Replaceable Dielectric Film for Low-Voltage and High-Performance Electrowetting-Based Digital Microfluidics.

Area of Science:

• Materials Science
• Microfluidics
• Surface Science

Background:

• Electrowetting-on-dielectric (EWOD) is crucial for digital microfluidic (DMF) applications, with the dielectric layer's properties dictating device performance.
• Existing dielectric layers face challenges in balancing driving voltage, reliability, and device lifetime.

Purpose of the Study:

• To develop a novel composite film for EWOD devices that offers high efficiency, stability, and low-voltage operation.
• To investigate the potential of ion gel (IG)-based materials for advanced hydrophobic dielectric layers.

Main Methods:

• Fabrication of a polymer (P)-ion gel-amorphous fluoropolymer (PIGAF) composite film.
• Integration of the PIGAF film as a dielectric layer in EWOD-DMF devices.
• Characterization of droplet contact angle changes, hysteresis, actuation voltage, and droplet motion velocity.

Main Results:

• The PIGAF dielectric layer enabled EWOD devices to achieve a large contact angle change (∼50°) with low hysteresis (≤5°) at 30 V_rms.
• Actuation voltage remained stable across varying PIGAF film thicknesses (several to tens of microns).
• Stable droplet actuation was demonstrated at 30 V_rms, with a maximum velocity of 69 mm/s at 140 V_rms, and maintained performance over ≥50 cycles and 1 year of storage.

Conclusions:

• The PIGAF composite film is a promising, stable, and reliable dielectric material for high-efficiency EWOD-DMF devices.
• The developed EWOD-DMF system is suitable for applications in digital chemical reactions and biomedical sensing.
• The thickness-independent actuation voltage offers design flexibility for microfluidic devices.