Apparatus for generating electrical energy and method for manufacturing the same

An apparatus for generating electrical energy including a first electrode, a second electrode and one or more nanowires, and a method for manufacturing the apparatus for generating electrical energy. The second electrode may have a concave portion and a convex portion. The first electrode and the nanowire are formed of different materials. The nanowire is formed on the first electrode and is positioned between the first electrode and the second electrode. Because the nanowire is formed on the first electrode, the nanowire may be grown vertically and the uniformity and conductivity of the nanowires may be improved. When a stress is applied to the first electrode or the second electrode, the nanowire is deformed and an electric current is generated from the nanowire due to a piezoelectric effect of the nanowire and a Schottky contact between the nanowire and the electrode which makes contact with the nanowire. Accordingly, when the apparatus for generating electrical energy is bent or pressed in part, electrical energy is generated in response to the applied stress.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Korean Patent Application No. 10-2008-77595 filed on Aug. 7, 2008, and Korean Patent Application No. 10-2008-123612 filed on Dec. 5, 2008, and all the benefits accruing therefrom under 35 U.S.C. §119, the contents of which in its entirety are herein incorporated by reference.

BACKGROUND

Exemplary embodiments relate to an apparatus for generating electrical energy and a method for manufacturing the same, more particularly to an apparatus for generating electrical energy using a Schottky contact formed between a nanowire exhibiting a piezoelectric effect and an electrode placed on the nanowire.

2. Description of the Related Art

A touch sensor detects the stress applied to devices, and may be used in a touchscreen or other applications. When a user touches the screen with a finger or other body part, the touch sensor detects the stress applied to the screen and registers the applied stress as an input signal.

In such a touch sensor, a voltage may be applied to one or more edge portions of a screen. When a user's finger or body part contacts the screen, the stress applied to the screen from the finger or body part may be detected as on a resistance change or voltage drop.

SUMMARY

In one exemplary embodiment there is provided an apparatus for generating electrical energy which generates electrical energy in response to applied stress. In another exemplary embodiment, there is provided a method for manufacturing the apparatus for generating electrical energy.

In another exemplary embodiment, there is provided an apparatus for generating electrical energy including a first electrode, a second electrode and a nanowire. The second electrode may have a concave portion and a convex portion. The nanowire is formed on the first electrode and is positioned between the first electrode and the second electrode. The first electrode and the nanowire are formed of different materials. When a stress is applied to the first electrode or the second electrode, the nanowire is deformed, and an electrical current is generated from the nanowire owing to the piezoelectric effect of the nanowire and a Schottky contact that is formed between the nanowire and the electrode which makes contact with the nanowire.

In another exemplary embodiment, there is provided a method for manufacturing the apparatus for generating electrical energy. In another exemplary embodiment, the apparatus for generating electrical energy is manufactured by forming a nanowire on a first electrode layer disposed on a substrate, the first electrode layer and the nanowire being formed different materials; preparing a second electrode layer having a concave portion and a convex portion facing the first electrode layer, the second electrode layer being spaced apart from the first electrode layer; with the nanowire of the first electrode in proximity to the second electrode layer; and connecting the first electrode layer with the second electrode layer using a conductor.

DETAILED DESCRIPTION

In the drawings, like reference numerals in the drawings denote like elements. The shape, size and regions, and the like, of the drawing may be exaggerated for clarity.

FIG. 1is a perspective view of an apparatus for generating electrical energy according to an exemplary embodiment, andFIG. 2is a front view of the apparatus for generating electrical energy illustrated inFIG. 1.

Referring toFIGS. 1 and 2, in one exemplary embodiment the apparatus for generating electrical energy comprises a first electrode10, a second electrode20and a nanowire30disposed between the first electrode10and the second electrode20.

The first electrode10may be a lower electrode which supports the nanowire30. In another exemplary embodiment, the first electrode10may be formed on a substrate1made of glass, silicon (Si), polymer, sapphire, gallium nitride (GaN) or silicon carbide (SiC). In another exemplary embodiment, the first electrode10may be a metal film or conductive ceramic formed on the substrate1.

