Traditional Electrochemical Methods Research Articles

Experimental treatment of pickled vegetable wastewater by electrofenton method based on modified PbO2 electrode

The pickle industry is acknowledged as one of the most environmentally harmful sectors within the food industry. The elevated concentrations of chemical oxygen demand (COD), total phosphorus (TP), ammonium nitrogen (NH4+-N), and salinity found in pickle wastewater present significant environmental challenges. To tackle these issues, this study investigates the efficacy of a La-doped Ti/SnO2-Sb2O5/La-PbO2 electrode employing an electro-Fenton method for the treatment of pickle wastewater. Experimental design was performed using response surface methodology to identify optimal operational parameters. Results demonstrate that all processes adhere to pseudo-first-order reaction kinetics. Under conditions where the degradation temperature is maintained at 65 °C, current density at 100 mA cm−2, pH at 4.1, FeSO4 concentration at 3.03 mmol L−1, and H2O2 concentration at 2.07 mmol L−1 with six additions over a degradation period of 240 minutes, COD removal achieved an impressive rate of 92.87 %, while ammonium nitrogen removal reached a remarkable rate of 95.26 %. In comparison to traditional electrochemical methods, both COD and ammonium nitrogen removal rates exhibited substantial improvements; furthermore, hydroxyl radicals (•OH) played a pivotal role in facilitating the radical quenching degradation process. The operation cost analysis shows that the electric Fenton process has a lower operation cost, which provides a good opportunity for the food industry to treat Pickled vegetables wastewater. The operating cost for COD removal rate is 1.262 $ m−3kg−1, and the operating cost for ammonia nitrogen removal rate is 1.355 $ m−3kg−1.

Prediction of Corrosion Rate for Carbon Steel Using Regression Model with Commercial LPR Sensor Data

In this study, a model was proposed to predict the corrosion rate (Mils per Year, MPY) of carbon steel in a 3.5% NaCl solution, with the objective of comparing the effectiveness of a commercial LPR sensor against traditional electrochemical methods, using potentiostat-based LPR techniques. The primary factors considered in the experiments were temperature, flow velocity, and pH, tested through a full factorial design to identify the most influential variables. Statistical analysis showed that temperature and flow velocity had a significant effect on corrosion rate, with their interaction having the most substantial impact. In contrast, pH had no statistically significant influence within the tested conditions, likely due to the dominant effects of temperature and flow velocity in the high-salinity environment. The MPY data were validated through Tafel plots, immersion coupon tests, and other electrochemical techniques to confirm the reliability of the measurements. A regression model trained on 54 MPY data points demonstrated high accuracy, achieving a coefficient of determination (R2) of 0.9733. The model also provided reliable predictions for factor combinations excluded from the training dataset. Additionally, scenario-based evaluations highlighted the model’s performance under simulated operating conditions, while revealing challenges related to sensor contamination during long-term use. These findings emphasize the potential of commercial LPR sensors as effective tools for real-time corrosion monitoring and demonstrate the utility of the regression model in marine environments.

Evaluation of the Antibacterial Activity of Antibiotics with different Antibacterial Mechanisms using Electrochemical Signals of Heat‐Treated Escherichia Coli

AbstractElectrochemistry with purines as indicators may be a promising new method for antibiotic activity testing. However, the traditional electrochemical detection method (S‐LSV) requires a long accumulation time for purines and has low signal intensity. High‐temperature treatment of bacterial samples may significantly enhance the signal intensity and speed of detection. However, this process may also impact the structure and metabolism of bacteria. Further research is necessary to determine how electrochemical signals respond to antibiotic antibacterial activity. In this paper, the electrochemical detection method based on heat‐treated Escherichia coli (E. coli, H‐LSV) was used to investigate the effects of 11 antibiotics with four different antibacterial mechanisms on the electrochemical behavior of E. coli. The results showed that compared to the S‐LSV, the electrochemical signal of E. coli detected by the H‐LSV increased by 362%, and showed a strong linear relationship with bacterial counts up to 1.88×108 CFU/mL, with a detection limit of 1.15×106 CFU/mL. The electrochemical signal consistently correlated with changes in viable E. coli counts following treatment with the four different antibacterial mechanisms. HPLC analysis further confirmed that the changes in purine contents in bacteria after antibiotic treatment were consistent with the trends in electrochemical signals. The evaluation of antibiotic antibacterial ability by H‐LSV showed good consistency with results from plate counting and turbidity methods, but was closer to the results of plate counting. The inhibition rates of antibiotics on E. coli detected by H‐LSV and S‐LSV also showed high consistency, indicating that short‐term high‐temperature treatment of E. coli did not affect the response of the bacterium to the inhibitory activity of antibiotics.

