Initial Electrical Conductivity Research Articles

Enhancing the properties of epoxidized natural rubber-graphene nanocomposites through crosslinking with imidazole-activated dicarboxylic acid-cured system

The epoxidized natural rubber containing 25 mol% epoxide (ENR-25) was cured through crosslinking reactions with dodecanedioic acid (DA), both with and without activation by 1,2-dimethylimidazole (DMI). Analysis of the Fourier Transform Infrared (FTIR) spectroscopy of the DMI-activated DA-cured ENR revealed new absorption peaks at 1440 cm−1 and 1505 cm−1, indicating the presence of C-N stretching vibrations and carboxylate ions compared to samples without DMI activation. Additionally, ENR-graphene (GP) nanocomposites with various GP loadings were investigated, which revealed the formation of inter- and intramolecular hydrogen and covalent bonds within the ENR and GP networks. Furthermore, DMI activation of ENR cured with dicarboxylic acid accelerated the crosslinking reaction, reducing scorch and cure times while enhancing properties such as tensile strength, toughness, and 100 % modulus. Moreover, the incorporation and increased loading of GP in ENR nanocomposites synergistically enhanced strength properties, delta torque, crosslink density, initial relaxation modulus, thermal resistance, and electrical conductivity. This enhancement is attributed to interactions between the polar functional groups on GP surfaces and the functional groups of ENR adducts cured with DMI-activated dicarboxylic acid. Moreover, the ENR-GP nanocomposites exhibited a low percolation threshold concentration at 1.25 phr, enabling the formation of fully conductive GP networks within the ENR matrix. The significance of this study is to simplify the curing and production processes of ENR composites, offering promising self-healing capabilities and potential for reuse and recycling.

Dynamic behavior of electro-osmosis in variable charge soils: Insights on termination and direction reversal

Electro-osmosis offers an effective method for dewatering and remediating low permeability soil. Long-term observations on nonlinear behavior of electro-osmosis and the influencing factors are not commonly reported. Connection between cessation and direction reversal of electro-osmotic flow (EOF), and the evolution of electro-chemical parameters inside of the soil mass thus remains unclear. The dynamic response of EOF in variable charge soil could be significant, whereas the investigations on which are currently lacking. A series of electro-osmotic experiments were performed with two natural variable charge soils. The results indicated that initial electro-osmotic rate was positively proportional to electric current and initial electrical conductivity of the pore fluid, which could be explained by the ion migration model. The dynamic evolution of electro-osmotic rate and electro-chemical parameters corresponding to the solute and pH conditionings at the electrode compartments demonstrated that: 1) coupling effects of non-uniform distribution of voltage gradient and pH determined the magnitude and direction of EOF rate; 2) compared to the final pHIEP value, the bigger, close and smaller values of the novel index “voltage gradient weighed mean of spatial pH″ represented the forward, terminated and reversed EOF respectively; 3) the classical Helmholtz-Smoluchowski model are proved to be more applicable interpreting the coupled nonlinearity of electro-osmosis during the later steady phase. This work would facilitate future research for a comprehensive electro-osmotic model, and provide guidance to condition the initial and boundary conditions in application of electro-osmotic dewatering and electrokinetic remediation.

Influence of physical and water quality parameters on residual chlorine decay in water distribution network

Chlorine is the most common disinfectant in drinking water distribution practice. World Health Organization recommends 0.2–5.0 mg/l of residual chlorine in drinking water. This paper analyzed influence of physical and water quality parameters on chlorine decay in drinking water distribution. Principal component analysis, directed tree and regression were used to investigate influence of these parameters on chlorine from water treatment plant to water consumption points. Results show that initial chlorine, electrical conductivity and distance explain 62 % of chlorine decay with estimated error of 0.045 mg/l. The decision-tree feature importance scores of initial chlorine and electrical conductivity were 0.47 and 0.23 respectively. The combined feature importance scores of physical parameters of distance (0.09), pipe diameter (0.06), flow velocity (0.03), pressure (0.02) and travel time (0.046) were less than that for initial chlorine concentration (0.47) alone. These results show that conventional chlorination at water treatment plants removes largely fast inorganic reactants leaving traces of slow organic reactants as the dominant secondary contaminants in water distribution system. The key policy recommendation is to use water quality parameters more than physical parameters in order to enable water utility managers maintain residual chlorine within safe public health standards.

