Instrumentation & Measurement Magazine 23-6 - 18

Changes in Sensors Technologies
during the Last Ten Years:
Evolution or Revolution?
Carlo Trigona, Salvatore Graziani, and Salvatore Baglio

T

he full implementation of new ecologies, such as the
Internet of Things, the Internet of Food, Precise Agriculture, Smart Grids, Cities, and Homes, just to
mention some of the most intriguing ones, requires novel devices. These need to exploit new technologies and need to be
capable of providing functionalities that cannot be obtained by
conventional silicon-based electronics.
Applications in fields such as augmented reality and rehabilitation require unconventional approaches, e.g., flexible or
stretchable electronics. Moreover, many other envisaged applications have raised in recent decades the need for sensors
as an extension of perceptive functions, thus boosting the interest toward sensors that are in fact probably among the most
ubiquitous devices.
In fact, even though the discovery of transduction mechanisms and the invention of many sensors goes back decades
and centuries (e.g., the first electric thermostat, invented by
Warren Seymour Johnson, came to the market in 1883; the first
motion detector that exploited ultrasonic waves was invented
in the early 1950s by Samuel Bagno), research efforts, R&D
teams and the sensors market are still rapidly and steadily
increasing. Many manufacturers focus on new processes, technologies, improved designs and suitable solutions for the
ever-increasing number of applications. It is worth noting that
the introduction of low-cost smart systems imposes developing sensors for a wide range of applications. They are used in
our daily life such as those integrated in smartphones, security
systems, automotive, cars, medical devices, aviation, robotics,
artificial intelligence, agriculture, and industrial applications.
Furthermore, with the advent of the fourth industrial/agricultural revolution and in the perspective of its evolution [1], as
predicted by visionaries, various new paradigms have overcome "ordinary sensors," polarizing novel sensing systems
to be smarter and intelligent [2] while providing, at the same
time, higher performance.
From a more general point of view for both ordinary sensors and the evolution seen over the last ten years (which
includes smart solutions, intelligent sensing elements, selfsustained sensors, smaller scale and greener devices), several

18	

transduction mechanisms have been proposed in order to
measure various quantities. In this context, the literature presents varied working principles and associated electrical
outputs, including voltage, optical, resistive, capacitive, inductive, etc., to implement different types of sensors. Referring
to the sensed quantity, sensors can be classified as chemical,
proximity, temperature, presence, displacement, flow, optical,
pressure, position, force, magnetic, electric, just to mention the
most common ones. The distinction between analog and digital output is also an important feature which classifies all of the
aforementioned devices [3], [4].
The evolution of sensing scenarios has produced both incremental improvements of existing technologies and the
introduction of novel disruptive ones. The focus of this contribution will be on some totally new paradigms that have
deeply changed the sensors' state of the art. Restricting the attention on the last decade, the main changes can be found in
the adoption of various technologies and processes [4] starting from systems on a centimeter scale through millimeter
scale, devices up to silicon-based solutions, micro-machined
systems (MEMS) and nano-scale approaches (NEMS). Other
approaches exploited during the last years regard polymeric
materials capable of converting deformations into an electrical
power. In particular, Ionic-electroactive polymers (IEAPs) [5]
have been the object of various manuscripts considering that
they conjugate mechanoelectrical conversion features, with
interesting properties of lightness and flexibility. The most
largely investigated IEAPs are realized by using NafionĀ®, a
polymeric ionomer which is considered un-green, considering the presence of fluorine in its chemical structure. It should
be noted that this evolution has been polarized towards solutions that are green, eco-friendly, biodegradable and nontoxic
for the environment. This intriguing feature has been pursued
through novel materials with lead-free characteristics, an absence of toxic metals, and very recently, bacterial cellulose [6],
which has been proposed as a suitable and green compound
for the realization of sensors.
Some of these technologies are still at an embryonic stage
and are the object of vivid lab research activity. Others are

IEEE Instrumentation & Measurement Magazine	
1094-6969/20/$25.00Ā©2020IEEE

September 2020



Instrumentation & Measurement Magazine 23-6

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