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An improved approach for comparative study of plant cells for long term and continuous monitoring using electrical impedance spectroscopy is demonstrated for tomato and tobacco plant cells (MSK8 and BY2) in suspensions. This approach is based on the locations and magnitudes of defining features in the impedance spectra of the recently reported unified equivalent circuit model. The ultra-wide range (4 Hz to 20 GHz) impedance spectra of the cell lines were measured using custom probes, and were analyzed using the unified equivalent circuit model, highlighting significant negative phase peaks in the ~ 1 kHz to ~ 10 MHz range. These peaks differ between the tomato and tobacco cells, and since they can be easily defined, they can potentially be used as the signal for differentiating between different cell cultures or monitoring them over time. These findings were further analysed, showing that ratios relating the resistances of the media and the resistance of the cells define the sensitivity of the method, thus affecting its selectivity. It was further shown that cell agglomeration is also an important factor in the impedance modeling in addition to the overall cell concentration. These results can be used for optimizing and calibrating electrical impedance spectroscopy-based sensors for long term monitoring of cell lines in suspension for a given specific cell and media types.

Supramolecular self-assembly is a key process in natural systems, allowing for the formation of structures across all length scales with a wide range of functionalities. Notable progress has been m...

Laser powder-bed fusion (LPBF) method is one of the most important additive manufacturing (AM) technologies. AM-LPBF parts frequently need post-printing coatings for electrical and thermal conductivity enhancement, or matching decoration considerations. The current study presents a methodology for surface finishing of AM-LPBF AlSi10Mg artifacts coated with electroless gold. For this purpose, gold was deposited on AM-LPBF AlSi10Mg disk-shaped specimens and coins, resulting in an appearance similar to the original objects. The gold coating was characterized as a function of deposition time and gold film thickness. Mass and dimension measurements, optical profilometry, light microscopy observation, XRD analysis and a FIB-SEM technique were applied to characterize the coated samples. The roughness of the plated specimens was slightly reduced as the thickness of the gold film was increased. AM-LPBF AlSi10Mg disk-shaped specimens were coated successfully for the first time by electroless gold plating technique. The developed surface finish technique can be used for various applications, including 3D-printed replicas of ancient prestige artifacts and coins for museum exhibitions.

We report a new approach to design flexible functional material platforms based on electropolymerized polyaniline (PANI) polymer nanofilms modified with bimetallic nanoclusters (NCs) for efficient electro-oxidation of small organic molecules. Composition defined ligand free Pt0.75Ni0.25 NCs were synthesized in the gas phase using the Cluster Beam Deposition (CBD) technology and characterized using RToF, HAADF-STEM, XAFS and XPS. NCs were then directly deposited on PANI coated templates to construct electrodes. Dopamine (DP) molecules were used as a representative organic analyte and the influence of the NC-PANI hybrid atomistic structure on the electrochemical and electrocatalytic performance was investigated. The as prepared, nearly monodispersed, Pt0.75Ni0.25 NCs of ca. 2 nm diameter featuring a PtOx surface combined with a shallow platelet-like Ni–O(OH) phase formed a densely packed active surface on PANI at ultralow metal coverages. Electrochemical measurements (EIS and CV) show a 2.5 times decrease in charge transfer resistance and a remarkable 6-fold increase at lower potential in the mass activity for Pt0.75Ni0.25 NCs in comparison with their pure Pt counterparts. The enhanced electrochemical performance of the Pt0.75Ni0.25 NC hybrid’s interface is ascribed to the formation of mixed Pt metal and Ni–O(OH) phases at the surface of the alloyed PtNi cores of the bimetallic NCs under electrochemical conditions combined with an efficient charge conduction pathway between NCs.

Electrical impedance spectroscopy has been suggested as a sensing method for plants. Here, a theoretical approach for electrical conduction via the plant stem is presented and validated, linking its living electrical characteristics to its internal structure. An electrical model for the alternating current conduction and the associated impedance in a live plant stem is presented. The model accounts for biological and geometrical attributes. It uses the electrically prevalent coupled transmission line model approach for a simplified description of the complicated vessel structure. It considers the electrode coupling to the plant stem (either Galvanic or Faradic), and accounts for the different interactions of the setup. Then the model is simplified using the lumped element approach. The model is then validated using a four-point probe impedance spectroscopy method, where the probes are galvanically coupled to the stem of Nicotiana tabacum plants. The electrical impedance data was collected continuously and the results exhibit an excellent fitting to the theoretical model, with a fitting error of less than 1.5% for data collected on various days and plants. A parametric evaluation of the fitting corresponds to the proposed physically based model, therefore providing a baseline for future plant sensor design.

