A biodegradable chipless sensor for wireless subsoil health monitoring

System configuration

The chipless sensor tags had been designed to endure and function by means of the agricultural cycle that includes seed sowing, crop development, fertilizing, and harvesting. On the onset of the crop season, furrows of appropriate depths are created to distribute the sensor tags alongside the seeds with the assistance of a seed planter such that every seed has a sensor tag in its neighborhood to observe the soil well being parameters surrounding the seed (Fig. 1a). As soon as a batch of sensor tags is buried, a drone carrying a reader module interrogates the sensors tags by steadily scanning the sphere to gather info on soil properties (Fig. 1b). Whereas scanning the sphere, an interrogation sign is distributed by the reader module on the drone concentrating on the sensor tags and the mirrored sign from the sensor tag is collected. The resonant peak on the mirrored sign spectrum depends on the soil circumstances and will be correlated to particular soil parameters, equivalent to VWC. The collected info in addition to the placement of the sensor tag will be transmitted to the receiving station utilizing long-range transmission gateways. Since every measurement takes lower than a minute, the drone can cowl a big space of land in a number of hours. To scale back the environmental affect of subsoil sensors, the sensor tags are fabricated from biodegradable supplies that enable a number of months to years of operation with out efficiency depreciation adopted by a gradual managed degradation. The speed of degradation depends upon numerous elements, such because the moisture content material and the microbial exercise within the soil, which fluctuate primarily based on climate patterns and seasons (Fig. 1c). DIRTS, being a biodegradable chipless sensor tag, is designed and manufactured to fulfill these two necessities—carry out reliably by means of the crop season and disintegrate into environmentally pleasant merchandise after its lifespan.

The Schematic in Fig. 1d illustrates the working precept of the system. A chipless sensor tag consists of a resonant construction able to backscattering the incident sign whereas embedding an electromagnetic signature within the type of resonance within the mirrored sign. When the reader antenna sends an interrogation sign to the sensor tag, the sensor tag backscatters alerts with most amplitude at its resonant frequency. The resonant frequency of a chipless sensor tag relies upon broadly on two parameters—the geometry of the metallic sample that types the resonator and the efficient dielectric fixed of the medium within the neighborhood of the resonator. For a sensor tag fabricated from microstrip strains, the resonant frequency is given by the equation³³,

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$$f_{r} = frac{c}{{2L_{r} sqrt {varepsilon_{eff} } }}$$

(1)

The place ({f}_{r}) stands for the resonant frequency; (c), the pace of sunshine; ({L}_{r}), the size of the resonator; and ({varepsilon }_{eff}) the efficient dielectric fixed of the media surrounding the sensor tag. For our software, the sensor tag is buried within the soil the dielectric fixed of which modifications primarily based on the VWC of the soil. Since ({varepsilon }_{eff}) when the soil is dry is decrease than ({varepsilon }_{eff}) when the soil is moist, ({f}_{r}) of the sensor tag is larger in dry soil than in moist soil.

To interrogate the sensor tag from a drone, a custom-designed readout unit that consists of a low-payload, light-weight, transportable reader antenna was developed and built-in into the drone. The transportable reader antenna on the drone operates in a dual-polarization mode together with a depolarizing sensor tag to cut back the noise margin of the ({S}_{21}) spectrum and enhance the readability of the backscattered sign (Supplementary Textual content ST1). To design a miniaturized system, a meander line construction was chosen as a depolarizing sensor tag as it will possibly scale back the scale of the system by means of a folding method. The cross-sectional schematic of a meander line construction is proven in Fig. 1e. The capacitance distribution related to the meander line construction in Fig. 1e demonstrates how the construction can be utilized in a sensing software. The capacitance throughout the adjoining meander strains types a set distributed capacitance by means of the passivation layer and is denoted as ({C}_{p}). Moreover, the electrical subject strains traverse by means of the medium surrounding the sensor tag and kind a distributed variable capacitance denoted as ({C}_{sense}), the worth of which modifications primarily based on the dielectric properties of the medium. {The electrical} equal of the sensor tag is proven in Fig. 1f. The inductance (({L}_{meander})) of the meander line construction depends upon the size and width of the traces. The inductance, ({L}_{meander}), and the general capacitance, ({C}_{p}+{C}_{sense}), kind a tank circuit that resonates at ({f}_{r}). Since ({C}_{sense}) is the one variable within the circuit, a correlation will be obtained between ({C}_{sense}) and ({f}_{r}), and therefore between ({varepsilon }_{eff}) and ({f}_{r}). The radiation resistance (({R}_{rad})) of the construction depends upon the geometry of the construction in addition to the wavelength of operation. The impact of radiation resistance will be illustrated by simulating a meander line construction in CST microwave studio. Determine 1g reveals the far-field radiation sample of a meander construction with 10 vertical segments. Meander line constructions present a donut-shaped radiation sample with most radiation alongside the road of sight of the middle of the construction and minimal radiation within the lateral course. Determine 1h reveals the scattering sample when (phi) =0°. The scattering sample signifies that the primary lobe course is at (theta) = 0°, which is alongside the road of sight of the middle of the construction. The radiation sample obtained from the simulation outcomes reveals the potential for studying the sensor tags utilizing a drone scanning over the sphere at an affordable elevation with very excessive directionality within the angular vary of (theta) = 0° to 45° Though the radiation depth of the meander line construction is orientation-dependent, the excessive directionality of the construction between 0° and 45° helps in decreasing cross discuss and interference whereas measuring a number of sensor tags utilizing the drone.

