Inverse electrowetting energy harvesting and scavenging methods, circuits and systems

An inverse electrowetting harvesting and scavenging circuit includes a first substrate having first and second surfaces. An electrode is formed proximate the first surface and includes an insulating layer covering a surface of the electrode. An electromechanical systems device includes a moveable mass extending over the first surface of the first substrate that may be displaced relative to the first substrate in three dimensions responsive to external forces applied to the moveable mass. The movable mass includes a moveable electrode and a conductive fluid is positioned between the insulating layer of the electrode and the movable electrode. Energy harvesting and scavenging circuitry is electrically coupled to the moveable electrode and the other electrode and is configured to provide electrical energy responsive to electrical energy generated by the moveable electrode, conductive fluid and the electrode through the reverse electrowetting phenomena due to movement of the moveable electrode relative to the electrode and to the conductive fluid on top of the electrode.

BACKGROUND

Technical Field

The present disclosure relates generally to energy harvesting and scavenging, and more specifically to inverse electrowetting structures and methods for energy harvesting and scavenging.

Description of the Related Art

Energy harvesting and energy scavenging are processes by which electrical energy is derived from an external power source, such as solar power, thermal energy, wind energy, or kinetic energy (motion or vibrations). This electrical energy is captured and stored for use to power an electronic device. The energy source for energy harvesting and scavenging is present as an ambient or background source of energy and is inherently present and thus free, in contrast to large scale electrical power generation where an input fuel like natural gas, oil, coal, or water is used in power generation. The two terms energy harvesting and energy scavenging are many times used interchangeably but are typically distinguished by the nature of the energy source. Energy harvesting is most accurately applied to situations where the external energy source is well known and regularly present, whereas energy scavenging applies where the external energy source is not well known and may be irregular or intermittently present.

Electrowetting may be defined as the utilization of an applied electric field to modify the wetting properties of a surface of a solid material, where wetting is the ability of a liquid to maintain contact with the surface due to molecular interactions when the liquid and solid surface are brought together. Reverse or inverse electrowetting is a process by which the interface between the liquid and solid surface is changed due to movement of the liquid relative to the surface, and these interface changes are utilized to generate electrical energy. The terms electrowetting and reverse or inverse electrowetting, along with the physical phenomenon associated with each of these terms, will be understood by those skilled in the art and thus will not be described in detail herein.

While the inverse electrowetting phenomenon will not be described in detail, to facilitate a better understanding of the present disclosure the inverse electrowetting process will now be briefly described. In the reverse electrowetting process, the liquid is a conductive liquid and the interface is formed between a droplet of the liquid and an electrode that forms the solid surface, with an intermediate insulating layer between the liquid and the electrode. Multiple droplets and interfaces between these droplets and one or more electrodes would actually be utilized but only the interface between a single droplet and electrode is discussed herein by way of example to describe the generation of electrical energy through inverse electrowetting. Air or other gas (or gases) can fill the device, between the liquid (or fluid) and the electrode.

An electrical circuit provides a bias voltage between the droplet and the electrode. External mechanical or kinetic energy, typically in the form of movement of a user where the liquid and electrode are part of a structure contained in a portable electronic device, causes relative movement of the droplets over the surface of the electrode. This movement of the droplet results in a change in an overlap of the droplet with the surface of the electrode, which would typically be a dielectric-film-coated electrode. The change in overlap of the droplet and the surface of the electrode results in a decrease of a total charge that can be maintained at the liquid-solid (i.e., droplet-electrode) interface. As a result of this change in the total charge, extra electrical charge that can no longer be maintained at the droplet-electrode interface flows back through the electrical circuit that is connected to apply the bias voltage to the droplet and the electrode. This extra electrical charge flowing through the electrical circuit results in a current through the electrical circuit that can be used to power external electrical circuitry. In this way the inverse electrowetting process can be used in an energy harvesting and scavenging system.

Energy harvesting and scavenging are utilized to provide a very small amount of electrical energy that may be utilized to supply power to low-power electronic devices. The electronic device is typically a small, wireless device like those contained in portable electronic devices like smart phones or in wearable electronics such as a smart watch, an activity or fitness tracker, and so on. In such a wearable electronic device, a user wears the device and the mechanical or kinetic energy in the form of movement of the user may be harvested or scavenged to generate electrical energy. Inverse electrowetting may be utilized in such energy harvesting and scavenging systems but there is a need for improved techniques and structures that increase the amount of generated electrical energy from such inverse electrowetting systems.

BRIEF SUMMARY

One embodiment of the present disclosure is an inverse electrowetting harvesting and scavenging circuit that includes a first substrate having a first surface and a second surface. An electrode is formed proximate the first surface. An electromechanical systems device includes a moveable mass that extends over the first surface of the first substrate and may be displaced relative to the first substrate in three dimensions responsive to an external force applied to the moveable mass. The movable mass includes a moveable electrode and a conductive fluid or liquid positioned between the movable electrode and the other electrode, with the other electrode being coated with an insulating layer. Energy harvesting and scavenging circuitry is electrically coupled to the moveable electrode and the other electrode and is configured to provide electrical energy responsive to electrical energy generated by the moveable electrode, conductive fluid and the other electrode through the reverse electrowetting phenomena due to conductive fluid deformation caused by movement of the moveable electrode relative to the electrode. The electromechanical systems device may be a microelectromechanical systems (MEMS) device.

