Virtual microwells for digital microfluidic reagent dispensing and cell culture

Area of Science:

• Microfluidics
• Biotechnology
• Materials Science

Background:

• Digital microfluidic (DMF) systems utilize active (electrostatic) or passive (surface tension) mechanisms for precise liquid handling.
• Current DMF methods face challenges in reproducible dispensing of small volumes and compatibility with certain applications like cell culture.

Purpose of the Study:

• To develop a simple and effective Teflon-AF liftoff protocol for patterning hydrophilic sites on DMF devices.
• To enable precise passive dispensing of reagents, forming virtual microwells for microtitre plate-like functionality.
• To demonstrate the advantages of passive dispensing over active electrostatic methods for DMF applications.

Main Methods:

• Implementation of a Teflon-AF liftoff protocol to create hydrophilic patterns on a two-plate DMF device.
• Characterization of reagent dispensing reproducibility across a volume range of ~80 to ~800 nL.
• Evaluation of passive dispensing compatibility with DMF operation in both air and oil environments.

Main Results:

• The developed protocol allows for reproducible dispensing with coefficients of variation (CVs) ranging from 0.7% to 13.8%.
• Passive dispensing demonstrated improved control over dispensed volumes compared to active electrostatic dispensing.
• The technique proved advantageous for cell culture, with the first reported reagent dispensing on a single-plate DMF device.

Conclusions:

• The Teflon-AF liftoff protocol offers a straightforward and effective method for precise passive reagent dispensing in DMF devices.
• This technique enhances control over nano- and micro-litre volumes and is compatible with various operating conditions.
• The method holds significant promise for diverse applications, especially those involving adherent cell culture and analysis.