Three dimensional transformation of Parylene thin film structures via thermoforming

Non-planar, three dimensional structures, not possible with conventional microfabrication processes, were achieved using post-fabrication thermal annealing of thin film Parylene-C structures facilitated by a mold (“thermoforming”). We demonstrate thermoforming of Parylene-Parylene and Parylene-metal-Parylene (PMP) structures for increased structural and mechanical functionality such as strain relief, formation of open-lumen sheath structures, and conformation-matching of curved surfaces that broaden applications for Parylene MEMS. Characterization of the material and mechanical properties as a function of thermoforming temperature is also presented. Thermoformed Parylene consistently retained bulk/surface chemical material properties following the treatment regardless of temperature, and thermoforming at higher temperatures increased structural stiffness, which is attributed to increased crystallinity of the polymer. By varying the thermoforming process parameters, the final shaped structure can be mechanically and structurally tuned for broad range of applications, most notably, structured implantable neural interfaces with integrated channels for tissue ingrowth and improved integration.