Two micro-generators are on their way to powering pacemakers and other implanted medical devices. The two operate in drastically different ways. The first from Alois Pfenniger of the University of Bern and Bern University of Applied Sciences in Switzerland have developed a turbine that is placed in one of the heart's arteries. Pfenniger explains the concept, "The heart produces around 1 or 1.5 watts of hydraulic power, and we want to take maybe one milliwatt. A pacemaker only needs around 10 microwatts." In a test, Pfenniger used a millimeter-wide tube that would mimic the internal thoracic artery. Using 3 different turbine, that he did not make, he was able to get 800 microwatts from the most efficient. Which is 80 times the power needed to power a pacemaker. The main issue comes from turbulance caused by the turbines, and the possibility of blood clotting.
The other micro-generator comes from Paul Roberts of Southampton University Hospitals NHS Trust. His design works by using the blood pressure changes, externally, of a beating heart to move a magnet back and forth for a miniature Faraday generator. Roberts placed this device inside of a test pig and was able to get 2 microwatts from the device on average. This is far less than what is needed for the average pacemaker. Roberts talks of his next steps, "the drive for all of this is to potentially reduce sizes of devices, and equally to accommodate increasing demands placed on devices, such as more diagnostics and wireless communications." To do all this, Roberts is seeking partners and government funding.
Pic via Alios Pfenniger, one of the turbine rotors