In another exemplary embodiment, the second electrode20may be spaced apart from the first electrode10, and is electrically connected to the first electrode10by a conductor40. In another exemplary embodiment, the second electrode20is formed on a substrate2made of glass, silicon (Si), polymer, sapphire, gallium nitride (GaN) or silicon carbide (SiC).

In another exemplary embodiment, the second electrode20has one or more concave portions A1, and one or more convex portions A2, and is formed in a ripple shape facing the first electrode10.

In another exemplary embodiment, at least one of the first electrode10and the second electrode20is formed of a flexible electrode which can be deformed by an applied stress. In another exemplary embodiment, the first electrode10and the second electrode20may be formed of a transparent electrode.

In another exemplary embodiment, the first electrode10and the second electrode20may be formed of at least one of ITO, carbon nanotubes (“CNT”), a conductive polymer, a nanofiber, a nanocomposite, gold-palladium alloy (AuPd), gold (Au), palladium (Pd), platinum (Pt) and ruthenium (Ru).

In another exemplary embodiment, the substrate1on which the first electrode10is disposed and the substrate2on which the second electrode20is disposed may be formed of a flexible material which can be deformed by an applied stress. In another exemplary embodiment, the substrates1,2may be formed of a transparent material such as but not limited to glass.

In another exemplary embodiment, the nanowire30is disposed between the first electrode10and the second electrode20. In another exemplary embodiment, the nanowire30extends in a direction D1perpendicular to the first electrode10and the second electrode20. In another exemplary embodiment, the nanowire30is aligned with the concave portion A1of the second electrode20.

The number of the nanowires30illustrated inFIGS. 1 and 2is non-limiting. The number of the nanowires30may be varied depending on the size and application of the apparatus.

In another exemplary embodiment, the nanowire30is formed on the first electrode10. It may have several advantages to form the nanowire30on the first electrode10. For example, a conductivity of the nanowire energy generating system may be improved since the nanowire30is formed on the first electrode10which is a conductor. Further, it may become easier to control the growth of the nanowire30. For example, the nanowire30may be grown vertically on the first electrode10. Furthermore, a uniformity of the shapes or longitudinal directions of the nanowires30may be improved.

In another exemplary embodiment, when a stress is applied to the apparatus for generating electrical energy or a part thereof, the distance between the first electrode10and the second electrode20is changed resulting in the nanowire30between the first electrode10and the second electrode20being deformed.

In another exemplary embodiment, if the distance between the first electrode10and the second electrode20is decreased, the nanowire30at the corresponding location may become bent in the lengthwise direction D1. The bent nanowire30exhibits a piezoelectric effect which results in each portion of the nanowire30having different electric potentials depending on the compressive stress or tensile stress applied thereto.

In another exemplary embodiment, the nanowire30may be made of a material exhibiting a piezoelectric effect, such as ZnO, for example, but is not limited thereto. Upon the application of a stress the nanowire30made of ZnO is bent, resulting in each portion of the nanowire30having a different electric potentials due to the asymmetric crystal structure of the ZnO, resulting in an electrical energy being generated. This will be described in further detail when referring toFIG. 3.

In another exemplary embodiment, the nanowire30may be made of other materials which exhibit a piezoelectric effect when a stress is applied. In another exemplary embodiment, the nanowires30may be made of lead zirconate titanate (“PZT”) or barium titanate (BaTiO3), for example, but is not limited thereto.

FIG. 3is a front view showing the apparatus for generating electrical energy illustrated inFIG. 1where a stress is applied to the apparatus.

Referring toFIG. 3, in one exemplary embodiment, as a stress is applied on top of the substrate2, a portion B of the substrate2and the second electrode20may be bent downward, as illustrated. As a result, the distance between the first electrode10and the second electrode20is decreased, and the nanowire30positioned between the first electrode10and the second electrode20may be bent with respect to the lengthwise direction of the nanowire30. The bent nanowire30exhibits a piezoelectric effect. In another exemplary embodiment, the nanowire30is made of ZnO, a portion A3of the nanowire30corresponding to where a compressive stress is applied has a negative electric potential, and a portion A4of the nanowire30corresponding to where a tensile stress is applied, opposite the portion A3of the nanowire, has a positive electric potential.

