Thermal Driving Method and Displacement Properties of a Thin-Film Polyimide Diaphragm for a MEMS Actuator
A thin-film polyimide diaphragm for a MEMS actuator was fabricated and its process and mechanical characteristics were investigated. Owing to its low elastic modulus and the thin-film process, a thin-film polyimide diaphragm has a merit in terms of producing a large displacement. Given that merit, spin coating was used for forming a thin film of polyamide, and deep-RIE (Bosch process) was used for fabricating the diaphragm section of the actuator. Thin-film polyimide diaphragms with micrometer-order thickness were fabricated. To drive the diaphragm as an actuator, the following two methods were applied: heat expansion by applying an electric current and volume expansion of a gas-liquid phase-change material confined in a cavity between polyimide diaphragms. As for the former method, an aluminum thin film is deposited on the diaphragm. As for the latter, paraffin (vaporized by heating) is used as the phase-change material. Displacement characteristics for each method were revealed by the experiments. In the case of both methods, displacements of tens of micrometers were outputted. Experiments of driving actuator confirmed that the proposed systems work as actuators. The actuators developed in this research are applicable to micro-pumps for medical and other uses.
Tojiro Aoyama, Hideki Aoyama, Atsushi Matsubara, Hayato Yoshioka and Libo Zhou
S. Mifuji et al., "Thermal Driving Method and Displacement Properties of a Thin-Film Polyimide Diaphragm for a MEMS Actuator", Key Engineering Materials, Vols. 523-524, pp. 563-568, 2012