IEEE TRANSACTIONS ON AGRIFOOD ELECTRONICS, VOL. 2, NO. 1, MARCH/APRIL 2024
43
A Stand-Alone, In Situ, Soil Quality Sensing
System for Precision Agriculture
Marios Sophocleous , Senior Member, IEEE, Andreas Karkotis , Antri Papasavva , Michale Goldberger ,
Loukia Vassiliou , Jose Vicente Ros-Lis , Yosi Shacham-Diamand ,
and Julius Georgiou , Senior Member, IEEE
Abstract—The pressure on agricultural efficiency is nowadays
greater than ever, hence there has been an abrupt technological
involvement in this sector in the last decade. In this article, a
stand-alone, in situ, soil quality sensing system is presented for
the first time, capable of monitoring chemical parameters in the
soil without any human intervention. The system is capable of
measuring potassium and nitrate concentrations with a sensitivity
of ∼0.6 µA/mM (R2 = 0.9775) and ∼2 µA/mM (R2 = 0.9708) in
the range of 0.1–10 mM, pH with a sensitivity of ∼−30 mV/pH (R2
= 0.9068) in the range of 4–10, and temperature with a sensitivity of
∼1.6 Ω/o C (R2 = 0.9999) in the range of −30 to 60 ◦ C. It includes
an impedance probe for impedance measurements up to 1 MHz.
A unique packaging was also developed to protect the array from
the soil while allowing enough time for the sensors to take precise
measurements. The thick-film multisensor array was connected
to a stand-alone, electronic node, while the complete system was
deployed in the field, taking measurements every 30 min, showing
the capability to track watering and fertilizing times.
Index Terms—Precision agriculture, screen-printing, sensing
systems, soil quality, soil sensors, thick-film technology.
I. INTRODUCTION
S THE population grows, so does the need for more
food production. Historically, humanity has utilized its
intelligence to evolve different farming methods for various
types of crops [1]. Technological breakthroughs, such as those
of the industrial revolution, were initially directed at making
A
Manuscript received 25 August 2023; revised 7 November 2023 and 3 January
2024; accepted 5 January 2024. Date of publication 26 January 2024; date of
current version 11 April 2024. This work was supported by the Research &
Innovation Foundation of Cyprus under Grant POST-DOC/0718/0163. This article was recommended by Associate Editor: Danilo Demarchi. (Corresponding
author: Marios Sophocleous.)
Marios Sophocleous, Andreas Karkotis, Antri Papasavva, and Julius Georgiou
are with the Department of Electrical & Computer Engineering, University
of Cyprus, 2109 Nicosia, Cyprus (e-mail: marios_sophocleous@hotmail.com;
karkotis.andreas@ucy.ac.cy; papasavva.t.antri@ucy.ac.cy; julio@ucy.ac.cy).
Michale Goldberger is with the Department of Physical Electronics, School
of Electrical Engineering, Tel Aviv University, Tel Aviv 69978, Israel (e-mail:
michaleg25@gmail.com).
Yosi Shacham-Diamand is with the Department of Physical Electronics,
School of Electrical Engineering, Tel Aviv University, Tel Aviv 69978, Israel, and
also with the Head of The Scojen Institute for Synthetic Biology Center, Reichman University, Herzliya 4610101, Israel (e-mail: yosef.shacham@runi.ac.il).
Jose Vicente Ros-Lis is with the Department of Inorganic Chemistry, University of Valencia, 46010 Valencia, Spain (e-mail: j.vicente.ros@uv.es).
Loukia Vassiliou is with the Agricultural Research Institute, Ministry of Agriculture, Rural Development and Environment, 1516 Nicosia, Cyprus (e-mail:
lvassiliou@ari.moa.gov.cy).
Digital Object Identifier 10.1109/TAFE.2024.3351953
tools and machines that assisted farmers to cultivate and irrigate
the land faster and more efficiently [2]. Despite the spectacular
technological developments, humanity still struggles in the 21st
century to eradicate hunger, which is due to the large population
increase, but also to the lack of water in several areas of the
world [3]. In addition, the lowering of the water table and the
increase in soil salinity, due to the overextraction of groundwater, pose difficulties to the cultivation of crops [4]. Moreover,
the reckless and extensive use of pesticides and fertilizers has
resulted in the development of resistance of various organisms
causing pests and diseases rendering the fields infertile in many
areas [5]. It further resulted in the pollution of the aquifer, water
in rivers, lakes, and underground water reservoirs, disturbing to
a great extent the balance of ecosystems.