Largely enhanced performance of Cu2Se film by doping sulfur for flexible thermoelectric generators

Herein, a facile method to prepare flexible S-doped Cu2Se thermoelectric films on porous nylon membranes is developed. First, S-doped Cu2Se powders with nominal compositions of Cu2Se1-xSx (x = 0, 0.02, 0.04, or 0.06) are synthesized by a hydrothermal method. Then, the as-prepared powders are deposited onto nylon substrates by vacuum-assisted filtration and hot-pressing. By adjusting the amount of S doping, the carrier concentration and mobility of the films are tuned, and the thermoelectric properties of the films are effectively optimized. As a result, the Cu2Se0.96S0.04 film displays a highest power factor of ∼662.2 μW m−1 K−2 at 300 K, representing one of the highest values reported for Cu2Se-based flexible films. The film also exhibits excellent flexibility (after 1500 bending cycles around a 4 mm radius rod, 90.8% of the initial electrical conductivity is retained). Additionally, a six-leg flexible thermoelectric generator is assembled with the Cu2Se0.96S0.04 film and outputs a peak power of 1.89 μW at a temperature difference of 23.1 K. This work presents a new method for preparing cost-effective and high-performance Cu2Se flexible thermoelectric films.

Preparation and Properties of Flexible CuI/Polyvinylpyrrolidone Nanocomposite Thermoelectric Film

A facile preparation method for flexible p-type CuI/polyvinylpyrrolidone (PVP) nanocomposite thermoelectric (TE) film is developed. First, CuI powder was synthesized by a one-pot method; second, PVP was coated in situ with the CuI powder; third, the CuI/PVP nanocomposite film was prepared on a nylon membrane by vacuum filtration and then hot-pressing. Transmission electron microscopy (TEM) observation indicates that the film consists of CuI nanograins with an average size of ~15 nm and PVP distributed at the inner wall of nanopores and the surface of the CuI nanograins. The composite film shows a large Seebeck coefficient of ~605 µVK−1 and a power factor of ~8.05 µWm−1K−2 at 300 K. The nanocomposite film also exhibits excellent flexibility (~96% of initial electrical conductivity retention after being bent 1000 times along a 4 mm radius rod). A single-leg TE module outputs a voltage of ~3.6 mV when the temperature difference is 6 K. This work provides a fast, simple, and environmentally friendly method by which to prepare flexible CuI/PVP nanocomposite TE film with a large Seebeck coefficient, which could be used as a wearable sensor.

High thermoelectric performance of flexible Ag/Ag2Se composite film on nylon for low-grade energy harvesting

In this work, Ag/Ag2Se composite films with excellent thermoelectric (TE) properties and flexibility are prepared based on a simple one-pot method. By adjusting the nominal ratios of Ag/Se, an optimal Ag/Ag2Se composite film shows a large power factor of ∼2275 μW m−1 K−2 at 300 K. Such an outstanding TE performance of the composite film is due to the unique microstructure and the synergistic effect between the Ag and Ag2Se. Meanwhile, the composite film also shows outstanding flexibility (∼91.8% of the initial electrical conductivity is maintained, and the S is unchanged after 1500 bending cycles with a bending radius of 4 mm). Furthermore, a 4-leg flexible TE generator assembled with the optimal film produces a voltage of 14.06 mV and 4.96 μW at a temperature difference of 30.4 K. This work provides a new inspiration for the preparation of flexible Ag2Se-based films with excellent TE performance near room temperature.

