PORTLAND, Ore.—A MEMS chip can harvest energy from vibrations inside car tires allowing a tire pressure monitoring systems (TPMS) to run battery-free, according to Belgian research institute IMEC. The new MEMS energy harvester technology from IMEC, which can be used to power any low-current wireless sensor node, was reported Wednesday at the IEEE International Electron Devices Meeting in Washington.
The maximum output of the MEMS energy harvester was just under 500 microWatts at its natural resonant frequency of 1 KHz. Energy generation dropped to just over 40 microWatts in automobile tire traveling at 40 miles per hour, but was still enough to qualify the part for powering the pressure sensor and wireless communications circuitry for TPMS systems, according to IMEC.
The MEMS energy harvester consists of a cantilever with a piezoelectric layer (aluminum nitride) sandwiched between metallic electrodes to form a capacitor. A mass attached to one end of the cantilever, enables it to act as a transducer converting vibrations into electricity as the piezoelectric layer flexes. The voltage across the capacitor can then be harvested to drive wireless circuits.
IMEC demonstrated that the tiny energy harvesters can be packaged using vacuum processing on six-inch wafers. IMEC predicts that its MEMS energy harvester will be used to power wireless sensor nodes in many applications where changing a battery is inconvenient—from automobile engines to industrial appliances.
MEMS energy harvester generates power from vibrations inside tires, eliminating the need for batteries in tire pressure sensors.
The application is usually referred to as Tire Pressure Monitoring System (TPMS), and the sensors are secured to the wheel, with a counterweight on the opposite side, and a nice, sturdy zip tie around the whole works, to make sure it stays in place (if the adhesive fails!)
My personal favorite for the system was an RFID-type of system that used an evacuated cavity which would deform according to the pressure in the tire, thus changing its' resonant frequency. A transmitter in the wheel well supplied the stimulus, and the re-radiated frequency was proportional to the pressure. Simple, and no batteries.
One of the long term problems for embedding into tyres is the machinery necessary to do it in existence? RFID tags have been in existence for decades and are only now appearing in manufactured tyres.
Pirelli promised a piezo tyre which should have launched last year but I have heard and seen nothing of it.
I note the article says car tyres and does this mean that truck tyres are more of a problem? Distance to transmit, more rigidity in the tyre, ability to survive recapping. Tyres are a complex world so I would be not surprised to see 5-10 years before this may become commercial.
This MEMS chip has been optimized for the thump-thump-thump of a tire going round at 100s of revs per minute....so no!
My understanding is that there are many different types of pace maker and modes of operation and energy requirements but it should be possible to find some form of energy scavanging principle that can help. But you might want batteries, at least as a back up.
This is really a good development. Energy harvesting techniques are really useful for such applications where micro power is required. Supplying such a power through conventional batteries will sometimes be bulky. Moreover the natural drain from the battery will be much more than the actual circuit operating requirement. In times to come more and more such energy harvesting applications especially in standalone systems such as Automotive or mobile devices will become feasible.
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