ABSTRACT:

The current evolution of the traditional medical model toward the participatory medicine can be boosted by the Internet of Things (IoT) paradigm involving sensors (environmental, wearable, and  implanted) spread inside domestic environments with the purpose to monitor the user’s health and activate remote assistance.

RF identification (RFID) technology is now  mature to provide part of the IoT physical layer for the personal healthcare in smart environments  through low cost, energy-autonomous, and disposable sensors. It is here presented a survey on the state-of-the-art of RFID for application to body centric systems and for gathering  information (temperature, humidity, and other gases) about the user’s living environment.

Many available options are described up to the application level with some examples of RFID systems able to collect and process multi channel  data about the human behavior in compliance with the power exposure and sanitary regulations. Open challenges and possible new research trends are finally discussed.

ENVIRONMENTAL PASSIVE SENSORS

People’s wellness and healthcare assessment in living and medical environments may benefit from a continuous and reliable monitoring of critical parameters such as the temperature, the presence/level of humidity, and some other gases. Sensing volatile compounds through a noninvasive and direct way may, moreover, support clinical diagnosis by means of breath analysis in order to recognize marker gases for discrimination between healthy and sick people.

FID Passive Chemical Sensors. (a) Moisture sensor integrating Pedot: PSS Exposed to Humidity Cyclic Variations . (b) Array of Six RFID Chemical Sensors Exposed to Different Vapors .

A. Volatile Compound Sensors:

Volatile compounds can be sensed by properly shaped tag’s antenna hosting specialized chemically interactive materials (CIMs) capable to selectively change their electromagnetic properties and, accordingly, the tag response during gas exposure. Changes in turn-on power 1 or backscattered power can be, hence,  monitored and decoded by the reader, obtaining information about the presence and the concentration of specific gases.

B. Temperature Tags:

Three classes of passive UHF RFID temperature sensors have been experimented in the last few years, and in some cases even commercialized, ranging from threshold sensors, continuous sensors up to better performing digital data-logger.

BODY -CENTRIC RFID

Autonomous RFID tags suited to be put in contact with the body or in its close proximity are the key enabling devices to develop body-centric healthcare systems which are fully transparent to the user.

Wearable, and even more, implantable passive UHF tags have been a technical taboo for a long time because of the huge power attenuation caused by the human tissues. The body-centric networks investigated so far are mostly based on active devices.

A. Wearable RFID Tags:

The human body is characterized by high electromagnetic losses and, therefore, the energy scavenging efficiency of a wearable antenna is really poor as well as, in case of passive systems, the expected read distances.

The antenna-body electro-magnetic interaction can be, however, minimized by using multi layer tags, for instance, involving dipoles with dielectric insulators, or more effectively folded patches, which are also suited to be embedded into plasters.

a) Example of Wearable Flexible Tag Suitable to be Integrated with Clothes and Plasters . (b) Horizontal Read Regions in [m] by Using Two Tags Over. front and rear torso.

RFID technology has been demonstrated to be potentially useful to take care of the human health-state from the inside by labeling body prosthesis, sutures, stents or orthopedic fixing. Each item could be monitored in real time or on demand by the IoT infrastructure for the ambitious goal of monitoring bio physical process in evolution, such as tissue regrowth and prosthesis displacement. In this case, tags will be embedded into prosthesis,turning them into multi-functional devices capable to generate data beside providing the original medical functionality.

a) Application of UHF RFID Technology to Monitor. (b) The in-stent Restenosis Inside a Carotid Stent. (c) A First Prototype of a STENTag. (d) Measured Backscattered Power Averagedover Frequency) with Respectto the Variation of the Restenosis grade (right to left).

DATA PROCESSING AND HUMAN BEHAVIOR ANALYSIS

The interactions between people and their habitat bring precious information on behavioral parameters concerning the activity rate during the different phases of the day and of the night. The environment itself may have the role of continuous “sampling ” the state of an user by means of specific and nonspecific devices at the purpose to support diagnostics and even to activate remote alarms in case of precursors of anomalous events.

By processing physical data, mostly back-scattered signals, from previously reviewed sensor-oriented RFID devices, the specific patterns of daily actions may be recognized, e.g., cooking, eating, bathing, taking medicine and sleeping, without altering the everyday life-style of the person.

SAFETY COMPLIANCE ISSUES

The social and sanitary acceptance of personal RFID healthcare systems, and their positioning in the emerging IoT paradigms cannot skip the concerns about the compliance of radio emission from RFID readers with the human safety. The wearable and environmental tags have to be reached within a typical room under the constrain that the electric field emitted into the environment and the power absorbed by the humanbodyspecific absorption rate (SAR), both averaged over 6 min, are lower than countries-specific safety limits.

OPEN CHALLENGES AND FUTURE RESEARCH

The above survey has drawn a possible synthesis of existing RFID research and technology for application to an IoT personal healthcare environment. Nevertheless, many issues are still open and even challenging, especially concerning the reliability of the sensors and the true autonomy of the reader ’s node.

Moreover, many other possible research paths may be currently envisaged, based on the fruitful synergy between the Material Science, the Neuro science, and the Sociology with potentiality to develop, in the next years, new devices and new knowledge.

CONCLUSION

The reviewed RFID technology for IoT Healthcare and the personal experience of the authors tell a story of mixed opportunities and fragmentation. Worldwide university laboratories are now researching and making prototypes of RFID sensors,both passive and semi-active that can be interrogated from a distance compatible with the interaction with a network infra-structure.

On the other side, only few products are commercially available for large-scale applications. A very focused effort is, therefore, needed to manage the conversion from experiments to the real use and mass production within a so potentially fast growing market. The overcoming of the slowing factors demands a coordinated activity of the IoT community to stimulate interest in potential final users and  in parallel, to boost the evolution of readers, software, and devices toward a more interconnected perspective.

Source: IEEE
Authors: Sara Amendola | Rossella Lodato | Sabina Manzari | Cecilia Occhiuzzi | Gaetano Marrocco

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