Highly conductive and stretchable filament for flexible electronics

Conductive and stretchable filaments are crucial for advancing additive manufacturing, particularly in flexible electronics. However, existing conductive filaments suffer from limitations in conductivity and stretchability. To overcome these challenges, this study presents a highly conductive and stretchable filament for material extrusion type 3D printing. The developed filament achieves an initial electrical conductivity of 558 S/cm and maintains low resistance up to 60 % strain with 10 vol% silver loading. This significantly surpasses the performance of commercial filaments and previous literature reports. The addition of polyethylene glycol (PEG) as a plasticizer for the silver filled thermoplastic polyurethane (Ag-TPU) composite enhances extrusion and improves filament surface quality. The printability of the filament in material extrusion 3D printing was evaluated, and the electrical conductivity of the printed objects was assessed. Two demonstrator structures, an electrical interconnection and a capacitive strain sensor, were successfully prototyped, showcasing the potential applications of this filament in stretchable electronics. The developed filament paves the way for creating intricate and stretchable electronic devices using material extrusion printing techniques. These advancements contribute to the field of additive manufacturing and enable the fabrication of flexible electronic components with enhanced conductivity and stretchability.

Electrochemical Performance According to High-Capacity Silicon Active Materials in Lithium Ion Batteries

Carbon has been used as stable anode material for lithium-ion secondary batteries. However, instead of graphite with a low capacity, a new material with a high capacity that can increase the energy density per volume or mass of a lithium ion secondary battery is required. Among the various candidates, silicon has a high capacity of about 4000 mAh/g, making it a major research subject. Graphite is a combination of 6 carbon atoms and 1 lithium ion, but silicon accepts 4.4 lithium ions per atom, resulting in high volume expansion. In this way, excessive volume expansion causes cracks in the electrode and electrochemical disconnection, which eventually leads to a decrease in battery capacity. The large volume change and low electrical conductivity of silicon limits its application to anodes. Potential silicon-based materials include silicon oxide-based (SiOx), carbon-silicon composite (SiC), and pure silicon (pure Si). Silicon-based oxides have the advantages of high capacity and stable battery life, but have the limitations of low initial efficiency and low electrical conductivity. Carbon-composite silicon has high initial efficiency, high ionic conductivity, high capacity, and can be applied in the same slurry system as existing graphite electrodes. Selection of a stable binder and conductive material is important for active use of silicon-based materials. Promising binders include polyvinyl alcohol (PVA), polyacrylic acid (PAA), and polyacrylamide (PAM), and conductive materials include single-walled carbon nano tube (SWCNT), multi-walled carbon nano tube (MWCNT), and carbon-based conductive materials. In this study, we applied poly(vinyl alcohol-co-acrylic acid) random copolymer polymer as a binder and analyzed the characteristics of silicon-based batteries with various conductive materials. Slurry analyzes such as slurry dispersibility, phase stability, and rheology were performed. The initial efficiencies and cycle performances of different types of silicon-based materials were compared. It was confirmed that the type of silicon-based negative electrode material and the type of conductive material affect battery performance.

Highly Stretchable and Highly Conductive Organic Transparent Conductors Based on Aqueous‐Processable Conducting Polymer/Ionic Liquid Composites

AbstractDeformable (semi)conducting polymers have attracted great attention for realizing next‐generation wearable and stretchable electronics. A conductive π‐conjugated polymer, poly(3,4‐ethylenedioxythiophene) : poly(styrenesulfonate) (PEDOT : PSS) is considered as a key component based on the promising electrical characteristics and aqueous processability. However, the general trade‐off relationship between electrical and mechanical performance in PEDOT : PSS is a crucial issue for its practical application as a stretchable conductor. Herein, a simultaneous improvement in electrical conductivity and mechanical stretchability was achieved from PEDOT : PSS by introducing a water‐soluble ionic liquid, 1‐ethyl‐3‐methylimidazolium dicyanoimidazolate (EMIM : DCIM). The electromechanical improvement is closely related with the EMIM : DCIM contents, in which EMIM : DCIM not only causes a morphological transition but also acts as a plasticizing agent. As a result, highly stretchable and highly conductive PEDOT : PSS/EMIM : DCIM composites were obtained with an initial electrical conductivity of ≈550 S cm−1 and maximum strain of 70 % while maintaining the initial electrical properties. Finally, a potential application of PEDOT : PSS/EMIM : DCIM as a stretchable transparent conductor was successfully demonstrated with given high visible transparency and eco‐friendly processability.

