Bubbles And Whisper - Glass Bubbles Make Great Strides In Detecting Nanoparticles

Researchers at the Okinawa Institute of Science and Technology (OIST) have been able to detect the presence of microparticles by literally hitting light by the technology created using glass microbubbles.

This technology comes from certain physical phenomena known as "whispering galleries". In 1878, a British personal physicist Sir Rayleigh (John William Strut) named after the acoustic effect in the gallery at St. Paul 's Cathedral in London, but it was murmured on one side of a circular domed gallery The whispers sound clear even on the other side. This effect of sound waves traveling to the opposite side along the wall of the dome utilizes the light in a small-width glass sphere called the whispering gallery resonator (WGR), which is also less than the width of the human's hair Can be reproduced.

When light is irradiated inside the sphere, it creates an optical carousel while reflecting the inner surface of the sphere many times. A photon that reflects inside the small sphere sometimes moves a long distance as much as 100 meters. However, every time a photon bounces off the inner surface of a sphere, a small amount of light escapes outside. This leaked light is known as the "Evanescent light field". This leaked light creates something like a kind of aura around the ball. Furthermore, when nanoparticles come inside the field of this evanescent light, it distorts the wavelength and effectively changes the color of the field. By monitoring this color change, you can use WGR as a sensor. In the past, several research groups have used such sensors for the purpose of detecting individual viruses in solution. However , researchers of OIST's light-material interaction unithave designed more sensitive sensors based on the results of previous research. The result of this research was announced to Optica.

Dr. Jonathan Ward of OIST is using WGR to detect microparticles more efficiently than before. According to the doctor, the WGR produced this time is rather like a glass bubble of a hollow rather than a sphere. "I heated the glass tube with a laser and blown the air, this method is very similar to traditional glass blowing," explains Dr. Ward. By sending air into the heated glass tube, a spherical space is created that can support the field of highly sensitive light. The most noticeable difference between the blown glass and this precision instrument is the scale. The glass bubble of this precision instrument has a minimum size of only about 100 microns, which is very small, less than a few hundredths of a millimeter. Because of such a small size, although it is fragile, there is malleability at the same time.

Dr. Ward indicated that we can start this research from a theoretical model and use a sphere (that is, a bubble-like one) with a hollow inside just a solid sphere to increase the field of light. Having a large light field increases the detectable range of particles and increases the detectability of the sensor. Dr. Ward continues its explanation. "We knew both the technology to make WGR and the material to use.The next step is to demonstrate that WGR's performance is better than the currently used type of particle detector, We had to demonstrate. "

To prove the concept of this device, the research team devised a relatively simple test. First we filled the glass bubbles with a solution containing fine particles of polystyrene and lighted along the glass filament to create a field of light inside the filled with that liquid. As a result, it has been observed that as the particles pass within the field of light, they shift the wavelength much more remarkably than the standard spherical WGR.

The OIST research team, which is now able to use more effective tools, is trying to find an application method of this technology as a next task. By knowing what changes the different materials can bring about the field of light, Dr. Ward would like to identify what will bring about that change and also want to control that behavior to the research subjects I will.

Although it has the disadvantage of being fragile, although it is easy to make this new WGR, it can be used in a wide variety of fields because it can be transported safely if a custom made case is used. For example, it will be possible to detect toxic molecules in water to detect contamination, and to detect bloodborne viruses in remote areas where only limited health care activities can be provided.

Dr. Ward says there is more room for improvement. "We are always pursuing to find the smallest particles that the sensor can detect by increasing the sensitivity, we want to push the detection limit to the physical limit."