Measuring absolute static pressure at one or more positions along a microfluidic device

A method of measuring flow rate between two or more positions along a microfluidic channel transporting a working fluid that is immiscible in a first selected gas environment, comprising the steps of:

• (a) providing a first fluid conducting channel having an atmosphere provided by the first selected gas environment under a sealed environment and in communication with the microfluidic channel at a first point of communication;
• (b) providing a first visual scale adjacent to the first fluid conducting channel;
• and
• (c) transporting the working fluid under pressure conducted by the microfluidic channel into the first fluid conducting channel such that the volume transported into such first fluid conducting channel varies depending upon the absolute static pressure of the working fluid in the microfluidic channel at the first point of communication, whereby the absolute static pressure at the first point of communication is visually determined depending on the position of the interface of the working fluid and the first selected gas environment in the first fluid conducting channel when compared with the first visual scale;
• (d) providing a second fluid conducting channel having an atmosphere provided by the second selected gas under a sealed environment and in communication with the microfluidic channel at a second point of communication;
• (e) providing a second visual scale adjacent to the second fluid conducting channel;
• (f) transporting the working fluid under pressure conducted by the microfluidic channel into the second fluid conducting channel such that the volume transported into such second fluid conducting channel varies depending upon the absolute static pressure of the working fluid in the microfluidic channel at the second point of communication, whereby the absolute static pressure at the second point of communication can be visually determined depending on the position of the interface of the working fluid and the second selected gas environment in the second fluid conducting channel when compared with the second visual scale;
• (g) providing an additional fluid conducting channel having an atmosphere provided by an additional selected gas under a sealed environment and in communication with the microfluidic channel at an additional point of communication;
• (h) providing an additional visual scale adjacent to the additional fluid conducting channel;
• (i) transporting the working fluid under pressure conducted by the microfluidic channel into the additional fluid conducting channel such that the volume transported into such additional fluid conducting channel varies depending upon the absolute static pressure of the working fluid in the microfluidic channel at the additional point of communication, whereby the absolute static pressure at the additional point of communication can be visually determined depending on the position of the interface of the working fluid and the additional selected gas environment in the additional fluid conducting channel when compared with the additional visual scale;
• (j) calculating the average static pressure gradient between any two of the points of communication by dividing the difference in absolute static pressure measured at the two points of communication by the separation distance between the two points of communication;
• and
• (k) calculating the flow rate of the working fluid through the microfluidic channel between any two of the points of communication from the average static pressure gradient between any two of the points of communication and the physical properties of the working fluid using predetermined formulae for laminar flow in microchannels with various cross-sections.