DIRTS design

To establish the optimum geometry and size of the sensor tag required to attain an efficient efficiency throughout the frequency vary of curiosity, meander line antennas of varied lengths had been investigated. Meander strains are shaped by folding a microstrip line³⁴ into a particular variety of vertical segments (N) of size, (l), spaced aside by a niche, (g), and shorted on alternating ends (Fig. 2a). A spread of values of N was analyzed with a view to make the sensor tag successfully small and procure a frequency of operation that gives the utmost depth of penetration of RF alerts. The dimensions of the sensor tag was restricted to 2 cm × 2 cm, a typical dimension of sensors that may be distributed simply and routinely within the subject utilizing a seed planter. From a sensible manufacturing perspective, the width of the construction ((w)) and the hole between two vertical segments ((g)) had been mounted at 1 mm. Lastly, the higher restrict of the frequency of operation was determined primarily based on the depth of penetration and was recognized as 1.5 GHz³⁵.

To satisfy these restrictions, numerous values of (N) starting from 2 to 12 had been simulated (Supplementary Textual content ST2). The simulation leads to Fig. 2b present that the minimal worth of (N) required to acquire ({f}_{r}) ≤1.5 GHz is 6. Whereas growing (N) from 6 supplies a decrease ({f}_{r}) and because of this, a better penetration depth, growing (N) past 12 doesn’t yield any vital variation in ({f}_{r}) . After figuring out the vary of (N) as 6–12, sensor tags with numerous values of N between 6 and 12 had been investigated to establish the design that gives the utmost sensitivity to modifications within the VWC of the soil surrounding the sensor tag. For simulating the VWC of the soil that varies with the dielectric fixed of the soil, the Topp equation ³⁶ was used, because it supplies a correlation between VWC and ({varepsilon }_{eff}) for soil present in agricultural fields (Fig. 2c, Supplementary Textual content ST3). Topp equation will be written as,

$$VWC=4.3times {10}^{-6}{varepsilon }_{eff}^{3}-5.5times {10}^{-4}{varepsilon }_{eff}^{2}+2.92times {10}^{-2}{varepsilon }_{eff}-5.3times {10}^{-2}$$

(2)

Simulations had been carried out to review the impact of VWC on ({f}_{r}) for (N) from 6 to 12 with the assistance of the Topp equation. As proven in Fig. 2d, the sensor tag with N = 6 demonstrated a median change of 16.29% when VWC was modified from 2 to 18%. For a similar change in VWC, N = 12 demonstrated an elevated frequency shift of 21% (Fig. 2e). As proven in Fig. 2f, amongst numerous values of N starting from 6 to 12, N = 10 supplies the optimum frequency vary because it operates at a middle frequency of ~ 915 MHz, which is the middle frequency of the Industrial, Scientific, Medical (ISM) band broadly used for business functions. As a meandered line construction with 10 vertical segments supplies a 25-fold space discount compared with a microstrip line of size 10 cm³³ that satisfies the identical frequency vary, it constitutes a really perfect miniaturized sensor for ISM band functions.