AuNPs@MoS2 functionalized copper metal organic framework for boosting electrocatalytic glucose oxidation

A novel non-enzyme glucose sensor based on functionalized copper metal–organic framework composite material, AuNPs@MoS2/Cu-MOF, was developed for rapid glucose analysis. Cu-MOF nanomaterial was prepared via a hydrothermal method, followed by the surface loading of core–shell structured AuNPs@MoS2 to synthesize AuNPs@MoS2/Cu-MOF composite material. Consequently, a novel gold nanoparticle @ molybdenum disulfide/copper metal–organic framework (AuNPs@MoS2/Cu-MOF/GCE) non-enzyme glucose sensor was constructed. Scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and X-ray powder Diffraction (XRD) was used to verify that the non-enzyme glucose sensor had been constructed effectively. Traditional electrochemical characterization methods were employed to study the electrocatalytic performance of the AuNPs@MoS2/Cu-MOF/GCE sensor and its catalytic oxidation of glucose. The experimental results demonstrated a good linear correlation between the concentration of glucose and the peak current within the range of 0.05–14.85 mM, with a detection limit of 16.7 μM. The AuNPs@MoS2/Cu-MOF/GCE sensor exhibited rapid electrochemical response to glucose (within 0.5 s), along with long-term stability and excellent selectivity. This is because Cu(II) in Cu-MOF can serve as active sites for the electrocatalytic oxidation of glucose, while the core–shell structure of AuNPs@MoS2 with excellent conductivity can lower the energy barrier in the reaction, further accelerating this catalytic reaction. The AuNPs@MoS2/Cu-MOF/GCE sensor is cost-effective, easy to operate, and suitable for accurate rapid quantification of glucose.

Bipolar electrochemical growth of conductive microwires for cancer spheroid integration: a step forward in conductive biological circuitry

The field of bioelectronics is developing exponentially. There is now a drive to interface electronics with biology for the development of new technologies to improve our understanding of electrical forces in biology. This builds on our recently published work in which we show wireless electrochemistry could be used to grow bioelectronic functional circuitry in 2D cell layers. To date our ability to merge electronics with in situ with biology is 3D limited. In this study, we aimed to further develop the wireless electrochemical approach for the self-assembly of microwires in situ with custom-designed and fabricated 3D cancer spheroids. Unlike traditional electrochemical methods that rely on direct electrical connections to induce currents, our technique utilises bipolar electrodes that operate independently of physical wired connections. These electrodes enable redox reactions through the application of an external electric field. Specifically, feeder electrodes connected to a power supply generate an electric field, while the bipolar electrodes, not physically connected to the feeder electrodes, facilitate the reduction of silver ions from the solution. This process occurs upon applying a voltage across the feeder electrodes, resulting in the formation of self-assembled microwires between the cancer spheroids.Thereby, creating interlinked bioelectronic circuitry with cancer spheroids. We demonstrate that a direct current was needed to stimulate the growth of conductive microwires in the presence of cell spheroids. Microwire growth was successful when using 50 V (0.5 kV/cm) of DC applied to a single spheroid of approximately 800 µm in diameter but could not be achieved with alternating currents. This represents the first proof of the concept of using wireless electrochemistry to grow conductive structures with 3D mammalian cell spheroids.

Electrochemical detection of benzenediols using carbon-supported catalysts

A novel implementation of an electrochemical sensors making use of Screen-Printed Electrodes (SPE) has been discussed. SPE's modified with Carbon-supported Platinum (Pt/C) and Gold (Au/C) were used to detect the three benzenediol isomers, Catechol (CC), Hydroquinone (HQ) and Resorcinol (RS) in acidic media using traditional electrochemical analytical methods such as Cyclic Voltammetry (CV), Chronoamperometry (CA) and Differential Pulse Voltammetry (DPV). Detection of each benzenediol in isolation was possible by CV measurements, and peak oxidation potentials for each isomer were noted. Simultaneous detection of more than one, or all analytes in the same solution was also observed through DPV, once again noting the peak oxidation potentials. Quantification limits were observed using CA's across concentration values ranging from close to saturation down to 1 mM for CC and HQ, and 100 nM for RS, until the recorded current values were nearly indistinguishable to a blank 1 M HCl solution containing no analyte(s), and also evaluating the maximum possible linear range of sensing. The analytes were introduced to the sensor elements in controlled amounts and the electrochemical responses of the sensor elements were recorded and processed. Measurements were repeated across two potentiostats to ensure reproducibility. With these results, successful detection of benzenediols in acidic environment was possible using modified SPE's, proving a potential viable mechanism for quick, simple and inexpensive Volatile Toxic Organic Compounds (VTOC) detection and monitoring.

