Nanoliter Liquid Based System
Advantages over other nanoliter liquid based systems:
Advantages over other nanoliter air based systems:
A system for accurate low-volume delivery of liquids in the micro to nanoliter range makes use of an integrated miniature flow sensor as part of an intelligent feedback control loop driving a micro-solenoid valve. The flow sensor is hydraulically connected with the pressurized system liquid in the dispensing channel and located downstream from the pressure source, above the solenoid valve. The sensor measures in real-time to the instantaneous flow rate as the solenoid valve opens and the integral of the flow rate delivered by the sensor is directly proportional to the volume of liquid sample being dispensed from the nozzle. The quantitative information is utilized to provide active control of the effectively dispensed or aspirated volume by closing the solenoid valve once the volume requested has been reached.
This process significantly enhances the precision of the fluid delivery. The system furthermore compensates automatically for any changes in the viscosity of the dispensed liquid. The data delivered by the flow sensor can be saved and backtracked in order to confirm and validate the aspiration and dispensing process in its entirety. The collected dispense information can be used for quality control assessments and automatically be made part of an electronic record.
Aspiration and dispense of the liquid sample are driven by vacuum or positive pressure. In order to allow high performance at low volumes down to 25 nL, the dispenser uses a system liquid that acts as hydraulic medium to transmit pressure as the solenoid valve opens. The system liquid allows large liquid acceleration, necessary to reach a jetting speed at the nozzle within miliseconds, ensuring clean jet start and breakoff at the valve closure.
As the valves opens, the inline MEMS Flow sensor measures the instantaneous flow rate, which is integrated in real time by the electronic controller. When the volume set point is reached, the electronic controller closes the valve, ensuring a high precision, independent of the sample liquid properties.