Dec 3 2018
It is not known how long small gears and other tiny moving parts will last before they wear out, and there are no warning signs on when these components are going to fail, which may probably occur in just a few tenths of a second.
In an attempt to overcome these issues, scientists at the National Institute of Standards and Technology (NIST) have now come up with a new technique that enables tracking of microelectromechanical systems, or MEMS, more rapidly as they work and also as they cease working, which is just as significant.
By applying this technique for microscopic failure analysis, manufacturers and researchers alike can possibly enhance the reliability of the MEMS components that are being developed by them. These components range from tiny drones and robots through to sensors for detecting trace amounts of deadly chemicals as well as very small forceps for eye surgery.
In the past 10 years, NIST researchers have calculated the interactions and motion between MEMS components. In their latest study, they have successfully made these measurements many times faster, on the scale of thousandths, instead of tenths, of a second.
This faster time scale allowed the team to overcome intricate details of the irregular and transient motions that may take place before as well as at the time of MEMS failure. Moreover, the faster measurements enabled repetitive testing—required for evaluating the robustness of the tiny mechanical systems—to be performed more rapidly. The NIST scientists, including Craig Copeland and Samuel Stavis, have detailed their work in the Journal of Microelectromechanical Systems.
Similar to their earlier study, the researchers used fluorescent particles to label the MEMS components so as to track their motion. Then, with the help of sensitive cameras and optical microscopes to observe and image the light-emitting particles, the team tracked rotations as small as several millionths of a radian and displacements as tiny as a few billionths of a meter. A single microradian is the angle equivalent to an arc of roughly 10 m along the earth’s circumference.
Larger fluorescent particles, which produce more light, and a faster imaging system offered the researchers with the tools needed to carry out their particle-tracking measurements many times more quickly than before.
If you cannot measure how the components of a MEMS move at the relevant length and time scales, then it is difficult to understand how they work and how to improve them.
Craig Copeland, Researcher, National Institute of Standards and Technology.
In the new test system, part of a microelectromechanical motor was tested by Copeland, Stavis, and their colleagues. The test component snapped back and forth and rotated a gear via a ratchet mechanism. While this system is one among the more dependable MEMS that are capable of transferring motion via parts in sliding contact, it can still have problems like untimely failures and erratic performance.
The researchers observed that within the system, the shoving of contacting parts—whether contact between the parts shifted between several points or occurred at just a single point—and wear of the contacting surfaces may all have a vital role to play in the robustness of MEMS.
Our tracking method is broadly applicable to study the motion of microsystems, and we continue to advance it.
Samuel Stavis, Researcher, National Institute of Standards and Technology.