While medical device technology continues to grow more and more advanced, one component that seems to be lagging behind is battery technology. As you know, batteries are what makes all of our electronic devices portable. One of the specs I look at when researching a notebook computer, cell phone, or mp3 player is the battery life. With current technology, you can increase the battery life easily, but at the expense of size, as more power requires a larger battery. Recently, Apple switched their MacBook notebook line to an internal, non-replaceable battery so that a larger battery can be placed inside the notebook.
With medical devices, especially implants, battery and power is extremely crucial. A company can develop the world's most advanced implant that can prevent many problems, but if the battery needs to be replaced often, then much of the advantage is lost. This is even more important to senior citizens, whose risk of complications under general anesthesia increase with age.
The power system utilized can vary from device to device, however, how can medical devices as a whole be made to deliver results without needing their batteries replaced frequently? Here are a few technologies, current, future, and even fictional, that may be the answer:
- Conventional: a battery is attached to the device itself. It is very low-maintenance, however, as mentioned above, minor surgery must be performed to replace the battery. This system is most suitable for implants with low power applications.
- RF: this system uses an implanted receiver with control circuitry powered by an external source. Power is sent from an external source (e.g. belt-worn battery pack) wirelessly to the receiver using RF energy. This system eliminates the need to replace an internal battery, however, the external power source must be worn in close proximity to the receiver in order to receive power.
- RF + rechargeable: the newest type of system utilizes the battery feature of a conventional system with the wireless telemetry of an RF system to recharge the battery. The external power source is worn for a few hours every few weeks to recharge the battery. The battery must eventually be replaced, however, rechargeable systems last longer than conventional systems.
- Biomechanical: also known as "power-walking", there have been a few research projects that utilize the movement of our limbs while walking to generate electricity. It's only enough electricity to power small handheld devices like a cell phone or GPS, but it might be enough to power a medical implant. One company called Lightning Packs develops electricity-generating backpacks that use the body's vertical movement, similar to how a pedometer works. The latest is a study from the University of Michigan, Simon Fraser University in Canada, and the University of Pittsburgh that uses an electricity-generating knee brace.
- Nuclear: in the late Michael Crichton novel, The Terminal Man, the main character, a man suffering from violent epilepsy, has electrodes implanted in his brain to control the seizures. The electrodes are powered by a plutonium pack in his shoulder, which theoretically, would last his entire lifetime and would be removed after his death. This system would eliminate the need for any maintenance, however, as the world is still a little hesitant to embrace nuclear energy to power our cities, plutonium to power our implants will probably be left to the pages of fiction for a while. (In case you were wondering, the main character's computer "takes over" his personality and he goes crazy in the end. Read it. The book is amazing and Michael Crichton was a genius!)
