Modelling and analysis of polymer diaphragms for micro sensing and actuation

Micro sensors and actuators have potential applications in the domains like biomedical, energy harvesting and MEMS. The thin diaphragm as a primary micromechanical element is commonly seen in most of these systems. In recent days polymer-based diaphragms are being used instead of metallic diaphragms as they are more compliant, biocompatible and economical to process. Among polymers, Polydimethylsiloxane (PDMS) is by far the most widely used polymer. Fabrication and prototyping of microfluidic chips is a major area where PDMS is used. PDMS being bio-stable is used for biomedical applications such as drug delivery system and blood-contacting biomaterials. In the present work, the analysis is performed to investigate the behavior of PDMS films along with Parylene and Polyimide films. The deflection of the polymer diaphragms is computed using the analytical and finite element (FE) approaches. The deflection is computed considering the edges of the diaphragm to be fixed and the diaphragm subjected to uniform pressure. Three geometries (Circle, Rectangle, and Square) and three thicknesses are considered for each of the above materials. The results of the FE model and analytical computation are found to be in good agreement with each other. It is observed that the PDMS diaphragms with circular geometry exhibited larger deflection. The deflection values appear to be suitable for enhancing diaphragm performance in applications like micro pumps and energy harvesting devices.