Electrode-skin Contact Impedance Research Articles

Multichannel microneedle dry electrode patches for minimally invasive transdermal recording of electrophysiological signals.

The collection of multiple-channel electrophysiological signals enables a comprehensive understanding of the spatial distribution and temporal features of electrophysiological activities. This approach can help to distinguish the traits and patterns of different ailments to enhance diagnostic accuracy. Microneedle array electrodes, which can penetrate skin without pain, can lessen the impedance between the electrodes and skin; however, current microneedle methods are limited to single channels and cannot achieve multichannel collection in small areas. Here, a multichannel (32 channels) microneedle dry electrode patch device was developed via a dimensionality reduction fabrication and integration approach and supported by a self-developed circuit system to record weak electrophysiological signals, including electroencephalography (EEG), electrocardiogram (ECG), and electromyography (EMG) signals. The microneedles reduced the electrode-skin contact impedance by penetrating the nonconducting stratum corneum in a painless way. The multichannel microneedle array (MMA) enabled painless transdermal recording of multichannel electrophysiological signals from the subcutaneous space, with high temporal and spatial resolution, reaching the level of a single microneedle in terms of signal precision. The MMA demonstrated the detection of the spatial distribution of ECG, EMG and EEG signals in live rabbit models, and the microneedle electrode (MNE) achieved better signal quality in the transcutaneous detection of EEG signals than did the conventional flat dry electrode array. This work offers a promising opportunity to develop advanced tools for neural interface technology and electrophysiological recording.

The Three-Lead EEG Sensor: Introducing an EEG-Assisted Depression Diagnosis System Based on Ant Lion Optimization.

For depression diagnosis, traditional methods such as interviews and clinical scales have been widely leveraged in the past few decades, but they are subjective, time-consuming, and labor-consuming. With the development of affective computing and Artificial Intelligence (AI) technologies, Electroencephalogram (EEG)-based depression detection methods have emerged. However, previous research has virtually neglected practical application scenarios, as most studies have focused on analyzing and modeling EEG data. Furthermore, EEG data is typically obtained from specialized devices that are large, complex to operate, and poorly ubiquitous. To address these challenges, a wearable three-lead EEG sensor with flexible electrodes was developed to obtain prefrontal-lobe EEG data. Experimental measurements show that the EEG sensor achieves promising performance (background noise of no more than 0.91 μVpp, Signal-to-Noise Ratio (SNR) of 26--48 dB, and electrode-skin contact impedance of less than 1 K Ω). In addition, EEG data from 70 depressed patients and 108 healthy controls were collected using the EEG sensor, and the linear and nonlinear features were extracted. The features were then weighted and selected using the Ant Lion Optimization (ALO) algorithm to improve classification performance. The experimental results show that the k-NN classifier achieves a classification accuracy of 90.70%, specificity of 96.53%, and sensitivity of 81.79%, indicating the promising potential of the three-lead EEG sensor combined with the ALO algorithm and the k-NN classifier for EEG-assisted depression diagnosis.

Pure Conducting Polymer Hydrogels Increase Signal-to-Noise of Cutaneous Electrodes by Lowering Skin Interface Impedance.

Cutaneous electrodes are routinely used for noninvasive electrophysiological sensing of signals from the brain, the heart, and the neuromuscular system. These bioelectronic signals propagate as ionic charge from their sources to the skin-electrode interface where they are then sensed as electronic charge by the instrumentation. However, these signals suffer from low signal-to-noise ratio arising from the high impedance at the tissue-to-electrode contact interface. This paper reports that soft conductive polymer hydrogels made purely of poly(3,4-ethylenedioxy-thiophene) doped with poly(styrene sulfonate) present nearly an order of magnitude decrease in the skin-electrode contact impedance (88%, 82%, and 77% at 10, 100, and 1kHz, respectively) when compared to clinical electrodes in an ex vivo model that isolates the bioelectrochemical features of a single skin-electrode contact. Integrating these pure soft conductive polymer blocks into an adhesive wearable sensor enables high fidelity bioelectronic signals with higher signal-to-noise ratio (average 2.1dB increase, max 3.4dB increase) when compared to clinical electrodes across all subjects. The utility of these electrodes is demonstrated in a neural interface application. The conductive polymer hydrogels enable electromyogram-based velocity control of a robotic arm to complete a pick and place task. This work provides a basis for the characterization and use of conductive polymer hydrogels to better couple human and machine.

