Fraunhofer EMFT’s research and manufacturing portfolio includes piezoelectrically actuated silicon micro diaphragm pumps with passive flap valves. Research and development in the field of microfluidics have been dedicated for many years to the use of micropumps for generating positive and negative pressures, as well as delivering various media. However, for some applications, only small amounts of fluid need to be pumped, compressed, or evacuated, and until now, only macroscopic pumps with high power consumption have been able to achieve the necessary flow rate and pressure, especially for compressible media such as air. To address these requirements, one potential approach is to use a multistage of high-performing micropumps optimized to negative pressure. In this paper, we present several possible ways to cascade piezoelectric silicon micropumps with passive flap valves to achieve these stringent requirements. Initially, simulations are conducted to generate negative pressures with different cascading methods. The first multistage option assumes pressure equalization over the piezo-actuator by the upstream pump, while for the second case, the actuator diaphragm operates against atmospheric pressure. Subsequently, measurement results for the generation of negative gas pressures down to −82.1 kPa relative to atmospheric pressure (19.2 kPa absolute) with a multistage of three micropumps are presented. This research enables further miniaturization of many applications with high-performance requirements for micropumps, achievable with these multistage systems.

A small, robust and high flow silicon micropump with chip size of 5x5x0.6 mm3 is demonstrated with seven times higher air and water flow rate as current state of the art micropumps of that size. High self-pumping frequencies of minimum 290 min-1 and 30 min-1 for air and water have been achieved by reducing fluidic resistances and enhancing piezo mounting processes. Thus, leading to sufficient air ...

Subcutaneous injection is crucial for the treatment of many diseases. Especially for regular or continuous injections, automated dosing is beneficial. However, existing devices are large, uncomfortable, visible under clothing, or interfere with physical activity. Thus, the development of small, energy efficient and reliable patch pumps or implantable systems is necessary and research on microelectromechanical system (MEMS) based drug delivery devices has gained increasing interest. However, the requirements of medical applications are challenging and especially the dosing precision and reliability of MEMS pumps are not yet sufficiently evaluated. To enable further miniaturization, we propose a precise 5 × 5 mm2 silicon micropump. Detailed experimental evaluation of ten pumps proves a backpressure capability with air of 12.5 ± 0.8 kPa, which indicates the ability to transport bubbles. The maximal water flow rate is 74 ± 6 µL/min and the pumps’ average blocking pressure is 51 kPa. The evaluation of the dosing precision for bolus deliveries with water and insulin shows a high repeatability of dosed package volumes. The pumps show a mean standard deviation of only 0.02 mg for 0.5 mg packages, and therefore, stay below the generally accepted 5% deviation, even for this extremely small amount. The high precision enables the combination with higher concentrated medication and is the foundation for the development of an extremely miniaturized patch pump.

A miniaturized drug delivery system for accurate dosing of drugs for therapy of cancer is presented. The weight of the system is less than 8 grams. Silicon micropumps with a stroke volume of 88 nl, and blocking pressure of 6 bar, drive the system. A novel and accurate flow monitoring principle based on capacitance measurement was developed and implemented into the drug delivery system. To prevent free flow, a self blocking safety valve was adapted to the drug micropump. Moreover, further safety features like catheter blockage detection, pump failure detection, bubble detection and a bubble separator was realized. System control and driver electronics to supply the pumps with high voltage was realized on a tiny flex PCB and integrated. System tests showed, that test dosing volumes of 12 μl can be delivered reliably with accuracy better than 4 %. The system is now ready for animal trial (rat model) for a new cancer therapy approach.

Meeting demands of industrial customers of micro fluidic actuators in application fields like drug delivery systems, lubrication dosing or lab technology, a black box concept has been carried out. Various practical problems and drawbacks of micro pumps like weak dosing accuracy, particle vulnerability, gas bubble intolerance, back pressure dependence and free flow problem are addressed and solved within that black box. To solve these particular problems new concepts and ideas as well as a theoretical understanding and technological optimization of the challenges of the micro dosing systems has been realized.

In this paper, the design and fabrication of a multi-material high-performance micropump is presented. Exceptional flow rates of 90 ml/min were achieved by appropriate design optimization. Manufacturing steps such as laser welding and hot embossing were successfully realized and provide a robust and scalable production technique for the micropump. Characterization of the pump demonstrated high repeatability of the air flow rate as well as long life. Analytical modeling successfully predicts the behaviour of the pump with regard to inertial effects.

The development and first test results of a novel micropump aimed at achieving elevated now rates are presented in this paper. The concept is based on the combination of silicon microvalves and a metal pump chamber. This permits an increase of the displaceable volume while the amount of employed silicon can be minimized. The microvalves are derived from a prior micropump design and optimized for elevated flow. Alternative valve sizes were employed and show the anticipated effect on the pump's flow characteristics. Flow rates of up to 85 ml/min with water and 310 ml/min with air have thus been achieved. These results promise application potential beyond the intended use in medical air humidification. Full self priming ability and bubble tolerance were maintained. Sustainable backpressures of 75 hPa with air and 350 hPa with water have been demonstrated so far.

In this paper, the design of a multi-material micropump will be described. The micropump inhibits a very simple design and therefore is very cost efficient. The pump consists of one plastic part, one metal diaphragm, and three piezo lead-zirconate titanate (PZT) ceramics. The PZT ceramics, glued on a metal diaphragm, form two active valves (inlet and outlet valve) and one actuation diaphragm. The valve seats, the pump chamber, and the inlet/outlet interfacing channels are formed in the plastic body. Due to its function principle, the micropump is able to pump bidirectionally. The design of the micropump covers bubble tolerant and self-priming features. Therefore, design measures have been carried out to realize a large compression ratio and to reduce the capillary pressures of bubbles in the pump chamber. The pump is able to handle gases and liquids. The plastic body is made of poly-ether-ether-ketone, and the metal diaphragm is made of stainless steel. Therefore, a good chemical resistance will be given. First prototypes of the actuation unit have been manufactured and tested successfully. Each actuation unit is able to performa stroke ofmore than 40 μm. Furthermore, the plastic body has been realized by milling, and preliminary measurements were carried out. For future work, the development and optimization of an improved micropump using microinjection moulding instead of milling are envisaged.