Rapid fabrication and characterization of MEMS Parylene C bellows for large deflection applications

We present a rapid, high-yield fabrication process for Parylene C microbellows for large deflection applications and their characterization. Bellows having different convolution number, wall thickness, inner diameter and outer diameter and layer height were fabricated using a lost wax-like process. The effect of design parameters on overall bellows performance was evaluated through load-deflection testing and finite element modeling (FEM) simulations. Large deflection (similar to mm) was achieved under relatively low applied pressure (similar to kPa). The onset of bellows hysteresis (4.19 kPa or 0.60 psi) was determined in mechanical testing and approximated by FEM. For the bellows tested, convolution number, wall thickness and outer diameter had the greatest impact on load-deflection (axial extension) performance. Demonstration of bellows for fluid pumping was achieved through integration with electrochemical actuators operated under low power (similar to 3 mW). Combined with the biocompatibility, chemical inertness and low permeability of Parylene C, microelectromechanical systems (MEMS) bellows have the potential to enable novel applications in MEMS actuators and microfluidic systems.