A polymer-based MEMS loudspeaker featuring a partially stiffened membrane actuated by a PZT thin film.

Miniaturized loudspeakers are increasingly relevant for wearable and transparent electronics, but achieving consistent acoustic performance, particularly at low frequencies, remains a challenge. Here we show a polymer-based loudspeaker that features a partially stiffened membrane actuated by a transferred thin film of lead zirconate titanate. The flexible polymer reduces overall stiffness, while the localized stiffening broadens the frequency response. The piezoelectric film is integrated through a transfer process that employs a donor substrate. We evaluate functionality through electrical, mechanical, acoustic, and optical measurements, including sound pressure level and resonance frequency, in both open field and in-ear conditions. The results confirm the device's ability to operate under different acoustic loads and demonstrate compatibility of the fabrication process with flexible and transparent substrates. This approach enables the integration of transparent piezoelectric actuators and is suitable for compact, bendable, and optically transparent audio systems.