Because bubbles can be visualized, the hypothesis is that eliminating the bubbles eliminates the problem. Yet through experimental work aimed toward achieving very accurate dispense volumes, IDEX Health & Science has learned that while removing the bubbles upstream of the dispense pump helps a great deal, it does not totally eliminate the problem. To achieve completely accurate dispensing, active degassing or debubbling is necessary.
Currently, many of the IVD instruments involve very rapid aspiration/dispense steps. This quick pull/push impels a cavitation as atmospheric pressurized water exerts a vacuum force that draws reagent or sample fluid into the probe, and then the fluids return to atmospheric pressure quickly prior to dispense. This rapid negative pressure fluctuation can lead to bubble formation in the syringe or dispense fluids that cannot be removed with rapid purges, passive debubblers, or traps. In reality, a passive device will allow bubbles to re-enter the fluid stream during aspiration or small negative fluctuations in pressure, and for this reason, bubble traps and passive devices can only be placed upstream of the syringe or positive displacement pumps in pressurized fluidic zones.
Active degassing and debubbling differ from so-called passive measures in that a vacuum source continually interacts with the fluid, drawing off bubbles and dissolved gas, even during slight negative pressure cavitations during aspiration. With an active debubbler, the vacuum source continually draws gas out of the system, enabling maintenance-free, trouble-free instrument operation and dispense precision. Therefore, an active debubbler or degasser is the best solution to improve dispense precision on high-throughput IVD instruments.
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