Science and technology now offer a possible solution to the
problem with the concept of precision agriculture, encompassing
the timely response to the needs of the plants by monitoring
several soil, environmental, or other plant parameters, as well
as forecasting the weather [6], [7], [8]. To achieve this level, the
environmental conditions and soil quality must be monitored
in real time and assessed for each specific plant since different
plants have different soil and environmental preferences to optimally grow [9], [10]. Currently, a huge plethora of environmental
sensing systems and weather stations exist that can be implemented to cover that part of the overall approach [11]. However,
soil quality monitoring is a major stumbling block toward real
precision agriculture [12], [13]. Soil quality is nowadays evaluated using the standard soil sampling methodology followed by
wet chemistry tests either in the field using soil quality kits or in
the laboratory when more precise measurements are needed [14].
Unfortunately, none of these two approaches allow for real-time
monitoring of soil quality, which is needed for automated control
and direct response. The only available soil sensors that are
compatible with the real-time monitoring approach are the soil
salinity and moisture sensors from which the soil pH can be
estimated based on correlations [15]. There are no soil sensors
commercially available or reported in the literature that can
monitor soil nutrients in real time [16].
In this article, a holistic approach is described featuring for the
first time, a stand-alone, in situ, soil quality sensing system for
monitoring soil quality, fertilization, and moisture. The sensing
system consists of a multisensor array that is based on thick-film
technology and an electronic system to accommodate the sensors
including a solar panel and batteries for energy harvesting.
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IEEE TRANSACTIONS ON AGRIFOOD ELECTRONICS, VOL. 2, NO. 1, MARCH/APRIL 2024
The reason for choosing this technique is that it can be mass
produced at a very low cost and detect almost all aspects of
soil quality while utilizing its unmatched resistance to harsh
environments [17]. The system has been designed, fabricated,
and tested in the laboratory and the field showing extremely
promising results.
II. THICK-FILM MULTISENSOR ARRAY
The multisensor array can measure pH, nitrates, potassium,
temperature, and soil impedance (both magnitude and phase).
Each one of the sensors is described in the following sections.
A. Impedance Probe
The impedance probe is based on a previously reported conductivity probe [18]. The conductivity probe was then improved,
redesigned, simulated, and tested previously [19] expanding it
from a conductivity probe at 1 kHz to an impedance probe within
the range of 100 Hz–1 MHz. This significant improvement
allows the measurement of resistivity at lower frequencies and
identifies the time constant of the soil. Knowing the resistance
part of the time constant, the capacitance part can be calculated.
It is proven that the resistivity of the soil at lower frequencies
(∼ 1 kHz) is correlated with the salinity and the amount of water
in the soil, and the capacitance of the soil is correlated with
the water content of the soil, since soil permittivity is approximately 3, depending on the soil type, and approximately 80 for
water [20]. The probe is equipped with guarding electrodes that
are proven to help with the electric field uniformity and shows
a linear response with the medium’s resistivity using a 1-kHz
sinusoidal input current with a sensitivity of 0.163 mV/Ωm in
the range of 2.5–50 Ωm in a medium with relative permittivity
of 20. In addition, the phase shift shows a linear relationship to
the medium’s relative permittivity and a sensitivity of 0.1◦ /εr in
the range of 5–81 using a 1-MHz sinusoidal input current. The
equivalent circuit models of the probes were constructed and the
values of the components have been extracted. The experimental
and simulated values are within a ±6% error margin [19].
B. Referenceless pH Sensor
The preexisting pH sensor was based on the classical ionselective-electrode (ISE) and reference electrode (RE) approach.
However, REs suffer from significant long-term drift and very
short lifetimes [21], [22], [23]. Hence, to overcome this challenge, the novel approach using two pH ISEs (referenceless
potentiometric sensors) with different sensitivities was implemented. The potential difference between the two ISEs (potentiometric sensor) would also be proportional to the pH of the
medium under test. It was decided to develop custom inks/pastes
for the pH sensor with one of them being based on ruthenium
oxide (RuO2 ) and the other one based on iridium oxide (IrO2 ).
