Atomic force microscopy (AFM) enables scientists to study the surface at the atomic level. The technique is based on the basic concept of using a probe on the cantilever to "feel" the shape of the sample. In fact, people have used AFM for more than three decades. Users can easily use traditional micromechanical probes in their experiments. But to provide users with the standard size of the probe is not the only way manufacturers provide services.
In general, scientists need uniquely designed probes - either very long probes or probes with special shapes that make it easy to explore the bottom of deep troughs. However, although micromachining can be used to make non-standard probes, it is very expensive.
Now a research group at KIT, Germany, has developed a new technology that uses custom 3D AFM-based 3D direct laser writing to make custom AFM probes. The results of the study will be published on the cover of Applied Physics Letters magazine published by AIP.
The 3D laser direct writing method based on two-photon polymerization is suitable for creating custom-designed probes. (A) Schematic of two-photon polymerization printing on a cantilever. This illustration shows an electron micrograph of the probe scan.
Two-photon polymerization is a 3D printing technique that enables construction with excellent resolution. This process uses a powerful infrared femtosecond laser pulse to excite a UV light curable resist material. This material promotes two-photon adsorption and initiates polymerization. In this way, freely-designed components can be precisely 3D-printed at the intended location, including tiny objects like the AFM probe on a cantilever.
According to the team, the radius of a small probe is as small as 25 nanometers, which is about one-thousandth of the width of a human hair. Any shape of the probe can be used in the traditional micro-mechanical cantilever beam.
In addition, prolonged scan measurements reveal low probe wear rates, demonstrating the reliability of AFM probes. "We can also prove that the probe's resonant spectrum can be tuned to multi-frequency applications with a stiffening structure on the cantilever," says Hlscher.
Making ideal AFM tips provides an infinite choice of sample analysis and greatly increases the resolution.
Nanotechnology experts are now able to use two-photon polymerization in future applications. "We expect other working groups in the area of ​​scanning probes to take advantage of our approach as soon as possible," Hlscher said. "It could even become an internet business where you can design and order AFM probes over the Internet."
HLscher added that researchers will continue to improve their methods and apply them to other research projects, such as optical and photonic biomimetics.