In another exemplary embodiment, the nanowire30is aligned to correspond and be positioned adjacent to the concave portion A1of the second electrode20. Accordingly, when the distance between the first electrode10and the second electrode20is decreased, the nanowire30is bent and contacts the second electrode20.

In another exemplary embodiment, the portion A3of the nanowire30where the compressive stress is applied has a negative electric potential and the second electrode20does not have an electric potential. Accordingly, the portion A3where the compressive stress is applied and the second electrode20forms a forward-biased Schottky diode, and an electric current flows from the second electrode20toward the nanowire30. The current flows through a closed loop formed by the second electrode20, the nanowire30, the first electrode10and the conductor40.

In another exemplary embodiment, the portion A4of the nanowire30corresponding to where the tensile stress is applied has a positive electric potential. Accordingly, the portion A4of the nanowire30where the tensile stress is applied and the second electrode20forms a reverse-biased Schottky diode, and an electric current does not flow.

In another exemplary embodiment, a stress is applied to the second electrode20and the distance between the first electrode10and the second electrode20is decreased, an electric current flows due to a Schottky contact between the portion of the nanowire30where a compressive stress is applied and the second electrode20. Accordingly, it is possible to generate an electrical current in response to the applied stress.

In another exemplary embodiment, illustrated inFIG. 3, a stress is applied to the second substrate2and the second electrode20is bent. The same effect is achieved if a stress is applied to the first electrode10and the second electrode20. The same effect is also achieved by pressing a portion of the first electrode10or the second electrode20, or by bending the first electrode10or the second electrode20.

Referring toFIG. 1throughFIG. 3, in another exemplary embodiment, the concave portions A1and the convex portions A2are formed only on the second electrode20.

FIG. 4is a perspective view of an apparatus for generating electrical energy according to another embodiment, andFIG. 5is an exploded view of the apparatus for generating electrical energy illustrated inFIG. 4.

In another exemplary embodiment, illustrated inFIGS. 4 and 5, the construction and function of substrates1,2and a nanowire30may be the same as those described referring toFIGS. 1 through 3. Therefore, a detailed description thereof will be omitted.

In one exemplary embodiment, the first electrode11and the second electrode21may be a plurality of first and second electrodes. The plurality of the first electrodes11extend along a direction D2on the substrate1, and are disposed so as to be spaced apart from one another. The plurality of the second electrodes21extend along a direction D3perpendicular to the direction D2on the substrate2, and are disposed so as to be spaced apart from one another.

In another exemplary embodiment, the plurality of the first electrodes11and the plurality of the second electrodes21extend in directions perpendicular to each other, and form a matrix type array. The number of the first electrodes11and the second electrodes21illustrated inFIGS. 4 and 5is not limiting, and the number of the first electrodes11and the second electrodes21may be varied depending on the size and application of the apparatus.

In another exemplary embodiment, using the apparatus for generating electrical energy, it is possible to detect the electrode where an electric current flows to the plurality of the first electrodes11and the electrode where an electric current flows to the plurality of the second electrodes21. Therefore, it is possible to detect the position where a stress is applied. Accordingly, the apparatus for generating electrical energy may be applied in, but not limited to, a touch sensor to detect the position where a stress is applied.

In another exemplary embodiment, illustrated inFIGS. 4 and 5, the nanowire30is disposed on the plurality of first electrodes11. The nanowire30is disposed only on the positions where the first electrodes11and the second electrodes21cross each other.

In another exemplary embodiment, the second electrodes21may extend in the direction perpendicular to the first electrodes11. In another exemplary embodiment, the second electrodes21may extend along a direction inclined to the length direction D2of the first electrodes11.

FIG. 6is a cross-sectional view of an apparatus for generating electrical energy according to another embodiment.

In another exemplary embodiment, illustrated inFIG. 6, the construction and function of substrates1,2and a nanowire30may be the same as those described referring toFIGS. 1 through 3. Therefore, a detailed description thereof will be omitted.

In one exemplary embodiment, an elastic material50is disposed between the first electrode10and the second electrode20. The elastic material50may prevent the nanowire30from being broken when the apparatus for generating electrical energy is pushed or bent. Accordingly, a durability and reliability of the apparatus for generating electrical energy may be improved.

