Researchers from Nagoya University in central Japan have published a study in the Journal of Materials Chemistry C on a pressure-sensitive material known as fluorenylidene-acridane (FA). Their research has potential applications for technologies related to pressure sensors, recording and playback devices.
Mechanochromic materials change color in response to external stimuli, such as mechanical pressure. However, previous research on mechanism was limited to qualitative reports, such as whether the color changed. Until now, quantitative analysis has been lacking.
To quantitatively describe the color change, a research team led by Professor Yutaka Matsuo, of the Department of Chemical Systems Engineering, Graduate School of Engineering, Nagoya University, FA, analyzed a type of mechanochromic material. When conducting several tests on materials containing FA, they found that it changed color from yellow to dark green when touched. But, unlike other mechanochromic materials, it changed color by absorbing it, rather than changing color by emitting light. This makes it unique.
Previously, the mechanochromic behavior of FA was usually observed in force form. However, for their current study, the research team first fabricated a thin film of FA, which allowed them to perform subsequent measurements. Then, to quantify color changes, researchers applied measurement techniques called diffuse reflectance ultraviolet-visible (UV-vis) spectroscopy.
In addition, to indirectly measure the structural changes of FA, they used Kelvin force microscopy. Increasing mechanical pressure gradually changed the color from yellow to green. Moreover, the more pressure applied, the more the FA structure changed. These data elucidated the quantitative relationship between the amount of mechanical pressure and the degree of color change of an FA-containing material. This is FA’s first report to use quantitative data.
The researchers’ measurements also showed that FA has a high spatial resolution. The FA film detected pressure applied over a width of only 50 nanometers, providing spatial resolution 1000 times better than other commercially available pressure-sensitive films. In addition, when treated with ethanol, the film color returned to yellow.
This is important because to reverse the color change, previous studies used only strong solvents, such as chloroform. But now widely available solutions such as alcohol can be used with this technology.
Quantitative measurement of FA opens up many possibilities for technologies such as disk storage. “Optical disc devices, such as CDs and DVDs, use laser light to write data,” said Professor Matsuo. “We could use color changes after mechanical pressure to store information,” he continued.
In addition, the measurement techniques for FA from this study may also be applicable to other types of mechanochromic materials in addition to FA. This means that this study could also contribute to future research on pressure sensor technology.
Finally, color can tell us whether a material surface has been touched and whether it has been wiped with alcohol afterwards. This can have consequences for keeping surfaces clean. For example, it is now possible to envision a future table that changes color when touched and then wiped clean, a technology that would be valuable in a hospital or other environment that wants to reduce the transmission of viruses through contact with contaminated surfaces. to prevent.
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Keisuke Ogumi et al, High-resolution quantitative mechanical pressure detection functions of mechanochrome fluorenylidene-acridane, Journal of Materials Chemistry C (2022). DOI: 10.1039/D2TC01988D
Quote: Research Reveals Quantitative and High-Resolution Pressure Functions of Pressure-Sensitive Materials (2022, September 30) Retrieved September 30, 2022 from https://phys.org/news/2022-09-reveals-quantitative-high-resolution-pressure-functions. html
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