New Development Direction of Motion Sensor Technology

Today's phones and most other mobile devices are equipped with sensors that track geographic locations. Digital compasses, gyroscopes, and accelerometers installed in mobile devices are distributed in a variety of location-based service programs and are also applied in some new ways of controlling mobile devices, such as controlling devices through micro-swaying and flicking motions. . Now, the emergence of a new sensor manufacturing method will make this technology more cost-effective to implement, the device is more compact.

Spain's Baolab Microsystems used a simpler manufacturing method to create a new type of digital compass. Next year, this technology will be applied to GPS devices. The company also manufactures accelerometer and gyroscope prototype devices and plans to integrate these three types of sensors on a single chip.

The traditional method of manufacturing a digital compass is a Complementary Metal Oxide Semiconductor (CMOS) manufacturing method. This method is also the most common method for making microchips and electronic control circuits. However, some of the structures included in the compass created by this method, such as magnetic concentrators, need to be added after the chip is manufactured, thereby increasing the complexity and cost of the chip. "The basic difference is that the compass we make is entirely within the standard complementary metal oxide semiconductor manufacturing method.

This new method can be realized because the compass uses the Lorentz force phenomenon. While most commercial digital compasses use a different phenomenon, the Hall Effect, the compass works by passing current through a conductor and measuring the voltage change due to the Earth's magnetic field.

Lorentz force, on the other hand, is the force generated by a magnetic field when current passes through a conductor material. A mobile device can apply Lorentz force to an object and determine the orientation of the earth's magnetic field by measuring the displacement of this object.

Baolab's chip is a nano-scale micro-electromechanical system (MEMS) that is etched on a conventional silicon chip. In this nanoscale MEMS device there is an aluminum sheet suspended by a spring element. When a mobile device drives a beam of current through the aluminum sheet, any magnetic field that exists will generate a Lorentz force that acts on the sheet and affects its resonance. Two metal sheets on both sides of the aluminum sheet will detect changes in the aluminum sheet. The mobile device can measure the magnetic field in one direction by measuring the tiny changes in capacitance generated on the two metal plates. Using a set of three such sensors, the mobile device can determine the direction and orientation of the Earth's magnetic field.

Hiroshi Mizuta, professor of nanoelectronics at the Southampton University Nanogroup in the United Kingdom, said, “Compared with traditional sensors, this combination of MEMS and complementary metal oxide semiconductors will increase the sensitivity of sensors and reduce the size of sensor chips. Volume, reducing the cost of the chip.” Each Nano MEMS sensor from Baolab is less than 90 microns in length, and integrating three types of sensors on a 3 mm long chip is possible.

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