Effect of Fabric Electrode Surface Coating Medium on ECG Signal Quality under Dynamic and Static Conditions

This study intends to explore the influence of a fabric electrode skin interface filling medium on ECG signals under dynamic and static conditions, so as to be able to better monitor both stable and dynamic ECG signals. In this paper, cotton fabric electrodes were prepared using electroless silver-plated conductive cotton fabric, and then the electrodes were integrated into a physiotherapy-grade elastic bandage to assemble the fabric ECG tape. The electrode impedance tester and the BIOPAC physiological recorder were used to measure the fabric electrode-skin impedance and electrocardiogram under dynamic and static conditions, respectively. Later, the influence of the fabric electrode coated medium on the acquisition effect of an electrocardiogram signal under dynamic and static conditions is discussed. The results show that in the absence of a dielectric reagent coating, the cotton fabric electrode is easily disturbed by external noise which leads to large electrode-skin contact impedance. However, the electrode-skin contact impedance is greatly reduced after coating the fabric electrode with the dielectric reagent. At the same time, after applying the conducive paste coating, the corresponding change curve of the fabric electrode became more stable, and the impedance value was less than 0.005 MΩ·cm2, which meets the standard requirement for textile dry electrode skin impedance. In a state of rest, a clear and stable ECG can be collected regardless of whether the medium reagent is coated or not. However, only after applying the conductive paste can a stable ECG signal be collected under the three motion modes, or can a P wave, QRS wave group, or T wave be clearly distinguished. In addition, there is a high correlation with the disposable gel electrode, which can satisfy the requirements of the long-term monitoring of ECG signals under dynamic conditions.

Dependence of Skin-Electrode Contact Impedance on Material and Skin Hydration.

Dry electrodes offer an accessible continuous acquisition of biopotential signals as part of current in-home monitoring systems but often face challenges of high-contact impedance that results in poor signal quality. The performance of dry electrodes could be affected by electrode material and skin hydration. Herein, we investigate these dependencies using a circuit skin-electrode interface model, varying material and hydration in controlled benchtop experiments on a biomimetic skin phantom simulating dry and hydrated skin. Results of the model demonstrate the contribution of the individual components in the circuit to total impedance and assist in understanding the role of electrode material in the mechanistic principle of dry electrodes. Validation was performed by conducting in vivo skin-electrode contact impedance measurements across ten normative human subjects. Further, the impact of the electrode on biopotential signal quality was evaluated by demonstrating an ability to capture clinically relevant electrocardiogram signals by using dry electrodes integrated into a toilet seat cardiovascular monitoring system. Titanium electrodes resulted in better signal quality than stainless steel electrodes. Results suggest that relative permittivity of native oxide of electrode material come into contact with the skin contributes to the interface impedance, and can lead to enhancement in the capacitive coupling of biopotential signals, especially in dry skin individuals.

Wearable ring bioelectrical impedance analyzer for estimation and monitoring of body fat

The World Health Organization has declared obesity as one of the fastest growing global epidemics. People suffering from obesity are at an increased risk of serious health conditions including stroke, diabetes, high blood pressure, and other chronic diseases caused by excess fat in the body. To study and control this obesity epidemic, precise measurement of the body fat mass is necessary. Bioelectrical impedance analysis (BIA) is a common yet effective method for body composition, especially fat mass, measurement in which the electrical impedance of a human body is measured. Here we report a novel wireless BIA device, in the form of a wearable ring, for estimating the body fat as well as a smartphone application for users to manage and track their health data. The wearable analyzer was compared with an off-the-shelf body fat monitor in terms of performance for 40 healthy volunteers. In addition, the small, dry electrodes used in the ring analyzer are compared with traditional gel-based electrodes. Although the dry electrodes impose a larger skin-electrode contact impedance (5.18 ± 0.655 kΩ) than gel-based electrodes (933.37 ± 40.06 Ω), the designed system provides critical compensation for the higher electrode impedance and the parasitic effects for the dry electrodes. With the compensation implemented, these two types of electrodes are highly correlated with correlation coefficients r = 0.96 for resistance and r = 0.93 for reactance. Body fat estimation equations proposed by four different groups are analyzed and compared using the results from the wearable ring device. Our ring analyzer and the reference monitor demonstrate a linear regression with a strong correlation (r = 0.90) for estimating fat mass. Furthermore, the Bland-Altman plot shows that only 2 out of 40 subjects lie outside the 95% limit of agreement. All these findings show that the ring BIA system is highly portable, easy to use, and with comparable performance to large reference analyzers.

