First microlasers capable of detecting individual molecules and ions could one day aid diagnosis
Scientists have created the first microlasers capable of detecting individual molecules and even single atomic ions, a breakthrough that could significantly advance early disease diagnosis and molecular-scale medical testing.
Microlasers are tiny glass beads measuring around just 0.1 mm - (the width of a human hairI) to 0.01mm – (the length of a single bacterium). With a central cavity that acts as a tiny mirror, they emit and bounce light in a circular motion around the bead. This circular path of trapped light is known as whispering gallery modes (WGM) laser technology. Light continuously circulates around the sphere’s inner boundary, enabling the device to detect extremely small disturbances on its surface. Previous research has shown that such microlasers can even be inserted into living cells, acting as optical barcodes to track cellular movement inside organisms. Now, researchers at the University of Exeter’s Living Systems Institute have published their work in Nature Photonics. Funded by the Engineering and Physical Sciences Research Council, the paper opens up new possibilities for microlaser biosensing technology, including “lab-on-a-chip” technology capable of instant medical testing and diagnosis.
Physicist Professor Frank Vollmer, at the University of Exeter’s Living Systems Institute, led the work. He said: “For the first time, we’ve created microlasers capable of detecting materials smaller than ever before – on the scale of individual atoms and molecules. This is an exciting innovation because it moves us closer to a new generation of lab-on-a-chip devices, which could diagnose conditions such as cancers or dementia early, and be used for swift -testing viruses. It could also enable us to detect small structural changes in proteins, such as those associated with enzyme activity and protein signalling, which no technology is capable of currently. Such an advance would mean a huge leap in our understanding of the mechanisms underpinning processes such as disease development.”
The research team used a number of different techniques to enhance the lasers to become sensitive to single-molecule and even single atomic ions. The microlaser itself is highly precise, able to register tiny changes in the light circulating inside it. The researchers then added gold nanorods to the surface, which concentrate light into tiny nanometre-scale ‘hot spots’, compressing it down to the size of molecules and amplifying the effect of a single molecule or ion binding there.
Finally, they used a technique called self-heterodyne beatnote detection. When a molecule or ion binds at one of these nanometre-scale hot spots, it slightly changes the beatnote frequency produced by the clockwise and counterclockwise laser waves inside the sphere. Rather than measuring a barely perceptible shift in light directly, the system detects this tiny change in frequency.
By tracking several laser beatnotes at once, the researchers can confirm the activity of single-molecule events across multiple signals. This improves the reliability of the system and strengthens its ability to detect and verify molecular interactions with high confidence.
The work was led from the University of Exeter’s Living Systems Institute. Study co-author Dr Samir Vartabi Kashanian said: “The Living Systems Institute brings physicists, biologists and chemists together under one roof. That stimulating interdisciplinary environment allows us to cross boundaries between physics, chemistry and biology, which is essential for translating advances in optical physics into practical biosensing applications.
The paper is titled ‘Single Atomic Ion Detection with Plasmon-Enhanced Whispering Gallery Mode Microlasers ‘, and is published in Nature Photonics.
END
Microlasers are tiny glass beads measuring around just 0.1 mm - (the width of a human hairI) to 0.01mm – (the length of a single bacterium). With a central cavity that acts as a tiny mirror, they emit and bounce light in a circular motion around the bead. This circular path of trapped light is known as whispering gallery modes (WGM) laser technology. Light continuously circulates around the sphere’s inner boundary, enabling the device to detect extremely small disturbances on its surface. Previous research has shown that such microlasers can even be inserted into living cells, acting as optical barcodes to track cellular movement inside organisms. Now, researchers at the University of Exeter’s Living Systems Institute have published their work in Nature Photonics. Funded by the Engineering and Physical Sciences Research Council, the paper opens up new possibilities for microlaser biosensing technology, including “lab-on-a-chip” technology capable of instant medical testing and diagnosis.
Physicist Professor Frank Vollmer, at the University of Exeter’s Living Systems Institute, led the work. He said: “For the first time, we’ve created microlasers capable of detecting materials smaller than ever before – on the scale of individual atoms and molecules. This is an exciting innovation because it moves us closer to a new generation of lab-on-a-chip devices, which could diagnose conditions such as cancers or dementia early, and be used for swift -testing viruses. It could also enable us to detect small structural changes in proteins, such as those associated with enzyme activity and protein signalling, which no technology is capable of currently. Such an advance would mean a huge leap in our understanding of the mechanisms underpinning processes such as disease development.”
The research team used a number of different techniques to enhance the lasers to become sensitive to single-molecule and even single atomic ions. The microlaser itself is highly precise, able to register tiny changes in the light circulating inside it. The researchers then added gold nanorods to the surface, which concentrate light into tiny nanometre-scale ‘hot spots’, compressing it down to the size of molecules and amplifying the effect of a single molecule or ion binding there.
Finally, they used a technique called self-heterodyne beatnote detection. When a molecule or ion binds at one of these nanometre-scale hot spots, it slightly changes the beatnote frequency produced by the clockwise and counterclockwise laser waves inside the sphere. Rather than measuring a barely perceptible shift in light directly, the system detects this tiny change in frequency.
By tracking several laser beatnotes at once, the researchers can confirm the activity of single-molecule events across multiple signals. This improves the reliability of the system and strengthens its ability to detect and verify molecular interactions with high confidence.
The work was led from the University of Exeter’s Living Systems Institute. Study co-author Dr Samir Vartabi Kashanian said: “The Living Systems Institute brings physicists, biologists and chemists together under one roof. That stimulating interdisciplinary environment allows us to cross boundaries between physics, chemistry and biology, which is essential for translating advances in optical physics into practical biosensing applications.
The paper is titled ‘Single Atomic Ion Detection with Plasmon-Enhanced Whispering Gallery Mode Microlasers ‘, and is published in Nature Photonics.
END