Fused Deposition Modeling is one of the most common Additive Manufacturing methods for polymers. For some applications, parts manufactured by this method need post-printing surface coating. The present research aims at examining the surface finishing properties of Fused Deposition Modeling Acrylonitrile Butadiene Styrene parts coated for the first time with laboratory-developed electroless gold. Such coating can be applied for electrical purposes and as a decorative cover for 3D-printed prototypes, as well as on top of printed replicas of archaeological artifacts. Gold was deposited by electroless plating on top printed disk-shaped specimens, making them look like an ancient artifact. The electroless gold film was studied by various methods, including dimensions and mass measurements, qualitative pilling test, multifocal light microscopy, optical profilometer and X-ray diffraction analysis. The gold layer thickness was studied as a function of deposition time. The laboratory-developed electroless gold coating was deposited from a cyanide free bath and was compared to a commercial one deposited from a cyanide bath. The results displayed high-quality gold, and a satisfactory appearance. The roughness of the laboratory gold plated samples was somewhat reduced as the thickness of the gold film was increased, and the surface appearance was improved correspondingly. The developed gold coating can be adapted for various applications, including 3D printed artifacts for museum exhibitions.

Additive manufactured selective laser melting (AM-SLM) parts often need post-printing coatings. The current research presents a method for surface finishing of AM-SLM AlSi10Mg parts coated by electroless silver plating. Such coating can be applied as a decorative film on printed replicas of antique artifacts. For this purpose, silver was deposited for the first time on AlSi10Mg printed disk-shaped specimens and coins, making their appearance close to the original artifact. The silver was plated with and without adhesion-promoting silane self-assembled monolayers. Dimensions and mass measurements, pilling test, light microscopy, optical profilometer, SEM–EDS examination, XRD analysis, and FIB-SEM technique were applied to characterize the coated samples. The results displayed good silver quality with a satisfactory appearance. The roughness of the plated samples was slightly reduced as the thickness of the silver layer was increased. The developed coating can be adapted for different applications, including printed replicas of coins in museum exhibitions.

Low loss electromagnetic energy transport over long distances motivates the development of different types of waveguiding systems. Requirements of high quality optically polished waveguide surfaces needed in high-frequency applications and low-cost manufacturing are practically incompatible in current realizations. Here we demonstrate a new paradigm solution, based on surface functionalization with subsequent electroless plating of conductive micron smooth copper layer on the inner surface of flexible non-conducting poly-carbonate tubes. The structure was shown to support reasonable guiding performances (∼5·10−3 cm−1) at Ku-band. The mechanically flexible design of the system allows shaping the waveguide network almost on demand. In particular, an efficient energy guiding over a closed loop with 8 lambda radius was demonstrated. The new platform of high quality metalized flexible waveguiding systems opens new opportunities in designs of cheap and efficient networks, operating over a broad spectral range, approaching tens of GHz and even higher.

World population growth and desertification are the most severe issue to agricultural food production. Smart agriculture is a promising solution to ensure food security. The use of sensors to monitor crop production can help farmers improve the yield and reduce water consumption. Here we propose a study where the electrical impedance of green plants' stem is analyzed in vivo, along with environmental conditions. In particular, the variations associated with the daily cycle are highlighted. These analyses lead to the possibility of understanding plant status directly from stem impedance.

This paper presents the dielectric behaviour of suspensions of tomato cells (MSK8) and tobacco cells (BY2) in Murashige and Skoog, and Phosphate Buffer solutions. The behaviour of various concentrations of such suspensions is studied over a wide range of frequencies (1 kHz to 20 GHz). A distinct trend is observed in the relation between cell concentration and the capacitance of the first dispersion (i.e. at low frequencies), whilst the capacitance of the second dispersion (at medium frequencies) shows a clear relationship with the medium used. As the concentration of the cells increases, the capacitance observed increases for both cell types in both media. Furthermore, the capacitance observed for the MSK8 cells is higher than that for the BY2 cells in both media; furthermore, the normalized impedance magnitude of the MSK8 cell suspensions at low frequencies is higher than that of the equivalent normalized impedance magnitude for BY2 cells. Finally, the capacitance corresponding to the second dispersion is higher in Phosphate Buffer solution compared to that in Murashige and Skoog solution.

Body channel communication (BCC) is a technique which uses the human body as the medium for carrying various signals, interfacing multiple devices — for example, sensors — with a single gateway. Plant body channel communication (PBCC) is a new technique based on the same fundamentals as BCC, using the plant’s body for signal transmission. As a feasibility study for PBCC, a four-electrode setup — two for the transmitter and two for the receiver — was installed on Nicotiana tabacum plants, and the signal attenuation through the stems was studied in both frequency and time domains. We show that for multiple plants, the attenuation follows a consistent trend with respect to frequency.

Nanostructured electrodes detecting bacteria or viruses through DNA hybridization represent a promising method, which may be useful in on-field applications where PCR-based methods are very expensive, time-consuming, and require trained personnel. Indeed, electrochemical sensors combine disposability, fast response, high sensitivity, and portability. Here, a low-cost and high-surface-area electrode, based on Au-decorated NiO nanowalls, demonstrates a highly sensitive PCR-free detection of a real sample of

With the growth of world population and food demand, it is crucial to optimize water consumption for agriculture cultivation. Here we propose a method to monitor plant status, relating the measured parameters to the watering or drying situation of a single plant. Plant trunk electrical impedance measurements and environmental parameters were analyzed with a statistical approach. Correlation and causality among the data are showed and analyzed. In this way, it was possible to easily obtain the needed information about plant status.