Conductance stable and mechanically durable bi-layer EGaIn composite-coated stretchable fiber for 1D bioelectronics

Deformable semi-solid liquid metal particles (LMP) have emerged as a promising substitute for rigid conductive fillers due to their excellent electrical properties and stable conductance under strain. However, achieving a compact and robust coating of LMP on fibers remains a persistent challenge, mainly due to the incompatibility of conventional coating techniques with LMP. Additionally, the limited durability and absence of initial electrical conductivity of LMP restrict their widespread application. In this study, we propose a solution process that robustly and compactly assembles mechanically durable and initially conductive LMP on fibers. Specifically, we present a shearing-based deposition of polymer-attached LMP followed by additional coating with CNT-attached LMP to create bi-layer LMP composite with exceptional durability, electrical conductivity, stretchability, and biocompatibility on various fibers. The versatility and reliability of this manufacturing strategy for 1D electronics are demonstrated through the development of sewn electrical circuits, smart clothes, stretchable biointerfaced fiber, and multifunctional fiber probes.

Large-area photo-patterning of initially conductive EGaIn particle-assembled film for soft electronics

Eutectic-gallium-indium particle (EGaIn*) is considered one of the promising conducting materials for soft electronics due to its enhanced stability compare to bulk EGaIn and constant conductance under strain. However, its practical implementation has thus far been limited due to the challenges of achieving initial electrical conductivity and the incompatibility with well-developed fabrication strategies. Here, we report materials and manufacturing methods that allow large-area multi-layered patterning of ‘polystyrene sulfonate (PSS)-attached EGaIn* (EGaIn*:PSS)’ thin-film with the conventional cleanroom process. PSS enhances the stability of EGaIn*, which allow uniform thin-film coating and photographic lift-off at a wafer-scale down to 10 μm features of varying thicknesses. Using dimethyl sulfoxide as the solvent during lift-off induces cohesion between EGaIn*:PSS, resulting in initial electrical conductivity without an additional activation process. Demonstrations of stretchable display, multilayer pressure sensing systems, and soft artificial finger validate the versatility and reliability of this manufacturing strategy for soft electronics.

Use of Compost Based on Invasive Algae Rugulopteryx okamurae as a Peat Alternative in Nursery Growing Media

The invasion of the macroalgae Rugulopteryx okamurae is causing several environmental and economic problems along Spanish Mediterranean coasts. The use of composts based on R. okamurae as a peat alternative in nursery production could be a valid alternative for the exploitation of this organic material. The present study evaluated three different composts as peat substitutes in potting media to grow tomato seedlings: compost of R. okamurae, compost of green horticultural residues (two-thirds) and R. okamurae (one-third), compost of garden pruning residues (two-thirds) and R. okamurae (one-third). Each compost was used to formulate two different substrates to reduce the use of peat (40% compost, 40% peat, 20% perlite) or entirely substitute it (80% compost, 20% perlite), using a control treatment with 80% peat and 20% perlite. Only the control treatment received mineral fertigation during the trial. The results showed that the high initial electrical conductivity and ion concentration were remarkably reduced thanks to the fast leaching of salt that occurred with customary irrigation. Generally, compost-based treatments allowed us to obtain tomato seedlings with satisfactory morphological parameters. The substrates that contained 40% compost of R. okamurae or a compost of garden pruning residues and R. okamurae led to the best results in term of seedling parameters. It is therefore concluded that composts based on R. okamuare could be used as a seedling growing medium for the valorization of algae.

Effects of water and salt stresses on plant growth and xylem hydraulic properties of tomato.