After optimizing the construction of the sensor tag, simulations had been carried out to estimate the radius of the sensitivity zone of the sensor tag (Supplementary Textual content ST4 and Fig. S1). Simulations revealed that DIRTS is delicate to modifications in VWC inside 1 cm of its proximity. A localized sensitivity zone of 1 cm permits a wide-area distribution of sensors with out interference or coupling between them, which is essential for PA because the really helpful sampling distance for large-scale distribution of sensors is 30 m³⁷. As DIRTS can present a high-resolution mapping of soil moisture throughout the sphere with the assistance of its localized sensitivity zone, the spatial variability of VWC within the soil will be precisely captured.

Sensor fabrication

The construction of the sensor includes a conductive steel hint encapsulated between two layers of biodegradable polymeric materials. To attain scalable manufacturing of the sensors, 3D printing^38,39 and laser processing^40,41 have been broadly employed in earlier research. As proven in Fig. 3, on this course of, the conductive traces had been laser lower and had been encapsulated with 3D printed biodegradable polymers. Because the mostly used materials mixtures for chipless sensors, equivalent to copper on FR4⁴² and aluminum on PET/paper⁴³, should not biodegradable, zinc on polylactic acid (PLA) is used because the biodegradable various. Zinc has a conductivity of the order of ~ 10⁷ S/m and has a better Q-factor than different biodegradable metals, equivalent to Iron, at excessive frequencies⁴⁴. Furthermore, the manufacturing means of zinc is simpler as a result of availability of metalized tape that may be patterned with laser processes⁴⁵. PLA shaped the substrate and superstate and was manufactured with the assistance of 3D printing strategies (see Strategies for particulars). PLA is a commercially out there thermoplastic, broadly utilized in natural digital units⁴⁶, wi-fi drug supply programs⁴⁷, and printed circuit boards⁴⁸, because of its low melting temperature, low value, biodegradability, and moisture resistance. Consequently, PLA can kind a moisture-resilient coating across the biodegradable zinc traces, thereby stopping the degradation of the conductive properties of zinc. PLA’s distinctive traits enable them to be an appropriate structural materials for DIRTS that’s required to keep up secure operation for a sure length inside the sphere however steadily degrade over a protracted time period.

Moveable DIRTS reader

To combine the reader onto a drone and carry out wi-fi measurements of the fabricated system, the readout system was miniaturized right into a mountable low-payload unit. The custom-designed light-weight unit consisted of a conveyable Vector Community Analyzer (VNA) linked to a conveyable dual-polarized antenna by means of an influence amplifier (Fig. 4a). The output energy from the transmission port of the VNA was amplified by the ability amplifier and was radiated from the vertically polarized ridge of the transportable antenna. The horizontally polarized ridge of the antenna was linked to the receiver port of the VNA to gather and analyze the backscattered alerts from the sensor tag. The VNA communicated with a custom-made software program system automated with a python interface to facilitate the on-demand availability of VWC info to the sphere station.

The totally assembled model of the custom-designed miniaturized reader unit that consists of a conveyable VNA, energy amplifier, and a light-weight antenna is demonstrated in Fig. 4b. The full energy delivered to the antenna’s vertically polarized ridge was 12 dBm. The antenna linked to the output of the ability amplifier was a pair of cross-polarized log-periodic antennas that might present a achieve of 9 dBi within the 698–960 MHz band lined by DIRTS as proven within the simulations and was, due to this fact, best for our measurements.

Experimental research

To check the efficiency of the sensor tags in a variety of related subject circumstances, soil samples with totally different volumetric water contents had been ready, as proven in Fig. 5a. For the experiments, the sensor tag was positioned at a depth of 5 cm within the soil pattern (Fig. 5b) because the optimum seeding depth for small grains is 4–5 cm. The soil pattern with the sensor tag buried beneath was positioned within the line of sight of the reader to acquire most reflections (Fig. 5c). The sensor efficiency was examined in lab circumstances utilizing a conveyable antenna and was in contrast with the readings from a stationary horn antenna to evaluate the effectiveness of the transportable readout system. The sensor efficiency was obtained from the resonance spectrum illustrated within the type of an ({S}_{21}) vs. frequency plot, the place ({S}_{21}) is the ratio of the backscattered energy acquired by the reader to the ability transmitted by the reader. The ({S}_{21}) measurements had been calibrated with a view to get rid of the environmental noise and ({S}_{21(cal)}) was reported within the outcomes (See Strategies for calibration).