Ionic liquid regenerated cellulose membrane electroless plated by silver layer for ECG signal monitoring

Nowadays, more and more attention has been paid to flexible electrodes, which can be used to make wearable devices so as to monitor health signals, such as those in ECG, EMG and EEG. However, the contact impedance of many membrane electrodes is high due to the bad fit between the sensors and the skin, or the poor sensitivity caused by low conductivity. Therefore, we fabricated a skin-like conductive electrode via electroless silver plating on the surface of regenerated cellulose membrane, which was prepared from the cellulose dissolved in ionic liquid [Bmim]Cl. The as-prepared biocompatible electrodes with low skin-electrode contact impedance can be used as a dry electrode for a long time. Its impedance at 700 Hz is only 8 kΩ/cm2 and the conductivity reaches 252 s/cm. After 5 h of wearing, the electrode-skin contact impedance at 700 Hz is only 10 kΩ/cm2 when 0.20 mol/L AgNO3 is used. In short, the prepared electrode can not only ensure stable and clear ECG signals but also can greatly reduce electrode–skin contact impedance when used for long-term health monitoring.

Electrochemical Characteristics Based on Skin-Electrode Contact Pressure for Dry Biomedical Electrodes and the Application to Wearable ECG Signal Acquisition

Based on one simulated skin-electrode electrochemical interface, some electrochemical characteristics based on skin-electrode contact pressure (SECP) for dry biomedical electrodes were analysed and applied in this research. First, 14 electrochemical characteristics including 2 static impedance (SI) characteristics, 11 alternating current impedance (ACI) characteristics and one polarization voltage (PV), and 4 SECP characteristics were extracted in one electrochemical evaluation platform, and their correlation trends were statistically analysed. Second, dry biomedical electrode samples developed by the company and the laboratory, including textile electrodes, Apple watch, AMAZFIT rice health bracelet 1S, and stainless steel electrodes, were placed horizontally and vertically on the “skin” surface of the electrochemical evaluation platform, whose polarization voltages were quantitatively analysed. Third, electrocardiogram (ECG) collection circuits based on an impedance transformation (IT) circuit for textile electrodes were designed, and a wearable ECG acquisition device was designed, which could obtain complete ECG signals. Experimental results showed SECP characteristics for dry electrodes had good correlations with static impedance and ACI characteristics and the better correlation values among 2-10 Hz. In addition, polarization voltages in vertical state were smaller in horizontal state for dry biomedical electrodes, and polarization voltage of electrode pair (PVEP) values for Apple watch bottom was always smaller than ones for Apple watch crown and LMF-2 textile electrode. And the skin-electrode contact impedance of IT textile electrodes was less than the traditional textile electrodes.

Wearable Smart Textiles for Long-Term Electrocardiography Monitoring-A Review.

The continuous and long-term measurement and monitoring of physiological signals such as electrocardiography (ECG) are very important for the early detection and treatment of heart disorders at an early stage prior to a serious condition occurring. The increasing demand for the continuous monitoring of the ECG signal needs the rapid development of wearable electronic technology. During wearable ECG monitoring, the electrodes are the main components that affect the signal quality and comfort of the user. This review assesses the application of textile electrodes for ECG monitoring from the fundamentals to the latest developments and prospects for their future fate. The fabrication techniques of textile electrodes and their performance in terms of skin–electrode contact impedance, motion artifacts and signal quality are also reviewed and discussed. Textile electrodes can be fabricated by integrating thin metal fiber during the manufacturing stage of textile products or by coating textiles with conductive materials like metal inks, carbon materials, or conductive polymers. The review also discusses how textile electrodes for ECG function via direct skin contact or via a non-contact capacitive coupling. Finally, the current intensive and promising research towards finding textile-based ECG electrodes with better comfort and signal quality in the fields of textile, material, medical and electrical engineering are presented as a perspective.