Methanol‐Facilitated Surface Reconstruction Catalysts for Near 200% Faradaic Efficiency in a Coupled System

AbstractThe coupling of the carbon dioxide reduction reaction (CO2RR) and methanol oxidation reaction (MOR) holds great promise for the energy‐efficient production of HCOO−. However, anode catalysts' limited selectivity (<80%) and stability (<15 h) have impeded electron utilization and HCOO− production rates. To overcome it, copper‐copper(I) oxide‐copper(II) oxide nanowires (Cu─CuO─Cu2O NWs) catalysts have been developed, which exhibit exceptional performance in promoting the MOR with a faradic efficiency of nearly 100% at commercially viable current densities, and long stability over 100 h at 100 mA cm−2. Interestingly, the unique structure of the catalysts, when exposed to methanol, facilitates a transition from Cu/CuO to Cu2O. This phenomenon promotes the MOR while inhibiting the competitive oxygen evolution reaction (OER). By coupling the anodic reaction with cathodic CO2 reduction, the system demonstrates exceptional performance in HCOO− production, achieving an overall faradic efficiency of nearly 200% at 100 mA cm−2 with a low cell voltage of 2.382 V. Techno‐economic analysis indicates that the production costs of HCOOH are ≈US$0.37 and 0.35 kg−1 at 100 and 150 mA cm−2, respectively, significantly lower than those associated with traditional electrochemical methods.

Orientation-modulated oxygen evolution reaction in epitaxial SrRuO3 films.

The SrRuO3 films were grown on SrTiO3 using a lattice matching strategy. Scanning electrochemical microscopy imaged local oxygen evolution reaction (OER) performance, exploring the relationship between micro-area activity and the termination layer. Combined with traditional electrochemical methods and DFT calculations, the OER activity was correlated with the electronic structure.

Power and Sensitivity Management of Carbon Nanotube Transistor Glucose Biosensors.

Continuous glucose monitoring (CGM), which is significant for the daily management of diabetes, requires a low-power-consumption sensor system that can track low nanomolar levels of glucose in physiological fluids, such as sweat and tears. However, traditional electrochemical methods are limited to analytes in micromolar to millimolar ranges and entail high power consumption. Carbon nanotube (CNT) film field-effect transistors (FETs) are promising for constructing extremely sensitive biosensors, but their wide applications in CGM are limited by the strong screening effect of physiological fluids and the zero charge of glucose molecules. In this study, we demonstrate a glucose aptamer-modified CNT FET biosensor to realize a highly sensitive CGM system with sub-nW power consumption by applying a suitable gate voltage. A positive gate voltage can enlarge the effective Debye screening length at the double layer to reduce the local ion population nearby and then improve the sensitivity of the FET-based biosensors by 5 times. We construct CNT FET sensors for CGM with a limit of detection of 0.5 fM, a record dynamic range up to 109, and a power consumption down to ∼100 pW. The proposed field-modulated sensing performance scheme is applicable to other aptamer-based FET biosensors for detecting neutral or less charged molecules and opens opportunities to develop facilely modulated, highly sensitive, low-power, and noninvasive CGM systems.

Rapid Electrochemical Diagnosis of Battery Health and Safety from Cells to Modules

Rapid electrochemical diagnosis of battery health and failure is critical for ensuring reliable battery performance and battery safety. Traditional battery health diagnostics such as capacity measurements and DC pulse tests are reliable and well-understood, however, these measurements of battery capacity and resistance do not capture all aspects of battery degradation. Other aspects of degradation, such as electrolyte decomposition, lithium-plating, and particle cracking are difficult to detect electrochemically but are crucial to measure to get a full picture of battery safety and flag out potential failures. In this work, lab- and field-aged commercial lithium-ion batteries and modules of various chemistries and formats are tested using a variety of traditional electrochemical characterization methods as well as using 2-minute pseudo-random DC pulse sequences at rest and during charge/discharge. The electrochemical measurements are compared to physical cell measurements, cell efficiency, drive cycle performance, physical and thermal heterogeneity, and qualitative safety metrics using statistical and machine-learning methods to discover if a comprehensive ‘battery health map’ can be accurately identified using only rapid DC measurements.

