | 2/11/2008 |
