Active implantable devices such as cardiac defibrillators and pacemakers can literally be lifesavers. That is, as long as their power supplies last.
Batteries that power these products have a limited life span. Many need to be replaced within seven to 10 years. And, with increasing demand on the devices to perform new functions and to make them smaller, their lifetimes will only decrease.
Replacing batteries usually means more surgery, which can cost $15,000 to $20,000.
Not such a great solution for a patient who has probably already undergone several procedures.
New products in the pipeline also pose problems for traditional battery power systems. Sensors for neurostimulation and blood glucose are one example. These tend to be very small. Bulky batteries may not work in them.
Clearly, finding a way to improve power sources is needed.
The answer may lie within the human body. At least two groups of researchers are looking to harness the energy created by “two feet and a heartbeat” to power implantables.
SweetPower (Victoria, BC, Canada; www.sweetpower.com) has developed a reliable glucose fuel cell to power implantable devices. The unit, based on a silicon chip, uses glucose produced in human blood to make electricity. The cell can generate power ratings of 400 mV and 100 nW, and is self-sustaining. Since nontoxic materials are used, the only by-products are harmless carbon dioxide and water.
Some applications for the glucose fuel cell include neurostimulation, diabetes, and drug-delivery devices.
Another group of scientists thinks it can use a different part of the body to produce energy. A UK-based consortium is working on prototyping a device that can harvest energy from movement in or on the body, including joint movement and heartbeats. The self-energizing implantable medical microsystem (SIMM) project will use a microgenerator manufactured as a MEMS to gather the energy.
SIMM project leader David Hatherall says, “Providing an in-body power supply will reduce the dependence on batteries for implantable devices, and facilitate the design of new self-powered devices for applications currently not feasible due to battery life and space restrictions.”
The prototype design is expected to achieve 10–100 times more power than previous attempts to harvest human energy.
New applications are emerging for devices such as activity monitors, bladder control valves, and cochlear and retinal implants.
The need for a reliable, nontoxic power supply will only increase.
It looks like the Zen masters might be right. The answer could very well be within ourselves.