To estimate the utmost learn distance (RD) of DIRTS, a dry soil pattern of VWC = 4% and a moist soil pattern of VWC = 20% had been examined by various the elevation of the transportable reader from 10 to 60 cm (Fig. 5d). In each soil circumstances, ({f}_{r}) remained unchanged as ({f}_{r}) was not a operate of RD, as proven in Eq. (1). Nonetheless, in each instances, the amplitude of the resonant peak diminished by ~ 9 dB as RD was diversified from 10 to 60 cm. Contemplating the potential losses from the misalignment with respect to the reader and obstacles within the path, a protected noise margin for the learn distance was outlined at − 25 dB. In each instances, the amplitude of the resonant peak surpassed the noise margin when RD > 40 cm. Because the backscattered sign considerably weakened under the noise margin, 40 cm was outlined as the utmost learn vary of the sensor tag when buried within the soil at a depth of 5 cm. Because the essential measurement interval for many cereal grain crops is the preliminary few weeks that encompass seed germination and seedling development, the interference attributable to small seedlings will likely be negligible at a learn distance of 40 cm. Along with the learn distance, the sensitivity of the sensor tag to angular orientation was examined by various (theta) when positioned at RD = 40 cm (Supplementary Textual content ST5). The outcomes indicated that the optimum angular orientation required to acquire an amplitude discount of < 3 dB is 0° to 45° (Fig. S2) corroborating the simulation outcomes obtained from the radiation sample in Fig. 1h.

After figuring out the optimum learn distance as 40 cm and the very best angular orientation as 0°–45° the response of the sensor tag to various moisture circumstances was studied utilizing the custom-designed transportable reader setup in Fig. 5c. The bottom fact VWC measurements had been obtained from a Teros 12 reader and had been correlated to the ({f}_{r}) obtained from the transportable reader measurements to develop a calibrated curve. As proven in Fig. 5e, when the VWC of the soil was elevated from 3.67% to 17.7%, ({f}_{r}) was diminished from 1.015 GHz to 0.794 GHz, indicating an general shift of 21.77%. A discernible frequency spectrum was obtained as much as 23.5% of VWC. The resonant peaks obtained from the soil experiments had been extracted and plotted in Fig. 5f to investigate the outcomes from the simulations, anechoic chamber take a look at, and transportable antenna take a look at. As proven in Fig. 5f, the resonance peaks obtained for numerous values of VWC from the anechoic chamber exhibit an in depth match with the readings from the simulations. Determine 5f additionally reveals the outcomes from the transportable reader, which illustrate the identical development within the frequency roll-off traits because the simulations and supply an affordable match with the simulations.

To research the sensitivity of DIRTS within the soil, the readings obtained from the simulations, horn antenna, and transportable antenna had been in contrast utilizing Fig. 5f. In all of the instances, DIRTS demonstrated a excessive sensitivity of above 40% to VWC values under 6%. When the VWC was above 6%, a low sensitivity area was attained the place a sensitivity of 9.21 MHz/%, 8.7 MHz/%, and 9.07 MHz/% was noticed from the simulations, stationary horn antenna readings, and transportable antenna readings, respectively. This examine confirmed that the sensor tag offered comparable performances within the presence of a conveyable reader unit in addition to a stationary horn antenna. Moreover, the simulation outcomes had been in a position to estimate the sensitivity of the sensor tags within the soil with affordable accuracy. Though the horn antenna might present readings as much as 30% of VWC because of its superior cross isolation, they had been restricted to laboratory circumstances because of their bulkiness and unwieldiness. The transportable antenna, alternatively, might cowl the everyday VWC readings noticed within the agricultural fields whereas offering simpler integration to a low-payload drone and was, due to this fact, your best option for drone-assisted measurements in subject circumstances.

