Fluidic Bypass Structures for Improving the Robustness of Liquid Scanning Probes.

Area of Science:

• Microfluidics
• Bioanalytical Instrumentation

Background:

• Liquid scanning probes are vital for bioanalytical applications but suffer from operational failures.
• Key failure modes include flow path obstructions and inconsistent probe-sample gap distances.

Purpose of the Study:

• To enhance the operational robustness of liquid scanning probes.
• To address critical failure modes: flow path obstruction and gap distance deviation.

Main Methods:

• Introduced a multi-functional microfluidic bypass channel.
• Operated the bypass channel in direct current (dc) mode for obstruction prevention.
• Utilized alternating current (ac) mode for gap distance monitoring.

Main Results:

• In dc mode, the bypass passively diverts liquid to prevent leakage and pressure buildup during obstructions.
• In ac mode, the gas-filled bypass exhibits capacitive behavior, enabling gap distance monitoring via phase shifts.
• Significant phase shift changes were observed up to a 25 μm gap distance with 4 Hz pressure modulation.

Conclusions:

• The passive microfluidic bypass channel effectively counters both major failure modes.
• This design offers a simple, highly compatible solution for improving liquid scanning probe reliability.