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Fudzilla.com (EUA)

Boffins make optical fibre out of agar

Publicado em 28 julho 2020

Sweet treats on on your neural networks

A team of Brazilian boffins has emerged from smoke filled labs having created an optical fibremade of agar.

The University of Campinas (UNICAMP) in the state of São Paulo, Brazil, said the fibre is edible, biocompatible and biodegradable which are exactly what you need to get a good stream from Netflix.

It can be used in vivo for body structure imaging, localised light delivery in phototherapy or optogenetics (e.g., stimulating neurons with light to study neural circuits in a living brain), and localised drug delivery.

Another possible application is the detection of microorganisms in specific organs, in which case the probe would be completely absorbed by the body after performing its function.

The research project, which was supported by São Paulo Research Foundation—FAPESP, was led by Eric Fujiwara, a professor in UNICAMP's School of Mechanical Engineering, and Cristiano Cordeiro, a professor in UNICAMP's Gleb Wataghin Institute of Physics, in collaboration with Hiromasa Oku, a professor at Gunma University in Japan.

Agar is a natural gelatin obtained from marine algae. Its composition consists of a mixture of two polysaccharides, agarose and agaropectin.

"Our optical fibre is an agar cylinder with an external diameter of 2.5 millimeters [mm] and a regular inner arrangement of six 0.5 mm cylindrical airholes around a solid core. Light is confined owing to the difference between the refraction indices of the agar core and the airholes", Fujiwara wrote.

"To produce the fibre, we poured food-grade agar into a mold with six internal rods placed lengthwise around the main axis," he continued. "The gel distributes itself to fill the available space. After cooling, the rods are removed to form airholes, and the solidified waveguide is released from the mold. The refraction index and geometry of the fiber can be adapted by varying the composition of the agar solution and mold design, respectively."

The researchers tested the fibre in different media, from air and water to ethanol and acetone, concluding that it is context-sensitive. "The fact that the gel undergoes structural changes in response to variations in temperature, humidity and pH makes the fiber suitable for optical sensing", Fujiwara said.

Another promising application is its simultaneous use as an optical sensor and a growth medium for microorganisms. "In this case, the waveguide can be designed as a disposable sample unit containing the necessary nutrients. The immobilized cells in the device would be optically sensed, and the signal would be analyzed using a camera or spectrometer", he said.