Detects Robot Fingertip Movement and Force... Development of Ultra-Small 3-Axis Magnetic Sensor [Reading Science]

KIMM Develops 500-μm Sensor Capable of Measuring Magnetic Fields in X, Y, and Z Directions
Eliminates Need for Reset Circuit, Triples Vertical Sensitivity
Technology Expandable to Tactile Sensors

An ultra-small 3-axis magnetic sensor has been developed that can precisely measure movement and position even in confined spaces, such as robot joints or fingertips. This technology enables a single sensor measuring 500 micrometers in both width and height to detect magnetic fields in three directions. It can also be expanded into a tactile sensor capable of sensing pressing or pushing forces.

On October 6, the Korea Institute of Machinery and Materials announced that a research team led by Seonjong Oh, Principal Researcher at the Bio-Medical Research Lab of the AI & Robotics Research Institute, has developed an ultra-small 3-axis magnetic sensor using superparamagnetic nanoparticles that simultaneously measures magnetic fields in the x, y, and z directions. According to the research team, this is the world’s first implementation of a planar 3-axis magnetic sensor applying a flux guide based on superparamagnetic nanoparticles.

Ultra-small 3-axis magnetic sensor applying flux guides based on superparamagnetic nanoparticles developed by the research team at the Korea Institute of Machinery and Materials. Provided by the research team

Existing planar magnetic sensors can measure magnetic fields from side to side and front to back but struggle to detect magnetic fields entering perpendicular to the sensor’s surface. The research team addressed this issue by creating a "flux guide" on top of the sensor that redirects the magnetic field’s direction.

The flux guide made of superparamagnetic nanoparticles leads magnetic fields entering vertically to the sensor’s detectable planar direction. Through this, it becomes possible for a single sensor to measure magnetic fields in all three directions.

Eliminated Reset Circuit, Tripled Sensitivity to Vertical Fields

Conventional flux guides primarily used ferromagnetic materials such as nickel or permalloy. However, due to "magnetic hysteresis" — a phenomenon in which magnetism remains even after the magnetic field is gone — a separate reset circuit was required to reinitialize the sensor. These guides also required complex fabrication processes, such as electroplating or precision machining.

The research team applied superparamagnetic nanoparticles, which lose their magnetism along with the disappearance of the external magnetic field. This allows for the magnetic field to be repeatedly measured without an additional reset circuit, and the nanoparticles can be made into an ink and printed directly onto the sensor, simplifying the manufacturing process.

Research Achievement on Triaxial Magnetic Sensor Based on Superparamagnetic Nanoparticles Featured on Front Cover. Provided by Korea Institute of Machinery and Materials

The team also applied a technique that aligns the nanoparticles in the vertical direction by applying an external magnetic field as the nanoparticles solidify. As a result, the sensitivity to vertical (z-axis) magnetic fields was increased about threefold compared to existing sensors. The conversion efficiency in redirecting the vertical magnetic field into a measurable direction for the sensor reached up to 40%.

The sensor measures 500 micrometers by 500 micrometers, and when operating all four detection elements simultaneously, the power consumption is about 16 milliwatts.

Detects Not Only Movement But Also Pressing and Pushing Forces

The research team took a step beyond magnetic field measurement and applied this technology to tactile sensing in robots. By combining an elastic body containing a permanent magnet on top of the sensor, they developed a multi-axis tactile sensor capable of measuring the force of pressing or pushing an object.

This means that a single sensor platform can measure not only the movement and position of robot joints or hands but also the force generated when coming into contact with objects. The research team expects that the technology can be used in robotic hands, soft robots, wearable devices, human-machine interfaces, and medical devices.

Research team of Seonjong Oh, Principal Researcher at the Bio-Machine Research Laboratory of Korea Institute of Machinery and Materials (from the left in the photo: Mijin Kim, Postdoctoral Researcher; Seonjong Oh, Principal Researcher; Changyeop Jeon, Postdoctoral Researcher). Provided by Korea Institute of Machinery and Materials.

Principal Researcher Oh commented, "By utilizing superparamagnetic nanoparticles, we solved the magnetic hysteresis issue of existing 3-axis magnetic sensors and realized ultra-small, low-power sensors through a simple printing process. We expect this technology to see broad application in areas requiring small and precise sensors, such as robots and wearable devices."

This research was jointly conducted by the Korea Institute of Machinery and Materials and Professor Chulgi Kim's research team at Daegu Gyeongbuk Institute of Science & Technology (DGIST). The results were published in the June issue of the international journal Advanced Functional Materials and featured as the cover paper for that issue.

This content was produced with the assistance of AI translation services.