Electrical and Fluidic Relations in a Piezoelectric Micro Diaphragm Pump

Inhalt:
Accurate dosing is essential for drug delivery applications, as most medical therapeutics can have severe side effects or even lead to death when overdosed. Piezoelectric micro diaphragm pumps already serve in the administration of drugs due to their ability to offer precise dosing volumes. Nevertheless, these volumes can show significant variations for individual pumps due to high tolerances of the mostly manual production process. Therefore, pumps must be calibrated with water flow measurements or need a volume control circuit added to their driving electronics. However, calibrating every pump with water results in a contamination of their pump chamber. This prevents the pumps from being conveniently applied in a biomedical environment. The pumping cycle of the applied micro diaphragm pumps is based on the inverse piezoelectric effect. This leads to a direct relation between electrical and fluidic parameters of the pump. Consequently, the first approach to correlate fluidic with electric values, is to assess the impedance of the piezoelectric actuator for different load conditions of the pump. In a second approach we directly compare the measured electrical power acting on the piezoelectric ceramic with the fluidic power simultaneously produced by this actuator, thus the micro pump. A model is derived to predict pump stroke volumes from electrical characterization measurements by avoiding contamination of the pump chamber. This can facilitate the application of micro diaphragm pumps in biomedical applications like drug delivery or organ-on-chip without the need of an additional in-built volume sensor and a corresponding control loop.