Strategy for repetitive pinched injections on a microfluidic device

Area of Science:

• Microfluidics
• Analytical Chemistry
• Biotechnology

Background:

• Microfluidic devices enable miniaturized analytical systems.
• Efficient sample injection is crucial for high-throughput microfluidic assays.
• Existing pinched injection valves face limitations in speed and precision for repetitive tasks.

Purpose of the Study:

• To develop and evaluate a novel microfluidic valve for enhanced repetitive pinched injections.
• To improve sample loading speed and precision in microfluidic analysis.
• To assess the performance of the new valve design at various injection frequencies.

Main Methods:

• Fabrication of a microfluidic chip featuring a cross intersection and two strategically placed tee intersections.
• Utilizing electrokinetic forces for sample mobilization and controlled diffusive transport.
• Implementing "pullback" conditions for rapid sample loading.
• Testing injection frequencies from 1 to 10 Hz with a 0.5 duty cycle.
• Evaluating peak area precision and peak width under repetitive injection conditions.

Main Results:

• The microfluidic valve demonstrated high precision, with a relative standard deviation of 1.6% for peak areas over 15 injections.
• Achieved injection frequencies of up to 10 Hz.
• Observed an increase in peak width (4sigma) from 71 to 96 microm compared to standard pinched injections due to the tee intersection.
• The addition of tee intersections facilitated rapid loading and unidirectional transport.

Conclusions:

• The novel microfluidic valve design enables rapid and precise repetitive sample injections.
• The integrated tee intersections enhance sample loading efficiency and control.
• This design represents a significant advancement for high-frequency analysis in microfluidic devices.
• Further optimization may mitigate the observed increase in peak width.