DETAILED DESCRIPTION

FIGS. 1A-1Care a simplified cross-sectional schematic diagrams of a reverse electrowetting energy harvesting and scavenging (EHS) device100that includes a moveable electrode102that is moveable relative to a second electrode and to a drop of a conductive fluid or liquid104on top of the second electrode to generate electrical energy through the phenomena of reverse electrowetting according to embodiments of the present disclosure. In operation, mechanical energy in the form of motion from an external source, such as from the movement of a person utilizing a portable electronic device containing the EHS device100, causes movement of the moveable electrode102relative to the fixed conductive liquid104. Most prior reverse electrowetting approaches utilize structures in which from the frame of reference of the electrodes the conductive liquid moves across the surfaces of the electrodes responsive to mechanical energy from an external source and the contact area of liquid and electrodes is changed due to relative motion. In contrast, in the EHS device100from the frame of reference of the moveable electrode102the moveable electrode moves in a vertical direction106as indicated by the arrow106responsive to mechanical energy from an external source and the contact area is changed due to a deformation of the liquid.

This approach to forming reverse electrowetting EHS devices enables the utilization of microelectromechanical systems (MEMS) structures containing moveable masses to form the moveable electrode102to enhance liquid deformation. In some embodiments, MEMS structures form the moveable electrode102that is movable in three-dimensions relative to the conductive liquid104, as will be described in more detail below. Reverse electrowetting EHS devices including such structures can increase the amount of electrical energy that can be harvested and scavenged through such devices while also allowing conventional semiconductor fabrication methods to be utilized in forming the devices, as will also be discussed in more detail below.

In the present description, certain details are set forth in conjunction with the described embodiments to provide a sufficient understanding of the present disclosure. One skilled in the art will appreciate, however, that embodiments of the disclosure may be practiced without these particular details. Furthermore, one skilled in the art will appreciate that the present disclosure is not limited to the example embodiments described herein, and will also understand that various modifications, equivalents, and combinations of the disclosed embodiments and components of such embodiments are within the scope of the present disclosure. Embodiments including fewer than all the components of any of the respective described embodiments may also be within the scope of the present disclosure although not expressly described in detail below. The operation of well-known components and/or processes has not been shown or described in detail below to avoid unnecessarily obscuring the present disclosure. Finally, components that are common among the described embodiments are given the same reference numbers or descriptors in the present application even though the detailed operation of such components may vary among embodiments.

Still referring toFIG. 1A, the reverse electrowetting EHS device100ofFIG. 1Afurther includes an electrode108having a dielectric layer110formed on an upper surface of the electrode. The drop of conductive liquid104sits on the surface of the dielectric layer110and covers a surface area S on the surface of this dielectric layer. Mechanical energy from an external source, such as from the movement of a user of a portable electronic device containing the EHS device, causes movement of the moveable electrode102, relative to the electrode108, in the vertical direction106in this simplified example. This movement of the moveable electrode102relative to the electrode108results in a change in the surface area S of the conducive liquid104on the surface of the dielectric layer110, as seen inFIG. 1B. Due to the downward movement of the electrode102, the conductive liquid104now has a surface area (S+ΔS) on the surface of the dielectric layer110. In the EHS device100, the moveable electrode102, conductive liquid104, dielectric layer110and electrode108effectively functions as a variable capacitance device, with the capacitance being a function of the surface area of the conductive liquid104on the dielectric film110. As a result of this change in capacitance, the voltage across the electrodes102,108changes as well and the resulting current harvested or scavenged to generate electrical energy. The voltage is shown as being V inFIG. 1Aand (V+ΔV) inFIG. 1B.FIG. 1Cshows a structure where the EHS device100further includes a second dielectric layer112formed on the surface of the moveable electrode102. This second dielectric layer112changes the effective capacitance and thus the voltage (V+ΔV′) across the electrodes102,108for the same surface area (S+ΔS) of the conductive liquid104on the surface of the dielectric layer110.

FIGS. 2A and 2Bare cross-sectional schematic diagrams of a reverse electrowetting EHS device200including a three-dimensional comb-like electrode202and an electrode206that are moveable one with respect to the other in three dimensions. A conductive fluid204on the electrode206is in contact with the three-dimensional comb-like electrode according to one embodiment of the present disclosure.FIG. 2Aillustrates movement of the electrode202relative to the electrode206along a Z-axis or in the Z direction as illustrated by arrow208relative to the conductive fluid204and the three-dimensional comb-like electrode202. The three-dimensional comb-like electrode202includes a horizontal plate210having an upper surface212and a lower surface214. A number of vertical projections216extend from the lower surface214of the horizontal plate210towards the electrode206and into the conductive fluid204. Only five vertical projections216are shown inFIGS. 2A and 2Bmerely by way of example and to simply the figures, with embodiments of the electrode202including any suitable number of such vertical projections. Embodiments of the EHS device200may include a much larger or lower number of such vertical projections216formed along the X- and Y-axes220,222on the lower surface214of the horizontal plate. A first dielectric film or layer218is formed over the lower surface214of the horizontal plate210and over the surfaces of the vertical projections216. In another embodiment, a second dielectric layer (not shown) is formed over the upper surface of the electrode206.FIG. 2Billustrates movement of the electrode202relative to the electrode206along the X-axis as illustrated by arrow220and along the Y-axis222, which is into and out of the page in the figure. The same structure shown for the interdigitated electrode202in the X direction can be designed in the Y direction in a two-dimensional (2D) segmented structure (not shown inFIGS. 2A and 2B). The horizontal plate210and vertical projections216of the electrode202and the other electrode206are formed from a suitable material, such as Silicon with at least one metal electrode created on top (not shown).

