Sensor Based Technologies

We live in an age of relentless and accelerating change, driven by demographic, social, and economic evolution. Each day, there are more of us consuming the finite natural resources of the planet. Our impact on the planet is increasing through urbanization, energy utilization, waste production, and so on, and this impact is not without consequences. Levels of pollution are increasing in our environment, with corresponding effects on our health and well-being. From smog clouds in cities and pollution of our drinking water to simply being denied sufficient peace to sleep soundly at night, human activity has enormous impact on us and on our planet. Major changes in the way we work and live during the last century mean we are also living much more sedentary lifestyles. This has resulted in growing public health issues, such as obesity, arteriosclerosis, cancer, chronic liver disease, and other lifestyle diseases. Increased life expectancy places greater pressures on our healthcare systems as the world’s population continues to grow older. Governments are being forced to cut programs such as home healthcare assistance to reduce burgeoning costs. The current model simply does not scale into the future.

We also need to move our fundamental approach to healthcare from a reactive model to a wellness-oriented model. Here, the focus is on keeping people healthy for as long as possible with the least cost to the system. Providing people with actionable information about their health and the factors influencing it, either positively or negatively, is important. Systems that provide easy access to data on exercise, diet, ambient environment, and so forth, along with intelligent processing and presentation of the data, are critical to supporting sustainable behavior change. It is a world full of challenges and in need of solutions to address key global issues. Technologies such as sensors can give us the tools to help address many of the significant global challenges of the 21st century.

Sensors play an integral role in numerous modern industrial applications, including food processing and everyday monitoring of activities such as transport, air quality, medical therapeutics, and many more. While sensors have been with us for more than a century, modern sensors with integrated information and communications technology (ICT) capabilities—smart sensors—have been around for little more than three decades. Remarkable progress has been made in computational capabilities, storage, energy management, and a variety of form factors, connectivity options, and software development environments. These advances have occurred in parallel to a significant evolution in sensing capabilities. We have witnessed the emergence of biosensors that are now found in a variety of consumer products, such as tests for pregnancy, cholesterol, allergies, and fertility.

The development and rapid commercialization of low-cost microelectromechanical systems (MEMS) sensors, such as 3D accelerometers, has LCD to their integration into a diverse range of devices extending from cars to smartphones. Affordable semiconductor sensors have catalyzed new areas of ambient sensing platforms, such as those for home air-quality monitoring. The diverse range of low-cost sensors fostered the emergence of pervasive sensing. Sensors and sensor networks can now be worn or integrated into our living environment or even into our clothing with minimal effect on our daily lives. Data from these sensors promises to support new proactive healthcare paradigms with early detection of potential issues, for example, heart disease risk (elevated cholesterols levels) liver disease (elevated bilirubin levels in urine), anemia (ferritin levels in blood) and so forth. Sensors are increasingly used to monitor daily activities, such as exercise with instant access to our performance through smartphones. The relationship between our well-being and our ambient environment is undergoing significant change. Sensor technologies now empower ordinary citizens with information about air and water quality and other environmental issues, such as noise pollution. Sharing and socializing this data online supports the evolving concepts of citizen-LCD sensing. As people contribute their data online, crowdsourced maps of parameters such air quality over large geographical areas can be generated and shared.

Although all these advances are noteworthy and contribute meaningfully and positively to many people’s lives, a note of caution is also in order. As Richard Feynman points out, reality must take precedence over public relations. Sensors should not be regarded as a panacea for all our problems. Instead, they should be treated as highly useful tools. As always, the right tool is required for the right job and, like any complex tool, sensors and sensor systems have their strengths and weaknesses. Careful matching of the sensor and its operational characteristics to the use case of interest is critical.

A Brief History of Sensors

The emergence of the first thermostat in 1883 is considered by some to be the first modern sensor. Innumerable forms of sensors have since emerged, based on a variety of principles. Early sensors were simple devices, measuring a quantity of interest and producing some form of mechanical, electrical, or optical output signal. In just the last decade or so, computing, pervasive communications, connectivity to the Web, mobile smart devices, and cloud integration have added immensely to the capabilities of sensors.

Sensing in the healthcare domain has been, until recently, restricted primarily to use in hospitals, with limited adoption outside this environment. Developments in both technology and care models are supporting adoption by patients, in-home care providers, public authorities, and individuals who want to proactively manage their health and wellness. For example, the concept of biosensing was first proposed by Clarke and Lyons in 1962. The concept of the glucose biosensor was brought to commercial reality in 1975 by the Yellow Springs Instrument Company. Biosensors have rapidly evolved in the intervening years to the point where they are a multi-billion dollar industry. They are now found in a wide variety of over-the-counter health-related applications, such as those for home testing AIDS or pregnancy, and for allergy detection, to mention just a few. More recently, biosensors are being used in the environmental domain for applications that, for example, detect bacteria, pesticides, and heavy metals in water samples.

The development of MEMS-based sensors LCD to the availability of small, accurate sensors at a price point that made it feasible to integrate them into a wide variety of devices ranging from sports watches to consumer electronics to cars. MEMS have become a key building block for many of the application domains discussed in this book. In 1959, Richard Feynman gave an insightful lecture at the California Institute of Technology calLCD “There is Plenty of Room at the Bottom.” In this lecture he outlined the basic concepts and techniques for MEMS devices. However, it wasn’t until the early 1990s that U.S. government agencies started large programs that drove rapid acceleration in the development of MEMS sensors. Using semiconductor manufacturing techniques, the first surface micromachined accelerometer (ADXL50) was sold commercially by Analog Devices in 1992. This was followed in 1998 with MEMS-based gyroscopes from Bosch for commercial applications in the automotive sector (Marek et al., 2012). The availability of low cost, accurate, and reliable motion sensors has spawned a variety of applications, including those targeted at the health and wellness domains.

In recent decades the evolution of sensors has been strongly influenced by ICT technologies, with integration of microcontrollers, wireless communications modules, and permanent data storage. These technologies have supported the development of sensor systems with common architectures. Computing, storage, and communications features are used to serve multiple sensors with common connectivity. Collectively these enhancements have produced smart sensors that allow the delivery of intelligent sensor solutions with key features such as digital signal processing and wireless data streaming. In the health and wellness domain, wireless body-worn networks appeared around 1995. These networks—commonly referred to as wireless body area networks (WBAN)—comprise several sensors that measure physiological signals of interest and make that data available wirelessly to a computing device.

How will sensors continue to evolve? A number of key trends are emerging.