Reliability of microcantilevers in liquid environments

Saline soak tests to determine the short-term reliability of an in situ thin film resistance temperature detector

“…Also, chemical interactions between micro-structures and the environment may be more pronounced in liquids than in air or vacuum, since the surface area to volume ratio is large for micro-devices compared to macro-devices [8]. For example, devices operating in corrosive liquids can undergo stress corrosion cracking and wear resulting in structural failure [7].…”

“…An understanding of the chemical interactions with a liquid environment is necessary for operation of MEMS under cyclic stresses since small cracks on the order of micro-structural features experience increased crack growth rates in corrosive environments [7]. This could be a significant problem from the onset of use of a MEMS device in a corrosive environment, such as saline, since the fabrication techniques used for MEMS may produce devices with intrinsic defects and cracks.…”

“…Our understanding of the reliability of MEMS in such environments cannot be extended to predict their reliability in liquids. Fluid properties like viscosity, thermal conductivity, and diffusivity are different in gases and liquids, especially at the micro-scale [7]. Also, chemical interactions between micro-structures and the environment may be more pronounced in liquids than in air or vacuum, since the surface area to volume ratio is large for micro-devices compared to macro-devices [8].…”

“…Interaction with a liquid environment leads to the formation of superficial coatings, reaction byproducts, and corrosion [7,[9][10][11][12]. An understanding of the chemical interactions with a liquid environment is necessary for operation of MEMS under cyclic stresses since small cracks on the order of micro-structural features experience increased crack growth rates in corrosive environments [7].…”

“…To determine interaction between these solutions and the MEMS devices, the analysis of the devices were often the main focus [10,11,14], but other researchers examined the actual solutions as well [18,19]. The solutions used to create the saline environments were phosphate buffered solution (PBS), Dulbecco's phosphate buffered solution (DPBS), and approximately 1% sodium chloride (NaCl) [7,11,16,17]. The solutions used for the in vitro reliability testing were kept at a range from room temp to near 100°C, and the MEMS devices were kept immersed for a duration ranging from several days to almost ten years [7,9,10,12,16,17].…”