In operation, a bias voltage source (not shown) supplies a DC bias voltage across the electrodes202and206while an electronic device containing the EHS device200receives mechanical energy in the form of motion from an external source, such as in the form of movement of a person utilizing the portable electronic device. This mechanical energy results in the electrode202moving relative to the conductive fluid204and the electrode206. This is illustrated inFIG. 2Awith the conductive liquid204having the illustrated shape and overlap with the interdigitated electrode202moving relative to the electrode206in the Z-direction208, while inFIG. 2Bthe conductive liquid has the illustrated shape due to movement of the electrode202relative to electrode206in the X- and Y-directions220,222. This change in area or overlap is seen betweenFIGS. 2A and 2B. For example, the conductive liquid204overlaps or covers a portion of the surface of the far left vertical projection216inFIG. 2Aand does not overlap this vertical projection inFIG. 2B. The change in overlap of the conductive liquid204with the four remaining vertical projections204to the right is seen betweenFIGS. 2A and 2Bas well. This change in area or overlap of the conductive liquid204on the surface of the dielectric layer218results in a change in capacitance of the EHS device200and a resulting flow of charge that generates a harvested and scavenged voltage VHARV across the electrodes202,206through the reverse electrowetting phenomena as described above. The generated VHARV voltage may then be utilized to power circuitry (not shown) of the electronic device containing the EHS device200.

FIG. 3Ais a cross-sectional schematic diagram of an EHS device300including an interdigitated electrode structure302for generating dual voltages VHARV1, −VHARV2relative to a voltage reference node VREF according to another embodiment of the present disclosure. The interdigitated electrode structure302includes a three-dimensional comb-like movable electrode304that is moveable in three dimensions relative to a conductive fluid306on a segmented electrode308according to one embodiment of the present disclosure. The three-dimensional comb-like movable electrode304is moveable along X-, Y- and Z-axes as shown in the lower left of the figure and has a structure that is the same as or similar to the electrode202ofFIGS. 2A and 2Bin the embodiment ofFIG. 3A. Accordingly, the movable electrode304includes a horizontal plate310having an upper surface312and a lower surface314. A number of vertical projections316extend from the lower surface314and the lower surface and vertical projections are covered by a first dielectric layer318.

The vertical projections316extend into the conductive fluid306and towards the segmented electrode308. The segmented electrode308includes a plurality of electrode segments320, one of which is shown in and will be described in more detail with reference toFIGS. 3A and 3B. Each electrode segment320includes a vertical projection portion322that extends upward towards the moveable electrode304as seen inFIG. 3A. The vertical projection portions322are interdigitated with the vertical projections316of the moveable electrode304. Thus, each vertical projection portion322is positioned between adjacent vertical projections316of the moveable electrode304. Each vertical projection322is formed by first and second L-shaped electrodes324and326with a vertical dielectric layer328positioned between the vertical-portions of the L-shaped electrodes to electrically isolate the two L-shaped electrodes. A second dielectric layer330is formed over an upper surface of each electrode segment320, and is thus formed over upper surfaces of the L-shaped electrodes and an upper edge surface of the vertical dielectric layer328. On the ends of each of the horizontal portions of each L-shaped electrode324,326a vertical dielectric layer332is formed to electrically isolate each of the L-shaped electrodes from the L-shaped electrode (not shown inFIG. 3B) of the adjacent electrode segment320.

In operation, responsive to movement of the moveable electrode304in three dimensions along the X-, Y- and Z-axes relative to the conductive fluid306on the electrode segments320, the EHS device300generates the first dual voltage VHARV1on the L-shaped electrodes324and the second dual voltage −VHARV2on the L-shaped electrodes326. Note that in this embodiment, the voltage −VHARV2is negative relative to the voltage on the reference voltage node VREF while the voltage VHARV is positive relative to the voltage on the reference voltage node. The reference voltage node VREF is coupled to ground GND in one embodiment of the EHS device300.

FIG. 4is a cross-sectional schematic diagram of an EHS device400including another interdigitated electrode structure402for generating dual isolated voltages VHARV1, VHARV2according to yet another embodiment of the present disclosure. Each voltage VHARV1, VHARV2is isolated in that each voltage has an independent voltage reference node VREF1, VREF2instead of the common reference voltage node VREF as in the EHS device300ofFIGS. 3A and 3B. In the EHS device400components406-432correspond to the components306-332previously described with reference toFIGS. 3A and 3Band thus will not again be described in detail with reference toFIG. 4.

The difference between the EHS device400and the EHS device300ofFIGS. 3A and 3Bis that the EHS device400includes a moveable electrode404that also has a segmented structure as described for the segmented electrode308ofFIGS. 3A and 3B. Thus, in the EHS device400both the moveable electrode404and the electrode408have a segmented structure. In the embodiment ofFIG. 4, the structure of each of the moveable electrode404and the electrode408has the same segmented structure as for the electrode308ofFIGS. 3A and 3B. Thus, each of the electrode segments for the electrodes404and408has the same structure as the electrode segment320shown inFIG. 3B. Other embodiments of the EHS device400include different segmented electrode structures for one or both the electrodes404and408. In operation, responsive to movement of the moveable electrode404in three dimensions along the X-, Y- and Z-axes relative to the conductive fluid406on the electrode408, the EHS device400generates a first isolated voltage VHARV1relative to the first reference voltage node VREF1and a second isolated voltage VHARV2relative to the second reference voltage node VREF2. Voltage signals VHARV1and VHARV2, for example, may be managed independently to improve the generation efficiency.

FIG. 5is a cross-sectional schematic diagram of an EHS device500including yet another electrode structure502having vertical projections on a lower one of the electrodes that function to confine conductive fluid503on this lower electrode between adjacent vertical projections according to a still further embodiment of the present disclosure. The electrode structure502includes an electrode504having a structure similar to the structure of the electrode202ofFIGS. 2A and 2B. The electrode structure502further includes an electrode506having a horizontal plate508with an upper surface510and fluid confinement projections512formed spaced apart on the upper surface of the horizontal plate. A dielectric layer513covers each of the fluid confinement projections512. The fluid confinement projections512function both as stoppers to prevent electrodes from crashing one against the other and to contain or confine a particular volume of conductive liquid503between adjacent fluid confinement projections512. Thus, in the embodiment ofFIG. 5the conductive fluid503on the left is confined between the leftmost fluid confinement projection512and the middle fluid confinement projection while the conductive fluid on the right is confined between the middle fluid confinement projection and the rightmost fluid confinement projection.