The two pastes were developed using RuO2 and IrO2 powders
and a commercially available screen-printing ink without a filler.
1) Thick-Film Fabrication: The fabrication procedure of the
pH sensor is relatively simple compared with the potassium and
nitrate sensors. The underlying conductor layer is printed using
Fig. 1. (a) Fabricated pH Sensor. (b) Potentiometric response versus pH in the
same buffers.
the same screen and ink as the platinum resistance thermometer
(PRT). Both custom inks were based on the use of DP8155
(DuPont) fillerless paste and the addition of iridium oxide
powder (206237 Sigma Aldrich) and ruthenium oxide powder
(238058 Sigma Aldrich). The paste-to-powder weight ratio was
approximately 2:3 for iridium oxide and 8:21 for ruthenium
oxide.
2) Sensor Performance: The sensor [see Fig. 1(a)] was designed, printed, and tested in pH buffers (4–10), first each ISE
individually against a commercial Ag/AgCl RE, and then, as
a complete sensor. The sensor was immersed in pH buffers
for approximately 120 s in each buffer in a specific sequence
(7-4-7-10-7-4) to observe any hysteresis. The measurements
were obtained using the PalmSens4 potentiostat. The voltage
was measured every 1 s for 120 s in each buffer. The sensor
showed a sensitivity of approximately 30 mV/pH at 25◦ C with a
stability of <4 mV in 120 s, however, some hysteresis (<20 mV
at pH 7) has been observed. This hysteresis is comparable with
other screen-printed pH sensors with hysteresis of approximately 10 mV at pH 7 [23].
C. Platinum Resistance Thermometer
The thermometer was based on the classic PRT approach. PRT
is based on the properties of platinum to change its resistance
with temperature while the characteristics of the sensor depend
on its geometry. The sensor follows the linearized model of
RT = R0 × (1 + aT ) where RT is the resistance at the temperature to be measured (Ω), R0 is the resistance at 0 ◦ C (Ω), a is the
temperature coefficient of electrical resistance for platinum, and
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SOPHOCLEOUS et al.: STAND-ALONE, IN SITU, SOIL QUALITY SENSING SYSTEM FOR PRECISION AGRICULTURE
45
its performance. Printing multiple layers (3) of the ink to ensure
continuity significantly decreased the total resistance of the PRT,
hence, decreasing its sensitivity.
D. Amperometric Potassium and Nitrate Sensors
Fig. 2.
(a) Fabricated PRT. (b) Calibration curve of PRT.
T is the temperature (◦ C). Therefore, the higher the resistance
of the device at 0 ◦ C and the higher the a, the more sensitive the
device is.
1) Thick-Film Fabrication: In order to accommodate for the
particularities of this sensor geometry, the fabrication procedure
was significantly more difficult. A high-purity platinum ink
was used (DP9141). Based on the manufacturer’s specifications,
when fired, the ink produces a film of approximately 10 μm in
thickness with a resistivity of 60–100 mΩ/square and a temperature coefficient of resistance (α) of 0.0035 Ω/Ω/◦ C (ideal
for pure platinum is 0.004). To ensure high resistance of the
device, very narrow tracks of 0.1-mm width and ∼1 m in length
were designed and printed on the alumina substrate. The printing
of this layer was attempted with polyester screens of 230 and
330 mesh, and it was found that the 230 mesh printed the layer
with better continuity and lower thickness. The printed version
of the sensor is shown in Fig. 2 below. The blue layer on top
is a dielectric layer to protect the PRT from the solutions and
subsequently the soil. The dielectric paste used was ESL 4905-C
(electro science).
2) Sensor Performance: The sensor was fabricated, as shown
in Fig. 2, and it has been tested in an environmental chamber
from −30 to 60 ◦ C showing an extremely linear response and
a sensitivity of approximately 1.6 Ω/◦ C. This follows the aforementioned model. It is worth mentioning here that repeatability
in the fabrication of this sensor was a major factor that affected
The nitrate and potassium sensors are based on the classic three-electrode, electrochemical approach and methodology [24]. Two versions of these sensors were developed, one
with a conducting polymer [25] as the medium between the
electrodes and one with a potassium nitrate (KNO3 ) gel. In both
cases, an ion-permeable membrane (IPM) was placed on top to
allow only the ion of interest to enter the sensor.
