Instrumentation & Measurement Magazine 26-1 - 36

the use of plants as additional nutrients for the whole conversion
process [24], [25]. The principle of such a solution, purely
oriented toward power generation, is well known in the literature,
and although it was developed about 100 years ago,
the research shows strong activity in recent years [26]. Going
toward sensing systems, Fig. 2 shows the evolution from
soil-based sensors to living sensors. Specifically, it illustrates
the trend from sensors based on soil and its metabolic process,
through the adoption of plants and the exploitation of sensing
properties, in order to realize the living sensors.
Focusing the attention on soil, researchers have recently
demonstrated the possibility of using it as a sensor [27]. In
particular the principle is based on modifying the metabolic
processes of natural organisms within the soil as a function of
applied temperature. Thanks to its content of microbes and living
organisms which consume the nutrient elements (such as
glucose), the soil is used as sensitive material, and during this
metabolic process, electrons and hydrogen are released.
The transduction process starts from the anode, and
through a resistive load, a current flow in the circuit is created
with a measurable differential of potential across the resistor.
It is worth noting that in presence of O2
in the air and H+ in the
Fig. 1. The greenest paradigm based on a fully biodegradable device able to
absorb CO2
.
beyond this technology, the greenest paradigm is represented
by sensors and transducers that are completely biodegradable,
with no CO2
emissions during production, considering the absence
of manufacturing and foundries processes, but also have
devices that during regular use are able to absorb the CO2
ready present in the environment (Fig. 1).
alThis
latter characteristic can be obtained considering the
natural life and photosynthetic processes of vegetation and
plants used as sensors. It
is worth noting that systems
based on plants can
absorb about 167 kg of CO2
per year [23]. This paper
will address a synthesis
of a research activity that
hinges on the adoption of
a soil-plant system as sensor,
its chemo-electrical
transduction, the biological
operating principles,
models and features.
Transduction
Principles in SoilPlant
Systems
The most famous solution,
where microorganisms are
adopted for transduction
and energy generation,
concerns microbial or plant
microbial fuel cells with
36
soil, the system will produce water in the final transduction
process. Fig. 2 synthetizes the mechanism described. Focusing
the attention on the measurand (the temperature), the voltage
generated will be a function of the applied physical quantity
taking into the account that the metabolic process of microorganisms
in soil is correlated with the applied temperature [27].
Obviously, the family of living organisms determines the
performance of the entire sensor in terms of resolution, operating
range, influences, capability to sense a specific quantity
(rejecting quantities of no interest) and sensitivity. To demonstrate
this process, with the aim of developing a descriptive
Fig. 2. Evolution of sensors based on microorganisms and plants.
IEEE Instrumentation & Measurement Magazine
February 2023
Instrumentation & Measurement Magazine 26-1

Table of Contents for the Digital Edition of Instrumentation & Measurement Magazine 26-1
