DGIST professor Cheol Song’s research team successfully developed an optical interference sensor system for simultaneous ultra-precise force and depth measurement

□ A research team led by Professor Cheol Song at the Department of Robotics and Mechatronics Engineering, Daegu Gyeongbuk Institute of Science and Technology (DGIST; President Kunwoo Lee), has successfully developed an optical interferometer-based sensor system that can simultaneously measure ultra-precise force and depth information. As this sensor system can detect even small forces while simultaneously providing distance information, it is expected to be widely used in medical procedures and precision robotics in the future.

□ The research team applied an optical interferometer, which uses the interference of light, in the development of the sensor. Most importantly, the principles of optical coherence tomography (OCT),^[1] used in medical imaging, and an Fabry–Pérot interferometer,^[2] used in precision measurement, are combined in the development of a novel and precise measurement method. The team confirmed that performance remained consistent across multiple sensors.

□ To prove the performance of the sensor system, the research team conducted experiments on the actual eye of a pig. The results demonstrated that a surgical needle with the sensor could accurately pierce the sclera and retina of the pig eye while simultaneously detecting precise depth and forces. The measurements were stable even when the operator injected the needle by hand at an inconsistent speed.

□ Previously, such a feature required a larger probe,^[3] and it was not easy to use. The fiber optics-based sensor system developed by the research team is very small and light and can perform both procedures (force and depth measurements) simultaneously.

□ These results hold significance as the sensor is lighter and more practical. In the future, by improving its structure and diversifying materials, the sensor system is expected to measure precise force and distance in not just biological tissues but also industrial sites. Its usage can expand into ultra-precise drug injectors, medical devices for precision surgery, and tactile sensors for next-generation robots.

□ “This study holds significance as the sensor we developed is applicable to a surgical needle for safely and precisely drilling small holes in the cornea or retina of the eye,” said Professor Cheol Song at DGIST. “We will prove its safety for clinical applications and develop it into a platform for a variety of precision surgery, micromanipulation, force control, and robotic tactile sensors.”

□ Meanwhile, this study was supported by the Robot Industry Technology Development Project of the Ministry of Trade, Industry and Energy, and the results were published in IEEE/ASME Transactions on Mechatronics, one of the world’s most authoritative international journals in the field of mechatronics.

^[1] Principles of optical coherence tomography (OCT): It refers to a technique that uses the interference of light to image the internal structure of an object in the form of layers (slices). It interprets signals reflected by light as it passes through tissue and can noninvasively obtain highly precise internal cross-sectional images.

^[2] Fabry–Pérot interferometer: This is a device in which light is reflected multiple times between two parallel mirrors to form interference patterns. As only certain wavelengths resonate depending on the spacing between mirrors, they can be used for measuring high-precision wavelength and frequency or conducting spectroscopy.

^[3] Probe: It refers to a needle with a sensor.