The sensors were tested using a potentiostat performing initially cyclic voltammetry, identifying the potential of interest,
and eventually, during the field deployment, the chosen voltage
was provided to the potentiostat and the current was measured
at the working electrode in an automated manner.
1) Thick-Film Fabrication: The sensors were fabricated using thick-film technology on an alumina (Al2 O3 ) substrate with
an Aurel C920PA automatic screen-printing system. The screens
were made of polyester. The sensors comprise four or five printed
layers. The base layer was gold (8881-B ESL Electroscience,
England), covered by silver/platinum solder pads (9512-G ESL
Electroscience, England). The third layer was a dielectric (4905C ESL, Electroscience, England) used to protect the nonsensing
metallic area of the sensor from interacting with the electrolyte.
The fourth layer was Ag/AgCl (C2130809D5 Sun Chemical,
USA) for the RE. For the first version of the sensors, the
fifth layer was poly(3,4-ethylenedioxythiophene) polystyrene
sulfonate (PEDOT:PSS) Clevios SV3HV (Heraeus, Germany).
Only some of the electrodes were coated with PEDOT:PSS,
while others remained without this layer. PEDOT:PSS is a
conductive, p-type polymer, which changes its resistivity by
absorbing certain ions from the electrolyte. The ions fill up
spaces in the polymer chain, decreasing the flow of holes, and
thus, current, in the layer. The inks were all cured according to
the supplier recommendations using the FALC Muffle Furnace
FM 22. The working electrode has a diameter of 1.50 mm.
The fabrication procedure used for the potassium IPM has
been described elsewhere [24]. The IPM for the nitrate sensor
was based on a commercially available recipe from SigmaAldrich. For the preparation of the cocktail (∼192.3 mg),
1.15 mg of tetraoctylammoniium chloride was dissolved in
0.9615 mL of tetrahydrofuran (THF). In total, 90.6 mg of dibutyl
phthalate was also added to the solution, and then, 90.6 mg
of polyvinyl chloride was also added to the mixture while
continuously stirring to ensure a homogeneous mixture. Finally,
10 mg of nitrate ionophore VI was added to the mixture. It
is important to state here that THF is a very volatile liquid,
hence to ensure that the ratios between quantities are correct, the
whole procedure should be completed quickly and preferably at
low temperatures. Once the nitrate ionophore is also added, the
mixture is continuously stirred allowing the THF to evaporate
and making the mixture more viscous. Using a pipette the IPM is
drop-casted on the sensors ensuring full coverage of the devices.
The sensors were stored in the fridge for 48 h before use.
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IEEE TRANSACTIONS ON AGRIFOOD ELECTRONICS, VOL. 2, NO. 1, MARCH/APRIL 2024
Fig. 3.
Fabricated amperometric potassium and nitrate sensors.
Fig. 4.
Stability of PEDOT:PSS-based nitrate sensors.
Fig. 5. (a) Cyclic voltammetry of potassium sensors. (b) Calibration curve of
potassium sensors.
In the final version of the potassium and nitrate sensors, since
the measured currents from the initial versions were significantly
low, the size of the working electrode was increased and the RE
was placed in between the working and the counter electrode
with an increased surface area for better stability (see Fig. 3).
Furthermore, due to the instability of the PEDOT:PSS layer
(see Fig. 4), that layer was replaced with a KNO3 gel to ensure
continuity and high conductivity of the medium below the IPM
for both potassium and nitrate sensors. The gel was prepared by
warming 100 mL of deionized water up to approximately 100
◦
C, and then, adding 2 g of gelatine. Then, KNO3 was added
to a concentration of 0.01 M and the mixture was very well
stirred. Using a pipette it was drop-casted on top of the electrodes
ensuring that all the electrode area was fully covered by the gel.
Finally, the sensors were placed in the fridge for approximately
24 h to allow the gel to solidify.