In one exemplary embodiment, the elastic material50has a relatively high elasticity. At the same time, the elastic material50is formed of a material flexible enough to allow the nanowire30to be bent. For example, the elastic material50may be formed of at least one of silicone, polydimethylsiloxane (PDMS), and urethane. Alternatively, the elastic material50may be formed of other suitable material.

If the nanowire30is completely covered with the elastic material50, the nanowire30may not contact the second electrode20. Therefore, in another exemplary embodiment, a first distance L1between the first electrode10and a top surface of the elastic material50is not greater than a second distance L2between the first electrode10and the top surface of the nanowire30. Accordingly, an end of the nanowire30may be exposed, so that the nanowire30may contact the second electrode20when the nanowire30is bent.

In another exemplary embodiment, the apparatuses for generating electrical energy described herein are used in an electronic device for sensing a stress, for example but not limited to, a touch sensor. In another exemplary embodiment, the apparatuses for generating electrical energy described herein are used in a display device, such as but not limited to a touch panel, a touchscreen, etc. or a robot skin.

FIGS. 7athrough7fare cross-sectional views illustrating an exemplary embodiment of a process of preparing a first electrode and a nanowire of an apparatus for generating electrical energy.

In an exemplary embodiment, referring toFIG. 7a, a first electrode layer100is disposed on a substrate1. The substrate1may be a substrate made of glass, silicon or polymer. In another exemplary embodiment, the first electrode layer100may be made of a flexible conductive material which can be deformed by an applied stress. In another exemplary embodiment, the first electrode layer100may be made of a transparent material.

In another exemplary embodiment, the first electrode layer100may be formed of at least one of ITO, CNT, a conductive polymer, nanofibers and a nanocomposite. The first electrode layer100may also be formed of at least one of AuPd alloy, Au, Pd, Pt and Ru.

The first electrode layer100may serve as a lower electrode which supports the nanowire which will be described later.

Next, referring toFIG. 7b, a nanomaterial layer300is disposed on the first electrode layer100. The nanomaterial layer300may be disposed having a small thickness on the first electrode layer100by spin coating or other methods. As a non-limiting example the nanomaterial layer300may have a thickness of 3 nm to 50 nm. According to exemplary embodiments, the nanomaterial layer300may be formed of zinc acetate.

Next, referring toFIG. 7c, the substrate1on which the nanomaterial layer300(FIG. 7b) has been formed is heated to form one or more nanonuclei301. As a non-limiting example the nanonucleus301is formed by heating the substrate1on which the nanomaterial layer has been formed at a temperature of 100° C. to 200° C. followed by drying.

Next, referring toFIG. 7d, the substrate1on which the nanonucleus301has been formed is immersed in a solution of a nanomaterial so as to grow a nanowire30from each nanonucleus301.

This results in the formation of the first electrode and the nanowire of the apparatus for generating electrical energy.

Next, referring toFIG. 7e, an elastic material layer500is disposed on the first electrode layer100on which the nanowire30has been formed. The elastic material layer500may prevent the nanowire30from being broken. The elastic material layer500may be formed of a material having a relatively high elasticity. And the elastic material layer500may be formed of a material flexible enough to allow the nanowire30to be bent. For example, the elastic material layer500may be formed of at least one of silicone, PDMS, and urethane. Alternatively, the elastic material layer500may be formed of other suitable material.

In another exemplary embodiment, the elastic material layer500is disposed on the first electrode layer100using spin coating, dip coating, nozzle printing, or other suitable methods. For example, the elastic material layer500may be disposed using nozzle printing by spraying a material on the first electrode layer100with a fine nozzle and drying the sprayed material.

In another exemplary embodiment, illustrated inFIG. 7e, a first distance L1between the first electrode layer100and a top surface of the nanowire30is greater than a second distance L2between the first electrode layer100and the top surface of the nanowire30. Alternatively, the first distance L1may be equal to or less than the second distance L2.

In another exemplary embodiment, if the first distance L1is greater than the second distance L2, a portion of the elastic material layer500is removed to expose an end of the nanowire30. When the first distance L1is greater than the second distance L2, the nanowire30is completely covered with the elastic material layer500and the nanowire30may not contact metal. Therefore, a portion of the elastic material layer500may be removed so that the first distance L1is equal to or less than the second distance L2. The elastic material layer500may be partially removed by etching methods using ultraviolet (UV) radiation or oxygen (O2) plasma, or other suitable methods.