Xylem is the main tissue for water transport in plants, and the changes of hydraulic properties in which would affect plant water relations and fruit water accumulation. It remains unclear regarding the responses of xylem anatomy and hydraulic properties to water and salt stresses in tomato plants and their relationships with plant growth and fruit water content. We conducted a pot experiment in a greenhouse to investigate the responses of plant growth, fruit water content, and xylem hydraulic properties of a cherry tomato (Hong Baoshi) and a medium-fruited tomato (Beifan 501). There were three treatments, control with a soil water content (θ) of 75%-95% of field capacity (FC) and an initial electrical conductivity (EC) of 0.398 dS·m-1; water stress with θ of 75%-95% of FC (before flowering) and 45%-65% of FC (from flowering until maturity) and an EC of 0.398 dS·m-1; and salt stress with θ of 75%-95% of FC and an EC of 1.680 dS·m-1. Results showed that water and salt stresses decreased the cross-sectional stem area and xylem vessel diameter by 22.0%-40.7% and 10.0%-18.3%, respectively, and reduced the specific hydraulic conductivity of stem and the hydraulic conductivity of peduncle by 8.8%-41.1% and 12.9%-28.4%, respectively. Those changes inhibited plant growth and reduced aboveground fresh weight, fruit size, fresh weight and water content, with a more pronounced negative effect in the medium-fruited tomato. More-over, fruit water content was positively correlated with the specific hydraulic conductivity of stem and peduncle. In conclusion, water and salt stresses would inhibit plant growht, fruit fresh weight, and consequently tomato yield, due to their negative effects on xylem hydraulic properties of the tomato plant. Medium-fruited tomatoes are more susceptible to water and salt stresses than cherry tomatoes.

SWCNTs/Ag2Se film with superior bending resistance and enhanced thermoelectric performance via in situ compositing

High power factor contributes high power generation output while high bending resistance extends the service life in flexible thermoelectric device. Here, we report an in situ grown 10 mol% single-walled carbon nanotubes (SWCNTs) and Ag2+ySe (named as 10 mol% SWCNTs/Ag2+ySe) film, which shows a high power factor of 19.36 μWcm−1 K−2 at 300 K and excellent bending resistance. Such a high power factor is attributed to the enhanced carrier concentration and enlarged effective mass, induced by the additional interstitial Ag in the in situ grown Ag2Se on SWCNTs. Moreover, the 10 mol% SWCNTs/Ag2+ySe film can remain 95 % of the initial electrical conductivity after 1000 bending cycles at the radius of 5 mm, indicating an excellent bending resistance. In addition, this film was assembled into a flexible thermoelectric power generator, which can achieve an output power of 0.72 μW and an open-circuit voltage of 18.17 mV at a temperature difference of 30 K. This study indicates that in situ compositing Ag2Se on SWCNTs can realize the increased thermoelectric performance and bending resistance, which drives the application of Ag2Se-based flexible films.

Understanding the effect of meat electrical conductivity on Pulsed Electric Field (PEF) process parameters and the ability of PEF to enhance the quality and shorten sous vide processing for beef short ribs

The aim of this research was to investigate how the electrical conductivity of short ribs affected Pulsed Electric Field (PEF) process parameters and the ability of PEF to enhance their quality and reduce sous vide (SV) processing time. Short ribs with different range of electrical conductivity (3–6, 6–9, and 9–12 mS/cm) values were treated using input voltage of 10 kV, pulse width of 20 µs, pulse frequency of 50 Hz and pulse number, of either 1600 (low intensity PEF/LPEF) or 5200 (high intensity PEF/HPEF), followed by SV processing at 60 °C for either 24 or 36 h. The quality parameters assessed were cooking loss (%), Texture Profile Analysis (TPA) parameters, and Commission Internationale d’Eclairage (CIE) L*a*b* colour parameters. There was a variation in electrical conductivity of short ribs according to the position of the bone in the short rib, which demonstrated good congruence with the distribution of fat and connective tissue. SV processing with or without PEF pre-treatment did not have a significant effect (p > 0.05) on cooking loss or CIE L*a*b* colour parameters. Short ribs with a medium conductivity (6–9 mS/cm) had a significantly lower hardness after high intensity PEF followed by SV for 24 h, whilst short ribs with an average conductivity of 3–6 and 9–12 mS/cm required longer SV time (up to 36 h) and had a significantly lower hardness compared to non PEF pre-treated samples. TPA values of short ribs treated with the same PEF intensity and SV processing parameters were comparable regardless of the short ribs initial electrical conductivity, which indicates that PEF treatment could ameliorate the biological electrochemical variability inherent to short ribs and PEF could be the potential tool to decrease their SV processing time and enhance their tenderness.