The electrode504has a structure similar to the structure of the electrode202ofFIGS. 2A and 2Bas mentioned above. Thus, the electrode504includes a horizontal plate514with vertical projections516extending from a lower surface of the horizontal plate and a dielectric layer518covering the vertical projections and portions of the horizontal plate. The vertical projections516are arranged spaced apart on the horizontal plate514so that they extend between adjacent fluid confinement projections512and into the conductive fluid503confined between such adjacent fluid confinement projections. In operation, responsive to movement of the electrode504relative to the electrode506in three dimensions along the X-, Y- and Z-axes and relative to the conductive fluid503on the electrode506, the EHS device500generates a voltage VHARV (not shown inFIG. 5) across the electrodes504and506. The electrodes504and506can have different structures, similar to what previously described forFIG. 3AandFIG. 4.

FIG. 6is a cross-sectional schematic diagram of a reverse electrowetting EHS device600including a microelectromechanical systems (MEMS) device602and a first semiconductor chip604according to one embodiment of the present disclosure. The MEMS device602includes the moveable electrode portion of the EHS device600, such as in the EHS devices100-500described above with reference toFIGS. 1-5, while the other electrode portion of the EHS device is formed in the first semiconductor chip604. The MEMS device602includes a moveable mass606that forms the moveable electrode portion of the EHS device600. The moveable mass606include a support layer608on which a moveable electrode610is formed. The moveable electrode610has the structure of any of the moveable electrodes of the EHS devices100-500described above with reference toFIGS. 1-5. The moveable electrode610is formed from a suitable conductive material and may include a suitable dielectric layer or layers as part of the moveable electrode, such as in the embodiments ofFIG. 1CandFIGS. 2-5.

The first semiconductor chip604may be, for example, an application specific integrated circuit (ASIC) or a system-on-a-chip (SOC) type integrated circuit or chip. The chip604includes a substrate612made of semiconductor material such as silicon, for example. The substrate612has a first face612aand an opposite second face612b. Formed on the first face612aof the substrate612is a structural layer614, and may be made of dielectric on the first face612aof the substrate. The structural layer614includes an upper surface614aon which bonding pads615are formed to provide for the electrical connection of the EHS device600to external circuitry (not shown). Inside the structural layer614may be present at least a level of conductive traces along with required dielectric layers to form an electrode616of the EHS device600. In the illustrated embodiment, the electrode616includes a number of individual electrode segments618formed in the structural layer614.

The specific structure of the individual electrode segments618varies in different embodiments of the EHS device600, and could correspond to the structures for the electrodes described for the EHS devices100-500ofFIGS. 1-5. In the embodiment ofFIG. 6, each of the electrode segments618is a conductive plate. In other embodiments, each electrode segment618includes a conductive portion along with a suitable dielectric layer or layers as part of the electrode segment, as in the embodiments ofFIGS. 1-5. A volume of conductive fluid620is then placed on each of the electrode segments618such that the conductive fluid is positioned between the electrode segments and the moveable electrode610. Although the electrode616is formed in the structural layer614in the embodiment ofFIG. 6, in other embodiments the electrode may be formed in the substrate612, or in both the substrate and the structural layer.

The EHS device600further includes energy harvesting and scavenging (EHS) circuitry622formed in the substrate612or, alternatively, in the structural layer614, or in both the substrate and structural layer. The EHS circuitry622could also be formed in neither the substrate612nor the structural layer614, but instead may be formed external to the chip604and be electrically coupled to the chip. In the embodiment ofFIG. 6, the EHS circuitry622is electrically coupled to each of the electrode segments618forming the electrode616. The EHS circuitry622is also electrically coupled to the moveable electrode610. In operation, the EHS circuitry622supplies a DC bias voltage across the moveable electrode610and electrode616and captures electrical generated responsive to mechanical energy causing three-dimensional motion of the moveable mass606and thereby the moveable electrode relative to the conductive liquid620and electrode616, as will be described in more detail below.

The MEMS device602includes a packaging structure624that is set directly on the top surface614aof the structural layer614in the embodiment ofFIG. 6. Alternatively, the MEMS device602can be set facing the top surface614aof the structural layer614but separated from the structural layer by means of one or more coupling layers, for example a layer of adhesive material (not shown). In this way, the packaging structure624of the MEMS device602is fixed with respect to the first semiconductor chip604. The packaging structure624defines an internal cavity626of the MEMS device602where the internal cavity houses the moveable mass606that is suspended within the internal cavity by means of a supporting structure628.

The supporting structure628suspends the moveable mass606within the internal cavity626such that the moveable mass is mobile or capable of moving in three dimensions. This three-dimensional movement of the moveable mass606is represented through X, Y and Z axes shown in upper center portion ofFIG. 6. In other embodiments the moveable mass606is moveable in fewer than three dimensions, but three-dimensional movement of the moveable mass is preferable since this should result in a larger capture of electrical energy responsive to movement of the moveable mass, as will be appreciated by those skilled in the art. The packaging structure624and the supporting structure628may be made of semiconductor material such as silicon in the embodiment ofFIG. 6, but in general the packaging structure and the supporting structure as well as the support layer608of the moveable mass606may be made of materials other than a semiconductor material. A suitable material would be selected, at least in part, on the basis of desired characteristics of flexibility and strength of the material for use in formation of the packaging structure624, the supporting structure628and possibly the support layer608as well.

