Crack-free and reliable lithographical patterning methods on PDMS substrate

Cracks commonly appear in metal patterns when fabricated on native poly(dimethylsiloxane) (PDMS) substrate using general micro-electro-mechanical systems (MEMS) fabrication processes such as lift-off and metal etching. This paper introduces simple, reliable and reproducible fabrication methods to realize crack-free metal patterns on PDMS using intermediate-parylene-deposited PDMS substrate and parylene-filled PDMS substrate. The fabrication parameters of crack-free metal patterning were optimized resulting in reliable and reproducible fabrication outputs. The adhesion of metals on these surface-modified PDMS substrates was evaluated by ASTM tape tests in wet and dry conditions. X-ray photoelectron spectroscopy (XPS) was used to characterize the element composition on the surface of parylene-filled PDMS. The surfaces of native PDMS, parylene-deposited PDMS and parylene-filled PDMS were investigated using scanning electron microscopy (SEM) and XPS for analysis of crack generation during the metal patterning processes. The mechanical properties, such as stress and strain, of native and surface-modified PDMS substrates were measured by standard tension tests. Based on these results, it was concluded that the proposed methods successfully generated reliable crack-free metal patterns based on PDMS substrate using general MEMS technologies, which can be used for various applications such as biomedical devices and flexible electronics.