AAA Battery Gets a Mini-Me
By Louise Knapp
http://www.wired.com/news/feedback/mail/1,2330,143,00.html

02:00 AM Oct. 08, 2003 PT

A new battery -- lauded as the smallest implantable battery in the world -- may soon be powering tiny bionic neurons,
devices that emit electrical micropulses to stimulate damaged nerves and muscles.

The battery measures 2.9 mm in diameter and 13 mm in length -- about the size of a pencil tip.

The tiny powerhouse helps keep the bionic neurons small. Even with the battery, the cylindrical devices are only 1/35
the size of a standard AA battery. The small size allows doctors to use minimally invasive techniques when implanting
the bionic neurons, reducing surgical trauma and the risk of infection.

While the battery may be small, it makes up in staying power what it lacks in size. California-based Quallion's battery
can, with recharging, last up to 10 years.

The team at Quallion, which developed the battery in conjunction with Argonne National Laboratory, says the key to the
lifespan of the battery is its chemistry.

The researchers isolated a phase of a polysiloxane polymer, a material that has the highest conductivity ever reported
for an electrical conductor.

Recharging is done wirelessly by an external electrical field, meaning implants no longer have to be surgically removed
and replaced when the battery runs out of juice.

The new battery may power implantables that could help millions of stroke victims and people suffering from urinary-
urge incontinence and neurological disorders such as Parkinson's disease.

Electrical pulses are already used for muscle stimulation as part of physical therapy, but current methods are not
without their drawbacks.

The most common treatment method uses an electrical stimulator on the surface of the skin. But the electrical jolts can
prove painful and the pulses may not hit the muscle in the right place.

Implants, which are less commonly employed, currently are powered by large, relatively short-lived batteries, which
cannot be recharged. Consequently, only a few implantable devices, such as cardiac pacemakers, are in use.

"Current ones sometimes last three or at most five years," said Wendy Fong, senior manager in business development at
Quallion.

"This is a concern for doctors, especially for those treating patients who are not so healthy, because (the patients)
have to be subjected to surgical intrusion when the implant needs replacing," Fong said.

Bionic neurons have the advantage of being small and can be implanted near the target muscle. They work by mimicking
nerve impulses from the brain: They reanimate the paralyzed muscles through electrical stimulation, just like the frog
in Frankenstein.

Other research into bionic neurons has experimented with external power supplies. One such project is being conducted
at the University of Southern California's biomedical engineering department. http://www.usc.edu/dept/biomed/

"If you have a complicated set of control parameters (for the stimulator), they can't fit into the implant. If you have
to have the control system outside the body, then you may as well have the power source outside, too," said Dr. Gerald
Loeb, professor of biomedical engineering at USC. "This way you can keep your implant smaller."

Loeb's device is powered by an external transmitter coil that emits a magnetic field. He admits that needing to be
constantly in proximity to the coil to power the stimulation means the method would not be feasible for all
applications.

"In the treatment of urinary incontinence, which is an area Quallion is focused on, the stimulation has to be delivered
all day long so there's no good place to put an external coil," Loeb said.

The Quallion team decided to focus on urinary incontinence partly because the problem requires constant stimulation,
but also because millions of people suffer from it.

"There are more adult's diapers sold in the world than children's ones," Fong said.

If tests prove the battery-powered bionic neurons effective, the devices could be used in a variety of treatments: to
help control muscle tremors brought on by Parkinson's disease, to stimulate stroke victims' muscles to guard against
atrophy, and to provide deep-brain stimulation for the treatment of migraines.

The rate of stimulation can be programmed into the device before it's implanted. A battery-management system developed
by Advanced Bionics allows for remote re-programming if the doctor feels the patient requires more or less stimulation.
This system also dictates recharging.

"The battery-management system communicates to the device and says, 'I'm low.' It works like a fuel gauge," Fong said.

Recharging is simple. The primary coil is already implanted within the device -- so it is inside the body -- while the
external coil can be incorporated into a pillow pad or belt. The patient sits on the pad, or straps on the belt, and 15
minutes later he or she fully charged.

How often the battery needs recharging depends on how often the electric pulses are given off -- recharging intervals
can vary from once a week to once a month.

"The system can be set up to either alert the patient to recharge, or the doctor can just let the patient know he or
she needs to recharge once a week -- providing a buffer time to allow for forgetful patients," Fong said.

The battery-powered implants are faring well in trials in the United States, Fong said, and those in the trade seem
confident in its abilities.

"One of Quallion's implants is already in use in Europe so we know it works -- it's a very exciting enhancement," Loeb
said.

One sticking point with the battery is its price. A single battery costs $400. But mass production would lower the
price, Fong said.

Fong said she was confident the battery will receive Food and Drug Administration approval within a year.

SOURCE: Wired News
http://www.wired.com/news/medtech/0,1286,60706,00.html

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