Wearable Ag-NyW textile electrode for continuous ECG monitoring

The diagnosis of unexplained syncope and sustained palpitations remains a challenging task for cardiology community. Continuous monitoring of cardiac activity is essential to know the pumping pattern of the heart for patients with mild and severe symptoms. Although attempts have been made towards developing wearable monitoring system, the demand for new system is still open due to affordability and accessibility to resource constrained settings. This research work proposes a wearable smart jacket with a single lead (Ag-NyW) textile sensor for continuous monitoring of electrocardiogram (ECG) signals. The wearable lead-I textile electrodes are evaluated in terms of visual inspection by the clinician, skin-electrode contact impedance characteristics; fidelity measures such as crest factor, signal band to noise band ratio, mean magnitude squared coherence; and ECG interval characteristics. Experimental study was carried with 212 healthy volunteers after due ethical clearance (age group 18–45 years), and RR variability and heart rate variability were assessed for different age groups and BMI levels. The study revealed that the proposed textile electrodes are comparable to disposable (conventional Ag/AgCl gel) electrodes in terms of fidelity measures, skin-contact impedance, and ECG interval measures. The HRV for different age groups and BMI levels were found to be within the limits as reported in the literature. From the current pilot study with Indian population, this cost-effective wearable ECG monitoring system will be helpful for long-term monitoring in resource constrained settings.

Performance of a flexible electrode based on natural leather

A novel electrode is developed to detect electrocardiogram (ECG) signals using the top grain leather and split leather of pig as the substrate due to their mechanical strength, flexibility, permeability, long-term durability and visual acceptance. The natural leather is pre-treated with Ar plasma and a thin silver paste coating is brush-painted on the surface to gain electrical conductivity. The sheet resistance of the electrodes is approximately 120 mΩ sq−1. The electrodes based on leather can reliably transmit low-frequency and low-voltage signals, which benefit the acquisition of cardiac signals. Although the electrode-skin contact impedance of the dry leather-based electrodes is higher than the silver/silver chloride (Ag/AgCl) electrodes, the contact impedance decreases at least 57.74% after wetting the skin. All cardiac waves obtained by the leather-based electrodes are clear and visible, and the signal-to-noise ratio (SNR) of electrodes are higher than the Ag/AgCl electrodes. The electrodes based on leather have great potential for smart wearable devices.

Soft ionic-hydrogel electrodes for electroencephalography signal recording

Wet gel electrodes have been widely used for electroencephalography (EEG) signal recording, which generally causes skin abrasion and longer preparation time. In this paper, we present soft ionic-hydrogel based electrodes to overcome such drawbacks. In order to conveniently measure the EEG signals, we design the claw-like and patch-like structures for robust connection between metal (Ag/AgCl) electrodes and skin scalps. Next, we experimentally show that the soft ionic-hydrogel based electrodes have similar performance with the conventional wet gel electrodes in terms of the short-circuit noise, electrical impedance, and skin-electrode contact impedance on unprepared human skin, significantly better than dry electrodes and water-based electrodes. We further perform the EEG measurements and steady-state visual evoked potentials (SSVEP) experiments with five subjects to verify the effectiveness of the soft ionic-hydrogel based electrodes. The experimental results demonstrate that our developed soft ionic-hydrogel electrodes can record high-quality EEG signals in a fast and clean way, being a compelling option for EEG-based brain-computer interfaces.

Development and Evaluation of 3D‐Printed Dry Microneedle Electrodes for Surface Electromyography

AbstractSurface electromyography (sEMG) allows for direct measurement of electrical muscle activity with use in fundamental research and many applications in health and sport. However, conventional surface electrode technology can suffer from poor signal quality, requires careful skin preparation, and is commonly not suited for long‐term recording. These drawbacks have challenged translation of sEMG to clinical applications. In this paper, dry 3D‐printed microneedle electrodes (MNEs) are proposed to overcome some of the limitations of conventional electrodes. Employing a direct‐metal‐laser‐sintering (DMLS) 3D printing process, a two‐step fabrication method is developed to produce sharp medical‐grade stainless steel MNEs. The developed MNEs are compared to needle‐free versions and to standard wet Ag/AgCl electrodes. Functional testing is conducted to analyze the electrode–skin impedance in healthy human volunteers and sEMG data are recorded from the biceps brachii muscle. Results show that microneedle electrodes display a greatly reduced (≈63%) electrode–skin contact impedance with respect to needle‐free electrodes and record sEMG at a signal‐to‐noise ratio comparable to clinical‐grade wet Ag/AgCl electrodes over a period of up to 6 h. Overall, a fabrication method and electrode type are presented which yield high‐quality sEMG signals when evaluated in humans, highlighting the potential of MNEs as a platform for biosignal recording.