Biodegradation research

To evaluate the general lifetime of the sensor tags, an accelerated take a look at state of affairs was created within the lab with protease enzymes that had been usually present in agricultural fields. The experimental samples had been uncovered to excessive ranges of protease enzymes to speed up the method of degradation, whereas the management samples had been uncovered to the soil for managed degradation. The enzyme causes the hydrolytic degradation of the PLA encapsulation by means of a bulk erosion mechanism which is analogous to the method of microbial degradation of PLA in soil. The degradation conduct of PLA was examined with electrochemical impedance spectroscopy (EIS) (See Techniques for particulars) and the speed of degradation was correlated to the lack of sensitivity of resonant frequency to VWC utilizing wi-fi measurements. The meander line construction of the sensor tag was linked to the working probe by means of a easy modification (Fig. 6a). Because the porosity of the samples measured by EIS is a mirrored image of the general degradation of PLA, a easy Randles mannequin was used to seize the pore resistance, ({R}_{p}). By measuring ({R}_{p}) utilizing this real-time evaluation methodology, the charges of degradation of the PLA had been obtained from the soil degradation atmosphere (Fig. 6b(i)) and accelerated degradation atmosphere (Fig. 6b(ii)) and had been subsequently utilized within the calculation of an acceleration issue.

EIS measurements had been analyzed with the assistance of Nyquist plots which offered a vectorial illustration of the measured impedance. The Nyquist plots obtained from the soil (Fig. 6c) illustrate a straight line with a slant at low frequencies, which will increase from day 1 by means of day 85 suggesting a comparatively small change within the porosity of PLA in a gradual degrading atmosphere. In distinction, the Nyquist plot obtained from the accelerated degradation atmosphere in the identical time interval (Fig. 6d) illustrates a straight line initially, indicating a really perfect insulating coating across the sensor tag. Subsequently, the plot transitioned right into a semi-circle indicative of the formation of pores and gradual uptake of water, exemplifying the varied levels of hydrolytic degradation usually noticed in polymers. Concurrently, to analyze the impact of degradation on the RF traits of the sensor tag, the sensor tags had been taken out of the enzyme resolution when a major variation was noticed within the Nyquist plots, and wi-fi sensitivity assessments had been carried out for VWCs starting from 4 to twenty%. To establish the prevalence of a major occasion within the degradation conduct, the variation in ({R}_{p}) was tracked over time. Within the preliminary days of the take a look at, PLA acted as a protecting barrier to the enzyme resolution, resulting in a excessive ({R}_{p}) of the order of 10 s of GΩ in each environments (Fig. 6e). Nonetheless, within the accelerated take a look at, a gradual degradation occurred within the polymer over time, resulting in extra pores and water uptake into the polymer matrix, which was evident after 55 days of immersion. Though a linear discount in ({R}_{p}) was noticed from day 55 to day 76 within the soil take a look at, a pointy lower of two orders of magnitude in ({R}_{p}) was noticed within the accelerated take a look at, suggesting a considerable enhance within the porosity of PLA. As a corollary, this decline in ({R}_{p}) was mirrored within the wi-fi sensitivity measurements carried out in tandem, the place a substantial lower in ({f}_{r}) was noticed between day 55 and day 76, resulting in a 4% loss in sensitivity at 20% VWC (Fig. 6f). The lack of sensitivity will be attributed to the unfold of pore formation within the PLA coating inflicting an increase within the seepage of water from the soil into the pores at excessive VWC. Total, the development in sensitivity deviation aligned with the gradual degradation within the preliminary part and a subsequent enhance in porosity and the uptake of water into the polymer noticed on this examine. Related findings by Hakkarainen et al.⁴⁹ and Maharana T. et al.⁵⁰ , the place the hydrolytic degradation of PLA was noticed to happen in levels with a gradual degradation within the preliminary stage adopted by fast degradation within the ultimate stage, corroborate the outcomes demonstrated in our examine.

To acquire the dependable practical interval of DIRTS, an acceleration issue was obtained from the linear area of degradation between day 20 and day 55 because the sensor tags demonstrated a 4% deviation within the RF sensitivity traits past this vary. An acceleration issue of seven.15 was obtained by calculating the ratio of degradation of DIRTS within the accelerated take a look at to that within the soil take a look at within the linear area, indicating that the dependable practical interval of the sensor tag within the soil is ~ 1 yr with a sensitivity deviation a lot lower than 4%. To estimate the time for full degradation of PLA, earlier research had been analyzed. Karamanlioglu M. et al.⁵¹ has proven that the biodegradation price of PLA was roughly 0.02 g/yr primarily based on the burden loss methodology. On the degradation price reported by Hakkarainen et al.⁴⁹ and Karamanlioglu M. et al.⁵¹, DIRTS was estimated to bear full biodegradation in ~ 80 years. Nonetheless, in distinction, different generally used polymers, equivalent to PET and acrylic⁵², have proven a 30-fold decrease degradation price⁵³ making PLA the appropriate selection for a biodegradable sensor for soil functions.