2) Potassium and Nitrate Sensor Performance: Initially,
both nitrate and potassium sensors were tested in KNO3 solutions in the concentration range of 0.1–10 mM at room temperature. In the first version, a PEDOT:PSS, a conducting polymer,
layer was printed between the IPM to amplify the signal and
simplify the operation of the sensor. However, it was found that
it created significant repeatability issues as shown in Fig. 4 not
only for nitrate sensors but also for potassium sensors.
The gel-based version of the potassium sensor showed a peak
at ∼−1.4 V and a sensitivity of ∼0.6 μA/mM in the range of
0.1–10 mM of KNO3 solution (see Fig. 5). It is worth noting
that as the concentration increases, the peak voltage increases
to approximately −1.1 V. Nonetheless, the linear fit on the
potassium concentration is recorded at −1.4 V. The gel-based
version of the nitrate sensors showed a current peak at ∼0.8 V
and sensitivity of ∼2 μA/mM in the range of 0.1–10 mM of
KNO3 solution (see Fig. 6). Several tests have been done to
evaluate other ion interference showing interference coefficients
of at least an order of magnitude lower than nitrate sensitivity.
E. Double-Sided Thick-Film Multisensor Array
The multisensory array (see Fig. 7) was fabricated on 50.8 ×
50.8 mm of alumina (Al2 O3 ) substrates. The alumina substrate
was laser-scribed by the manufacturer to allow breaking right
in the middle. The impedance probe is printed on the front side
of the substrate and the two pieces are mirror images of each
other (see Fig. 7). On the back side of the substrate, one half of
it includes the nitrate and potassium sensors and the other side
includes the temperature and pH sensors.
III. SYSTEM INTEGRATION AND DEPLOYMENT APPROACH
A stand-alone, electronic system encompassing all analog,
digital, and power management electronics was developed. An
initial version of the electronic system has been described and
characterized elsewhere [26].
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SOPHOCLEOUS et al.: STAND-ALONE, IN SITU, SOIL QUALITY SENSING SYSTEM FOR PRECISION AGRICULTURE
Fig. 8.
Circuit schematic of the electrical impedance spectroscopy sensor.
Fig. 9.
3-D printed multisensor array holder.
47
Fig. 6. (a) Cyclic voltammetry of the nitrate sensors in KNO3. (b) Calibration
curve of the nitrate sensors in KNO3.
B. Multisensor Array Packaging
Fig. 7. Two sides of the complete multisensor array. On the left-hand side,
the two parts of the front side of the multisensor array are seen, while on the
right-hand side, the two parts of the back side of the multisensor array are shown.
A. Impedance Analyzer Electronics
In this final design of the system, what was initially designed
to be a conductivity measuring circuit, has been upgraded to
an electrical impedance spectroscopy circuit capable of sweeping frequencies from 100 Hz to 1 MHz compatible with the
six-electrodes approach also described elsewhere [19]. The
schematic of the electrical impedance spectroscopy circuit is
presented in Fig. 8 below.
An investigation of the different deployment methods of the
multisensor array in the soil was performed. Fluid flow simulations with several packaging techniques have been performed on
SolidWorks to identify the best package to protect the sensors
from the soil’s harsh environment but also to ensure that the
sensors will be in contact with the soil/water medium for a certain
amount of time to allow the sensors’ output to stabilize. The
best-performing deployment method was designed, 3-D printed,
and tested in the laboratory to ensure its functionality. The sensor
holder is made up of two pieces. The top piece (shown on the
top right of Fig. 9) allows the water to flow in the sensor holder
through multiple narrow paths essentially filtering out any tiny
soil particles. Then, the water flows to the internal pool of the
bottom piece (shown on the top left of Fig. 9) and eventually to
the inside pool touching the back side of the multisensor array.
In order to enhance the lifetime of the sensors in the soil, the
concept of Pythagoras’ cup was implemented at the inside pool.
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48
Fig. 10.
IEEE TRANSACTIONS ON AGRIFOOD ELECTRONICS, VOL. 2, NO. 1, MARCH/APRIL 2024
Fully integrated system ready for deployment.
Fig. 11.
System fully deployed in the soil for field trials.
