A microscale pulsatile flow device for dynamic cross-slot rheometry

The design of micropumps received full attention since micromanufacturing and microfluidics techniques have become part of the engineering toolbox. The focus of most studies has been on the efficiency of these pumps: maximal net (mean) flow at minimal input power.we introduce a pulsatile micropump system, that is designed to dynamically perfuse a cross-slot micro-rheometer. To characterize complex materials dynamically, unsteady (oscillating and pulsating) flows with a frequency range of 0.1–20 hz at amplitudes of 10–100 nl/s are required. Hence, in our study the priority concerning micropumps shifts from efficiency to the ability to produce well-defined flow pulses.for this purpose, an oscillatory micropump, based on a deflecting diaphragm, is designed and tested. By periodically deflecting a steel plate into a rigid fluidic chamber using a voice coil, an oscillatory flow is produced. Plate deflection is governed by bending, such that the stroke volume is proportional to the current through the voice coil. The oscillatory flow is superimposed to the steady flow of a syringe pump. The pump system obtained is characterized by micro particle image velocimetry (µ-piv) measurements using fluorescence microscopy.the results show that the superposition of the mean flow of the syringe pump and an oscillatory flow of the diaphragm pump, is valid. A linear scaling of flow amplitude with frequency and driving voltage is found for frequencies up to 4 hz, after which excessive damping takes place. The causes for this behavior are identified and explain the results well. With this information, amplitude scaling for sinusoidal flow waves of different frequencies can be performed. In conclusion, with the present system, pulsatile flow with a well-defined waveform and a dynamic range up to 16 hz, can be created in an open-loop driven fashion.