Piezoelectric materials can convert ambient vibrations into electrical energy. In this letter, the capability of harvesting the electrical energy from mechanical vibrations in a dynamic environment through a piezoelectric drum transducer has been investigated. Under a prestress of 0.15 N and a cyclic stress of 0.7 N, a power of 11 mW was generated at the resonance frequency of the transducer ͑590 Hz͒ across an 18 k⍀ resistor. It is found that the energy from the transducer increases while the resonance frequency of the transducer decreases when the prestress increases. The results demonstrate the potential of the drum transducer in energy harvesting. © 2007 American Institute of Physics. ͓DOI: 10.1063/1.2713357͔With the recent advances in wireless and microelectromechanical systems technology, the demand for portable electronics and wireless sensors is growing rapidly. Since these devices are portable, it becomes necessary to carry their own power supply. Piezoelectric materials are ideal sources of such energy because they can convert mechanical strain energy into electrical energy or vice versa. Energy can be reclaimed and stored for later use to recharge a battery or power a device through a process called energy harvesting. Many researchers have studied the concept of utilizing piezoelectric material for energy generation over the past few decades. 1-5 In one prototype of power harvesting system, a polyvinylidene fluoride film was used and implemented in vivo on a mongrel dog. The feasibility of extracting energy from the expansion and contraction of the rib cage during breathing was explored in 1984. 6 The power harvesting system produces a peak voltage of 18 V, which corresponded to a power of about 17 W. Another investigation for power harvesting from ambulation to provide supplemental power to operate artificial organs by using lead zirconate titanate ͑PZT͒-based piezoelectric stacks during walking or jogging was performed by Antaki et al. in 1995. 7 An average power of 250-700 mW was extracted from walking, and over 2 W was obtained from jogging. The recent progress in power harvesting from mechanical vibration to power generation was performed at Pennsylvania State University. [8][9][10] These studies were made on a cymbal transducer having a ceramic dise with a diameter of 29 mm and 1 mm thickness. A power of 39 mW can be transferred across the low impedance load under a dynamic force of 7.8 N at 100 Hz. The effective piezoelectric field constant of the material is a crucial parameter for selecting an element of the piezoelectric energy harvesting device, which is proportional to the harvested power. In this letter, a drum transducer was studied as the energy harvesting device because it was reported previously that the drum transducer has good electrical and mechanical performance. 11 It is expected that the energy harvesting performance of the drum transducer can be better than that of the cymbal transducer. The electrical power generation from a single drum transducer element under a cyclic force ...