Adaptive Spatial Filtering of High-Density EMG for Reducing the Influence of Noise and Artefacts in Myoelectric Control.

Electromyography (EMG) is a source of neural information for controlling neuroprosthetic devices. To enhance the information content of conventional bipolar EMG, high-density EMG systems include tens to hundreds of closely spaced electrodes that non-invasively record the electrical activity of muscles with high spatial resolution. Despite the advantages of relying on multiple signal sources, however, variations in electrode-skin contact impedance and noise remain challenging for multichannel myocontrol systems. These spatial and temporal non-stationarities negatively impact the control accuracy and therefore substantially limit the clinical viability of high-density EMG techniques. Here, we propose an adaptive algorithm for automatic artefact/noise detection and attenuation for high-density EMG control. The method infers the presence of noise in each EMG channel by spectro-temporal measures of signal similarity. These measures are then used for establishing a scoring system based on an adaptive weighting and reinforcement formulation. The method was experimentally tested as a pre-processing step for a multi-class discrimination problem of 4-digit activation. The approach was proven to enhance the discriminative information content of high-density EMG signals, as well as to attenuate non-stationary artefacts, with improvements in accuracy and robustness of the classification.

Sacrificial layer-assisted one-step transfer printing for fabricating a three-layer dry electrode

A sacrificial-layer assisted one-step transfer printing method is presented to fabricate a three-layer dry electrode for detecting electrophysiological signals. First, an Au electrode layer was deposited on a silicon wafer covered by a Cu sacrificial layer. Then, a polyimide (PI) intermediate layer was patterned on the Au layer by a standard photolithography process, and subsequently the Au layer was patterned by wet etching, using the patterned PI layer as the etching mask. Finally, both the patterned Au layer and PI layer were transferred onto a stretchable film in one step to make a three-layer dry electrode by etching away the Cu sacrificial layer. This three-layer dry electrode exhibited excellent conformability and stretchability and low electrode-skin contact impedance. The performance of the three-layer dry electrode for long-term and dynamic electrocardiogram (ECG) monitoring was also examined. The quality of ECG signals was well maintained for 48 h, during which period the signal to noise ratio was kept at 40 dB. It was also found that the physical exercises had only slight effects on the ECG signal, where all features of the signal were clearly distinguishable when the volunteer ran at 5 km/h.

Fabrication and Analysis of Wearable Bioimpedance Analyzers on Paper and Plastic Substrates

Wearable flexible sensors have recently gained much attention as they have the potential to revolutionize the way we monitor activities of the human body. Electronic sensors fabricated on flexible substrates provide compactness, comfort, and flexibility. In this letter, we report a novel design of wearable and mechanically flexible bioimpedance analyzers. We fabricate the analyzers by printing electronic circuits on paper and plastic substrates. The sensor module is lightweight, comfortable, and can be worn on the wrist to measure the body impedance continuously. Failure analysis is performed by bending the flexible sensor modules with the circuit breaking angles at 53° ± 4° and 42° ± 3° for paper and plastic substrates, respectively. The performance of the flexible sensors is compared with an analyzer developed on a conventional rigid printed circuit board. In an active mode, the paper-based sensor consumes more power (83.3 mW) than the plastic (65.7 mW) and rigid (53.42 mW) sensors. The flexible sensor modules are integrated with dry electrodes, while gel-based Ag/AgCl electrodes are attached to the rigid sensor module for bioimpedance measurements. The experiments are conducted on 12 healthy human subjects by using all three sensor modules. The integrated dry electrodes of the flexible sensor modules provide lower skin-electrode contact impedance along with enhanced convenience, durability, and reusability, as compared to commercial Ag/AgCl electrodes.

A Novel Passive Method for the Assessment of Skin-Electrode Contact Impedance in Intraoperative Neurophysiological Monitoring Systems

Intraoperative Neurophysiological Monitoring is a set of monitoring techniques consisting of reading electrical activity generated by the nervous system structures during surgeries. In order to guarantee signal quality, contact impedance between the sensing electrodes and the patient’s skin needs to be as low as possible. Hence, monitoring this impedance while signals are measured is an important feature of current medical devices. The most commonly used technique involves injection of a known current and measurement of the voltage drop in the contact interface. This method poses several problems, such as power consumption (critical in battery-powered systems), frequency dependency and regulation issues, which are overcome by using a passive method. The fundamentals of the method proposed in this paper are based on the utilization of the variation suffered by the input random signal when a known resistance is connected in parallel to the input terminals of the low-noise amplifier (LNA) of the analog front-end of the acquisition system. Controlling the connection of the resistors and computing the root mean square of the LNA output voltage has been proved to be a useful tool to assess that the contact impedance is suitably low, allowing the user to know if the neural measurements obtained are valid.

