Real-time feedback control of pH within microfluidics using integrated sensing and actuation

Area of Science:

• Biomedical Engineering
• Chemical Engineering
• Microfluidics

Background:

• Precise control of microenvironments is essential for various applications, including chemical synthesis and biological assays.
• Existing microfluidic systems often lack sophisticated feedback mechanisms for real-time parameter control.
• Developing integrated systems for accurate monitoring and adjustment of solution properties is a key challenge.

Purpose of the Study:

• To develop and demonstrate a microfluidic system capable of high-precision pH control.
• To integrate an ion-sensitive field-effect transistor (ISFET) with microfluidic channels for real-time pH monitoring.
• To implement a feedback control loop for dynamic pH adjustment within a microfluidic reaction chamber.

Main Methods:

• A microfluidic system was designed with a 90 nL reaction chamber.
• An extended-gate ion-sensitive field-effect transistor (ISFET) and a pseudo-reference electrode were integrated for pH sensing.
• On-chip valves controlled by pulse-width modulated signals adjusted fluid flow for pH regulation.
• A feedback control system was implemented to manage pH setpoints.

Main Results:

• The system demonstrated real-time pH control with precise 0.14 pH increment adjustments.
• The microfluidic system achieved convergence to the setpoint pH within approximately 20 seconds.
• The integrated ISFET and feedback loop enabled accurate monitoring and dynamic control of the microenvironment's pH.

Conclusions:

• The integration of engineering feedback principles into microfluidics enables precise control over solution pH.
• This system offers a robust platform for applications requiring tight regulation of chemical microenvironments.
• The developed technology is a significant step towards fully automated and controlled microfluidic systems.