Fabrication of polymer microstructures for MEMS: sacrificial layer micromolding and patterned substrate micromolding

Area of Science:

• Materials Science
• Microfabrication Engineering
• Polymer Science

Background:

• Developing mechanically independent, freely suspended polymer microstructures is crucial for advanced microelectromechanical systems (MEMS).
• Traditional fabrication methods often face limitations in material compatibility and structural complexity for polymer-based devices.

Purpose of the Study:

• To present two novel soft lithography-based fabrication techniques for creating suspended polymer microstructures.
• To demonstrate the versatility of these methods for various polymer materials and microstructures.

Main Methods:

• Employing micromolding of thermoplastic polymers including poly(n-propyl methacrylate) (PPMA), poly(methyl methacrylate) (PMMA), and polystyrene.
• Utilizing two distinct release strategies: sacrificial layer micromolding (water-soluble layer) and patterned substrate micromolding (photolithographically patterned permanent substrate).
• Integrating a thermal bonding step to secure the polymer microstructures to the substrate.

Main Results:

• Successfully fabricated mechanically independent, freely suspended polymer microstructures with diverse geometries (e.g., microcantilevers, beams).
• Demonstrated the release of functional structures via water immersion for the sacrificial layer method.
• Showcased suspended polymer MEMS over defined voids in the patterned substrate method.

Conclusions:

• The presented soft lithography and thermal bonding processes are effective for fabricating suspended polymer microstructures.
• These methods offer flexibility in material selection (thermoplastic polymers) and microstructure design for tailored applications.
• The techniques hold potential for a wide range of polymer MEMS fabrication needs.