In which fields are MEMS sensors used?
1. Used in medical applications
MEMS sensors are used in non-invasive fetal heart rate monitoring. Detecting fetal heart rate is a highly technical task. Because the fetal heart rate is very fast, between 120 and 160 beats per minute, it is difficult to measure accurately using traditional stethoscopes or even just amplified Doppler ultrasound monitors manually. While Doppler ultrasound monitors with digital displays are expensive and only used in a few large hospitals, they are not widely available in small and medium-sized hospitals and rural areas. Furthermore, the ultrasonic vibrations acting on the fetus can have significant adverse effects. Even though the detection dose is very low, it still falls under the category of destructive detection and is not suitable for frequent, repetitive examinations or home use.
2. Applications in automotive electronics
MEMS pressure sensors are primarily used to measure airbag pressure, fuel pressure, engine oil pressure, intake manifold pressure, and tire pressure. These sensors use single-crystal silicon as the material, employing MEMS technology to fabricate a force-sensitive diaphragm within the material. Impurities are then diffused onto the diaphragm to form four strain gauges, which are connected in a Wheatstone bridge configuration to achieve high sensitivity. Common automotive MEMS pressure sensors include capacitive, piezoresistive, differential transformer, and surface acoustic wave types. MEMS accelerometers, on the other hand, are based on Newton's classical laws of mechanics and typically consist of a suspension system and a sensing mass. Acceleration is detected by the displacement of a micro-silicon mass. They are mainly used in automotive airbag systems, anti-skid systems, car navigation systems, and anti-theft systems. Besides capacitive and piezoresistive types, MEMS accelerometers also include piezoelectric, tunneling current, resonant, and thermocouple types. Among these, capacitive MEMS accelerometers are the mainstream product due to their high sensitivity and minimal temperature sensitivity. A micro gyroscope is an angular rate sensor primarily used for GPS signal compensation in automotive navigation and in automotive chassis control systems. Several types exist, including vibration-type and rotor-type. The most widely used is the vibration gyroscope, which utilizes the Coriolis effect generated when a vibrating mass of single-crystal or polycrystalline silicon is rotated by a base to sense angular velocity. For example, when a car is turning, the system uses the gyroscope to measure the angular velocity to indicate whether the steering wheel has turned to the correct position, actively applying appropriate braking to the inner or outer wheels to prevent the car from veering off the lane. Typically, it works in conjunction with a low-accelerometer to form an active control system.
3. Applied to motion tracking systems
In athletes' daily training, MEMS sensors can be used for 3D human motion measurement, recording every movement. Coaches analyze and compare the results repeatedly to improve athletes' performance. As MEMS technology further develops, the price of MEMS sensors will decrease, making them widely applicable in gyms.
In skiing, pressure sensors, accelerometers, gyroscopes, and GPS in 3D motion tracking provide users with highly accurate observation capabilities. Besides providing data on ski movement, it can also record the user's position and distance. The same applies to surfing; 3D motion tracking mounted on surfboards can record information such as wave height, speed, surfing time, paddleboard distance, water temperature, and calories burned.
4. Application in mobile phone photography
Before the advent of MEMS Drive, mobile phone cameras mainly achieved image stabilization by moving the lens assembly with a voice coil motor (referred to as lens stabilization technology), which was very limited. Another higher-end image stabilization technology on the market, multi-axis image stabilization, uses a moving image sensor to compensate for shake, but because this technology is bulky and consumes more power than the phone's capacity, it has not been able to be applied to mobile phones.
Thanks to breakthroughs in size and power consumption in microelectromechanical systems (MEMS), the latest MEMS Drive technology resembles a planar motor attached to the back of an image sensor, driving the sensor to move along three rotational axes. MEMS Drive's image stabilization technology uses a gyroscope to sense instantaneous shaking during the shooting process, relying on sophisticated algorithms to calculate the appropriate movement of the motor and make rapid compensations. All these actions must be completed within a hundredth of a second to ensure the image remains clear and unblurred due to shaking.
Mobile phone photography brings us convenience anytime, anywhere. However, in the face of complex environments and diverse shooting scenarios, hand-held photography inevitably results in shaky images, such as when walking, running, lying down to take a picture, or when stretching out your hand or holding a selfie stick. Regardless of the type of shaky image, thanks to the unique five-axis image stabilization of the MEMS DRIVE motor and its fast and precise control technology, clearer and sharper images can be presented.
