Behind seemingly ordinary scenes such as smartphone navigation, drone obstacle avoidance, and smartwatch step counting, there is a core technology that works silently - MEMS magnetic sensors. As a combination of microelectromechanical systems (MEMS) and magnetic induction technology, it is reshaping the way humans perceive direction, position, and motion with a millimeter sized body. This article will take you into the world of MEMS magnetic sensors, exploring their classification mysteries, application scenarios, and future evolution paths.

1、 From Compass to Chip: The Birth of MEMS Magnetic Sensors

Traditional magnetic sensors such as Hall elements have been widely used in the industrial field, but their large size and high power consumption have limited their further development. Until the 1990s, the maturity of MEMS technology brought revolutionary breakthroughs to magnetic sensors: by integrating micro magnetic field induction structures on chips through semiconductor processes, a leap in volume reduction by a hundred times and power consumption reduction by ten times was achieved. This "chip level" magnetic sensor not only has a lower cost, but can also be integrated with accelerometers, gyroscopes, and other sensors, becoming the "all-in-one sensing center" of smart devices.

2、 Four major technological schools: classification codes for MEMS magnetic sensors

There are various technological routes for MEMS magnetic sensors, which can be mainly divided into four categories, just like the four major sects in the martial arts world:

Hall Effect Sensor

Based on the Lorentz force principle, when a current passes through a conductor in a magnetic field, the charge is deflected to produce a voltage difference. This type of sensor is like a "magnetic field thermometer", suitable for measuring constant magnetic fields and widely used in mobile electronic compasses and motor speed detection.

Magnetic Resistance Effect Sensor (AMR/GMR/TMR)

Utilize the characteristic of the resistance of magnetic materials changing with the direction of the magnetic field.

AMR (anisotropic magnetic resistance): similar to "magnetic field direction detector", early used in automotive ABS systems;

GMR (Giant Magnetoresistance): Sensitivity ten times higher than AMR, it is the mainstay of hard disk magnetic heads;

TMR (Tunnel Magnetoresistance): Achieving higher precision through electronic tunneling effect, becoming a new favorite of consumer electronics.

fluxgate sensor

By periodically saturating the magnetic core and detecting the induced voltage, like a "magnetic field metronome", it is suitable for measuring weak magnetic fields and has great potential in geological exploration and satellite navigation.

New type of quantum sensor

Based on quantum effects such as nitrogen vacancy centers, achieving ultra-high precision magnetic field measurement, although still in the laboratory stage, may overturn traditional technologies in the future.

3、 Invisible Guardian of the Internet of Things: Full Scan of Application Scenarios

The application of MEMS magnetic sensors has penetrated into every corner of modern life, becoming the "nerve endings" of the intelligent era:

Consumer Electronics

Mobile/tablet: Implement electronic compass, geomagnetic navigation, and automatic screen rotation;

Wearable devices: combined with accelerometers to achieve step counting and gesture recognition;

TWS earphones: detect whether the earphones are placed in the charging case, automatically start and stop music.

Automotive Electronics

ABS anti lock braking system: Real time detection of wheel speed to avoid slipping;

Electronic power steering: Combining magnetic field and torque sensors to enhance driving safety;

Automatic parking: integrated with ultrasonic radar to achieve precise recognition of parking spaces.

Industry and Internet of Things

Drone: Geomagnetic navigation assists in positioning when GPS signals are lost;

Robot: Build a "digital map" to achieve millimeter level positioning of warehouse AGVs;

Smart meter: detects changes in the surrounding magnetic field to prevent electricity theft.

healthcare

Capsule endoscopy: tracking the position inside the body through magnetic field positioning;

Portable blood glucose meter: uses magnetic microbeads to separate specific components in the blood.

4、 Future Evolution Theory: Four Major Technological Trends

multi-sensor fusion

Future devices will integrate magnetic sensors, accelerometers, gyroscopes, and even barometers to form an Inertial Measurement Unit (IMU). For example, Apple's M-series chips have built-in dynamic six axis sensors to achieve a smoother AR experience.

Material Revolution

Flexible MEMS: Using polymer or graphene materials, it can adhere to skin or curved devices;

3D packaging: By using through silicon via (TSV) technology, sensors are vertically stacked with processing circuits to enhance integration.

Low power consumption and intelligence

Event driven architecture: only wakes up the system when a magnetic field change is detected, extending battery life;

Self calibration algorithm: compensates for temperature drift and hard magnetic interference through machine learning.

Expansion of new application scenarios

Brain computer interface: monitoring changes in neuronal magnetic fields to assist in the treatment of Parkinson's disease;

Quantum computing: providing precise magnetic field control for superconducting qubits;

Metaverse: Combining geomagnetic data with SLAM algorithm to achieve seamless spatial positioning of AR glasses.

5、 Conclusion: A Poem of Technology in the Magnetic Field

From electronic compasses in navigation systems to obstacle avoidance systems for drones, from step counting on smartwatches to in vivo positioning of capsule endoscopes, MEMS magnetic sensors are weaving an intelligent perception network with invisible magnetic fields. With the integration of materials science, artificial intelligence, and quantum technology, future magnetic sensors may break through physical limits, allowing devices to "see" weaker magnetic field fluctuations and even perceive small changes in the Earth's magnetic field. This "magnetic field revolution" driven by micro nano technology is quietly reshaping the way humans interact with the environment, allowing the forces of technology and nature to dance together on chips.

Source: Sensor Expert Network