Automated Precise Liquid Dispensing System for Protein Crystallization

Recently, high throughput protein crystallization requires that the volumes of sample solution in crystallization experiments should be reduced to increase the screening chance with a given amount of sample. This leads to the developments of automated liquid handling instruments that can transfer submicroliter volumes of fluid. In this paper, an automated solenoid based liquid handling system was developed, which could dispense submicroliter reagent without touching off. Also, the non-contact liquid dispensing process was investigated with computational fluid dynamics (CFD) models, which makes us understand the droplet breakup process more detailedly and makes dispensing droplet fall off successfully without attaching to the nozzle. The system is composed of assembled syringes, pneumatic devices, stepper motor, solenoid valve and other miscellaneous devices. The noncontact reagent dispensing is accomplished by rapidly opening and closing the solenoid valve while applying fluid pressure to it and the volume modulation is possible by altering the opening time of the valve and the flow rate. Experiments were carried out with different dispensing volumes, coefficient of variance (CV) has been shown to be below 3% at 1 mul and approach 8% at 50 nl.