Thermal assisted ultrasonic bonding method for poly(methyl methacrylate) (PMMA) microfluidic devices

Area of Science:

• Materials Science
• Microfluidics Engineering
• Polymer Processing

Background:

• Poly(methyl methacrylate) (PMMA) is a common material for microfluidic devices.
• Conventional bonding methods for PMMA often require high temperatures and pressures, leading to microstructure deformation.
• There is a need for low-temperature, low-pressure bonding techniques for delicate microfluidic structures.

Purpose of the Study:

• To develop and optimize a thermal assisted ultrasonic bonding method for PMMA microfluidic devices.
• To achieve high bonding strength with minimal dimensional loss and short bonding times.
• To demonstrate the efficacy of the bonding method using a functional microfluidic device (micromixer).

Main Methods:

• Utilized a thermal assisted ultrasonic bonding approach with preheating PMMA substrates below their glass transition temperature (T(g)).
• Applied low-amplitude ultrasonic vibration to generate interfacial heat for bonding.
• Optimized the bonding process parameters using the Taguchi method.

Main Results:

• Successfully bonded PMMA microfluidic chips at bulk temperatures significantly below T(g) and with pressures two orders of magnitude lower than conventional thermal bonding.
• Achieved high bonding strength of 0.95 MPa.
• Demonstrated low dimensional loss (0.3-0.8%) and short bonding times.
• Successfully fabricated and demonstrated the performance of a micromixer bonded using this technique.

Conclusions:

• The thermal assisted ultrasonic bonding method is highly effective for fabricating PMMA microfluidic devices.
• This technique offers significant advantages over conventional methods, including reduced deformation, high bond strength, and efficiency.
• The optimized method is suitable for producing complex microfluidic devices with preserved microstructures.