Bias-free driven ion assisted photoelectrochemical system for sustainable wastewater treatment

Photoelectrochemical (PEC) systems have emerged as a prominent renewable energy-based technology for wastewater treatment, offering sustainable advantages such as eliminating dependence on fossil fuels or grid electricity compared to traditional electrochemical treatment methods. However, previous PEC systems often overlook the potential of ions present in wastewater as an alternative to externally applied bias voltage for enhancing carrier separation efficiency. Here we report a bias-free driven ion assisted photoelectrochemical (IAPEC) system by integration of an electron-ion acceptor cathode, which leverages its fast ion-electron coupling capability to significantly enhance the separation of electrons and holes at the photoanode. We demonstrate that Prussian blue analogues (PBAs) can serve as robust and reversible electron-ion acceptors that provide reaction sites for photoelectron coupling cations, thus driving the hole oxidation to produce strong oxidant free radicals at photoanode. Our IAPEC system exhibits superior degradation performance in wastewater containing chloride medium. This indicates that, in addition to the cations (e.g., Na+) accelerating the electron transfer rate, the presence of Cl– ions further enhance efficient and sustainable wastewater treatment. This work highlights the potential of utilizing abundant sodium chloride in seawater as a cost-effective additive for wastewater treatment, offering crucial insights into the use of local materials for effective, low-carbon, and sustainable treatment processes.

In-Operando Isothermal Microcalorimetry to Accelerate Screening of New Battery Chemistries

Screening new cell chemistries using traditional electrochemical methods is a time prohibitive process that significantly slows the pace of research. These methods involve cycling the cell until signs of degradation or sufficient capacity fade are evident, and typically take months to complete. In-operando isothermal microcalorimetry is an established but underutilized technique for measuring the activity of parasitic, or non-reversible reactions during charge cycling [1,2,3,4]. A parasitic reaction is a blanket term for any side reactions that occur within a battery, including solvent breakdown, lithium plating, self-discharge reactions, and growth or decomposition of the solid electrolyte interphase. Battery formulations with high parasitic heat are strongly correlated with early cell failure. Compared to electrochemical cycling, the average parasitic heat over the full voltage range can be determined in a time frame as low as 2 weeks, allowing researchers to realize a time savings up to 75%. Additional time savings are also possible if only a narrow voltage range is of interest.In this study, we present results that demonstrate the measurement of the parasitic heat of a commercial 18650 lithium-ion battery using the TA Instruments Battery Cycler Microcalorimeter Solution. This method involves slow galvanostatic cycling at isothermal conditions with a simultaneous measurement of heat flow, voltage, and applied current. The parasitic heat is isolated from the total heat flow using the Integration-Subtraction method, with calculations performed automatically by the software [1]. The coulombic efficiency is also measured per cycle, showing an inverse relationship to the parasitic power. As a screening tool, this data could be used to select battery formulations most likely to meet performance goals in long-term cycling experiments, rather than wasting valuable time and lab space on a trial-and-error approach. The results highlight how in-operando isothermal microcalorimetry is a powerful screening tool for investigating the efficiency of new cell chemistries and electrolyte formulations in a fraction of the time compared to traditional methods.[1] L.J. Krause, L.D. Jensen, V.L. Chevrier. Measurement of Li-Ion Battery Electrolyte Stability by Electrochemical Calorimetry. J. Electrochem. Soc. 2017, 164 (4), A889-A896.[2] L.J. Krause, L.D. Jensen, J.R. Dahn. Measurement of Parasitic Reactions in Li Ion Cells by Electrochemical Calorimetry. J. Electrochem. Soc. 2012, 159 (7), A937-A943.[3] J.C. Burns, Adil Kassam, N.N. Sinha, L.E. Downie, Lucie Solnickova, B.M. Way, J.R. Dahn. Predicting and Extending the Lifetime of Li-Ion Batteries. J. Electrochem. Soc. 2013, 160, A1451.[4] E. R. Logan, A. J. Louli, Matthew Genovese, Simon Trussler,and J. R. Dahn. Investigating Parasitic Reactions in Anode-Free Li Metal Cells with Isothermal Microcalorimetry. J. Electrochem. Soc. 2021, 168, 060527.