Performance Evaluation of Woven Conductive Dry Textile Electrodes for Continuous ECG Signals Acquisition

Electrocardiogram (ECG) signal monitoring is one of the essential techniques for determining the physiological state of human beings. Long-term ECG monitoring is very much essential for the diagnosis and treatment of infrequent arrhythmic episodes. Although, most of the wearable microelectronic ECG implementations employ the well-established surface electrodes technology for bio-potential recordings; they are found to be susceptible to skin irritation and influence the skin-contact impedance to larger extent in long-term monitoring applications. Integration of such sensors into wearable intelligent biomedical clothing is not feasible. This specific research study determines the application of two different conductive textile fabric materials, namely, the woven conductive silver and conductive knitted jersey as dry textile electrodes for ECG biopotential acquisition. The skin-electrode contact impedance measurements for both electrodes presented reduced skin-contact impedance of less than 1 $\text{M}\Omega $ /cm2 compared to 1–5 $\text{M}\Omega $ /cm2 as reported in literature. The performance of the proposed textile sensors is evaluated qualitatively through visual inspection and quantitatively using metrics such as power spectral density, kurtosis, baseline wander analysis, and signal-to-noise ratio (SNR). The obtained quantitative measures were compared with standard clinical grade conductive-gel based disposable Ag/AgCl surface electrodes. The simulation and comparison studies showed that, the proposed textile electrodes exhibit acceptable performance for ECG acquisition and in some instances improved performance than the traditional commercial disposable gel-based surface electrodes.

Effect of Sweating on Electrode-Skin Contact Impedances and Artifacts in EEG Recordings With Various Screen-Printed Ag/Agcl Electrodes

In response to the growing clinico-economic need for comprehensive home-based sleep testing, we recently developed a self-applicable facial electrode set with screen-printed Ag/AgCl electrodes. Our previous studies revealed that nocturnal sweating is a common problem, causing low-frequency artifacts in the measured electroencephalography (EEG) signals. As the electrode set is designed to be used without skin abrasion, not surprisingly this leads to relatively high electrode-skin impedances, significant impedance changes due to sweating and an increased risk of sweat artifacts. However, our recent electrochemical in vitro investigations revealed that the sweat artifact tolerance of an EEG electrode can be improved by utilizing an appropriate Ag/AgCl ink. Here we have investigated in vivo electrode-skin impedances and the quality of EEG signals and interference due to sweating in the population of 11 healthy volunteers. Commercial Ag and Ag/AgCl inks (Engineered Conductive Materials ECM LLC and PPG Industries Inc.) were used to test electrode sets with differently constructed ink layers. Electrode-skin impedances and EEG signals were recorded before and after exercise-induced sweating. There was extensive variation in the electrode-skin impedances between the volunteers and the electrode positions: 14.6–200 $\text{k}\Omega $ (PPG electrodes) and 7.7–200 $\text{k}\Omega $ (ECM electrodes). Sweating significantly decreased ( $p ) the impedances in most cases. The EEG signal quality was assessed by comparing average band powers from 0.5 to 2 Hz before and after sweating. Only slight differences existed between the ECM and PPG electrodes; however, the lowest band power ratio ( i.e . the smallest increase in the band power due to sweating) was achieved with ECM electrodes.

Development of a Wearable Electrical Impedance Tomographic Sensor for Gesture Recognition With Machine Learning.

A wearable electrical impedance tomographic (wEIT) sensor with 8 electrodes is developed to realize gesture recognition with machine learning algorithms. To optimize the wEIT sensor, gesture recognition rates are compared by using a series of electrodes with different materials and shapes. To improve the gesture recognition rates, several Machine Learning algorithms are used to recognize three different gestures with the obtained voltage data. To clarify the gesture recognition mechanism, an electrical model of the electrode-skin contact impedance is established. Experimental results show that: rectangular copper electrodes realize the highest recognition rate; the existence of the electrode-skin contact impedance could improve the gesture recognition rate; Medium Gaussian SVM (Support Vector Machine) algorithm is the optimal algorithm with an average recognition rate of 95%.