The new direction of development of today's motion sensors

Introduction: Today's mobile 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 used in 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 the implementation of this technology more cost-effective, smaller equipment.

This advancement will also expand the range of applications for motion sensors, such as sensors in running shoes and tennis racquets, said Nigel Drew of Baolab Microsystems. Balab Microsystems, based in Barcelona, ​​Spain, developed this new technology.

Baolab used a simpler manufacturing method to create a new type of digital compass. Next year, this technology will also be applied to GPS devices. The company also manufactures accelerometer and gyroscope prototype devices and plans to combine 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 Lorentzforce 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 located 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.

"Compared with traditional sensors, this combination of micro-electromechanical systems and complementary metal oxide semiconductors will increase sensor sensitivity and reduce the size of the sensor chip and reduce the cost of the chip." Nanometer Group, University of Southampton, UK Nanoelectronics professor Hiroshi Mizuta said.

Each nanometer MEMS sensor of Baolab Company is less than 90 microns in length. Drew said it is possible to integrate the three types of sensors on a 3 mm long chip.