Programmable µChopper Device with On-Chip Droplet Mergers for Continuous Assay Calibration

Area of Science:

• Microfluidics
• Bioanalytical Chemistry
• Assay Automation

Background:

• Passive droplet microfluidic devices lack real-time control over droplet contents.
• Automated control is crucial for complex bioassays and reducing reagent waste.

Purpose of the Study:

• To develop an automated droplet-based microfluidic device for real-time control and analysis.
• To demonstrate the device's capability for accurate quantification and signal drift correction.
• To validate the system for homogeneous immunoassays with reduced reagent consumption.

Main Methods:

• Development of an automated microfluidic device with pneumatic pumps and salt water electrodes.
• Integration of custom control software for droplet generation and merging.
• Application of the μChopper method for lock-in fluorescence detection and real-time signal correction.

Main Results:

• Successful generation and merging of up to six aqueous-in-oil droplets.
• Real-time correction of analyte-independent signal drifts and excitation light intensity changes.
• Validation with insulin immunoassays achieving low limits of detection (LODconc = 2 ng mL−1, LODamt = 5 amol) in under 1 minute.
• Demonstrated 160-fold cost savings in reagents compared to standard well-plate formats.

Conclusions:

• The developed microfluidic device offers precise, real-time control for automated bioassays.
• The system significantly reduces reagent volume and cost while enhancing assay efficiency.
• This scalable technology is well-suited for assays requiring expensive reagents and real-time automation.