In the embodiment ofFIG. 6the MEMS device602is positioned on the semiconductor chip604, but the MEMS device may be mounted to or attached to other devices as well. Instead of the chip604, for example, the MEMS device602could be positioned on a substrate, in which for example the electrode616may be created, such as the substrate612made of a semiconductor material or a substrate made of another material, for example ceramic, glass or a printed circuit board (PCB) material that may be rigid or flexible. In such an embodiment, the EHS circuitry622could be formed in the substrate612or external to the substrate. In addition, although the embodiment ofFIG. 6includes the MEMS device602, other electromechanical systems (EMS) devices could be utilized in the EHS device600in place of the MEMS device602in other embodiments of the present disclosure. Such an EMS device could be a discrete system formed from discrete components or parts also created using different materials and assembled together, as opposed to the MEMS device602formed in a semiconductor substrate using semiconductor device fabrication technologies, as will be appreciated by those skilled in the art.

In operation of the EHS device600, external forces produce stresses that cause movement of the moveable mass606relative to the chip604and thereby relative to the conductive liquid620and the electrode segments618. The movement of the moveable mass606and thereby the moveable electrode610cause a change in surface overlap of the conductive liquid620on the moveable electrode, generating electrical energy across the moveable electrode and the electrode616through the reverse electrowetting phenomena as previously described.

FIG. 6Ais a functional diagram illustrating in more detail the operation of the EHS device600ofFIG. 6. External forces applied to an electronic device including the EHS device600result in movement of the moveable mass606relative to the electrode616and conductive liquid620. This movement of the moveable mass606can occur in three dimensions, namely along and X axis, Y axis, and Z axis as previously mentioned and as once again represented through these three axes shown in the upper left portion ofFIG. 6A. This movement of the moveable mass606results in changes in the overlap of the area of the conductive liquid620on the moveable mass (i.e., on the moveable electrode610) to thereby generate a harvested and scavenged voltage current IHARV and voltage VHARV across the moveable mass (i.e., moveable electrode610) and the electrode616through the reverse electrowetting phenomena.

The EHS circuitry622may include an AC/DC converter630having a first terminal630acoupled to the moveable mass606(i.e., the moveable electrode610) and a second terminal630bcoupled to the electrode616. The movement of the moveable mass606generates the current IHARV and voltage VHARV which vary as a function of time due to the movement of the moveable mass relative to the conductive fluid620. The AC/DC converter630converts this time varying current IHARV and voltage VHARV into a DC output voltage VOUT and current IOUT that can then be used to provide power to an electrical load632. Thus, the AC/DC converter630contained in the EHS circuitry622generates the DC output voltage Vout and DC output current Iout from the time varying voltage VHARV and current IHARV. The electrical load632may be contained in the first semiconductor chip604as shown inFIG. 6Aor may be external to the chip, and for example it may be another electronic system or an energy storage device like a battery or a super-capacitor. One skilled in the art will understand various suitable circuits that may be utilized for forming the AC/DC converter630. For example, the AC/DC converter630may include rectification circuitry that rectifies the time varying or AC voltage and current VHARV, IHARV to generate a rectified voltage that is then applied to a capacitive circuit to filter this rectified voltage and store electrical energy to thereby provide the output voltage Vout and current Iout from the AC/DC converter. The term “AC” is used to indicate a signal or quantity that is alternating or varying over time while the term “DC” is used to indicate a signal or quantity that is relatively constant over time, as will be appreciated by those skilled in the art. Thus, the time varying voltage and current VHARV, IHARV are AC signals while the output voltage Vout and current Iout are DC signals.

FIG. 6Bis a functional and schematic diagram illustrating another embodiment of the EHS circuitry622and MEMS device602ofFIG. 6in which two reverse electrowetting structures634aand634bare coupled in series. In this embodiment, the movable mass606includes two moveable electrodes610, each moveable electrode operable with a corresponding electrode616. Each electrode616would be formed from a group of electrode segments618formed in or on the structural layer614of the first semiconductor chip604. The electrode616of the reverse electrowetting structure634ais coupled to the moveable electrode610of the reverse electrowetting structure634b. The AC/DC converter630is contained in the EHS circuitry622and the terminal630ais coupled to the moveable electrode610of the structure634awhile the terminal630bis coupled to the electrode616of the structure634b. Once again, movement of the movable masses610in the structures634aand634bresults in generation of the time varying voltage VHARV and current IHARV are generated responsive to the movement and the based on the reverse electrowetting phenomena. The AC/DC converter602once again generates a DC output voltage Vout and a DC output current Iout from the time varying or AC voltage VHARV and current IHARV from the structures634aand634band supplies this output voltage and current to drive the electrical load632.

FIG. 6Cis a functional and schematic diagram illustrating another embodiment of the EHS device600ofFIG. 6including independent reverse electrowetting structures634a,634bfor generating dual independent voltages VHARV1, VHARV2and currents IHARV1, IHARV2. The first reverse electrowetting structure634aincludes a movable mass610coupled to terminal630aof a first AC/DC converter630acontained in the EHS circuitry622. The AC/DC converter630agenerates a DC output voltage Vout1and current Iout1that drive a first electrical load632a. Similarly, the second reverse electrowetting structure634bincludes a moveable mass610coupled to terminal630cof a second AC/DC converter630bthat generates a DC output voltage Vout2and current Iout2that drive a second electrical load632b. In a variation (not shown), the reverse electrowetting structures634aand634bmay be coupled in parallel to a single AC/DC converter630. In another variation (not shown), the AC/DC converters630a,630bmay be coupled in series or in parallel to a single electrical load632. The reverse electrowetting structures634aand634bare formed in one embodiment by the moveable electrode404and electrode408in the embodiment ofFIG. 4.

