An ultra-fine endoscope has been developed that can observe capillaries and the nervous system in 3D.

A joint research team led by Deputy Director Won-Sik Choi (Professor of Physics at Korea University) of the Center for Molecular Spectroscopy and Dynamics (Director Min-Haeng Cho) at the Institute for Basic Science (IBS, President Do-Young No) and Associate Professor Young-Woon Choi of the Department of Biomedical Engineering at Korea University has developed an endoscope technology thinner than a hypodermic needle and succeeded in obtaining three-dimensional images of biological structures smaller than bacteria using this technology.

An endoscope is an imaging device designed to acquire images of objects in confined spaces or the inside of the human body.

Generally, endoscopes receive signals by inserting a thin imaging device into the object to be observed; they obtain images either by directly observing with a camera attached to the tip (probe) or by using optical fibers that transmit information using light.

When using a camera sensor, the probe becomes thicker, and in some cases, it may be necessary to make an incision in the skin to insert it. On the other hand, endoscopes using fiber optic bundles can be manufactured in a thinner form, which can minimize the incision site and patient discomfort.

On the other hand, conventional fiber optic endoscopes had difficulty obtaining clear images due to the empty spaces between the cores (the material that allows light to pass through the optical fiber) of individual optical fibers.

Furthermore, self-reflection at the ends of optical fiber bundles interfered with the observation of only the desired signal, making it difficult to observe biological structures with low reflectivity. Although fluorescent staining was required for observation, there were limitations to its application to the human body.

The research team overcame the limitations of existing fiber optic endoscopes by developing a very thin endoscope capable of high-resolution observation without attaching lenses or any equipment to the ends of the fiber optic bundles. The team focused light onto a single fiber within the bundle to illuminate an object located at a certain distance from the fiber.

Light reflected from an object transmits information about the object through multiple different optical fibers. A high-resolution image was obtained by measuring the resulting reflection holographic image and correcting for the distortion occurring in each core.


The developed endoscope has no equipment attached to the end of the optical fiber, resulting in a probe diameter of 350 μm (micrometers), which is even thinner than a hypodermic needle (approximately 500 μm). Using this, image information was obtained without fluorescent staining even from biological samples that are difficult to observe due to their very low reflectivity, such as mouse villi (structures within the small intestine).

In particular, the endoscope developed this time is capable of capturing microscope-grade high-resolution images, which is not possible with conventional fiber optic bundle endoscopes. It is capable of distinguishing objects even when they are separated by a distance of about 850 nm (nanometers). For reference, the size of bacteria is about 1,000 nm (1 μm, or one millionth of a meter). By correcting the measured holographic information, multi-depth 3D images can also be restored, and objects can be distinguished even when they are separated by a depth of about 14 μm.

Deputy Research Director Choi Won-sik stated, “We have developed a groundbreakingly thin, high-resolution endoscope,” adding, “This opens up the possibility of early disease diagnosis with minimal skin incisions, reaching areas that were difficult to access with conventional endoscopes, such as the lungs, capillaries, and even the brain and nervous system.”

The research results were published in the online edition of the international academic journal Nature Communications (IF 17.69) on August 2.