In another exemplary embodiment, the process for removing a portion of the elastic material layer500may be omitted when the elastic material layer500is formed so that the first distance L1is equal to or less than the second distance L2.

FIGS. 8athrough8gare cross-sectional views illustrating an exemplary embodiment of a process of preparing a second electrode of an apparatus for generating electrical energy.

First, referring toFIG. 8a, a metal layer200is disposed on a template substrate3. According to exemplary embodiments, the substrate3may be a silicon wafer, and the metal layer200may be formed of aluminum (Al).

Next, referring toFIG. 8b, the metal layer200is anodized to form an anodic film201. The anodizing is an electrolytic process in an electrolytic solution, with the metal layer200as an anode. Through the anodizing, the thickness of the natural oxide layer formed on the metal layer200increases as the constituent material of the metal layer200dissolves into the electrolyte. The anodic film201which is formed as a result of this process is illustrated inFIG. 8b.

Next, referring toFIG. 8c, the anodic film201formed by the anodizing process is removed. The anodic film201may be removed, for example, but not limited to, by wet or dry etching. Upon the removal of the anodic film201, the surface of the template substrate3has a ripple-shaped structure with concave portions and convex portions.

Next, referring toFIG. 8d, a second electrode layer202is formed on the template substrate3. The second electrode layer202may serve as an upper electrode which contacts the nanowires and allows for the flow of electrical current.

According to exemplary embodiments, the second electrode layer202is formed of at least one of AuPd alloy, Au, Pt, Pd and Ru. Further, the second electrode layer202may be formed by ion sputtering.

Also, as in the first electrode layer described above, the second electrode layer202may be formed of a flexible conductive material capable of being deformed by an applied stress. Further, the second electrode layer202may be made of a transparent material.

For example, the second electrode layer202may be formed of at least one of ITO, CNT, a conductive polymer, nanofibers and a nanocomposite.

According to exemplary embodiments, an adhesion layer203is disposed on the second electrode layer202, as illustrated inFIG. 8e. The adhesion layer203may serve to improve adhesion between the second electrode layer202and a carrier substrate which is formed later in the process. According to exemplary embodiments, the adhesion layer203may be formed of nickel (Ni). Further, the adhesion layer203is formed by electroplating.

Next, referring toFIG. 8f, a carrier substrate2is attached on the adhesion layer203. In another exemplary embodiment, the carrier substrate2may be attached on the second electrode layer202, without the adhesion layer203. Further, the carrier substrate2may be formed of a polymer.

Next, referring toFIG. 8g, the second electrode layer202, the adhesion layer203and the carrier substrate2is separated from the template substrate3. The separated second electrode layer202has concave portions A1and convex portions A2because of the shape of the template substrate3.

In another exemplary embodiment, the second electrode which is connected to the first electrode and the nanowire may be formed as described above.

FIGS. 9aand9bare cross-sectional views illustrating an exemplary embodiment of a process of bringing into proximity a nanowire to a second electrode to manufacture an apparatus for generating electrical energy.

First, referring toFIG. 9a, the nanowire30is brought into proximity to the second electrode layer202. The nanowire30may either contact the second electrode layer202or be spaced apart from the second electrode layer202with a predetermined spacing. In another exemplary embodiment, the nanowire30includes a plurality of nanowires, and each of the nanowires30may be positioned in proximity to the concave portions A1of the second electrode layer202.

Next, referring toFIG. 9b, the first electrode layer100and the second electrode layer202are connected by the conductor40in order to complete the apparatus for generating electrical energy.

Although not shown inFIGS. 9aand9b, in another exemplary embodiment, an elastic material layer500(FIG. 7e) is disposed between the first electrode layer100and the second electrode layer200.

While the exemplary embodiments have been shown and described, it will be understood by those skilled in the art that various changes in form and details may be made thereto without departing from the spirit and scope of the present invention as defined by the appended claims.

In addition, many modifications can be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the present invention not be limited to the particular exemplary embodiments disclosed as the best mode contemplated for carrying out this invention, but that the present invention will include all embodiments falling within the scope of the appended claims.