On the Design and Modeling of a Full-Range Piezoelectric MEMS Loudspeaker for In-Ear Applications

Capillary effect based selective sealing strategy for boosting the piezoelectric MEMS speaker performance

“…Traditional electromagnetic speakers face technical challenges due to their large size, high power consumption and complex manual assembly 2 , making it di cult for them to adapt to the wave of intelligent device development. Therefore, the MEMS speaker technology has obtained signi cant attention in recent years, and different types of MEMS speakers have been proposed, including electromagnetic 3,4 , electrostatic 5,6 and piezoelectric ones [7][8][9][10][11][12][13][14][15][16][17] . Among them, the piezoelectric MEMS speaker has been treated as the most promising substitute due to its relatively simple structure, high operation reliability, low power consumption and moderate performance.…”

“…Till now, great progress has been achieved in this area and various piezoelectric MEMS speakers have been developed for high frequency 7 , broadband 8 and directional emission 9 applications. Based on the electro-acoustic transduction structure design, the piezoelectric MEMS speakers can be roughly categorized into three groups, namely fully clamped diaphragm 10 , partially clamped diaphragm [11][12][13][14] and cantilever beam like diaphragm 7,8,15,16 , in which the cantilever beam like diaphragm design has been attracting more extensively study owing to their distinct advantages as high SPL output capability, less sensitive to the fabrication process related residual stress and large linear operation range. In most cases, the speaker usually consists of multi cantilever beams 7,8 , and each of them can operate independently without any mechanical coupling.…”

“…Unfortunately, the air gaps surrounding the cantilever structures can provide the air leakage pathway, causing the "acoustic short circuit" issue. Under its associated acoustic loss effect, the generated SPL from the speaker will be weakened, especially in the low-frequency band 12,13 . In addition, the non-uniform size control during the fabrication can lead to inconsistency in the mechanical performance of these cantilever beams, thus changing their frequency responses.…”