Design Article
Toward pacemakers powered by heartbeats
10/17/2012 8:24 AM EDT
How it works
2. Piezoelectric devices
Piezoelectric converters use piezoelectric materials that generate charges under stress or strain. A cantilever-based piezoelectric energy harvester has been chosen to harvest energy from heartbeats (figure 5). The mass added at the free end enables to increase the output power and to decrease the mass-spring resonant frequency down to 20Hz while keeping small dimensions.
3. Electrostatic devices
Electrostatic converters are capacitive structures made of two plates separated by air, vacuum or any dielectric materials. In these devices, a relative movement between the two plates generates a capacitance variation and then electric charges .
As explained in [5], electrostatic devices are well-suited for size reduction and enable to decouple the mechanical system (mass-spring) from the mechanical-to-electrical converter. An electret-based converter has been chosen to enable a direct mechanical-to-electrical conversion. A schema of the device is introduced in figure 6a; patterned electrets are presented in figure 6b. Once again, a mass is added in order to increase the output power.
(a)
(b)
A first MEMS electrostatic prototype has been manufactured using cleanroom processes and is presented in figure 7a. The energy harvester has a total volume of 1cm³ and an output power of 10µW will be available as soon as the device is implanted in the heart. A schema of the future complete autonomous pacemaker, with its vibration energy harvester, is represented in figure 7b.
(a)
(b)
Figure 7: (a) MEMS electret-based vibration energy harvester (b) schematic of the future device
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1. For more information on electrostatic vibration energy harvesters: Electrostatic conversion for vibration energy harvesting, S. Boisseau, G. Despesse, B. Ahmed Seddik, Small-scale Energy Harvesting, Intech, 2012
Next: Power management ICs
2. Piezoelectric devices
Piezoelectric converters use piezoelectric materials that generate charges under stress or strain. A cantilever-based piezoelectric energy harvester has been chosen to harvest energy from heartbeats (figure 5). The mass added at the free end enables to increase the output power and to decrease the mass-spring resonant frequency down to 20Hz while keeping small dimensions.
Figure 5: HBS piezoelectric device developed by TIMA
3. Electrostatic devices
Electrostatic converters are capacitive structures made of two plates separated by air, vacuum or any dielectric materials. In these devices, a relative movement between the two plates generates a capacitance variation and then electric charges .
As explained in [5], electrostatic devices are well-suited for size reduction and enable to decouple the mechanical system (mass-spring) from the mechanical-to-electrical converter. An electret-based converter has been chosen to enable a direct mechanical-to-electrical conversion. A schema of the device is introduced in figure 6a; patterned electrets are presented in figure 6b. Once again, a mass is added in order to increase the output power.
(a)
(b)
Figure 6: (a) Electret-based energy harvester developed by CEA-LETI and (b) patterned electrets
A first MEMS electrostatic prototype has been manufactured using cleanroom processes and is presented in figure 7a. The energy harvester has a total volume of 1cm³ and an output power of 10µW will be available as soon as the device is implanted in the heart. A schema of the future complete autonomous pacemaker, with its vibration energy harvester, is represented in figure 7b.
(a)
(b)
Figure 7: (a) MEMS electret-based vibration energy harvester (b) schematic of the future device
Piezoelectric or electrostatic devices deliver an AC output voltage that cannot be used as is to supply electronic devices: a power management circuit is required.
1. For more information on electrostatic vibration energy harvesters: Electrostatic conversion for vibration energy harvesting, S. Boisseau, G. Despesse, B. Ahmed Seddik, Small-scale Energy Harvesting, Intech, 2012
Next: Power management ICs
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seaEE
10/17/2012 11:25 PM EDT
This is probably as close to a perpetual motion machine as you can get! :)
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mjacoby
10/18/2012 12:30 PM EDT
One step closer to the Matrix!!
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agk
10/19/2012 8:40 AM EDT
Piezo and electrostatic principles are applied for energy harvesting. Piezo will be able to generate more power at least 10 times more than the electrostatic device.Also piezo will have more life time than the other one.
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Sebastien Boisseau
10/31/2012 6:33 AM EDT
FYI : more information on Electrostatic and electret-based energy harvesters : http://www.intechopen.com/books/small-scale-energy-harvesting/electrostatic-conversion-for-vibration-energy-harvesting
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green_is_now
4/28/2013 4:26 PM EDT
Thanks for the link Sabastien
two thoughts
dump the full bridge rectifier for two half bridges.
1) efficiency may double at these low voltages!
2) the common mode noise voltage created by a full bridge currupts the analog front end, getting worse with miniturization due to proximity of the power conversion
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