Recent use of mobile phones as a multimedia device has increased the development of micro-speaker modules having high quality and a compact size. Micro-speakers use polymer diaphragms fabricated by the thermoforming process. To improve the sound quality, micro-speaker diaphragms are usually designed to contain a number of micro-corrugations. This study investigated the effects of the corrugation depth on the acoustic characteristics of the diaphragm, using finite element (FE) analysis. Structural FE analysis was performed to investigate the stiffness change according to the corrugation depth. Modal FE analysis was used to compare the change in natural frequencies for each case. Harmonic response analysis further investigated the resulting variation in acoustic power. The effects of the corrugation depth on the acoustic characteristics of the diaphragm were discussed by reviewing all the FE analysis results synthetically.

The present study uses an electron beam (e-beam) to modify the wetting characteristics of thermoplastic polymer surfaces. A high energy e-beam irradiated various polymer surfaces (PET, PMMA, and PC), with variations in irradiation time and applied current. The water contact angles were measured on the e-beam irradiated surfaces in order to investigate the changes in the surface energy and the relevant wettability. Furthermore, XPS analyses were performed to investigate the chemical composition change in the e-beam irradiated surfaces; the results showed that the hydrophilic groups (C-O) increased after the electron beam irradiation. Also, water collection tests were performed for various polymer samples in order to investigate the effect of the surface energy on the ability of water collection, from which it can be seen that the irradiated surfaces revealed better water-collecting capability than pure polymer surfaces.