Micropump based liquid dosing systems have the potential to enable many application scenarios. For example, their small size can realize implants and the ability to accurately dose small volume enables drug delivery as well as analytical devices. Their low energy demands can lead to stand-alone dosing systems. However, the wide range of use cases demands for quite different sets of performance and reliability requirements that are often challenging to meet. Due to an evolving pump design, existing dynamic models, like for the actuator motion or the flow rate determination, became more and more inaccurate and little is understood about flow stability and failure mechanisms. The goal of this work is to facilitate the efficient and accurate design of micropump systems by providing models, methods and standard procedures for performance and reliability. The performance behavior of micropump systems was investigated, as it is the key to an accurate design and constitutes the foundations to estimate the reliability characteristics. Therefore, the effect of system parameters and driving signal on the flow rate, liquid pressure ability, gas pressure ability for bubble tolerance as well as self-priming ability, energetic conversion efficiency, size and costs was evaluated. Analytical and numerical models were developed to simulate and optimize the static and dynamic behavior of actuator, valves and the whole micropump, embedded in a system environment. It was found that limitations of the flow rate mainly originate from viscous squeeze film damping, cavitation and valve efficiency. The design is restricted by prevailing stresses in the actuator diaphragm and its manufacturing method, available piezo ceramic properties, the valve sealing lip, the pump chamber height and pressure smoothing characteristics of the fluidic path. Reliability describes the ability to keep performance values within accuracy limits over a lifetime within a failure probability. The core task of a dosing system can be reduced to providing a flow rate over a time period. Both, inherent influences, like cavitation, actuator fatigue and valve sticking, as well as external influences, such as temperature, pressure and particle laden flow, affect the flow stability and were investigated. The required conditions and impact of each effect were identified and are described together with critical failure mechanisms. To avoid or reduce the impact of these influences, guidelines are given to adjust the architecture, pump design, manufacturing methods as well as operating conditions. The results show that cavitation, valve sticking as well as temperature and pressure variations are most critical for the short term flow stability, but are fully reversible effects. In contrast, actuator fatigue and particle laden flow usually alter the flow rate performance of the system irreversibly. A procedure to define the system architecture is proposed that starts with selecting the required functional components and is followed by their individual design, the specification of operating strategies and the implementation of system integration. Within this framework, matching solutions can be achieved with open-loop and closed-loop flow control. Based on the analysis of competing design directions, a process was developed to balance different goals for open-loop flow control. If no match can be found, but performance requirements alone can be met, closed-loop flow control can be implemented with direct or indirect flow sensing. Flow control modes, sensing technologies and suitable system setups were investigated to combine micropumps and flow sensors. Thermal calorimeter and differential pressure based flow sensors showed acceptable accuracy in measuring the highly pulsatile micropump flow in single stroke mode. To conclude, this work is able to expand the potential field of applications by providing insights, models and procedures for an accurate application specific design of micropump based liquid dosing systems.    «

Micropump based liquid dosing systems have the potential to enable many application scenarios. For example, their small size can realize implants and the ability to accurately dose small volume enables drug delivery as well as analytical devices. Their low energy demands can lead to stand-alone dosing systems. However, the wide range of use cases demands for quite different sets of performance and reliability requirements that are often challenging to meet. Due to an evolving pump design, existi...    »