FIG. 7is a top view showing in more detail the supporting structure628of the moveable mass606in the MEMS device602ofFIG. 6according to one embodiment of the present disclosure. The top view ofFIG. 7shows components contained within the internal cavity626of the MEMS device602with the top portion of the packaging structure624removed to expose the internal cavity. In the embodiment ofFIG. 7, the supporting structure628has four springs or balancers or arms700a-700d. Each arm700a-700dhas a first end702a-702dcoupled to a respective wall704of the packaging structure624(that is a frame in the section here shown inFIG. 7), where the walls704along with the top (not shown) form the internal cavity626of the MEMS device602. Each arm700a-700dfurther includes a second end706a-706dcoupled to the moveable mass606. More specifically, although not expressly shown inFIG. 7, the second ends706a-706dare coupled to the support layer608of the moveable mass606. The bonding pads615are also shown inFIG. 7although only selected ones of these bonding pads are labeled with reference number615merely to simplify the figure.

In the embodiment ofFIG. 7, the moveable mass606is a plate having a square shape but in other embodiments different shapes may be utilized. Obviously the shape of supporting structure628depends on the shape of moveable mass606. The respective first ends702aand702bof the arms300aand300bare coupled to the same wall704of the packaging structure624. Likewise, the respective first ends702cand702dof the arms700cand700dare coupled to the same wall704of the packaging structure624, where this wall is diametrically opposite to the704to which the first ends702a,702bof the arms700a,700bare coupled. Thus, the first ends702a,702bof the arms700aand700bare coupled to the wall704on the left ofFIG. 7and the first ends702c,702dof the arms700cand700dare coupled to the wall704on the right ofFIG. 7. The respective second ends706aand706dof the arms700aand700dare coupled to the same side of the moveable mass606, which is the top side inFIG. 7. The respective second ends706band706cof the arms700band700care coupled to the same side of the moveable mass706, which is the bottom side of the moveable mass606. Thus, the second ends706aand706dare coupled to a side of the moveable mass606that is diametrically opposite to the side of the moveable mass to which the second ends706band706care coupled.

Each arm700a-700dfurther includes between the corresponding first ends702a-702dand second ends706a-706drespective first arm portions708a-708dand second arm portions710a-710dhaving preferred directions of extension orthogonal to one another. With reference to the axes represented in the lower left portion ofFIG. 7, each of the first arm portions708a-708dhas a preferred direction of extension along the Y axis while the second arm portions710a-710deach has a preferred direction of extension along the X axis.

In operation, when the moveable mass606is subjected to an external force, bending or stretching of angles between the various portions708,710and ends702,706of the arms700occurs based upon the direction and orientation of the external force applied to the moveable mass. For example, in the case of a Y-directed force with an orientation from bottom to top inFIG. 7, such as due to inertial reaction to the force of gravity along the Y axis applied to the EHS device600, then the angles formed by second end706band second arm portion710band the second end706cand second arm portion710care stretched due to the external force. Conversely, in this situation the angles formed by the first arm portion708band the second arm portion710band the first arm portion708band the first end702bare bent. The same is true for the angles formed by the first arm portion708cand the second arm portion710cand the first arm portion708cand the first end702c, namely these angles are bent in this situation.

In a similar way, if the moveable mass606is subjected to an external force acting along the X axis, the moveable mass606is set in motion along the X axis through the supporting structure628in a manner similar to that just described for a Y-directed force. The supporting structure628also allows movement of the moveable mass606along the Z axis in an analogous manner. The same is true for external forces having components along multiple axes at the same time, such as along both the X axis and along the Y axis, for example, with the supporting structure628allowing movement of the moveable mass606responsive to the external force.

The arms700a-700dand the moveable mass606may be produced in the same etching step during manufacturing of the MEMS device602. More specifically, the arms700a-700dand the support layer608may be formed through the same etching step. In this case, the support layer608of the moveable mass606and the arms700a-700dare made of the same material, and no discontinuities are present between the support layer and the arms. The moveable mass606includes the moveable electrode610attached to the support layer608. The moveable electrode610has a suitable structure as previously discussed, and may be formed on or attached to the support layer608through any suitable techniques, as will be appreciated by those skilled in the art.

FIG. 8is a top view of a reverse electrowetting EHS device800that provides compensation for planarity errors between a moveable mass of a MEMS device802and electrode segments of a semiconductor chip804according to a further embodiment of the present disclosure. Components of the EHS device600ofFIGS. 6 and 7that are the same as or similar to corresponding components in the EHS device800have been given the same reference numbers and will not again be described in detail with reference toFIG. 8.

In the embodiment ofFIG. 8, instead of the first ends702a-dof the arms700a-dbeing coupled to a respective wall704of the packaging structure624(FIG. 6), the MEMS device802includes an additional frame801positioned between the first ends and the corresponding wall of the packaging structure. The first ends702a-dof the arms700a-dare coupled to a corresponding wall of the additional frame801and the additional frame is, in turn, coupled through resilient arms or springs803to the walls704of the packaging structure624. This structure allows for capacitive fine tuning or planarity error compensation of the EHS device800, as will now be described in more detail with regard toFIGS. 9A and 9B.

FIGS. 9A and 9Bare cross-sectional views of the EHS device800ofFIG. 8showing how the springs803coupled between the additional frame801and the packaging structure624along with vertical spacers900allow for the compensation of planarity errors between the moveable mass606and the electrode plates618of the electrode616formed in the first semiconductor chip804. InFIG. 9A, the MEMS device802is shown above the semiconductor chip804prior to being bonded or attached to the chip. The moveable mass606is ideally parallel to the upper surface614aof the structural layer614of the chip804so that the moveable electrode610is the same distance from each of the electrode segments618of the electrode616.

