High-pressure on-chip mechanical valves for thermoplastic microfluidic devices

Area of Science:

• Microfluidics
• Materials Science
• Mechanical Engineering

Background:

• Integrating functional components like valves into microfluidic devices is crucial for advanced applications.
• Thermoplastic microfluidic chips offer advantages in mass production, but integrating soft elastomeric components presents challenges.
• Existing methods for valve integration can be complex or compromise device performance.

Purpose of the Study:

• To present a facile method for integrating elastomeric valves into rigid thermoplastic microfluidic chips.
• To demonstrate a novel fabrication process using sacrificial molding for seamless integration.
• To evaluate the performance and robustness of the integrated valves.

Main Methods:

• Utilized discrete plugs of polydimethylsiloxane (PDMS) as elastomeric valves within a thermoplastic substrate.
• Employed poly(ethylene glycol) (PEG) as a sacrificial molding material to create smooth interfaces between PDMS and thermoplastic channels.
• Actuated the PDMS valves using a threaded stainless steel needle mechanism.

Main Results:

• Achieved reproducible proportional valving with minimal dead volumes in thermoplastic microfluidic systems.
• Demonstrated high burst pressures: >12 MPa over repeated cycles and >24 MPa in single use, indicating robustness.
• Successfully operated a multi-valve chemical gradient generator in cyclic olefin polymer chips using the developed valves.

Conclusions:

• The described method offers a straightforward and effective approach for integrating elastomeric valves into thermoplastic microfluidics.
• The developed valves exhibit excellent mechanical stability and precise control, suitable for demanding applications like high-performance liquid chromatography (HPLC).
• This technology enables the creation of sophisticated microfluidic devices with enhanced functionality and reliability.