| 초록 |
With the rise of wearable electronics, the flexible piezoelectric energy harvesting devices have been studied to efficiently convert the physical motion of the human body into the electrical energy for the wearable electronics. The major obstacles to realize the flexible piezoelectric generator is the insufficient output power generation and the poor efficiency at the low-frequency regime. Here, the recent developments for flexible piezoelectric generators have been reviewed. Also, a curved piezoelectric generator and a piezo-triboelectric hybrid generator favourable for wearable applications, generating a high output power have been demonstrated. The curved structure plays a key role to improve the power generation by effectively distributing the applied force across the piezoelectric layer as well as to operate at the low frequency vibration. Accordingly, this generator produces ~120 V of the output voltage, ~25 µA/cm2 of the current density in a cycle. Furthermore, our generator can operate in low frequencies below 50 Hz, generating ~55 V of output voltage and 250 µA of output current at 35 Hz, and even works at 1 Hz. With this generator, we successfully lit up 476 commercial LED bulbs. In addition, we experimentally demonstrate that the generator can be possible to apply to shoes, watch, and clothes as a power source for wearable devices. This hybrid generator combines high piezoelectric output current and triboelectric output voltage, which produces peak output voltage of ~370 V and current density of ~12 μA/cm2. The output power successfully lit up 600 LED bulbs by the application of a 0.2 N mechanical force and it charged a 10 μF capacitor to 10 V in 25 s. Our result will provide a framework to enhance the output power of the conventional piezoelectric generators, and open a new avenue to realize self-powered systems such as wearable electronic devices. |
