Wafer-level packaged flexible and bendable MEMS accelerometer for robotics and prosthetics

Flexible accelerometers, attached on robotic or prosthetic components are needed for sensing the motion or orientation to augment functionality and ensure safety of users. Flexibility, bendability and low profile enable ubiquitous presence without hindrance to the user. This paper presents design, simulation, fabrication and experimental characterization of MEMS accelerometers, wafer-level packaged between two polyimide layers and thus are bendable up to 1.0 cm radius of curvature with no performance degradation. The devices are compatible with robotic or prosthetic fingertips, which also have a similar curvature. Novelty lies in (1) wafer-level packaging with a polyimide substrate and a superstrate, (2) novel low-temperature fabrication process to maintain the integrity of the polyimide layers, (3) the use of double UV-LIGA process on a flexible substrate to achieve six-fold increase in sensitivity. The bendable packaged devices have increased sensitivity as high as 194 fF/g. The range of applied acceleration on the devices is ±4g.