Integrated Full-Range Droplet Actuation for Inkjet-Printed Digital Microfluidic Chip on Flexible Substrates

Area of Science:

• Materials Science
• Microfluidics
• Electrical Engineering

Background:

• Flexible printed electronic technology enables low-cost fabrication of digital microfluidic (DMF) chips.
• Inkjet printing on flexible substrates offers a cost-effective manufacturing approach for DMF devices.

Purpose of the Study:

• To fabricate low-cost flexible DMF chips (FDMFCs) using inkjet printing on PET and photo paper.
• To analyze the impact of printing parameters on silver line quality and optimize dispensing electrodes.
• To demonstrate full-range droplet actuation across various FDMFC configurations.

Main Methods:

• Fabrication of FDMFCs on PET and matte photo paper using inkjet printing with simplified dielectric and hydrophobic layer coatings.
• Comprehensive analysis of silver line surface quality, conductivity, and resolution under varying printing conditions (number of printings, line width, line gap).
• Optimization of dispensing electrodes to reduce droplet volume errors and investigation of droplet motion in different configurations (closed, open, hybrid, curved) via electrowetting-on-dielectric.

Main Results:

• Successfully fabricated low-cost FDMFCs on both PET and photo paper substrates.
• Characterized the electrical and physical properties of printed silver lines, demonstrating control over resolution and conductivity.
• Achieved full-range droplet actuation, including complex configurations, with performance comparable to traditionally fabricated chips.
• Demonstrated that droplet motion performance is primarily governed by electrode conductivity and gap, with reduced dependence on substrate surface quality.

Conclusions:

• Inkjet printing provides a viable rapid prototyping method for fabricating cost-effective flexible DMF chips.
• The developed FDMFCs support diverse droplet operations, achieving performance on par with conventional methods.
• This technology minimizes the influence of substrate surface quality, focusing performance on electrode characteristics.