The growing demand for thinner, lighter, and more energy-efficient electronic systems has driven the development of acoustic technologies toward compact and flexible sound generation platforms. Despite significant progress, conventional electromagnetic speakers remain limited by bulky structures, energy losses, and poor compatibility with modern ultrathin devices. In this review, recent advancements in piezoelectric acoustic systems are presented, demonstrating a new generation of speakers capable of producing high-fidelity sound from ultra-slim, lightweight, and mechanically compliant designs. Through refined structural configurations and efficient electromechanical coupling, these piezoelectric exciters achieve strong acoustic output, fast response, and wide frequency operation while drastically reducing component thickness. These exciters also show their suitability for seamless integration into flexible displays, wearable devices, and automotive panels, offering enhanced spatial audio practicality and multifunctional operation, including demonstrative output and sensing. This advancement marks a step toward the convergence of acoustic, haptic, and interactive technologies, for the realization of sustainable and immersive humanmachine interfaces in future electronic and automotive systems.
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Flexible piezoelectric cross-bar array sensors for upper-limb kinesthetic sensing via muscle dynamics Junki Lee, Jihun Choi, Hyunseung Kim, Min Gon Son, Dong Yeol Hyeon, Jung Hwan Park, Andris Šutka, Chang Kyu Jeong Journal of the Korean Ceramic Society.2026;[Epub] CrossRef
Pb(Sb0.5Nb0.5)x(Zr0.51Ti0.49)1-xO3 (abbreviation: PSN-PZT) ceramics were synthesized, using conventional bulk ceramic processing technology, with various PSN doping contents. The maximum density of PSN-PZT was 97% of the theoretical density in the samples sintered at 1,250℃. The maximum values of the piezoelectric properties achieved using the conventional processes were: kp of 0.625, d33 of 531 pC/N, and g33 of 33 mV·m/N. Finally, we fabricated a piezo-speaker with the optimized PSN-PZT ceramics. The SPL of the speaker was measured at a distance of 1 m, with a driving voltage of 40 Vrms in the frequency range of ~300 Hz to 9 kHz. The measured SPLmax was at a very high level (95 dB), which was superior in quality in comparison with those of other commercial products.
Piezoelectric thick films of soft Pb(Zr,Ti)O3 (PZT) based commercial material (S55) were fabricated using a conventional tape casting method. Ag-Pd electrodes were printed on the piezoelectric film at room temperature and all 5 layered films with a dimension of 12 ㎜× 16 ㎜were successfully laminated for a multi-layered piezoelectric ceramic actuator. The laminated specimens were co-fired at 1,100℃ for 1 h. A flat layered and dense microstructure was obtained for the 112 ㎛thick piezoelectric actuator after sintering process. Thereafter, a prototype piezoelectric speaker was fabricated using the multi-layered piezoelectric ceramic actuator which can operate as a bimorph. Its SPL (sound pressure level) characteristic was also evaluated for speaker application. Frequency response revealed that the output SPL with a root mean square voltage of 10 V increased gradually to the highest peak of 87.5 dB for 1.5 kHz and exhibited a relatively stable behavior over the measured frequency range (≤20 kHz) at a distance of 10 cm, implying that the fabricated piezoelectric speaker is potential for speaker applications.
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Development of Shoe-heating System based on Piezoelectric Energy Harvesting Seung-Jin Lee, Sang-Woong Lee, Hi-Geun Shin, Gi-Man Kim, Seong-Dae Choi Journal of the Korean Society of Manufacturing Process Engineers.2019; 18(7): 48. CrossRef
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