Power-free bistable threshold accelerometer made from a carbon nanotube framework

This paper presents a design and a method for fabricating and testing fully compliant, bistable threshold accelerometers made from a carbon-infiltrated carbon nanotube framework. Two different configurations based on differences in compliant beam angles are presented. Both configurations were tested under constant accelerations produced by mounting them on a spinning disk and under impulse accelerations by mounting them to the end of a swinging pendulum with a stop at the lowest point of the pendulum path. Tests were also performed to observe the potential effects of stress relaxation in the carbon nanotube material. This was done by placing the accelerometers in their second stable position (nonfabricated position) and then testing them after a period of 24 h. Results show that in eight of the twelve tests there was no significant change due to stress relaxation. In the other four tests, the change was relatively small, especially when compared to stress relaxation effects in other materials such as plastics. Measurements indicate that the accelerometers show very high repeatability individually. However, we also observed that there is significant variation in switching acceleration between accelerometers with identical geometric parameters. This may be due to random variation occurring during the fabrication process.