The idea was to allow enough water to flow inside the sensor
holder so that the sensors can take readings but once the level
of the water exceeds a certain point, the water would flush out
allowing the sensor to stay in a dry environment until the next
reading. The lifetime of the sensors when not immersed in a
liquid environment is significantly longer, hence this approach
would extend the overall lifetime of the multisensor array, on
the chemical analysis side of the substrate (see Fig. 9).
C. Full System Integration
The multisensory array is constructed as two pieces of alumina
substrate (25.4 × 50.8 mm each) facing each other. Those two
pieces were used to design and manufacture the 3-D printed
holder so that they can be inserted in slots (see Fig. 9). The
impedance probe side of the multisensory array comes in direct
contact with the soil while having the two sides open to allow
soil water to flow in and out of the monitored soil slot. The
two back sides of the array are immersed in the Pythagoras
cup allowing the water flowing through the soil to enter the
holder and get in contact with the electrochemical sensors of the
array. As shown in Fig. 9, a soil cloth was used to stop the soil
from flowing inside the cup as much as possible to enhance the
accuracy of the sensors and protect them from any particulate
matter interference. This allows enough time for the sensors to
perform the measurements, and when the fluid exceeds a certain
level, the fluid is flashed out expanding the lifetime of the sensors
(see Fig. 10). The depth of the cup is approximately 50 mm.
IV. IN-FIELD, SYSTEM VALIDATION
After the deployment of the system in the field (Fig. 11), data
were collected every 30 min for several days proving the capability of the system to operate in the soil, while the plants were
watered and fertilized at certain time intervals [once per week
fertilization (standard nitrogen–phosphorus–potassium (20–20–
20) fertilizer used 5 g/l of water (supergarden, general purpose
fertilizer)) and twice per week watering]. The data were analyzed
and presented in Fig. 12. The indicative impedance magnitude
presented is at 7 kHz, where the response is purely resistive,
however, the same trend has been observed at other frequencies
as well. The impedance phase measured up to 1 MHz was very
small, up to certain degrees because the capacitive behavior of
Fig. 12. Analyzed field tests results. [Dots are the normalized data before the
averaging while the lines are after the 48 points (24 h) averaging].
soil with the specific dimensions of the impedance sensor, is
dominant at higher frequencies. The purple points show the
actual data obtained, showing the temperature dependence of
impedance as expected (also shown by the PRT sensor), and
once an average of 48 points (24 h) was applied, a clear trend
was observed. Initially, the impedance magnitude was high and
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SOPHOCLEOUS et al.: STAND-ALONE, IN SITU, SOIL QUALITY SENSING SYSTEM FOR PRECISION AGRICULTURE
increases with time until the watering/fertilizing time where it
drops and then keeps increasing as the water in the soil continues
to evaporate.
In the case of the pH sensor, the pH of the soil is approximately
8.7 but once the fertilizer is added, the pH drops to approximately
8.2 since the added fertilizers were expected to maintain the pH
close to 8. Again, the effect of temperature on potentiometric
sensors was expected, hence, an average of 48 points was also
applied.
Finally, the nitrate and potassium sensors also responded to
the addition of the fertilizer, however, to emphasize the changes
in the concentrations, the results were normalized. Once again,
the effect of temperature on the results can also be seen, but
after averaging 48 points, a clear trend is shown where the
concentrations of both nutrients increase after the addition of
the fertilizer.
V. CONCLUSION
The first, stand-alone, in situ, system of soil quality monitoring is described both from the sensors’ point of view, the electronic system, and its in-field testing directly in the soil. There are
still many open challenges until the system can be reliably used
in real life, such as the relationship between the time the fertilizer
or water is provided to the soil and the point in time that the system will record the changes. This is highly dependent on the soil
type and packing, hence a detailed investigation in this direction
is part of future works. Although the responses from the system
are not yet standardized or compared with standard methods of
soil sampling, this study has demonstrated the feasibility of this
approach in the field. However, the long-term stability and the
lifetime of the system need to be further investigated to allow its
reliable long-term use in the field. Albeit the fact that the current
system’s performance might not be adequate for laboratory tests,
in-field readings do not require extreme accuracy but rather
low cost to allow its implementation in high-density networks.