Lastly, to examine the morphological results of biodegradation, cross-sectional scanning electron microscopy (SEM) pictures of DIRTS had been taken after 90 days of publicity in a sealed hermetic container (Fig. 7a,d), agricultural subject (Fig. 7b,e), and enzymatic resolution (Fig. 7c,f). Very minimal porosity was noticed for samples that weren’t uncovered to enzymatic degradation, whereas the samples positioned within the subject demonstrated comparatively larger ranges of porosity. The samples positioned within the enzymatic resolution, compared, demonstrated most porosity because of their long-term publicity to an accelerated biodegradation atmosphere (Supplementary Textual content ST6 and Fig. S3). The distinction in ({R}_{p}) between the samples positioned in soil and people within the enzymatic resolution was verified with the assistance of SEM pictures.

Discipline assessments with a stationary mount and transportable DIRTS reader

Deployments of the transportable reader system and the stationary mount for the antenna are proven in Fig. 8a (Supplementary Textual content ST7). The transportable antenna was configured to measure the sensor at two learn distances – 10 cm and 40 cm – as proven in Fig. 8b. As proven in Fig. 8c, when RD was elevated from 10 to 40 cm, ({S}_{21(max)}) decreased by 8.33 dB on day 1 and 9 dB on day 2 because of path loss, whereas ({f}_{r}) demonstrated a negligible deviation with RD, confirming the soundness of ({f}_{r}) to various elevations of the reader in each VWCs. The values of ({f}_{r}) extracted from the RF traits obtained on two separate days had been transformed to the corresponding VWCs utilizing the calibration curve developed from the lab take a look at as proven in Fig. 8f. After conversion, DIRTS offered a VWC of 5.2% (({f}_{r}) = 0.963 GHz) and eight.12% (({f}_{r})= 0.887 GHz), on day 1 and day 2, respectively. As compared, the bottom fact reader logged 6% on day 1 and 9% on day 2, offering a really low error margin of < 1%, therefore, validating the accuracy of the calibration curve for various subject circumstances.

After validating the working of the sensors within the subject, the effectivity of the drone-mounted transportable reader was examined (Supplementary Textual content ST8). The transportable antenna was loaded onto the underside of the drone by fastening it between the touchdown gear legs of the drone. The drone demonstrated a extremely secure alignment at a peak of 40 cm above the bottom the place the sensor was buried at a depth of 5 cm (Fig. 8d). The post-processed knowledge from the drone measurements is proven in Fig. 8e. Within the drone-assisted measurements, DIRTS recorded a VWC of 14.95% (({f}_{r}) = 0.819 GHz) and seven.3% (({f}_{r})= 0.984 GHz), on day 1 and day 2, respectively (Fig. 8f). Concurrent floor fact measurements confirmed a VWC of 14.5% on day 1 and 6% on day 2 demonstrating an excellent settlement with values obtained from the drone-assisted measurements. Regardless of using a flying drone, a tolerable error margin of < 1.5% was obtained within the excessive sensitivity area confirming the applicability of DIRTS in real-time measurements.

Lastly, as a sensible consideration for subject measurements, sure environmental parameters that may fluctuate in subject circumstances, equivalent to temperature, wind, and stress, had been thought of. Though soil temperature normally fluctuates between 10 and 40 °C, the dielectric fixed of PLA reveals negligible sensitivity to temperature within the vary of 10–75 °C at GHz frequencies⁵⁴. Because the sensor is buried at a depth of 5 cm, the affect of wind is insignificant. For day-to-day subject functions, a sprayer drone can be utilized for contactless VWC measurements in addition to the distribution of pesticides and water, thereby eliminating the soil stress attributable to large subject autos. Due to this fact, by combining chipless wi-fi sensors with drone-assisted telemetry, DIRTS can function reliably in subject circumstances throughout its practical interval with a view to measure soil parameters whereas being resilient to different environmental parameters. As a part of future work, DIRTS and multispectral imaging strategies can be utilized in a complementary configuration, as DIRTS can present subsoil measurements whereas multispectral imaging can carry out the floor scanning of the sphere paving new paths in drone-assisted precision agriculture.

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