RESEARCH PROGRESS OF LIQUID MICRO-FLOW MEASUREMENT TECHNIQUES

With the interdisciplinary research of fluid mechanics and multi-disciplinary fields such as life science, materials science, medical and health, energy technology, environmental sciences, advanced manufacturing, etc., liquid micro flow and microfluidic technology have gradually been widely applied in the above fields. At the same time, the need to measure liquid micro flow (microliters or nanoliters per minute, or even smaller) is becoming more and more prominent. With the shrink of characteristic scale under the microscale application, the original liquid flow measurement technology has been unable to meet the requirements of measurement accuracy of liquid micro flow. Therefore, the further development of flow measurement technology is needed to meet the needs of micro flow measurement and microscale integration of sensors. This paper mainly introduces the existing and developing liquid micro flow measurement technologies and discusses its application background and existing problems. Firstly, depending on whether external energy (such as electric energy, heat energy, etc.) is introduced in the measurement process, the existing and developing liquid micro flow measurement technologies are divided into active flow measurement technology and passive flow measurement technology. Then, their specific measurement technologies are discussed respectively, including mass flow measurement technology (Coriolis flow measurement, micro resonator), thermal flow measurement technology (heat loss flow measurement, calorimetric flow measurement, time of flight flow measurement), optofluidics technology (photobleaching flow measurement), pressure conversion flow measurement technology (pressure difference flow measurement, cantilever flow measurement, flexible film deformation flow measurement), particle image velocimetry technology, gravity measurement technology, meniscus tracking technology, etc.. The sensor measurement principle, measurement performance index, advantages and disadvantages of the above-mentioned liquid micro flow measurement technologies are discussed. Finally, combined with the development of liquid micro flow measurement technology and the construction of national advanced measurement system, the application prospect and challenges to be solved in micro flow measurement of liquid are summarized.