Nonetheless, this approach has the potential to be expanded into
large high-density sensor networks that could provide another
approach in soil monitoring with capabilities to expand the
sensor network in all four dimensions compared with the current
approaches of remote sensing and soil sampling that can only
look into surface soil quality. Furthermore, this approach can
pave the way toward fully automated, decision-making systems
that can automatically optimize inputs/outputs in agriculture but
also minimize as much as possible the environmental footprint
of agricultural practices.
ACKNOWLEDGMENT
The authors would like to thank Professor Eduardo GarciaBreijo (UPV, Spain) for his support and help with the fabrication
of the sensors. In addition, the authors would also like to thank
Dr. Laura Contat-Rodrigo (UPV, Spain) for their help on the
ion-permeable-membranes.
49
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in sensor systems design: A tutorial,” IEEE Sensors J., vol. 22, no. 11,
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[12] F. K. Shaikh, S. Karim, S. Zeadally, and J. Nebhen, “Recent trends
in internet-of-things-enabled sensor technologies for smart agriculture,” IEEE Internet Things J., vol. 9, no. 23, pp. 23583–23598,
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sensors and plant wearables for smart and precision agriculture,” Adv.
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advances in chemical sensors for soil analysis: A review,” Chemosensors,
vol. 10, no. 1, 2022, Art. no. 35. [Online]. Available: https://www.mdpi.
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[15] M. Sophocleous and J. Georgiou, “Precision agriculture: Challenges in
sensors and electronics for real-time soil and plant monitoring,” in Proc.
IEEE Biomed. Circuits Syst. Conf., 2017, pp. 1–4.
[16] M.-Y. Kim and K. H. Lee, “Electrochemical sensors for sustainable precision agriculture—A review,” Front. Chem., vol. 10, 2022, Art. no. 848320.
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[17] J. K. Atkinson, M. Glanc, M. Prakorbjanya, M. Sophocleous, R. Sion,
and E. Garcia-Breijo, “Thick film screen printed environmental and
chemical sensor array reference electrodes suitable for subterranean
and subaqueous deployments,” Microelectronics Int., vol. 30, pp. 92–98,
2013. [Online]. Available: https://www.sciencedirect.com/science/article/
pii/S0378377421006016
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“Modeling and performance comparison of screen-printed, impedance
spectroscopy probes for harsh environments,” IEEE Sensors J., vol. 20,
no. 5, pp. 2533–2542, Mar. 2020.
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and A. Ingenito, “The use of novel thick-film sensors in the estimation
of soil structural changes through the correlation of soil electrical conductivity and soil water content,” Sensors Actuators A: Phys., vol. 301,
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on performance of fabrication parameter variations of thick-film screen
printed silver/silver chloride potentiometric reference electrodes,” Sensors
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“Towards solid-state, thick-film K and Na ion sensors for soil quality
assessment,” in Proc. IEEE Sensors, 2020, pp. 1–4.
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bio-sensing applications: A review,” IEEE Sensors J., vol. 21, no. 4,
pp. 3977–4006, Feb. 2021.
[26] M. Sophocleous, A. Karkotis, and J. Georgiou, “A versatile, stand-alone,
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Trans. Emerg. Sel. Topics Circuits Syst., vol. 11, no. 3, pp. 449–457,
Sep. 2021.
Marios Sophocleous (Senior Member, IEEE) received the M.Eng. and Ph.D. degrees in thick-film underground sensors from the University of Southampton, Southampton, U.K., in 2011 and 2016, respectively.
Since 2016, he has been a Special Scientist with the
Holistic Electronic Research Laboratory, University
of Cyprus.
Dr. Sophocleous was the winner of the Fulbright
Schuman Fellowship 2021. He was nominated for
the Outstanding Young Engineer Award of the IEEE
Instrumentation and Measurement Society in 2019 while he was a Young
Scientist 2020 finalist in Cyprus. He is a Member of the Editorial Advisory Board
of Sensors and Actuators A: Physical Journal, Microelectronics International
Journal, the Lead Guest Editor of an IEEE SENSORS JOURNAL Special Issue and
an Associate Editor for IEEE SENSORS and IEEE TRANSACTIONS ON AGRIFOOD
ELECTRONICS JOURNALS.
