Experimental characterisation of piezoelectric silicon micropump for drug delivery applications

Abstract

Subcutaneous injection of medication is crucial for the treatment of many diseases. Especially if regular or continuous injections are beneficial, automated dosing units are advantageous. How-ever, existing devices are still large and therefore uncomfortable, visible under clothing, or inter-fere 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 gained increasing interest. However, the requirements of medical application are not yet fully met and especially dosing precision and reliability pose a challenge for MEMS pumps. To enable further miniaturization, we propose a precise 5x5 mm² sil-icon 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 at moderate backpres-sures. 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. This high precision enables the combination with higher concen-trated medication and is the foundation for the development of an extremely miniaturized patch pump.