A closed-loop intelligent control strategy for precise non-contact liquid dispensing

In biomedical, chemical and pharmacological areas, thousands of reagents with different viscosities need to be dispensed in submicroliter range. Most of the commercial automated liquid dispensing systems need to be calibrated through experiments to accurately dispense liquids when the reagents viscosities change, which is time consuming and less accurate. In this paper, a precise non-contact closed-loop liquid dispensing system with novel adaptive intelligent control method was developed. First, the non-contact liquid dispensing system construction is introduced. Secondly, a MEMS flow sensor was used for closed-loop control the dispensed volume, and the factors that affect dispensing precision are analyzed. Thirdly, a compound intelligent fuzzy control strategy is proposed to calculate valve open-time for each dispensing cycle, which makes the system immune to liquid viscosity, pressure fluctuation and some other disturbances. Finally, experiments results are presented with different dispensing volumes, coefficient of variance (CV) has been shown to be below 3% at 1μl and approach 4% at 100 nl.