Andreas Karkotis received the bachelor’s degree in
electrical and electronic engineering from the University of Cyprus, Nicosia, Cyprus, in 2018, and the
M.Sc. degree in advanced microelectronics from the
University of Southampton, Southampton, U.K., in
2019.
He is currently a Research Engineer with the
University of Cyprus. His research interests include
embedded programming, RF systems, PCB design,
FPGA firmware development, integrated circuit design, hardware design, and simulation.
Antri Papasavva received the Bachelor’s degree in
electrical engineering from the University of Cyprus,
Nikosia, Cyprus, in 2022.
She was a Specialist Research Scientist with the
University of Cyprus. Her research focuses on the
organic sensors.
Michale Goldberger received the B.S. degrees in
electrical engineering and economics in 2016 from
the University of Pennsylvania, Philadelphia, PA,
USA, and the M.S. degree in environmental engineering under professors Hadas Mamane and Yosi
Shacham in 2021 from Tel Aviv University, Tel Aviv,
Israel, where she is currently working toward the
Ph.D. degree.
In 2021, she joined SolarEdge Technologies as a
Systems Research Engineer. Her research focuses on
affordable water technologies for remote areas.
Loukia Vassiliou received the B.Sc. and M.Sc. degrees in horticulture, plant protection, and environment from the Agricultural University of Athens,
Athens, Greece, in 1997, and the second M.Sc. degree
in horticulture (floriculture), Cranfield University,
Cranfield, U.K., in 2009.
She is currently an Agricultural Research Officer
with the Agricultural Research Institute under the
Ministry of Agriculture, Rural Development, and Environment of Cyprus.
Jose Vicente Ros-Lis received the B.Sc. degree in
inorganic chemistry from the University of Valencia,
Valencia, Spain, in 2000, and the Ph.D. degree in inorganic chemistry from the Polytechnical University
of Valencia, Valencia, in 2005.
He is currently an Assistant Professor with the
Inorganic Chemistry Department of the Universitat de
Valencia and leads the REDOLí group. His research
interests include the development of chemical sensors, study of the enzyme–material interaction, and
sustainability.
Yosi Shacham-Diamand received the B.Sc. (summa
cum laude), M.Sc., and D.Sc. degrees in electrical
engineering from the Technion—Israel Institute of
Technology, Haifa, Israel, in 1978, 1980, and 1983,
respectively.
He has also been a Visiting Professor with CNRIMM, Rome, Italy, with Waseda University, Tokyo,
Japan, and with the Department of Electronics and
Telecommunication, Politecnico di Torino, Turin,
Italy, and a Distinguished International Chair Professor with Feng Chia University, Taichung, Taiwan.
He was the Head of the International Electrical Engineering School, Tel Aviv
University, an Endowed Chair Professor with the Thapar Institute of Engineering
& Technology, Patiala, India, and the Director of the TAU/TIET Food Security
Center of Excellence. Since 2023, he has also been the Head of The Scojen
Institute for Synthetic Biology Center, Reichman University, Israel. His research
interests include micro and nanoelectronics science and technology, specifically,
electroless plating of metals and alloys, interconnect technology for VLSI
circuits and flexible electronics, and electrochemical biosensors for the food,
medical, and agro applications.
Julius Georgiou (Senior Member, IEEE) received
the M.Eng. degree in electrical and electronics engineering and Ph.D. degree in micropower electronics
for neural prosthetics from Imperial College London,
London, U.K., in 1998 and 2003, respectively.
During the last two years of the Ph.D. studies, he
was heavily involved in a technology startup company, Toumaz Technology, as the Head of Micropower Design. In 2004, he joined the Johns Hopkins University, Baltimore, MD, USA, as a Postdoctoral Fellow, before joining the University of Cyprus,
Nicosia, Cyprus, as a Lecturer in 2005. His research interests include low-power
analog and digital ASICs, implantable biomedical devices, bioinspired electronic systems, brain–computer interfaces (BCIs), semiconductor device design,
as well as inertial and optical sensors and related systems.
Dr. Georgiou is a Member of the IEEE Circuits and Systems Society, the
BioCAS Technical Committee, and the IEEE Circuits and Systems Society
Analog Signal Processing Technical Committee.
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