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Powering The Augmented Form

Virtual reality environments tying directly into the neurons of the human brain. Worlds offering a better life, a happier life, providing feedback directly to your body. Embedded medical devices, feeding streams of wireless data to the home hospital; constantly regulating your bodily systems.

Bionic organs, artificial hearts and lungs. Internal radios, extra bodily functions, melding steel and flesh. Artificial eyes with 20/20 vision, self-repairing artificial hearing systems embedded deep in the skull. All these, and many, many more are marching steadily towards reality. Within a lifetime many, if not most of them will be available in some form or another.

Yet, for all the promise and wondrous splendour, there is one area oft overlooked in the drive to embed electronic devices inside the human form.

How are they going to be powered?

Under current practices, implanted devices are powered by batteries, typically lithium iodine. These can last for 5-10 years depending on the power requirements of the device. After that, the person has to undergo surgery, and have their innards opened up?to replace the battery. This is expensive for the health service or health insurer, whilst at the same time risky and traumatic for the patient. It is 5-10 years with one device. With two, there is no guarantee they were both implanted at the same time, or even in the same location within the body. What about 10? 20?

It is quickly clear that batteries are not going to be a sustainable way to power implanted devices. We require either a battery that has a lifespan considerably longer than expected life of the person with the implant, or a power source that renews itself, constantly generating a micro current.

Lithium-iodine pacemaker battery cell. Hooked up to a modern pacemaker, which regulates the heart, and connects to an outside computer via short wireless transceiver bursts, this battery is typical of the type most implants today use, to power their electronic components. Sometimes these fail within a year, but rarely. Usually they will average seven years of continuous power in microwatts -all that is required - and then require surgery to replace.

A nuclear-powered variant was developed in the 70s, with an expected power length of 20 years, potentially 40. However, this idea was dropped, due to the excessive regulatory requirements of personal atomic generator implants, and waivers against possibility of cancer.

Implantable biofuel cells are another approach being intensively studied in many places. These tiny devices work by stripping sugar and air molecules apart as they pass by in the bloostream. In particular, glucose and oxygen. The cell snags glucose molecules at one end, and oxygen at the other. electrons naturally strip away from glucose, running through conduits in the cell, to feed the oxygen at the other. Both promptly detatch.

The fuel is provided by the body, so these fuel cells basically have no operational limit in theory. Inpractice, they have yet to be implanted, but, are basically turning the food injested and the air breathed into fuel to power the implants, in the same way cells do naturally.

Implantable biofuel cells come in two types. The normal variety rely on natural electron flow, and yueld nominal current, but can run practically forever. The second type utilise enzymes to catalyse the reaction at each electrode. This yields a far superior reaction, but, unfortunately, the cells do not manufacture the enzyme and only have a finite supply, as with a batteryy, so when the enzyme unravels...

The best enzyme-based implantable cell will last for two years, much less than a battery, then it has to be replaced.

A new battery type, this one utilising zinc and silver chloride, is also under development. Like any other battery, it hasa finite lifespan. However, unlike lithium-iodine, it only has a lifespan of a week. Being developed at the University of Texas, the new battery type is so fine, it can be injected into the body, or punched into the skin. Then, when it dies, it passes out of the body, and a new one is injected in. No deep implantation, no surgery, and an almost painless regular ritual.

Kinetic energy is the energy of motion. Anything that is in motion haslatent kinetic energy. Energy just waiting to be used. An arm, a leg, abeating heart or diaphram. If thisenergy canbe tapped the implant will have power for as long as the person isalive. After that, it really does not matter.

The british government has launched aconsortium, half funded by them, half by industry, in an attempt to create kinetic powered implants. The fundamental technology is available - the swiss have been using such for years to power wrist watches. The difficulty laysin making it implantable.

Arelated attempt is that of piezoelectric generation. Piezoelectric energy comes from mechanical stress on crystaline formations. Inother words, again using bodily movements, but rather than the movements themselves, relying on the changes in force exerted to generate power. For example, a piezoelectric lattice under a muscle. Every time the muscle contracts, the compression force generates power.

The problem here, is that the power generated is extremely minute, more so than any other method. Zhong Lin Wang at the Georgia Institute of Technology is presently the only one pursuing this idea.


A brief history of cardiac pacing

Quest for Battery-Free Pacemakers

Engineers Devise Implantable Dosimeter to Track Success of Radiation Therapy

Eureka report on AdamHeller, designer of zinc and silver chloride batteries

Potentially implantable miniature batteries (Abstract)

Professor Zhong Lin Wang's Nano Research Group

Your body the powerplant

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