Microgenerators for energy autarkic pacemakers and defibrillators: fact or fiction?

Implantable devices for medical use like permanent pacemakers, defibrillators, and fluid pumps depend on an energy provided by batteries. Unfortunately, the battery usually determines the duration of life of these devices, while technical problems occur infrequent. Device replacement for battery exhaustion requires surgical procedures and account for up to 1/3 of all pacemakers sold. Attempts to provide unlimited power support using radio transmission, nuclear energy etc. did not gain clinical acceptance.

We therefore evaluated the potential role of a microgenerator (designed for use in wrist watches) to recharge pacemaker batteries. We used the Epson-Seiko Caliber 5M22 that uses a "Gold-Cap" for energy storage. The mass of the actuator is 1.6 g and an angle of > 10 degrees is needed to overcome friction. Output at a rotor frequency of 200 Hz is 1.8 mWatt To measure the power provided, various experiments were made with the microgenerator taped to the chest of a normal person working in an office. Range of 11 experiments over 8 hours each was 0.2 to 3.1 microWatt (median 0.5 microWatt). Therefore, the power generated was 10 to 100 times less than the calculated power needed to recharge a typical pacemaker battery. A second type of generator (Mondaine, Zurich, Switzerland) with less mechanical parts, available in a "black box" version only, generated not more power.

Thus, commercially available, yet not optimized microgenerators provided only between 1 to 10% of the power requirements of a pacemaker. However, modifications in design and mainly the orientation and weight of the actuator to generate more power from the G-forces during walking, would result in a more meaningful energy output.