Write with heat, erase with light: New tech could revolutionize data storage

Researchers from the Osaka Metropolitan University have developed a new molecular photoswitch that can be activated by both light and heat.  This can be a massive boost to several industries, such as 3D printing and data storage.

The research team synthesized a novel type of aza-diarylethene molecule incorporating benzothiophene-S,S-dioxide into its core structure.

They demonstrated that their new photoswitching molecules can be used as a rewritable recording medium, using light or heat to write, and erasing with light, as mentioned in a press release.

“Unlike previously reported aza-diarylethenes, which exhibit fast thermally reversible photochromism, the compounds synthesized here exhibited pseudo-photochemically reversible photochromism,” said the researchers in the study.

X-ray crystallography analysis reveals surprise

Using X-ray crystallography, the team successfully determined the structure of the colored isomer for the first time, revealing a bond formation between carbon and nitrogen atoms.

This bond formation is unexpected for this type of molecule and contrasts with the typical open-ring structure of the colorless isomer.

Furthermore, detailed kinetic analysis and NMR spectroscopy confirmed that the molecular structures of the light- and heat-activated isomers are identical, a finding supported by DFT calculations.

To showcase the practical applications of their photoswitch, the research team demonstrated its ability to create light- and heat-writable patterns on filter paper.

Demonstration of light- and heat-writable patterns

This was achieved by incorporating the aza-diarylethene molecule into a PMMA (polymethyl methacrylate) matrix, creating a solution that was then cast onto the filter paper.

Upon irradiation with ultraviolet (UV) light through a mask, the areas exposed to UV light underwent a photochemical ring-closing reaction, turning yellow, whereas those shielded areas remained colorless.

This created a visible pattern corresponding to the mask. The result was a light-written pattern on the filter paper.

Following the light writing, heat was applied to selected areas of the filter paper via hot soldering iron (at approximately 110°C). This triggered a thermal ring-closing reaction in previously un-written areas, creating additional yellow areas.

Subsequently, shining visible light on the entire filter paper induced a photochemical ring-opening reaction, erasing the pattern created through the application of heat.

This demonstrated that both photochemically and thermally generated patterns could be produced and subsequently erased through specific light irradiation, showing the versatility of this dual functionality for creating reversible patterns.

Its significance and future implications are big

The discovery of a photoswitch with both light and heat sensitivity marks a significant leap forward, offering a new level of control and versatility.

This technology could revolutionize fields like 3D printing, where precise control over material properties is crucial. It could also lead to new forms of rewritable data storage that surpass the limitations of current technologies like CD-RWs.

In the biomedical field, these photoswitches could be used to develop new drug delivery systems or light-activated therapies.

The research team, which includes student Shota Hamatani and Professor Seiya Kobatake beside Dr Daichi Kitagawa, is continuing to explore the potential of their discovery.

“For example, the energy difference between the open and closed ring isomers would be controlled by further chemical modifications or environmental effects such as polymer matrices, solvents, and acids, which would lead to the creation of novel negative photochromic molecules that are expected to be used in the life sciences,” concluded the researchers.