As a common ingredient, lotus root is rich in carbohydrates, dietary fiber, vitamins and minerals, known for its detoxifying and appetite-enhancing effects. But did you know that lotus root can also be made into a type of micro-fiber optic with optical transmission and biosensing capabilities, offering new possibilities for medical diagnostics, environmental monitoring, and optical communication?

The achievement comes from a research team at Jinan University. They extracted micro-fibers with a diameter of only 3-5 microns from lotus root slices. These lotus root silk not only have high biocompatibility and extremely low waveguide loss but also can achieve passive waveguiding in the visible light range, meaning they can transmit light signals without an external power source. Moreover, due to the small diameter and flexible micro-fiber characteristics, they can be used for biosensing applications in extremely small detection areas.

In modern biophysics and biomedicine, continuous monitoring of the physiological and pathological states of organisms is crucial. However, most traditional optical fibres are based on glass, semiconductor or metal materials, which are not entirely suitable for biological environments and are prone to physical damage from bending, twisting or compression. Additionally, due to poor biocompatibility, traditional optical fibres can adversely affect samples upon contact. Signal cross-interference is also a common thing, leading to low sensing sensitivity.

Lotus root, a truly natural substance, offers a solution to these challenges, yet the primary obstacle lies in its processing. Each node of the lotus root is replete with numerous fibrous bundles of lotus root silk, encased in a matrix of pectin and other constituents, meticulously arranged in a helical pattern. The extraction and utilization of these silk bundles at the micro/nanoscale necessitate meticulous manipulation and the deployment of cutting-edge techniques.

After more than two years of research, the research team finally succeeded in developing a chemically assisted physical separation technique, with the following steps:

1. Utilizing a series of robust alkali solutions and deionized water, meticulously liberate each pair of single silk micro-fibers from the silk fiber bundle. 

2. Employ a pair of precisely crafted, cone-shaped, and drawn optical fibers to skillfully align the fiber bundle, securing it at both extremities with a high-adhesion double-sided adhesive.

3. Gradually introduce the cone-shaped optical fibers between the silk bundles, applying a controlled transverse force to the broader section of the cones. 

4. Leveraging an optical fiber adjustment rack with exceptional precision, meticulously regulate the direction and intensity of the transverse force to achieve the desired separation of the single silk micro-fibers.

5. Immersing the micro-fibers in a sodium hydroxide solution with a precise mass concentration of 20g/L for two hours. Subsequently, employ an optical fiber to meticulously transfer the lotus root silk onto a pristine glass slide. Diligently rinse with deionized water six times to thoroughly eliminate any residual sodium hydroxide solution.

6. Employ an optical fiber adjustment rack, boasting an accuracy of 50 nanometers, to meticulously separate the spirally structured lotus root silk micro-fibers, ensuring the integrity and quality of the fibers throughout the process.

The processed micro-fiber exhibits a one-dimensional cylindrical structure, with a length greater than 600μm and a diameter of 3μm-5μm, not only uniform in diameter but also smooth in surface and with very few optical defects.

In experiments, researchers found that this type of lotus root silk micro-fiber not only can exhibit inherent fluorescence effects but also achieve the waveguiding effect of coupled light. These unique properties make the single-fiber sensor an excellent component with multiple sensing functions, which can be used for pH detection, and bacterial activity testing, etc. For instance, they designed a pH sensor using the reversible change in the fluorescence intensity of the lotus root silk micro-fiber with the solution's pH value, capable of detecting the acidity or alkalinity in liquid microenvironments. They also designed a bacterial sensor using the passive waveguiding characteristics of the lotus root silk micro-fiber, capable of detecting enzymatic substances during the apoptosis process of bacteria and cells.

This optical sensing technology based on micro-fibers from lotus root silk has the advantages of high biocompatibility, environmental friendliness, low carbon footprint and low cost. Provide new ideas and directions for optical devices, biosensing technology, environmental monitoring, etc. With further research and optimization in the future, it would expect to extend to more applications.