Sulfur Encapsulation and Sulfur Doping Synergistically Enhance Sodium Ion Storage in Microporous Carbon Anodes.

MOF-based materials are a class of efficient precursors for the preparation of heteroatom-doped porous carbon materials that have been widely applied as anode materials for Na-ion batteries. Thereinto, sulfur is often introduced to increase defects and act as an active species to directly react with sodium ions. Although the sulfur introduction and high surface area can synergistically improve capacity and rate capability, the initial Coulombic efficiency (ICE) and electrical conductivity of carbon material are inevitably reduced. Therefore, balancing sodium storage capacity and ICE is still the bottleneck faced by adsorbent carbon materials. Here, sulfur-encapsulated microporous carbon material with nitrogen, sulfur dual-doping (NSPC) is synthesized by postprocessing, achieving the reduced specific surface area by encapsulating sulfur in micropores, and the increased active sites by edge sulfur doping. The synergy between encapsulation and sulfur doping effectively balances specific capacity, rate capability, and ICE. The NSPC material exhibits capacities of 591.5 and 244.2 mAh g-1 at 0.5 and at 10 A g-1, respectively, and the ICE is as high as 72.3%. Moreover, the effect of nitrogen and sulfur on the improvement of electron/ion diffusion kinetics is resonantly demonstrated by density functional theory calculations. This synergistic preparation method may reveal a feasible thought for fabricating excellent-performance adsorption-type carbon materials for Na-ion batteries.

Interactive Aqueous Ink from Core‐Shell Liquid Metal and PEDOT:PSS

AbstractLiquid metals (LMs) and conjugated polymers are both critically important materials in modern technologies including soft robotics, printable circuits, and stretchable electronics. Although broadly applied, the joint use of LMs and conjugated polymers are rarely explored due to the notoriously interfacial challenges of the high surface tension of LMs and the unfavorable rigid backbones of conjugated polymer chains. This work successfully introduced conjugated polymers (poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate, (PEDOT:PSS)) into the system of liquid metals to provide a highly stable, aqueous, and electrically conductive ink (LM‐PEDOT:PSS inks, LMPInks) for flexible electronics. The PSS segments act as a strong ionic bridge to effectively stabilize core‐shell structure of the PEDOT and LMs in the homogenous ink. Different from previous insulated LM‐inks, LMPInk is aqueous and more importantly, electrically conductive without posttreatments due to the intrinsically conductive PEDOT:PSS. Interestingly, with low content of LM particles (<2 wt%), the printed circuits inherit the valuable transparency of PEDOT:PSS (transmission >92% in visible region), which has never been observed in LM‐based organic systems. Furthermore, such LMPInks show distinguished electrical robustness, which can automatically recover their initial electrical conductivity even after severe physical damage. With the above phenomenal advantages, various flexible circuits on different substrates are successfully provided.

Effect of multi-walled carbon nanotubes on DC electrical conductivity and acetone vapour sensing properties of polypyrrole

