Using channel depth to isolate and control flow in a micro free-flow electrophoresis device

Area of Science:

• Analytical Chemistry
• Microfluidics
• Electrophoresis

Background:

• Previous micro free-flow electrophoresis (mu-FFE) devices suffered from electrolysis product formation.
• These products, appearing as bubbles, reduced electric fields and disrupted flow, hindering performance and continuous operation.

Purpose of the Study:

• To develop a mu-FFE chip design that effectively removes electrolysis products.
• To enable continuous operation and enhance separation performance in mu-FFE devices.

Main Methods:

• Fabrication of a mu-FFE chip with differential channel depths (20-microm separation, 78-microm electrode channels).
• Utilizing channel depth differences to control buffer flow and remove electrolysis products.
• Particle velocimetry to confirm linear velocities and comparison with lubrication theory predictions.

Main Results:

• Achieved continuous operation by effectively removing electrolysis products.
• Applied a separation potential of 645 V, yielding an electric field of 586 V/cm in the separation channel (4-fold increase).
• Demonstrated separation of fluorescent standards with a 1.3-fold increase in resolution compared to previous designs.

Conclusions:

• Differential channel depth is crucial for effective electrolysis product removal in mu-FFE.
• The new mu-FFE design enables higher electric fields and improved separation resolution.
• Effective management of electrolysis products is key to advancing mu-FFE technology.