A Thin-Film Piezoelectric Speaker Based On An Active Microstructure Array

We report a thin-film acoustic speaker based on the actuation of a dense array of freestanding piezoelectric microstructures. The microstructure array is embossed on an ultra-thin polyvinylidene fluoride (PVDF) film in a self-aligned manner using vacuum and thermal treatments, and is also protected by a perforated passive layer on top. A 100 cm ² thin-film speaker (81 cm ² active area) achieves 75 dB sound pressure level (SPL) at 5 kHz and 50 cm distance using 20 V excitation. Its frequency response does not roll off below 100 kHz, owing to the microstructure design. Our speaker can be mounted on various surfaces, thereby rendering the surfaces acoustically active with high sensitivity at both audible and ultrasonic frequencies, which enables broader application prospects over prior PVDF speakers based on freestanding and curved designs. The simple structure, the uniform performance, and the scalable low-cost fabrication of our speaker constitute significant advantages over cellular-electret speakers for large-scale application. Therefore, this thin-film speaker could perform as a new acoustic platform for active noise control, robotics, and virtual/augmented reality.