Mystery of photo-induced force unraveled
- Writerkrissadmin
- Date2020-02-19 00:00
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Mystery of photo-induced force unraveled
- Findings shed light on origin of spectroscopic forces -
The Korea Research Institute of Standards and Science (KRISS, Acting President Seong-Jai Cho) became the first institute in the world to reveal the principle behind forces generated when nanomaterials react with light.
▲ Principal researcher Eun Seong Lee of the Nanostructure Measurement Center is adjusting parts to align laser light into the photo-induced force microscope.
The team, led by principal researcher Eun Seong Lee of the Nanostructure Measurement Center, revealed the physical principles of photo-induced force, produced from interactions between nanomaterials and light.
? The findings provide insights into the mechanism of photo-induced force, and are expected to accelerate the utilization of photo-induced force microscopes (PiFM), which probes photo-induced changes within nanodevices in a non-destructive manner.
The optical microscope is used to observe phenomena or characteristics of small objects. It has a lens that collects and magnifies light reflected off or passing through an object. If the object is nanosized and much smaller than the wavelength of light, such observations cannot be made due to the refractive limitations of the lens.
▲ Measurement principle of photo-induced force microscopes
Researchers around the world have turned to photo-induced force microscopes to address the above issues. A photo-induced force microscope collects light using a probe instead of a lens. When light illuminates the probe, nanosized optical near-fields are produced. The near-fields interact with the object, resulting in a push or pull acting on the probe, that is, the photo-induced force.
Optical properties of objects can be determined by measuring photo-induced forces. Prior to this study, the mechanism of photo-induced forces was unknown. Measurements unsupported by physical principles are not as reliable, and difficult to apply in industries.
▲ Principal researcher Eun Seong Lee of the Nanostructure Measurement Center is collecting light into a probe inside the photo-induced force microscope.
Principal researcher Eun Seong Lee and her team succeeded in unraveling the mystery of photo-induced forces based on two principles. They applied electromagnetic and thermodynamic theories to analyze spectroscopic properties of forces, and at the same time, experimentally observed vibrational resonances by directly probing nanomaterials.
? The results showed that photo-induced forces can be produced purely by electromagnetic effect or by a combination of electromagnetic and thermodynamic effects, depending on the type of nanomaterials.
Based on the findings, the team presented guidelines on the scope of nanomaterials in relation to forces. They demonstrated that image sharpness can be improved by coating microscopic probes with functional molecules to amplify thermodynamic interactions.
The enhanced understanding of photo-induced forces will significantly improve micropattern analysis under microscopes and the accuracy of inner defect measurements. Photo-induced force microscopy also enables preliminary assessment of the effectiveness of nanoparticles used in the diagnosis and treatment of diseases, including cancer.
▲ Principal researcher Eun Seong Lee of the Nanostructure Measurement Center is checking the alignment of a probe and a concave mirror which are important part of the photo-induced force microscope.
Principal researcher Eun Seong Lee said, “In 2018, KRISS developed photo-induced force microscopes capable of measuring up to a depth of 150 nm. Our study resolves the reliability issue of measurements obtained when the mechanism of photo-induced forces was unknown, and is expected to stimulate research on applications of photo-induced force microscopy.”
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