When bonding the MEMS device802to the upper surface614aof the structural layer614of the chip804, the MEMS device may be attached such that the moveable mass606may be no longer parallel to upper surface614a. This is illustrated inFIG. 9B, where more of an adhesive material902used to attach the MEMS device802to the chip804(or eventual other root causes of missed planarity) is present on the right hand side of the EHS device800as shown. As a result, if no additional frame801(FIG. 8), springs803and vertical spacers900were present, the moveable electrode610on the movable mass606would not be parallel to the upper surface614a. This would result in different portions of the moveable electrode610being different distances from the electrode segments618, which is undesirable, because it introduces a difference in performance among several EHS devices800due to the assembly process. Instead, as seen inFIG. 9Bthe frame801, springs803and vertical spacers900maintain the moveable mass606parallel to the surface614aeven in the presence of the uneven adhesive material902that resulted when the MEMS device802is attached to chip804. This is true because the additional frame801and vertical spacers900position the moveable mass606properly while the springs803flex as required to allow for variations in the ideal position of the packaging structure624resulting (as an example) from the process of attaching the MEMS device802to the chip804.

Vertical spacers900may be used to electrically couple the moveable mass606and the moveable electrode610with the chip804for example by means of pads (not shown) on upper surface614a. Moreover, using these pads and vertical spacers900it may be possible also to test electrically the correct alignment of the moveable mass606and the chip804for example using a current that can flow from a first one of the vertical spacers900(e.g., the vertical spacer on the left inFIG. 9B) and a second one of the vertical spacers900(e.g., the vertical spacer on the right inFIG. 9B).

FIG. 10is a top view of a reverse electrowetting EHS device1000including a MEMS device1002and semiconductor chip1004where the MEMS device includes multiple moveable masses1006a-daccording to yet another embodiment of the present disclosure. In the EHS device1000multiple energy harvesting and scavenging structures are replicated in order to increase the amount of electrical energy harvested and/or scavenged by the EHS device. The inclusion of multiple energy harvesting and scavenging structures increases the energy simply by having more such structures generating energy and may increase captured energy by selectively capturing energy based on the spatial and frequency characteristics of the mechanical energy that causes movement of the moveable masses by increasing the efficiency of EHS device1000, as will be explained in more detail below with reference toFIG. 11.

The MEMS1002includes a frame1008having walls that form four internal cavities1010a-d, each internal cavity housing a corresponding movable mass1006a-d. Each movable mass1006a-dis coupled to corresponding walls of the frame1008through a respective supporting structure1012a-d. The specific structure of the support structures1012a-dand of the moveable masses1006a-d, as well as the structure of the corresponding electrode structure (not shown inFIG. 10) for each moveable mass that is formed in the chip1004, may vary in different embodiments of the EHS device1000. For example, in one embodiment each moveable mass1006a-dhas the same structure as the moveable mass606ofFIGS. 6 and 7while the supporting structures1012a-dhave the same structure as the supporting structure628ofFIGS. 6 and 7. In this embodiment, the structure of the electrode (not shown) corresponding to each moveable mass1006a-dis the same as the electrode616(or electrode segments618forming the electrode616) ofFIGS. 6 and 7. In other embodiments, the structure of the moveable mass1006a, supporting structure1012a-dand electrode may have any suitable structure, such as structures for these components as previously described for the embodiments ofFIGS. 1-9.

FIG. 11is a functional and schematic diagram of an intelligent reverse electrowetting EHS device1100including a motion sensor1102and intelligent power generation management circuitry1104according to yet another embodiment of the present disclosure. The intelligent EHS device1100includes an EHS electrode array1106, which is represented in the figure through an array of squares, each square in the array representing an individual electrode structure or a portion of such electrode structure. A movable mass structure1108includes one or more moveable masses that are not expressly shown inFIG. 11, with each of these moveable masses being positioned relative to a corresponding individual electrode structure in the electrode array1106.

The motion sensor1102generates a signal responsive to movement of the moveable mass or masses in the moveable mass structure1108. A motion sensor circuit1110senses the signal generated by the motion sensor1102and processes this signal to detect the direction of movement of the moveable mass or masses in the moveable mass structure1108. The motion sensor1102can be a separate component, such as an accelerometer or gyroscope, which is suitable attached to moveable mass structure1108to detect the direction of movement. Alternatively, the motion sensor1102can be formed from a portion of the electrode array1106and moveable mass structure1108. Such an embodiment is illustrated inFIG. 11. In this sample embodiment of the motion sensor1102, the motion sensor includes a single moveable mass, such as the moveable mass602ofFIG. 6-8 or 1006ofFIG. 10. The motion sensor1102also includes a number of electrode segments, such as the electrode segments618ofFIGS. 6-8. In this embodiment the motion sensor1102is formed by the moveable mass602and several electrode segments618, which means that this moveable mass and electrode segments are not utilized in capturing electrical energy but instead are used to form the motion sensor. Other embodiments of the motion sensor1102are of course possible, for example increasing the number of moveable masses and increasing or decreasing the number of electrode segments. In another embodiment, not shown, the moveable mass606and electrode segments618could be formed in the corners of EHS electrode array1106to increase sensitivity of the motion sensor1102.

The voltage generated across each electrode segment618and the moveable mass606will vary as a function of the direction of movement of the moveable mass relative to the electrode segments. The motion sensor circuit1110processes these voltages generated across respective electrode segments618and the movable mass606to detect the direction of movement of the moveable mass, as will be appreciated by those skilled in the art. Note that the moveable mass606may also include multiple segments, such as where the moveable mass606has the structure of the moveable mass404ofFIG. 4, or multiple liquid drops deposited on the electrodes.