Localized corrosion evaluation of newly developed stainless-steel alloys in chloride medium through dynamic and localized micro electrochemical techniques

Novel Fe–Cr SS alloys were fabricated by alloying with 0, 0.10 and 0.20 wt-% Sn respectively to investigate the effect of the Sn addition on the microstructure, passive characteristics and localized corrosion behavior in chloride medium at room temperature. The advanced scanning micro-electrochemical techniques along with the traditional electrochemical methods were used for in-depth investigations. Potentiodynamic and potentiostatic test results exhibited that the addition of Sn in SS alloys increased the resistance against pitting corrosion in NaCl medium. The acquired dynamic impedance data confirmed the effective electrochemical stability of the alloy SS3 (SS with 0.20 wt-% Sn) at applied anodic potential, suggesting the presence of a compact and stable passive film in Sn containing alloys, which contributed to their improved localized corrosion resistance in chloride solution. The scanning electrochemical microscopic results corroborated that the alloy SS3 remained stable even after 24 h of exposure and displayed no noticeable surface heterogeneity. A reduced anodic current density in scanning vibrative electrode technique mapping images was observed even after 24-h of exposure in alloy SS3 compared to other samples, indicating that the anodic metal dissolution was successfully obstructed by forming a compact and dense passive film on this alloy.

Impact of microstructure evolution on the corrosion behaviour of the Ti–6Al–4V alloy welded joint using high-frequency pulse wave laser

In this work, a high-frequency pulsed laser-welding process was successfully implemented to fabricate a Ti–6Al–4V alloy butt joint. The microstructure of each zone of the welded joint was systematically characterized by carrying out scanning electron microscopy and electron backscatter diffraction measurements. In addition, the corrosion resistance of the welded joint was tested using traditional electrochemical and local electrochemical methods, while the main factors affecting corrosion resistance and the mechanism of the galvanic corrosion were also thoroughly investigated. From the acquired results, it was demonstrated that the α′ martensitic phases constituted the microstructure in the fusion zone (FZ), where the grain size, grain orientation, and misorientation distribution of the different zones varied, and the α′ martensitic and bulk α covered the heat-affected zone (HAZ). The corrosion resistance in the HAZ was slightly better than that in the base material, and both were worse than that of the FZ, which was related to the phase type. In addition, the corrosion current density values of FZupper were about 1/4.6 and 1/2.6 those of FZmiddle and FZdown, respectively, which was attributed to differences in the grain size and grain orientation. The FZ was protected as a cathode during galvanic corrosion, which is of great importance for ensuring the service life of the component during practical applications.

The process and mechanism of pulse electrolytic oxidation of ciprofloxacin antibiotic in wastewater on boron-doped diamonds

A novel process and method for treating ciprofloxacin (CIP) antibiotic wastewater using pulsed electrooxidation at boron-doped diamond (BDD) electrodes have been developed to address the issues of low efficiency and high energy consumption associated with traditional electrochemical oxidation methods. The effects of pulsed direct current (PDC), pulsed alternating current (PAC), and direct current (DC) on chemical oxygen demand (COD) removal were studied. It was found that complete degradation of CIP could be achieved within 45 min using PAC. COD removal reached 92.4% after 90 min of PAC electrooxidation for 90 mg·dm−3 CIP wastewater under optimized conditions of current density (j) = 30 mA·cm−2, initial pH (pH0) = 3, sodium sulfate concentration (c(Na2SO4)) = 50 mmol·dm−3, and frequency (f) = 100 Hz. The electrical energy consumption (EEC) was found to be 35 W·h·dm−3. The CIP degradation followed a quasi-first order kinetic law. The degradation pathway was found to involve hydroxylation of the quinolone moiety, cleavage of the piperazine ring, and fluorine substitution (OH/F substitution). The results showed that PAC electrochemical oxidation at all-BDD electrodes exhibited the highest removal efficiency and lowest EEC for CIP removal. This study provides a novel and effective approach for the efficient treatment of CIP antibiotic wastewater using bidirectional pulse current at all-BDD electrodes.

Consolidated designer waveform for maximizing analytical output of voltammetric measurements for complex chemical matrices

Electroanalysis has been widely used for quantitative analysis of electroactive (undergoing faradaic reaction) but also in lesser extent to non-electroactive (tensammetry) species. Traditional approach comprises of defining the best conditions to obtain specific signal for the individual constituent of interest. These conditions include selection of specific electroanalytical technique and its parameters and/or modification of chemical solution. Typically, the method development for every single species to be analyzed of a multiple-constituent matrix follows such a scheme and eventually a step-by-step analysis of all constituents of interest is performed.The new approach presented in this paper differs significantly from the traditional method development. Attention is focused on the development on a complex “consolidated designer waveform” that covers a wide range of electroanalytical conditions. This complex waveform is a combination of different electroanalytical techniques and/or parameters that cannot be described by a single, conventional technique, while its sub-waveforms (parts of the complex waveform) can be related to the traditional electrochemical method. This designer waveform is applied to the cell filled with the analyte solution and the resultant electrochemical output is used to predict the concentrations of multiple constituents of the complex matrix in a single run.

