Bubbles are an intrinsic problem in microfluidic
devices and they can appear during the initial filling of the
device or during operation. This report presents a generaliz-
able technique to extract bubbles from microfluidic networks
using an adjacent microfluidic negative pressure network over
the entire microfluidic channel network design. We implement
this technique by superimposing a network of parallel
microchannels with a vacuum microfluidic channel and char-
acterize the bubble extraction rates as a function of negative
pressure applied. In addition, we generate negative pressure
via a converging-diverging (CD) nozzle, which only requires
inlet gas pressure to operate. Air bubbles generated during the
initial liquid filling of the microfluidic network are removed
within seconds and their volume extraction rate is calculated.
This miniaturized vacuum source can achieve a vacuum pres-
sure of 7.23 psi which corresponds to a bubble extraction rate
of 9.84 pL/s, in the microfluidic channels we characterized.
Finally, as proof of concept it is shown that the bubble remov-
al system enables bubble removal on difficult to fill
microfluidic channels such as circular or triangular shaped
channels. This method can be easily integrated into many
microfluidic experimental protocols.

• Bubble removal with the use of a vacuum pressure generated by a converging-diverging nozzle