Flow control valves for analytical microfluidic chips without mechanical parts based on thermally responsive...

Area of Science:

• Polymer Science
• Microfluidics
• Materials Science

Background:

• Microfluidic devices require precise control of fluid flow.
• Traditional valves can be bulky, complex, or prone to mechanical failure.
• Stimuli-responsive polymers offer potential for integrated, non-mechanical valve solutions.

Purpose of the Study:

• To create and characterize a novel non-mechanical valve for microfluidic applications.
• To utilize the thermoresponsive properties of poly(N-isopropylacrylamide) for valve actuation.
• To assess the performance and durability of the polymer-based microfluidic valve.

Main Methods:

• Fabrication of monolithic poly(N-isopropylacrylamide) plugs within microfluidic channels via photoinitiated polymerization.
• Actuation of the valve using thermoelectric elements to control temperature (17-57°C).
• Monitoring fluid flow using laser-triggered photobleaching of a fluorescent dye.

Main Results:

• The poly(N-isopropylacrylamide) valve demonstrated rapid swelling and deswelling, effectively opening and closing microfluidic channels.
• Valve actuation times were 3.5 s for opening and 5.0 s for closing.
• The valve maintained function after 120 open-close cycles and withstood pressures up to 1.38 MPa.

Conclusions:

• Photoinitiated polymerization enables the creation of effective, non-mechanical microfluidic valves.
• The thermoresponsive nature of poly(N-isopropylacrylamide) provides reliable and rapid valve control.
• This polymer-based valve is robust, durable, and suitable for high-pressure microfluidic applications.