The evolution of electronic applications, both industrial and consumer, is moving mainly towards the embedded nature, therefore towards low-cost, small, battery-powered and multifunctional solutions. This type of solution requires a new model of interface between man and electronic device, which obviously is much closer to the human communication model than to that of the machine. This need does not come so much from an obvious aspiration to bring the machine to the level of human communication, as from the need for compatibility with the strong push for miniaturization related to the increasingly high level of complexity of the information processed and presented by such applications (multimedia) .
In this scenario of technological innovation of microelectronic applications, sensors and actuators play a role of great importance as fundamental components to connect the physical nature of the information with the abstract one represented in logical form in the machine. Microsystems are the technological answer to this need for innovation. Microsystems are the result of research that began in the sixties in the laboratories and then moved to industry.
Today, after four decades, we interact every day, without realizing it, with the products of this technology. MEMS (Microelectromechanical systems) devices, such as accelerometers and gyroscopes, have many applications, both established and emerging, in all sectors of electronics; pressure sensors are applied in the automotive sector and overlook the consumer electronics sector, are widespread in the printer head sector, dominate the sector of micro-mirrors for application in video projectors, etc.
Sensors, after years of development closely linked to the world of automation, have, in recent years, assumed the role of innovation technology for a wide range of applications that are also very different from automation. The world of communications and the consumer sector in general are, for example, application areas that are drawing interesting reasons for innovation from these devices. Companies like IST with a specialization in innovative sensor technology have made possible to obtain sensors that are not only more efficient, but also more versatile and miniaturized than in the past. The evolution of sensor technology has been very rapid in the last twenty years, but it is only in the last few years that the most innovative technologies have been brought into play. The increasingly marked trend towards the embedded implementation of applications has pushed academic and industrial research to field innovative solutions in the sensory field. Smart sensors are, together with those based on MEMS technology, the most interesting as, in addition to improving performance, they considerably extend the field of application.
In addition to the classical methodologies (counting, indirect, interpolation, etc.), advanced sensor techniques, in particular the so-called self-adaptive ones, allow to create applications with interfaces to the physical world capable of supporting particularly difficult functional conditions, without significantly affect the cost and size of the final application. Another very interesting technology for sensors is RF or wireless. One of these solutions is based on surface acoustic waves. These devices, in addition to being able to identify themselves by transmitting a number (ID number), are able to transfer physical measurements (temperature, pressure, humidity, acceleration, etc.), without requiring power. The sensor consists of a Saw (Surface acoustic waves) transponder and a radio transceiver. The Saw transceiver receives an RF burst and responds passively with an RF signal. The way the Saw sensor responds (amplitude, frequency, phase and delay) is directly related to the measurement performed at the time it is interrogated.
Another aspect of innovation in sensors is network management. In particular, wireless network management is at the attention of sensor and microcontroller manufacturers, as both these devices need to integrate this functionality within them, which allows a wide use of sensors in both industrial and consumer areas.
An Intelligent Micromachine
After 20 years of development in university and industrial research laboratories, relegated for years to niche application fields, now, the Micro Electro Mechanical Systems together with the new generation sensors, represent the perfect complement to the system functionality , increasingly embedded in nature and close to the user’s operating mode.
Mems technology allows to integrate, in a single component, mechanical elements together with electronic circuits for signal control and processing. By exploiting the excellent physical properties of silicon (more robust, with better thermal characteristics and a specific weight equal to one third of that of steel), it is possible to create microsensors for the detection of mechanical quantities: pressure, vibrations, linear and angular acceleration, and so on in addition to microactuators of various kinds. Furthermore, silicon implements the functions that transform these quantities into analog or digital data that can be easily interpreted by a complex electronic system. All in one device housed in a tiny package: an intelligent and complete micromachine.
Mems devices have now reached the technological maturity necessary to justify multiple applications, many of which are emerging and innovative in all areas of electronics. Mems technology allows the simultaneous exploitation of the electrical and mechanical properties of silicon and consequently is increasingly adopted in a wide range of consumer electronics applications, in addition to the now consolidated IT, industrial and automotive applications. Measuring or detecting movement (vibration, inclination, acceleration) allows you to make devices easier to use and to equip applications, such as electronic games, with new levels of realism and interaction.
The recent expansion of Mems-based applications was mainly motivated by the fact that the cost of Mems sensors has dropped, also thanks to the shift to production on 8-inch silicon wafers. In the consumer electronics sector, Mems sensors make it possible to create more intuitive and user-friendly man-machine interfaces. These possibilities, applied to consumer products such as game remotes or cell phones, MP3 players and handheld computers, allow for previously unimaginable control and interaction capabilities in low-cost and deeply embedded devices.
Potential and Applications
The potential for technological innovation offered by Mems not only allows to obtain new concept products, but also to put into practice models of interaction between the machine and the user that until now have found a solution only in computationally intensive technologies, such as Vocal recognition. Mems accelerometers, for example, allow you to interact with the machine through movement in a very effective and intuitive way and without excessive computational load on the system.
Mems sensors are also used in digital cameras to compensate and stabilize unwanted movements while taking pictures. In the emerging toy market, accelerometers and gyroscopes sense movements so that the toy knows its position in space and then acts accordingly. In applications with greater added value, such as IT, Mems sensors help protect the integrity of data in laptop computers where in the event of a free fall or other abnormal movement, a Mems sensor promptly gives the system the order to stop operations. to read and write on the hard disk, and to move the magnetic head that reads the hard disk in such a position as not to damage the storage surface. In the automotive field, Mems sensors have many applications, including airbag sensors, anti-theft alarms and navigation systems. In the latter case, they are used in assistive navigation systems where movement and distance traveled tracking is used to maintain correct positioning readings in the event of a temporary absence of the GPS signal. In the industrial sector, accelerometers are busy detecting vibrations in appliances, such as washing machines, dishwashers and other new appliances in order to alert users to unbalanced loads and detect excessive wear on mechanical parts before a malfunction occurs. For security systems, applications concern anti-theft devices based on Mems accelerometers, for example to protect cars, briefcases, laptop computers and any device that can be stolen from the owner by moving.