New Battery Technology Helps Stimulate Nerves

The lithium battery is the workhorse in implantable devices --stimulators used to jump start the heart and help the central nervoussystem make critical connections in, for example, Parkinson's andepilepsy patients. Designed to be extraordinarily reliable and workcontinuously for years, the tiny batteries that power implantables areindispensable in everything from pacemakers to the electronicstimulators that help restore function in the brains of Parkinson'spatients.

But lithium batteries don't last forever and new surgery to maintainmany devices seeded into the body is required, as it is to replacebatteries and devices at the end of their lives. Moreover, a newgeneration of tiny electrical devices to stimulate the nervous system,treat incontinence and overcome muscular impairment is coming on lineas scientists and engineers continue to shrink the components that makeup the devices.

Central to that ability, according to University ofWisconsin-Madison Professor Emeritus of chemistry Robert West, is newlithium battery technology, technology capable of making batteriessmaller, last longer and, soon, accept a charge from outside the bodywithout the need for surgery.

Using organosilicon compounds, West and his UW-Madison colleagues havedeveloped a new generation of rechargeable lithium ion batteries whoselifetimes are more than twice as long as the batteries now used in thetiny medical devices.

"It turns out the organosilicon compounds are really good for improvinglithium battery technology," says West, whose new battery technologypowers a "microstimulater" not much larger than a pencil lead and thatcan be injected near target nerves to help overcome the faulty nervoussystem wiring at the heart of Parkinson's, epilepsy and incontinence.

"The idea is that whenever you have a broken nerve connection, you cansupply the electrical impulse to complete the circuit," West explains.

The microstimulator was developed by a consortium includingUW-Madison's Organosilicon Research Center, Argonne NationalLaboratory, Advanced Bionics Corp., the Alfred Mann Foundation andQuallion, LLC. The device was recognized earlier this year with an"R&D 100 Award" from R&D Magazine.

West's group developed the electrolyte, theelectricity-conducting liquid that is the heart of the battery. The neworganosilicon compounds developed by the Wisconsin chemists, says West,have numerous advantages over traditional lithium battery chemistry.

"They're very flexible. They don't solidify. They're stable,nonflammable, non-toxic and they pose no threat to the environment,"says West, an international authority on silicon chemistry. Silicon,the stuff computer chips are made of, is one of the Earth's mostabundant elements. Organosilicons are compounds composed of silicon andother natural materials.

In the context of the lithium battery, West's group has beenmaking and testing "designer silicons" that are specially formulated toconduct electricity in a very compact environment. In the lithiumbattery, charge is maintained as lithium ions flow between thebattery's positive and negative electrodes.

"The battery requires something the ions can go through easily. We hadto tweak the (organosilicon) molecules to get higher conductivity andstability," says West.

A critical advantage of the new battery technology is lifespan: "Ifyou're going to implant these things, you want a (battery) lifetime ofat least 10 years," says West, whose organosilicon batteries areprojected to power the tiny implantable devices for more than 12 years.

In addition to implantable devices for medicine, lithium batteries are used in scores of applications, from spacecraft to iPods.

Patented through the Wisconsin Alumni Research Foundation, the neworganosilicon compound technology is also being developed through a newstart-up company, Polyron, Inc. The work to develop the neworganosilicon compounds was funded by the National Institute ofStandards and Technology, a federal technology agency that works withindustry to develop and apply technology, measurements and standards.