Acupuncture Sample Injection for Microchip Capillary Electrophoresis and Electrokinetic Chromatography.

Area of Science:

• Microfluidics
• Analytical Chemistry
• Biotechnology

Background:

• Microfluidic devices, particularly those made from polydimethylsiloxane (PDMS), are crucial for miniaturized analytical systems.
• Precise sample introduction is a key challenge in microfluidic applications like capillary electrophoresis (CE).
• Existing injection methods often suffer from sample loss and complex hardware requirements.

Purpose of the Study:

• To develop a simple, nanoliter-scale injection technique for PDMS microfluidic devices.
• To enable reproducible sample plug formation for microchip CE.
• To overcome limitations of conventional injection methods.

Main Methods:

• A novel acupuncture-inspired injection technique using a needle and external pressure was employed.
• Sample plugs of 3-nL were reproducibly injected into microchannels.
• The technique was applied to PDMS microchip-based capillary zone electrophoresis (CZE) and capillary electrochromatography (CEC).

Main Results:

• Well-defined, reproducible 3-nL sample plugs were successfully formed in PDMS microfluidic channels.
• Capillary zone electrophoresis (CZE) and capillary electrochromatography (CEC) were successfully performed using a simplified straight channel design.
• The acupuncture injection method demonstrated advantages over electrokinetic injection, including minimized sample loss and simplified hardware.

Conclusions:

• The developed acupuncture injection technique provides a simple, efficient, and versatile method for sample introduction in PDMS microfluidic devices.
• This technique facilitates miniaturized CE applications by enabling precise, reproducible, and flexible sample handling.
• The method's advantages, such as serial injection capability and independence from sample solution properties, enhance its utility in microchip CE.