ABSTRACT
With a microsystem or micropump, the release rate of drug delivery is able to be controlled easily to maintain the therapeutic efficacy. A piezoelectric membrane-valve micropump for implantable and carryhome drug delivery system is developed and tested. The influence elements of dynamic performance of the PZT actuator and valve were analyzed, and the calculation method of resonant frequency of the membrane valve was provided. Study results showed that the output performance of the micropump depended on the coupling effect of the actuator and valve. For a given actuator, the output value and the optimal frequency of a micropump could be enhanced only by valve design. Two micropumps with different valve dimensions were fabricated for comparing examination. The smaller -valve micropump obtained higher output values (the maximum flow rate and backpressure being 3.5 ml/min and 27 KPa, respectively) and two optimal frequencies (800 Hz and 3 000 Hz). The larger -valve micropump achieved lower output values (the maximum flow rate and backpressure being 3.0 ml/min and 9 KPa, respectively) and one optimal frequency (about 200 Hz). The test results suggest that the output values and optimal frequency of micropump can be improved by changing the valve dimension, and the viewpoint that checkvalve micropump works only with low acting frequency is wrong.
Subject(s)
Humans , Drug Delivery Systems , Equipment Design , Infusion Pumps, Implantable , Micro-Electrical-Mechanical SystemsABSTRACT
A novel double-chamber series piezoelectric pump has been presented and tested. The pump is a multi-layer circular planar structure, consisting of PMMA (polymethyl methacrylate) pump body, two PZT actuator membranes and three cantilever valves. The PZT actuators are driven at a phase difference of 180 degrees, which is equal to two one-chamber pumps running in series. The output performance depends on the geometrical parameters of the actuator membrane. The prototype pump, fabricated with the PZT membrane 0.18 mm in thickness and 50 mm in diameter of 50 mm, can deliver drug in either direct way (pumping liquid drug) or indirect way (pumping air to extrude liquid drug from a sealed container). The frequency-response characteristic of the two handling methods is of difference. The pump obtains optimum performance at low frequency for liquid as medium, and at high frequency for air as medium. For both the direct delivery and indirect delivery, the maximum flowrate achieved reached up to 220 ml/min and 35 ml/min, respectively; and the maximum backpressure obtained amounted to about 14 KPa and 21 KPa, respectively, at the applied voltage of 80 V with frequency of 20 Hz.