Piezo-Elements for Wearable Devices
Aspects of the present disclosure describe systems, methods, and structures that scavenge mechanical energy to provide electrical energy to a wearable, where the mechanical energy is scavenged by a bending-strain-based transducer that includes a non-resonant energy harvester. By employing a non-resonant energy harvester that operates in bending mode, more electrical energy can be generated that possible with prior-art energy harvesters. In some embodiments, the output of a bending-strain-based transducer element is used for both energy scavenging and as a sensor signal indicative of a user parameter, such as a step, respiration rate, heart rate, weight and the like. In some embodiments, a transducer element includes a plurality of piezoelectric layers that are electrically connected in parallel to increase the energy and/or power provided by the transducer element.
1 . An apparatus comprising:
a bending-strain-based transducer that includes:
(i) a first transducer element disposed on a first surface of a substrate, the first transducer element being a non-resonant energy harvester; and
(ii) a second transducer element disposed on a second surface of the substate, the first and second surfaces being on opposite sides of the substrate, wherein the second transducer element is selected from the group consisting of a resonant energy harvester, a non-resonant energy harvester, a force sensor, a load sensor, a pressure sensor, and a haptic device;
wherein the transducer has a quiescent shape that is non-planar; and
an energy-storage module for receiving a first output from the first transducer element and storing energy based on the first output.
2 . The apparatus of claim 1 further comprising:
a detection circuit configured to receive the first output and provide a first electrical signal that is based on the first output; and
a processor for estimating a first parameter based on the first electrical signal.
3 . The apparatus of claim 1 wherein the first transducer element includes a first plurality of piezoelectric layers, each piezoelectric layer of the first plurality thereof being disposed between and electrically connected to a pair of electrodes of a first plurality of electrodes.
4 . The apparatus of claim 3 wherein the piezoelectric layers of the first plurality thereof are electrically connected in parallel.
5 . The apparatus of claim 3 wherein the second transducer element includes a second plurality of piezoelectric layers, each piezoelectric layer of the second plurality thereof being electrically connected to a pair of electrodes of a second plurality of electrodes.
6 . The apparatus of claim 5 wherein the piezoelectric layers of the first plurality thereof are electrically connected in parallel and the piezoelectric layers of the second plurality thereof are electrically connected in parallel.
7 . The apparatus of claim 1 wherein the first transducer element is configured to generate a stimulus to a user in response to receipt of a drive signal from the processor.
8 . The apparatus of claim 1 wherein the wearable is a sole member.
9 . The apparatus of claim 1 wherein the substrate comprises a material selected from the group consisting of a metal, a polyimide and a glass.
10 . The apparatus of claim 1 wherein at least one of the first transducer element and second transducer element includes a piezoelectric layer comprising a low-K piezoelectric material.
11 . The apparatus of claim 10 wherein the low-K piezoelectric material is selected from the group consisting of undoped aluminum nitride, doped aluminum nitride, scandium-doped aluminum nitride, undoped zinc oxide, doped zinc oxide, and polyvinylidene fluoride.
12 . The apparatus of claim 1 wherein the substrate comprises steel and at least one of the first transducer element and second transducer element includes a piezoelectric layer comprising a material selected from the group of undoped aluminum nitride, doped aluminum nitride, and scandium-doped aluminum nitride.
13 . The apparatus of claim 1 wherein the substrate includes at least one flange, and wherein the substrate has a first thickness and the flange has a second thickness that is greater than the first thickness.
14 . An apparatus comprising:
a first bimorph transducer having a quiescent shape that is non-planar, the first bimorph transducer being configured to bend in response to a first force, wherein the first bimorph transducer includes:
(i) a first transducer element disposed on a first surface of a substrate, the first transducer element being a non-resonant energy harvester; and
(ii) a second transducer element disposed on a second surface of a substrate, the second transducer element being selected from the group consisting of a resonant energy harvester, a non-resonant energy harvester, a force sensor, a load sensor, a pressure sensor, and a haptic device;
an energy-storage module that includes an alternating-current-to-direct-current (AC/DC) conversion chip, the energy-storage module being configured to receive a first electrical signal from the first bimorph transducer at the AC/DC conversion chip and store energy based on the first electrical signal; and
a processor for estimating a first parameter based on a second electrical signal from the first bimorph transducer.
15 . The apparatus of claim 14 wherein the first electrical signal and second electrical signal are based on a first output of the first transducer element, and wherein the apparatus further includes a detection circuit for converting the second electrical signal into a third electrical signal and providing the third electrical signal to the processor.
16 . The apparatus of claim 14 wherein the substrate comprises at least one material selected from the group consisting of a metal, a polyimide, and a glass.
17 . The apparatus of claim 14 wherein the first transducer element includes a first plurality of piezoelectric layers, each piezoelectric layer of the first plurality thereof being disposed between and electrically connected to a pair of electrodes of a first plurality of electrodes, and wherein the piezoelectric layers of the first plurality thereof are electrically connected in parallel.
18 . The apparatus of claim 17 wherein the second transducer element includes a second plurality of piezoelectric layers, each piezoelectric layer of the second plurality thereof being disposed between and electrically connected to a pair of electrodes of a second plurality of electrodes, and wherein the piezoelectric layers of the second plurality thereof are electrically connected in parallel.
19 . The apparatus of claim 14 wherein the substrate comprises steel and at least one of the first transducer element and second transducer element includes a piezoelectric layer comprising a material selected from the group of undoped aluminum nitride, doped aluminum nitride, and scandium-doped aluminum nitride.
20 . The apparatus of claim 14 wherein the apparatus is a shoe insole that includes:
a plurality of bimorph transducers that includes the first bimorph transducer;
a wireless communications module;
a power-handling circuit; and
the energy-storage module;
wherein the plurality of bimorph transducers is operatively coupled with each of the power-handling circuit and the energy-storage module.
21 . The apparatus of claim 14 wherein the AC/DC conversion chip has a maximum input voltage and the first bimorph transducer has a maximum deformation from its quiescent shape, and wherein each of the first transducer element and second transducer elements is configured to generate an open-circuit voltage equal to the maximum input voltage when the first bimorph transducer undergoes its maximum deformation.
22 . The apparatus of claim 14 wherein the AC/DC conversion chip has a maximum input voltage and the first bimorph transducer has a maximum deformation from its quiescent shape, and wherein, when the first bimorph transducer undergoes its maximum deformation, the first transducer element generates a first open-circuit voltage and the second transducer element generates a second open-circuit voltage, the first and second open-circuit voltages being equal to twice the maximum input voltage, and further wherein the energy-storage module further includes:
a first voltage divider that receives the first open-circuit voltage provides a first pair of voltages to the AC/DC conversion chip; and
a second voltage divider that receives the second open-circuit voltage provides a second pair of voltages to the AC/DC conversion chip;
wherein each of the first pair of voltages and the second pair of voltages is substantially equal to the maximum input voltage.
23 . The apparatus of claim 14 wherein the first transducer element is configured to generate a stimulus in response to receipt of a drive signal from the processor.
24 . The apparatus of claim 23 wherein the stimulus is selected from the group consisting of a vibration, an audible tone, and a mechanical impulse.