Researchers at TU Wien have developed a new type of sensing element for atomic force microscopy, which enables a high measurement speed and can even image sensitive processes in living cells.
High-definition images of minute objects are standard these days including the imaging of bacteria and viruses, and even molecules and individual atoms in extremely fine details. Atomic force microscopy, which involves bringing a vibrating tip into contact with or close to the sample surface, is often used for this purpose. Until now, however, the choice was between fast imaging techniques, which run the risk of destroying sensitive samples, and gentle imaging techniques that take more time.
Now, researchers from the Faculty of Electrical Engineering and Information Technology at TU Wien have succeeded in finding a way around this dilemma: instead of the previous standard method, which just involves directly vibrating a tiny arm with a fine tip, this method involves vibrating a plate with a smaller customised arm with an ultra-fine tip attached to it. By skilfully connecting the two components, the possible measuring speed can be increased to such an extent that even videos of sensitive objects should be possible, such as living cells that are in the process of reacting to a medication. TU Wien has already applied for a patent for the microstructure consisting of a plate and an arm that is intended to form the core of advanced future atomic force microscopes.
Feeling an image point by point
“In an atomic force microscope, we use a tiny arm, known as a cantilever, which is just a few micrometres in size. When the cantilever is vibrated at its resonant frequency, it vibrates extremely quickly, typically a few hundred thousand times per second,” says Prof. Ulrich Schmid from the Institute of Sensor and Actuator Systems. The cantilever has an ultra-fine tip attached to it. When it comes very close to the surface of the sample, a force acts between the sample and the vibrating tip at the atomic level. This changes the vibrational movement of the cantilever; it vibrates in a slightly different way and this change is measured.
Source: “Atomic force microscopy: new sensing element for high-speed imaging”, Florian Aigner, TU Wein