In operation, the motion sensor circuit1110senses the signal generated by the motion sensor1102to detect the direction of movement of the moveable mass structure1108. The motion sensor circuit1110provides the detected direction of movement of the movable mass structure1108to the power generation management circuitry1104. Utilizing the detected direction of movement of the movable mass structure1108, the power generation management circuitry1104then controls a plurality of EHS circuits EHS1-EHSN that are coupled to the electrode array1106and moveable mass structure1108to capture electrical energy from selected electrodes and moveable masses in the array1106and moveable mass structure1108. Each of the EHS circuits EHS1-EHSN corresponds to the EHS circuit622ofFIG. 6in one embodiment, as will be discussed in more detail below with reference toFIG. 12.

In this way, the intelligent EHS device1100may optimize or improve the power generation of the device by harvesting or scavenging energy from electrodes or electrode segments that are generating the most electrical energy due to the direction of movement of the movable mass structure1108. The power generation management circuitry1104may in this way decide the best combination or coupling of the outputs from selected electrodes or electrode segments and inputs-outputs of selected EHS circuits EHS1-EHSN that will maximize the generated electrical energy in agreement with the direction of movement of the movable mass1108contained thereon relative to the EHS array1106.

FIG. 12is a cross-sectional schematic diagram of a Floating gate Avalanche MOS (metal-oxide-semiconductor) (FAMOS) transistor1200that may be utilized for voltage biasing in the reverse electrowetting EHS devices ofFIGS. 1-11according to another embodiment of the present disclosure. The FAMOS transistor1200is formed in a substrate1202and includes a drain region1204and source region1206formed in the substrate. A dielectric layer1208is formed on the substrate1202with an extended floating gate1210formed in the dielectric layer and a gate electrode1212formed on the dielectric layer. In operation or during a manufacturing process, a voltage bias is applied by injecting electrical charge into the Extended Floating Gate1210of the FAMOS1200, or into a Floating Gate of a standard FAMOS, connected to a capacitor plate (not shown). This increases energy harvesting efficiency as expected from reverse electrowetting physics, improving electrostatic induction due to injected electrical charges into the Extended Floating Gate. Multiple FAMOS transistors with common Floating Gates can speed up charging.

FIG. 13is a functional block diagram of an electronic device1300including a reverse electrowetting EHS device1302according to any of the previously described embodiments ofFIGS. 1-12. The electronic device1300in the example embodiment ofFIG. 13includes processing circuitry1304that controls the overall operation of the electronic device1300and also executes applications or “apps”1306that provide specific functionality for a user of the electronic device1300. In operation, the reverse electrowetting EHS device1302generates electrical energy in response to movement of the electronic device1300. The reverse electrowetting EHS device1302supplies this electrical energy, represented in the figure as an output voltage Vout from the reverse electrowetting EHS device1302, to power the processing circuitry1304and other components in the electronic device1300. The electronic device1300may be any type of electronic device, such as a smart phone, wearable electronic device like a heart rate or activity monitor, tablet computer, and so on. Depending on the type of electronic device1300, the reverse electrowetting EHS device2302may generate enough electrical energy to fully power the electronic device or only enough to drive some of the electronic circuitry in the device, or enough to charge or help charge a battery of the electronic device.

A power management subsystem1308of the electronic device1300is coupled to the processing circuitry1304and would typically include a battery for powering the electronic device, and also control circuitry for controlling power-related operating modes of the device such as charging of the battery, power-savings modes, and so on. As mentioned above, the electrical energy generated by the reverse electrowetting EHS device1302may be used to charge such a battery contained in the power management subsystem1308. The power management subsystem1308may also control operation of the reverse electrowetting EHS device1302, such as by activating and deactivating the EHS circuitry (not shown) contained in the EHS device. Although shown separately inFIG. 13, the reverse electrowetting EHS device1302may be considered part of the power management subsystem1308.

The electronic device1300further includes a video component such as a touch screen1310with a touch display (not shown) such as a liquid crystal display (LCD) and a touch panel (not shown) attached to or formed as an integral part of the touch display. In operation, the touch screen1310senses touches of a user of the electronic device1300and provides sensed touch information to the processing circuitry1304to thereby allow the user to interface with and control the operation of the electronic device. The processing circuitry1304also controls the touch screen1310to display desired visual content on the touch display portion of the touch screen. The action to touch the screen1310is also a mechanical stimulation that may be utilized in generating electrical energy by the reverse electrowetting EHS device1302.

The electronic device1300further includes data storage or memory1312coupled to the processing circuitry1304for storing and retrieving data including the apps1306and other software executing on the processing circuitry and utilized by the electronic device1300during operation. Examples of typical types of memory1312include solid state memory such as DRAM, SRAM and FLASH, solid state drives (SSDs), and may include any other type of memory suited to the desired functionality of the electronic device1300including digital video disks (DVDs), compact disk read-only (CD-ROMs), compact disk read-write (CD-RW) memories, magnetic tape, hard and floppy magnetic disks, tape cassettes, and so on.

Input devices1314are coupled to the processing circuitry1304and may include a keypad, whether implemented through the touch screen1310or separately, a pressure sensor, accelerometer, microphone, keyboard, mouse, digital camera to capture still and video images, and other suitable input devices. Output devices1316are coupled to the processing circuitry1304and may include, for example, audio output devices such as a speaker, printer, vibration device, and so on. The input devices1314and output devices1316collectively may include other types of typical communications ports for the electronic device1300, such as USB ports, HDMI ports, and so on. The electronic device1300further includes communications subsystems1318coupled to the processing circuitry1304and which may include Wi-Fi, GPS, cellular and Bluetooth subsystems for providing the device with the corresponding functionality. The specific type and number of input devices1314, output devices1316, communications subsystems1318, and even the specific functionality of the power management subsystem1308will of course depend on the type of the electronic device1300, which may be any suitable type of electronic device or system to which the reverse electrowetting EHS device1302may generate sufficient electrical power to improve the operation of the electronic device or system.