An implantable active microport based on a self-priming high-performance two-stage micropump

This paper reports on significant progress in the development of an implantable active microport system for an automated administration of aqueous drug suspensions. A novel piezoelectric two-stage micropump ensures the controlled release of minute amounts of fluid with flow rates between 0.1 μl/min and 50 μl/min. A modification of the chamber design reduces the detrimental effect of entrapped air bubbles. The absence of air bubbles in the pump chamber yields a significantly enhanced accuracy of the delivered fluid volumes. An optimized actuation scheme referred to as gas pumping mode is proposed for the transport of gas. For alternate gas and liquid pumping a critical compression ratio is analytically derived which is determined by the capillary pressure drop of a gas–liquid interface trapped in the pump chamber. Due to an increased compression ratio of the new pump chamber design the micropump has now a full capability to pump both gas and liquid which enables a reliable self-priming.