The current research presents a novel methodology for surface finishing of printed AlSi10Mg parts by electroless deposited gold&ndash, silver (electrum) alloys. The parts were printed by additive manufacturing laser powder-bed fusion (AM-LPBF). The electrum was chosen due to its appearance and good electrical and thermal properties and was deposited on disk-shaped specimens at 80 and 90 &deg, C. The coating quality and appearance were studied by different methods for various deposition times and film thicknesses. The results indicate that Au&ndash, Ag coatings of AM-LPBF AlSi10Mg yield satisfactory results. The XRD analysis revealed that the coatings were composed of Au&ndash, Ag crystalline phases and beneath them, a quasi-amorphous or mixed quasi-amorphous and nanocrystalline Ni&ndash, P interlayer. The mechanism of electrum formation was studied based on the XPS analysis results as a function of the temperature and concentration. At 80 &deg, C, the Ag was dominant at the beginning of the deposition process, while at 90 &deg, C the Au was first detected on the interface. This result was explained by the electrochemical properties of alloying metals and the binding energies required to form metal&ndash, Ni and Au&ndash, Ag bonding. The results indicate that the electrum coatings are satisfactory, and the developed surface finishing process could be used for many applications.

A simple, ultra-wide frequency range, equivalent circuit for plant cell suspensions is presented. The model incorporates both the interfacial interactions of the suspension with the electrode, dominant at low frequencies, and the molecule and cell polarization mechanisms dominant at higher frequencies. Such model is useful for plant cell characterization allowing a single set of parameters over >9 orders of magnitude, whilst allows electronic simulations over the whole frequency range using a single model, simplifying the design of electronic systems of integrated plant cell sensors. The model has been experimentally validated in the frequency range of 4 Hz–20 GHz with each component in the circuit representing a physical phenomenon. Various cell concentrations (MSK8 tomato cells in Murashige and Skoog media) have been investigated, showing clear correlations of the cell capacitance increasing within the range of 200–600 pF, whilst cell resistance (R) decreasing within the range of approximately 0.8–3 kΩ within the cell concentration X–Y cells/mL range. This is the first model ever reported that covers such a wide frequency range and includes both interfacial and polarization effects in this simple form.

We studied the stability of the mechanical properties and the fatigue endurance of Gd-doped ceria (CGO), which is a promising electromechanically active material for microelectromechanical systems (MEMS). Specifically, the fracture strength and long-term operation of plate-type circular (2 mm diameter) thermal actuators made of ≈1.15 μm thick Ce0.95Gd0.05O1.975 (CGO5) were investigated. Excitation voltage of 10 V at the frequency range between 1 and 2.1 MHz induces Joule heating effect that can generate an in-plane strain of ≈0.1 %. The operation temperature ranged from 25 °C to 80 °C and the temperature shift, caused by the AC heating, was about 80 K at 10 V. Critical fracture was found to occur at out-of-plane displacements between ∼35 and ∼42 μm, which corresponds to the average bending stress of ∼44 MPa at the center of the plate. During long-term operation, the actuators exhibit gradual decrease in the response, probably due to contact degradation. However, structural damage or mechanical fatigue was not found even after 107 cycles at a stress level of ∼30 % of the critical fracture strength.

Smart agriculture is a fast-growing research field. From one side, the increase of the human population is always demanding more food production. On the other side, the consciousness of the importance of diet quality requires a more controlled and higher quality production, both in terms of nutrition factors and lower use of pesticides. Thus, it is straightforward to apply the progress in electronics and sensors technology for reaching these different objectives. In this paper, we present an overview of the sensors applied for smart agriculture. Two different categories are presented: sensors for evaluating plant health and fruit conditions and sensors used to monitor the environmental condition where the plants are growing.

The performance of micro devices actuated using electroactive polymers is often limited by the high stiffness of metallic electrodes, which prevents the polymeric components extension. In this work we report on an approach allowing to reduce the use of metals to a minimum by incorporating softer conductive polymer electrodes. A multilayered actuator incorporating polyimide (PI) substrate and a thin electroactive polymer (EAP) layer of P(VDF-TrFE-CFE) squeezed between polyaniline (PANI) electrodes was fabricated and characterized. The PANI layer was electrodeposited on the electroactive structures using cyclic voltammetry. Our results show that while the use of conjugate conductive polymer electrodes is feasible, the influence of the thin metallic seed layers required for electro-deposition is significant. The proposed electro-deposition based polymeric process is highlighted by its simplicity and relatively low cost, compared to common Physical Vapor Deposition processes, and can be extended to other polymers.