Photomechanical materials made of photochromic crystals, which change their molecular structure reversibly in response to light, have the potential to impact fields from semiconductors to pharmaceuticals. For the first time in the world, an Osaka Metropolitan University team has developed a crystal patterning method demonstrating that it is possible to control the orientation of photochromic crystals known as diarylethenes.

Diarylethene crystals not only change color when exposed to UV light, but also undergo various shape changes as the molecular structure changes. Graduate School of Engineering student Mami Isobe, lecturer Daichi Kitagawa, and Professor Seiya Kobatake focused on patterning to control the position and orientation of the crystals on a substrate using the sublimation method.

The team fabricated convex structures with a height of several microns and a width of a dozen or so microns on a substrate in the shape of a straight line and numerals from 0 to 20. By sublimating powdered crystals of diarylethene onto the substrate, the researchers demonstrated the ability to control the orientation of the crystals, as well as create minute crystals of diarylethene on convex structures.

“We expect the crystal patterning method developed to be applicable to semiconductor materials and pharmaceuticals, which are low-molecular-weight organic compounds similar to diarylethene,” stated graduate student Isobe.

Professor Kobatake added, “To increase the versatility of this crystal patterning method in the future, we would like to analyze the effect of the size and shape of the convex structures on the substrate on crystal growth, and quantitatively explain the formation principle of the crystal patterns.”

These findings were published in Small Methods.

Funding
This work was partly supported by JSPS KAKENHI Grant Numbers JP23KJ1830 (M.I.), JP21K14603, JP23H01926 (D.K.), and JP21H02016 (S.K.) and by JST, the establishment of university fellowships towards the creation of science technology innovation, Grant Number JPMJFS2138.

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