• First time utilization of PPy/MWCNTs nanocomposite for acetone vapour sensing. • Effect of MWCNTs on thermal stability, electrical conductivity and acetone sensing performance of PPy. • Conductivity of PPy increased from 0.16 Scm −1 to 2.27 Scm −1 by incorporating MWCNTs. • Sensing performance in terms of sensing response, reversibility and long term stability. • PTh/MWCNTs sensor showed 7.44 times greater response than PPy sensor at 0.01 vol% acetone concentration. Polypyrrole (PPy) and polypyrrole/multi-walled carbon nanotubes nanocomposite (PPy/MWCNTs) were synthesized and characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmittance electron microscopy (TEM) and thermogravimetric analysis (TGA). PPy and PPy/MWCNTs were converted into pellets which were used in conductivity and acetone sensing experiments. The initial electrical conductivity of PPy increased from 0.16 Scm −1 to 2.27 Scm −1 by loading of MWCNTs into PPy matrix. At the same time, PPy/MWCNTs showed excellent conductivity retention properties as compared to PPy under both the isothermal and cyclic ageing conditions. A comparative acetone vapour sensing studies were carried out on PPy and PPy/MWCNTs sensors at different acetone concentration, i.e., 0.5, 0.4, 0.3, 0.2, 0.1, 0.05, 0.04, 0.03, 0.02 and 0.01 vol%. The PPy/MWCNTs sensor offered much-improved acetone vapour sensing performance as compared to PPy in terms of sensing response, reversibility and long term stability. PPy/MWCNTs sensor exhibited 2.44, 2.82, 3.06, 3.28, 3.88, 5.0, 5.42, 6.02, 6.08 and 7.44 times greater% sensing response than PPy sensor at 0.5, 0.4, 0.3, 0.2, 0.1, 0.05, 0.04, 0.03, 0.02 and 0.01 vol% acetone concentration, respectively.

Influence of temperature-dependent tissue parameters on monopolar coagulation model

Abstract The use of high-frequency (HF) generators for HF surgical treatment of biological tissue has become an indispensable part of today's surgical applications of all kinds. Generally, HF alternating electric currents between 300 kHz and 1 MHz are used to induce hemostasis by heating at the cellular level. This effect can be attributed to Joule heating, in which a current dissipated conductor converts the electrical energy into thermal energy. However, sound evidence on the reliability and effectiveness of application-specific HF generator modes is not sufficiently available. Usually, the evidence takes place empirically by means of preclinical or clinical studies. Nevertheless, a corresponding empirical data collection is time- and cost-intensive. Therefore, physiological and statistical modeling provides the opportunity to relate tissue response to the applied electrical energy to obtain a prediction of the tissue reaction. In this contribution, we establish a monopolar coagulation model of an already well-known model approach based on Pennes bioheat equation. Additionally, the vaporization of tissue water at the water boiling point is considered. Furthermore, a variation of temperature-dependent tissue parameters was performed to analyze their impact on the model output. The simulation results demonstrate that the initial electrical conductivity has the greatest influence on the temperature distribution as well as on the time until the tissue temperature reached the boiling point of water. In contrast, the tissue water content has the least impact on the model output. Depending on the desired coagulation effect, HF power control as a function of electrical conductivity or its reciprocal, tissue resistance, must be added next in an improved model.

Optimization of electrocoagulation–flotation treatment with an aluminum anode to enhance Microcystis aeruginosa cell removal efficiency

Cyanobacteria adversely affect drinking water treatment and the quality of the drinking water supply. Microcystis spp. are the most abundant cyanobacteria in many surface water bodies throughout the world. Electrocoagulation–flotation (ECF) treatment has attracted considerable attention as a means of cyanobacteria removal. In this study, ECF treatment was optimized by adjusting the initial pH, electrode distance, stirring speed, and electrical conductivity (k) to maximize Microcystis aeruginosa cell removal efficiency while meeting drinking water quality standards. The treatment was performed for 200 mL M. aeruginosa suspensions (~2 × 106 cells/mL) using an aluminum anode and a graphite cathode at a constant direct current of 100 mA. An initial pH of 6, a stirring speed of 200 rpm, an electrode distance of 1 cm, and k of 500 μS/cm were selected as optimum conditions for the ECF treatment. Under these conditions, M. aeruginosa at a cell density of ~2 × 106 cells/mL was completely removed at a current density of 4.0 mA/cm2 with an average energy consumption of 1.20 ± 0.03 Wh/L. The zeta potential varied from −18.49 ± 3 mV to 1.15 ± 0.38 mV, which confirmed the complete removal of cells. Most importantly, the pH, aluminum concentration, and total dissolved solids of the treated water met the drinking water quality standards of the World Health Organization. The optimized ECF treatment was thus shown to be promising for the removal of M. aeruginosa cells.