Powering Methods For WBAN Hofit Cohen Elad Kalif Course: Algorithms In Computer Networks.

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.

WBAN : Energy sources  Battery  Harvesting Energy: (Body heat, blood pressure, motion etc..)  Remote energy transfer: Wireless

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

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

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.

WPT: Power Coils  Electromagnetic induction.  Distance.  matching the resonant frequencies maximizes the energy transfer.

WPT: Power Coils

 Power Coils in service of WBAN:  Heart pump  Insulin pump  Implanted hearing device. AdvantagesDisadvantages WirelessDistance Can be used with rechargeable battery Mutual Effect

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?

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.

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.

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.

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).

Infrared Light In service of WPT (1)  Distributed resonator:  mirrors are retro-reflectors, it doesn’t subject to the law of reflection.

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

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

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.

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.

WPT: Acoustic Waves

 Possible usage in the field of Medicine:  Hydrocephalus  Pumps  The method is highly experimental.

To Sum Things Up  We reviewed the following methods:  ultrasonic  infrared light  Magnetic (short range)  What is the best method?

Bibliography  A. Denisov and E. Yeatman, "Stepwise Microactuators Powered by Ultrasonic Transfer," Procedia Engineering, vol. 25, pp ,  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 , 