Revealing the Selective Bifunctional Electrocatalytic Sites via In Situ Irradiated X-Ray Photoelectron Spectroscopy for Lithium-Sulfur Battery.

The electrocatalysts are widely applied in lithium-sulfur (Li-S) batteries to selectively accelerate the redox kinetics behavior of Li2 S, in which bifunctional active sites are established, thereby improving the electrochemical performance of the battery. Considering that the Li-S battery is a complex closed "black box" system, the internal redox reaction routes and active sites cannot be directly observed and monitored especially due to the distribution of potential active-site structures and their dynamic reconstruction. Empirical evidence demonstrates that traditional electrochemical test methods and theoretical calculations only probe the net result of multi-factors on an average and whole scale. Herein, based on the amorphous TiO2- x @Ni selective bifunctional model catalyst, these limitations are overcome by developing a system that couples the light field and in situ irradiated X-ray photoelectron spectroscopy to synergistically convert the "black box" battery into a "see-through" battery for direct observation of the charge transportation, thus revealing that amorphous TiO2- x and Ni nanoparticle as the oxidation and reduction sites selectively promote the decomposition and nucleation of Li2 S, respectively. This work provides a universal method to achieve a deeper mechanistic understanding of bidirectional sulfur electrochemistry.

Reduction reactions at metal/non-aqueous interfaces can be sensed with the turn-on fluorophore resazurin

Interfacial redox reactions are important in corrosion and catalysis, but traditional electrochemical methods cannot be used in non-conducting environments. A turn-on fluorescent dye can sense these reactions in non-aqueous solvents.

Fabrication of tungsten tips with controllable shape by a two-step rapid reciprocating electrochemical etching method.

Traditional electrochemical etching methods for the needle of a liquid metal ion source (LMIS) easily produce an exponential profile with an uncontrollable tip length and apex radius. Meanwhile, a ledge forms between the needle tip and the needle rod under the etching of the meniscus, which becomes an obstacle for the flow and replenishment of the liquid metal. This paper proposed a two-step rapid reciprocating etching method, which aims to fabricate LMIS tungsten needles with controllable tip length and apex radius, and also with a smooth transition region between the needle tip and the needle rod. In the first step of rough machining, the needle rapidly reciprocates up and down in the electrolyte and rotates to produce a uniform conical profile. However, an ellipsoidal residual portion is generated concomitantly at the needle tip. In the second step of finish machining, the needle shifts down for a given distance and continues to reciprocate until the sharp tip is formed. The tip length fabricated varied from 0.59 to 5.53mm at different reciprocating strokes. The apex radius ranged from 0.3 to 0.7 µm, and can also be increased to 2 µm by extra reciprocate etching in the electrolyte to meet the LMIS working requirement. A variable named transitivity was defined to quantitatively describe the smoothness of the region between the tip and rod during the etching process. The experimental results showed that a rotation speed of 600 rpm combined with a reciprocating speed of 0.5 mm/s can significantly improve the transitivity of the needle. Those fabricated needle tips have been tested for the indium LMIS and the maximum emission current of the needle tip reached 12 µA.

Electrochemical Detection of Ascorbic Acid in Finger-Actuated Microfluidic Chip.

The traditional quantitative analysis methods of ascorbic acid (AA), which require expensive equipment, a large amount of samples and professional technicians, are usually complex and time-consuming. A low-cost and high-efficiency AA detection device is reported in this work. It integrates a three-electrode sensor module prepared by screen printing technology, and a microfluidic chip with a finger-actuated micropump peeled from the liquid-crystal display (LCD) 3D printing resin molds. The AA detection process on this device is easy to operate. On-chip detection has been demonstrated to be 2.48 times more sensitive than off-chip detection and requires only a microliter-scale sample volume, which is much smaller than that required in traditional electrochemical methods. Experiments show that the sample and buffer can be fully mixed in the microchannel, which is consistent with the numerical simulation results wherein the mixing efficiency is greater than 90%. Commercially available tablets and beverages are also tested, and the result shows the reliability and accuracy of the device, demonstrating its broad application prospects in the field of point-of-care testing (POCT).