Achievements and Challenges in Sensor Devices

Sensor devices are supposed to send their data to readout electronics or computer processors in order to detect changes in the environment, so proper electronics are a fundamental requirement. Early sensors used to measure chemical, physical, or biological parameters were bulky. Additionally, they were often inaccurate, as the user had to manually read and decode the sensor signals.

Recently, nanotechnology-based interdisciplinary advances have spurred many advancements in the sensing field, opening many new solutions for highly engineered devices with excellent performance characteristics.

Sensors play a crucial role in improvements needed to meet social demands, such as hazard detection (Rasheed et al., 2018), pollution control and environmental remediation (Shak et al., 2018), energy production (Hou et al., 2018) and storage (Kawai et al., 2018), and biomedical treatments (Kumar and Liz-Marzán, 2019).

Generally, they can be categorized into chemical substances, physical conditions, or biological phenomena.

Their variety has steadily increased over the years, and we now have:

• Magnetic sensors

• Photonics based sensors

• Infrared sensors

• Gas Sensors

• Geo-sensors

• Touch sensing devices

• Nano-sensors

• Clothes-based sensors

• Crowd sensing devices

• Sensors decoding physical sensation

• Movement sensors

• Atmosphere sensors

• Position sensors

• Liquid sensors

• Sound sensors

• Medical sensing devices

A key sensor performance characteristic such as sensitivity, selectivity, stability, and usability must be enhanced to meet social demands. Researchers have therefore focused on developing new active sensing materials and improving the design of sensing mechanisms. Nanotechnology and material science play a key role in this regard and are continuously pursuing innovations for improved sensor devices.

In recent years, smart, safe, biocompatible, and environmentally “clean” sensor devices and instruments have been designed and developed. These sensor devices and instruments embrace multiple integrated functionalities, including wearable electronics, smartphones, and other commoditized gadgets. Through these technology platforms, different parameters/phenomena can now be monitored simultaneously, and new technologies and sensor types have been proposed.

Due to the advanced properties of many electronic sensor devices, including their small dimensions, low weight and cost, and reliability, they are strongly aligned with various markets. Optical sensor devices have lately been gaining interest, especially for specific applications in critical environmental applications (pipelines, power lines, perimeters, borders, etc.), due to their ability to reach places that are otherwise inaccessible. Optical fibers can monitor strain, temperature, pressure, and vibrations at millions of points, increasing the monitoring scalability capabilities of sensing devices (Fernández-Ruiz et al., 2020).

The limits of sensing devices in terms of sensitivity, selectivity, resolution, accuracy, and precision are continuously being improved. At the same time, their potential in terms of exploitation and applications is also rapidly expanding.

Simultaneously, we have witnessed the advent of the Internet-of-Things (IoT) that has changed the way we think about sensors and their usage, and their diffusion throughout society. IoT is a network of “intelligent” devices with embedded electronics, sensors, and network connectivity that can acquire and exchange data. IoT concepts and technologies have been implemented extensively in automobiles and have been used to create smart lighting in homes and streets and network water, power, temperature control, and alarm systems in cities (Vlacheas et al., 2013; Jin et al., 2014; Zanella et al., 2014; Zhu et al., 2015).

A device's biggest challenge in the IoT era is providing data in real-time so that the status of key parameters can be tracked, exchanging information with other devices, and learning the overall functionality of the system, acting even beyond its sensing function.

Wearable sensing devices have received a lot of attention recently, especially in the context of fitness applications and the Internet of Things. With the advent of smart-watches and wristbands, monitoring activities throughout the day is now possible without causing discomfort to the individual (Haghi et al., 2017). As wearable sensing capabilities have expanded into smart textiles, clothes embedded with electronics, and smart spectacles, the number of parameters that can be monitored has increased, from which patterns and trends can be extracted, to which personalized conditioning or care strategies can be optimized (Stavropoulos et al., 2017).

In particular, flexible and stretchable electronic devices have enabled innovation in medical applications, like employing new materials and devices with properties similar to human tissue (Wang et al., 2018; Lee et al., 2019; Niu et al., 2019; Yang et al., 2020). The increasing bio-integration of wearable electronics and biosensors with human tissue has widened the field of wearable bioelectronics.

By monitoring the electrical properties of tissues, these devices can provide real-time feedback, accurate diagnosis, and therapies based on "closed loop" treatment. Flexible and stretchable devices include electronic skins (e-skin) (Hanif et al., 2018; Park et al., 2019), glucose monitoring contact lenses (Kim et al., 2017; Pakr et al., 2018) and health monitors (Hong et al., 2018; Xie et al., 2020).

Well-being and healthcare may benefit from IoT by using sensors that are connected to the environment and provide autonomous communication and contextual information to aid clinicians in making clinical decisions and support caregivers, especially in caring for the elderly.

COVID-19 is demonstrating that sensors with the capability of providing accurate, rapid information play a crucial role in reducing the spread of infections, and thereby saving lives.

In order to develop modern sensing devices and instruments, researchers in this field are constantly exploring and developing more sensitive and selective detection strategies, measurement principles, and new analytical methodologies. Technology challenges for sensor devices include reducing their cost, size, and energy consumption. Designing and developing nanoscale sensing materials is essential to improving device performance. The integration of these novel materials and structures into sensor devices is another challenge that is often overlooked and underestimated. Integration of these devices must be scalable for the production of commercial devices, as their use will otherwise be limited to laboratory experiments, with very limited socio-economic impact.

The performance of sensing devices can be improved by utilizing 0D, 1D, and 2D materials, as well as flexible and bio-inspired concepts. For their integration, top down technology (conventionally used for microfabrication) must integrate synergistically with bottom up advances (mostly used for nanomaterial fabrication) for the combination of nanomaterials at a sensor device scale, allowing full exploitation of these materials.

The sensors also produce data, which is often overlooked in the field of sensing. Sensor technology research involves the processing and decoding of sensor data. In order to provide the final feedback to the end user in real-time, the sensed data has to be analyzed and transformed using artificial intelligence, deep learning, or other techniques to manage "big data." Managing these increasingly large data sets streaming from widely distributed and heterogeneous sources is a rapidly growing challenge in this field.

Due to all the variables involved in this multidisciplinary field of sensing devices, it is difficult to predict the real-time evolution in advance. Nevertheless, significant advances have been made that have had a huge impact on society, improving product quality, food and environment safety, disease diagnosis, medicine, health and wealth, process studies, and more.

It is certain that this trend will continue as new sensor technologies emerge and expand the scope and scope of their impact on our lives.

"Frontiers in Sensors" will provide a forum for the publication of quality research and for an informed discussion on trends and opportunities for Sensor Devices in particular, delivering a significant positive socioeconomic impact over the next several years.

Author Contributions

It is confirmed that the author is the sole contributor to this work and has approved it for publication.

Competing interests

According to the author, there were no commercial or financial relationships that could be construed as potential conflicts of interest in the research.