Microflow sensing and control using an in-channel birefringent biomembrane

Area of Science:

• Biomaterials Science
• Microfluidics
• Optical Sensing

Background:

• Microfluidic devices require accurate flow rate monitoring for precise control.
• Existing flow meters can be expensive or complex.
• Chitosan biomembranes offer unique optical properties suitable for sensing applications.

Purpose of the Study:

• To develop and characterize a novel, passive, low-cost microfluidic flow meter.
• To evaluate the performance of birefringent chitosan biomembranes as flow sensors.
• To demonstrate the application of this sensor in a closed-loop control system.

Main Methods:

• Fabrication of microfluidic devices incorporating birefringent chitosan biomembranes.
• Analysis of membrane optical properties using polarized microscopy under dynamic flow conditions.
• Integration of the sensor with a commercial pressure-driven pump and a PID controller.

Main Results:

• The flow meter demonstrated a linear operating range from 0 to 65 μL min⁻¹.
• Achieved a minimum response time of 250 ms and sensitivity of 2.03% × 10⁻³ μL⁻¹ min.
• Successfully implemented in a closed-loop system, reaching steady-state in under 15 seconds.

Conclusions:

• Birefringent chitosan biomembranes represent a viable, low-cost material for microfluidic flow sensing.
• The developed sensor enables stable closed-loop control of microfluidic systems.
• Further optimization may lead to even faster sensor response times.