An atomically sharp device records motion
Context: To build useful small devices, engineers must be able to see what they are doing, so they use atomic force microscopes to take pictures with nanometer resolution. To create images, the microscopes move a sharp tip across the surfaces of such tiny objects as silicon transistors or DNA molecules. The tip, just a few atoms across, moves slowly: at best, commercial atomic force microscopes can take only about one image every ten seconds. So they’re not much use in studying fast processes. Now, researchers at MIT have found a way to capture nanoscale images a million times faster.
Methods and Results: The technique developed by Mekhail Anwar and Itay Rousso yields high-speed movies of processes that repeat regularly. An object to be imaged is set in motion, and the tip captures information about surface height at one location only. Once enough data is collected, the tip moves a few nanometers to its next location, and the process is repeated. Each location thus becomes a pixel in a motion picture, and aligning the pixels in time produces a time-lapse movie of the process.
Unconstrained by the rate at which it can move forward, the tip collects data as quickly as its up-and-down movements can be recorded. Anwar and Rousso demonstrated the potential of their technique by imaging the motion of a microdevice with a time resolution of five microseconds.
Why it Matters: Because they scan slowly, atomic force microscopes are now used only to take snapshots of surfaces. Atomic force movies could help researchers analyze the motions of the microfluidic pumps used in the purification and analysis of DNA and proteins or provide moving images of biological processes.
Since any atomic force microscope could, in theory, be programmed to produce such movies, academic and industrial researchers have the means, motive, and opportunity to try the technique. Thus, nano moviemaking could become an important way to help researchers see what molecular devices are doing, analyze their performance, and determine how to improve them.
Source: Anwar, M., and I. Rousso. 2005. Atomic force microscopy with time resolution of microseconds. Applied Physics Letters 86:014101.