An Easy Method for Pressure Measurement in Microchannels Using Trapped Air Compression in a One-End-Sealed Capillary

Area of Science:

• Microfluidics
• Fluid Dynamics
• Measurement Science

Background:

• Accurate pressure measurement is crucial for controlling microfluidic systems.
• Existing methods often require complex microfabrication and specialized equipment.
• A need exists for simple, accessible pressure sensing techniques in microfluidics.

Purpose of the Study:

• To develop an easy, capillary-based method for measuring fluid pressure in microchannels.
• To investigate factors influencing the accuracy of the capillary pressure measurement.
• To demonstrate the application of this method in analyzing microfluidic system behavior.

Main Methods:

• Utilized a sealed capillary with calibrated scales to measure air-liquid interface height.
• Applied the ideal gas law to correlate interface height with applied pressure.
• Investigated effects of surface tension, gravity, air solubility, temperature, and capillary diameter.
• Validated measurements through experimental and simulation results.

Main Results:

• Achieved a pressure resolution of approximately 1 kPa over a 101.6-178 kPa range.
• Detected pressure drops as low as 0.25 kPa within a 0.5-12 kPa operating range.
• Successfully analyzed nonlinear flow-pressure drop relationships due to channel deformation.

Conclusions:

• The developed capillary method provides a simple, cost-effective alternative to microfabrication-based pressure sensors.
• This technique is easily implementable for real-time pressure monitoring in diverse microfluidic applications.
• The method offers high sensitivity and accuracy without requiring additional complex equipment.