Bosch sensors: Changing lives for the better

Although they are only as small as a pin head, they are changing everyday life in many fields: tiny Bosch micromechanical sensors. In fitness wristbands, they measure physical activity and help people achieve better health and well-being. In cars, sensors identify dangerous situations and instantly alert the control electronics to keep the vehicle on the road. Because sensors detect the earth’s gravity, smartphones can change their screen orientation to suit users’ needs. Bosch is the world’s leading manufacturer of MEMS sensors (micro-electromechanical systems). Since the start of production in 1995, the company has manufactured more than six billion of them. “The key challenge in the ongoing development of our MEMS sensors is their energy consumption. For example, more intelligence in sensors makes it possible for us to reduce energy consumption,” says Dr. Franz Lärmer, a Bosch sensor expert. It is hard to put a number on the many potential applications of sensors. They are a key technology for the internet of things (IoT).

Three approaches for lower energy consumption

Users of mobile devices such as smart watches, augmented-reality glasses, or wearables often wish for longer battery runtimes, smaller designs, more affordable products, and more functions. Until now, the capacity of the batteries in such devices has often not been enough to keep the sensors and their analysis chips constantly supplied with power. Devices have to be recharged more frequently if the sensor-supported functions are constantly in use. Moreover, better battery performance also opens the door to a wider range of intelligent applications. With the aim of reducing sensors’ energy consumption, Lärmer and his team in Renningen have joined forces with Bosch researchers in Palo Alto, California, to pursue three different approaches.

The first approach: energy can be harvested from changes in ambient pressure, vibration, or temperature. As part of the publicly funded joint project 9D-Sense, Bosch is working with partners to research this kind of energy harvesting. Tiny rechargeable batteries can store even the most minuscule amounts of energy gathered in this way to provide sensors with power over a long period of time, maintenance-free. The second approach: sensors can be programmed to gather and transmit their data only when absolutely necessary. If a smartphone is lying still on a table, for example, its sensors do not need to be active. The third approach: at its research centre in Palo Alto, Bosch has developed the world’s smallest and most energy-efficient sensor unit. The contents of the BMI160’s tiny housing, which measures 2.5 x 3.0 x 0.8 millimeters, include an accelerometer and a yaw-rate sensor (gyroscope). In a smartphone, the sensor unit measures things such as position. It can also be found in tablet computers and smart watches. In full operational mode, the BMI160’s typical power consumption amounts to a mere 950 microamperes, which is less than half the market standard, as well as a world record. This and other Bosch sensors can be found in three-quarters of all smartphones in the world today.

Every object capable of gathering information

“In the future, nearly all everyday objects are likely to be equipped with sensors. This is a revolutionary development that will allow almost every object to gather information about itself and its environment. As a result, the potential applications of these objects will increase tremendously,” Lärmer says. “But other things are also playing an increasingly important role, such as the combination of several sensors and the integration of software intelligence.” One example comes from the world of physical fitness. By measuring atmospheric pressure, one sensor can determine which floor of a building the wearer is located on, while another sensor registers every movement the wearer makes. Together with the data from a tiny heart-rate sensor, which is attached to the user’s skin, the sensor automatically transmits a fitness profile containing information about things such as changes in heart frequency while climbing stairs. If desired, a smartphone app can transmit the profile to a trainer. Applications related to early screening and diagnosis are also conceivable. “Changes in how people move can be an early sign of conditions such as dementia or postural defects. They could be measured in a similar way using MEMS sensors. This would allow us to diagnose and treat illnesses at the earliest possible stage,” Lärmer says. “There is no end in sight to the wide range of possible applications for connected sensors. Our research examines these possibilities.”

The latest technical equipment for sensitive sensors

At its new research center in Renningen near Stuttgart, Bosch is working on the big future of these tiny components. It wants to make them even smaller and more energy efficient, thus paving the way for new applications. The best possible conditions are needed to manufacture MEMS, and the same goes for research into new MEMS generations. Even the tiniest grains of dust can cause major problems in the development and production of MEMS structures. At its new research campus, therefore, Bosch has constructed a suite of clean rooms to the latest technical specifications. All air in the building is subject to thorough filtering, resulting in no more than 370 particles per cubic meter. By comparison, air in a typical urban environment contains some 35 million particles per cubic meter.

Tiny structures, extremely sensitive

Microscopically fine structures are etched into silicon during MEMS production. On the sensor, the teeth of tiny comb-like silicon structures intermesh. Less than one-quarter the thickness of a human hair, these comb-like structures are pushed up against each other during movement. The distance between the teeth changes, leading to a change in the electric current in the comb-like structures. This current can be measured and calculated as an electric signal that the sensor then transmits. MEMS sensors are extremely sensitive thanks to this technology, Lärmer explains. “In a laboratory, you can use them relatively easily to measure the earth’s rotation.” What is more, the fine silicon structures are already capable of measuring movements of just one femtometer. This is the unimaginably small distance of 0.000000000000001 meters (10-15 meters), and thus the same magnitude as the diameter of atomic nuclei.

Source: Bosch