Walking and working in shoes and clothing incorporating flexible piezoelectric generators in the soles and fabrics could provide a source of constant power for people on the job capable of recharging batteries.
In U.S. Patent Application 20090309456, Georgia Tech Research Corporation (Atlanta, GA) scientist David W. Stollberg reveals piezoelectric-coated carbon nanotube generators. Stollberg's carbon nanotube piezoelectric generator overcomes many of the limitations associated with zinc oxide nanowires used in piezoelectric devices. The flexible piezoelectric-coated carbon nanotube generators could be incorporated into fabrics and shoe soles and used to recharge batteries for people whose jobs require a constant power source (e.g., soldiers, miners, etc.) or used in medical implants. Device fabrication involves well known photolithographic methods.
In U.S. Patent Application 20090309456, Georgia Tech Research Corporation (Atlanta, GA) scientist David W. Stollberg reveals piezoelectric-coated carbon nanotube generators. Stollberg's carbon nanotube piezoelectric generator overcomes many of the limitations associated with zinc oxide nanowires used in piezoelectric devices. The flexible piezoelectric-coated carbon nanotube generators could be incorporated into fabrics and shoe soles and used to recharge batteries for people whose jobs require a constant power source (e.g., soldiers, miners, etc.) or used in medical implants. Device fabrication involves well known photolithographic methods.
Zinc oxide nanowires have been used to generate electricity. However, zinc oxide nanowires by themselves tend to be brittle and have a limited maximum length. This results in limited power generation and a relatively short service life.
There is a need for a nanoscale power generation system that has improved power generation and service life and piezoelectric-coated carbon nanotube generators may be the answer.
A piezoelectric material is one that forms an electrical potential difference between two regions of the material when the material is subjected to uneven mechanical forces. For example, when certain piezoelectric materials are bent, they develop a positive voltage in one region and a negative voltage in another region.
Many micro-scale and nano-scale machines have been proposed for such uses as in vitro medical devices. However, most of these machines are limited by the size of the power source that drives them. Specifically, many such designs rely on chemical batteries to supply electrical power to the devices. Therefore, they can be no smaller than the battery used and are useful only so long as the battery is able to provide power.
However, some of such devices need to be operational for long periods, rather than be limited by the lifespan of a battery. Also, it may be extremely difficult to change the batteries in some devices, such as environmental sensors.
In response to these problems, zinc oxide nanowires have been used to generate electricity. However, zinc oxide nanowires by themselves tend to be brittle and have a limited maximum length. This results in limited power generation and a relatively short service life, a problem overcome by a zinc oxide/ carbon nanotube generator.
Stollberg's generator includes a first conductive layer, a plurality of elongated piezoelectric nanostructures and a conductive electrode. The piezoelectric nanostructures extend upwardly from the first conductive layer and include a carbon nanotube core and a piezoelectric sheath enveloping at least a portion of the carbon nanotube core. Each piezoelectric nanostructure includes a first end disposed adjacent to the first conductive layer and an opposite second end. The conductive electrode is disposed adjacent to the second end of each of the piezoelectric nanostructures. The conductive electrode is configured so that a Schottky barrier is formed between the second end of at least one of the piezoelectric nanostructures and the conductive electrode when a force is applied to the generator that causes the conductive electrode to touch the piezoelectric nanostructures and to induce stress in the piezoelectric nanostructures.
FIGS. 1A-1B are schematic diagrams of a first embodiment of a piezoelectric-coated carbon nanotube generator system.
FIG. 2 is a schematic diagram of a second embodiment of a piezoelectric-coated carbon nanotube generator system.
As shown in FIG. 1, one representative embodiment of the invention is a generator 100 that includes a piezoelectric member 110 and an electrode member 130. The piezoelectric member 110 includes a conductive substrate 112, such as a silicon layer upon which may be disposed a silicon dioxide layer 114. Upon the conductive substrate is a conductive metal layer 116 that is used as a seed material from which a plurality of elongated carbon nanotubes 122 is grown. In one embodiment, the conductive metal layer includes iron. A piezoelectric sheath 124 surrounds each of the carbon nanotubes 122 to form a plurality of elongated piezoelectric nanostructures 120 extending from the conductive substrate 112. In one embodiment, the piezoelectric sheath 124 includes zinc oxide (although other piezoelectric materials could also be used, depending on the specific application). The carbon nanotubes 122 are extremely strong and, therefore, provide support for the piezoelectric sheath 124 thereby allowing relatively long piezoelectric nanostructures to be employed in the generator 100.
The electrode member 130 is disposed oppositely from the piezoelectric member 110. The electrode member 130 includes a conductive substrate 132, such as a silicon layer upon which may be disposed a silicon dioxide layer 134 (in some embodiments, the silicon dioxide layer 134 is merely an artifact of the fabrication process and can be removed). Upon the conductive substrate is a conductive metal layer 136 that is used as a seed material from which a plurality of elongated carbon nanotubes 142 is grown. A conductive sheath 144 surrounds each of the carbon nanotubes 142 to form a plurality of plurality of conductive structures 140 extending from the conductive substrate 132. In one embodiment, the metal layer 136 includes iron and the conductive sheath 144 includes a metal such as gold (although other metals could be used, depending on the specific application).
As shown in FIG. 1B, when a force is applied to the generator 100, a potential difference will form across the elongated piezoelectric nanostructures 120 and a Schottky barrier will form between the elongated piezoelectric nanostructures 120 and the conductive structures 140, thereby causing charge to flow in a single direction. This is evidenced by a change of electrical state in a load 10 coupled between the piezoelectric member 110 and the electrode member 130. A typical embodiment is shown in FIG. 2, in which many elongated piezoelectric nanostructures 120 and the conductive structures 140 are used to increase the current output of the generator. These structures could also be stacked and coupled in series to increase the voltage output.
A typical embodiment is shown in FIG. 2, in which many elongated piezoelectric nanostructures 120 and the conductive structures 140 are used to increase the current output of the generator. These structures could also be stacked and coupled in series to increase the voltage output.
The electrode member 130 is disposed oppositely from the piezoelectric member 110. The electrode member 130 includes a conductive substrate 132, such as a silicon layer upon which may be disposed a silicon dioxide layer 134 (in some embodiments, the silicon dioxide layer 134 is merely an artifact of the fabrication process and can be removed). Upon the conductive substrate is a conductive metal layer 136 that is used as a seed material from which a plurality of elongated carbon nanotubes 142 is grown. A conductive sheath 144 surrounds each of the carbon nanotubes 142 to form a plurality of plurality of conductive structures 140 extending from the conductive substrate 132. In one embodiment, the metal layer 136 includes iron and the conductive sheath 144 includes a metal such as gold (although other metals could be used, depending on the specific application).
As shown in FIG. 1B, when a force is applied to the generator 100, a potential difference will form across the elongated piezoelectric nanostructures 120 and a Schottky barrier will form between the elongated piezoelectric nanostructures 120 and the conductive structures 140, thereby causing charge to flow in a single direction. This is evidenced by a change of electrical state in a load 10 coupled between the piezoelectric member 110 and the electrode member 130. A typical embodiment is shown in FIG. 2, in which many elongated piezoelectric nanostructures 120 and the conductive structures 140 are used to increase the current output of the generator. These structures could also be stacked and coupled in series to increase the voltage output.
A typical embodiment is shown in FIG. 2, in which many elongated piezoelectric nanostructures 120 and the conductive structures 140 are used to increase the current output of the generator. These structures could also be stacked and coupled in series to increase the voltage output.
