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Powering Methods For WBAN Hofit Cohen Elad Kalif Course: Algorithms In Computer Networks.
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Motivation Technology in service of medicine. Deeply implanted medical devices VS. non implanted The more power – The better options. The big question: How to achieve maximum power with minimum space.
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WBAN : Energy sources Battery Harvesting Energy: (Body heat, blood pressure, motion etc..) Remote energy transfer: Wireless
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Battery vs. Battery less Diagnostic and telemetric VS. therapeutic. sensing capabilities: blood pressure, sugar level, temperature. therapeutic functions: hearing and sight recovery, cardiac stimulation, drug release (actuation nodes). Size
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Battery less Many actuation functions requires high energy demands. Example: 100 mW for a neural stimulation 250 mW for a retinal implant Harvested energy has low energy capacity. Example: 30 μW for thermoelectric 80 μW for human motion micro generators
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Wireless Power Transfer (WPT) There are many ways to transfer power: radio frequency ultrasonic infrared light Magnetic (short range) High wireless power transfer efficiency is paramount to ensure minimal heating of the surrounding tissues.
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WPT: Power Coils Electromagnetic induction. Distance. matching the resonant frequencies maximizes the energy transfer.
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WPT: Power Coils
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Power Coils in service of WBAN: Heart pump Insulin pump Implanted hearing device. AdvantagesDisadvantages WirelessDistance Can be used with rechargeable battery Mutual Effect
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WPT: Infrared Light infrared beams to carry power from a transmitter to a receiver. light can carry energy. Laser is a good source for high-power beams that can be sent over long distances How does it work? How does leaser created?
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Infrared Light Technology (1) Resonator device. One photon enters and two come out. This process of positive feedback combined with a gain mechanism creates a resonator.
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Infrared Light Technology (2) It’s important to note that only photons that travel exactly on the main axis. Photons that are slightly off-axis will stray away from the resonator and be lost. Power is concentrated along the main axis only.
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Infrared Light Technology (3) If one of the mirrors in the resonator is semi-transparent (allowing a small fraction of the power to leave the resonator) a very narrow, high-power light beam is created. This beam is known as a LASER.
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Infrared Light Technology (4) Laser beams can be used to power remote devices. this approach hasn't proved viable for consumer applications. The beam is inherently unsafe. The beam must be precisely aimed at the remote receiver (safety).
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Infrared Light In service of WPT (1) Distributed resonator: mirrors are retro-reflectors, it doesn’t subject to the law of reflection.
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Infrared Light In service of WPT (2) photons are emitted from the gain medium in different directions Only "lucky" photons that travel along the line connecting the two mirrors reach the second mirror and are reflected back These "lucky" photons are amplified while passing through the gain medium
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Infrared Light In service of WPT (3) Technology Merits: Light can travel long distances with little divergence and easily reach remote devices. Self Aligning Safe : transmitter deliver power to the receiver only No software or decision-making circuitry are involved
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WPT: Acoustic Waves Ultimate goal is to convert incoming mechanical energy to electrical form. Do we must convert energy? concept of using the mechanical energy of acoustic waves to directly.
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WPT: Acoustic Waves Existing state: Lateral shift by up to a third can result in up to 70% efficiency reduction. angular misalignment by as little as 5º can lead to more than 90% energy loss.
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WPT: Acoustic Waves
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Possible usage in the field of Medicine: Hydrocephalus Pumps The method is highly experimental.
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To Sum Things Up We reviewed the following methods: ultrasonic infrared light Magnetic (short range) What is the best method?
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Bibliography A. Denisov and E. Yeatman, "Stepwise Microactuators Powered by Ultrasonic Transfer," Procedia Engineering, vol. 25, pp. 685-688, 2011. A. Denisov and E. M. Yeatman, “Battery-less microdevices for body sensor/actuator networks,” in Proc. IEEE Int. Conf. BSN, 2013, pp. 1–5. Alexey Denisov and Eric M. Yeatman “Micromechanical Actuators Driven by Ultrasonic Power Transfer”, Microelectromechanical Systems, Journal of (Volume:PP, Issue: 99 ), 2013 J. Olivo, S. Carrara and G. De Micheli, "Energy Harvesting and Remote Powering for Implantable Biosensors," Sensors Journal, IEEE, vol. 11, pp. 1573-1586, 2011. http://www.wi-charge.com/
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