Self-powered wearables, such as watches, have existed for approximately 30 years. These wearables generate power using an eccentric rotor that rotates with movement. Certain types of motion facilitate energy generation better than others. However, harvesting energy from low-frequency motion, such as walking, has proven difficult, limiting the applications of low-frequency energy harvesters.

A new eccentric rotor design that includes a well-tuned rotational spring improves the amount of power generated by low-frequency motion up to 300 percent. Electricity is harvested from an optimized array of copper coils and magnets. Potential applications include low-power draw sensors, wearables, and communication systems.