Skin Impedance Research Articles

A fabric-based multifunctional sensor for the early detection of skin decubitus ulcers

Monitoring biosignals at the skin interface is necessary to suppress the potential for decubitus ulcers in immobile patients confined to bed. We develop conformally contacted, disposable, and breathable fabric-based electronic devices to detect skin impedance, applied pressure, and temperature, simultaneously. Based on the experimental evaluation of the multifunctional sensors, a combination of robust AgNW electrodes, soft ionogel capacitive pressure sensor, and resistive temperature sensor on fabric provides alarmed the initiation of early-stage decubitus ulcers without signal distortion under the external stimulus. For clinical verification, an animal model is established with a pair of magnets to mimic a human decubitus ulcers model in murine in vivo. The evidence of pressure-induced ischemic injury is confirmed with the naked eye and histological and molecular biomarker analyses. Our multifunctional integrated sensor detects the critical time for early-stage decubitus ulcer, establishing a robust correlation with the biophysical parameters of skin ischemia and integrity, including temperature and impedance.

Incremental Adaptive Gesture Classifier for Upper Limb Prostheses

Myoelectric pattern recognition is widely used to control upper limb prostheses. However, the non-stationary characteristics of electromyography (EMG) signals, caused by physiological changes (e.g. muscle fatigue) or non-physiological changes (e.g. the electrode- skin impedance), hinder the use of prostheses and deteriorate the performance of the myoelectric control system. In this paper, a set of robust features is proposed to be integrated with adaptive learning techniques in order to improve the myoelectric performance. Four types of features are proposed, namely the H, HI, AI, and AIH features. The H features correspond to the histogram-oriented gradient (HOG) algorithm of the High-Density surface Electromyography map (HD-sEMG map). On the other hand, the HI features are generated by combining the H features and the intensity feature that is evaluated from the HD-sEMG map. AI is the intensity features calculated from the segmented HD-sEMG maps constructed in the individual channel. Finally, AIH features are obtained by combining the H features and AI features. Offline and online adaptive tests are conducted to evaluate the proposed features. The results show that employing the proposed AI features with an adaptive classifier improves the classification accuracy from 91.58% to 97.2% in online classification setups. Results also show that the AI features are more robust against noise than TD features. The average classification accuracy is reduced by 0.7% when additive White Gaussian noise is applied, in comparison to 5.8% reduction in accuracy when TD features is used. The results confirm the robustness of the proposed features extracted from the HD-sEMG map.

Graphene electronic tattoos 2.0 with enhanced performance, breathability and robustness

Graphene electronic tattoos (GETs) have recently emerged as unique tools for personalized healthcare. The monolayer GETs have been used to monitor human electrophysiological signals, including brain, heart, and muscle activities, skin temperature, and hydration level. However, a few drawbacks of the earlier GETs hindered their perception by clinical and biomedical experts: they were not permeable to sweat, and the tattoo performance varied greatly. In this work, we introduce GETs 2.0: the skin wearable tattoo sensors with superior electrical properties, permeability to sweat, and robustness. We report on the categorical analysis of the graphene tattoos of different layer constitutions. When stacking the graphene monolayers within a single tattoo, we see a drastic enhancement in their electronic properties. The older monolayer GETs were susceptive to minor growth- or transfer-related discrepancies, resulting in highly scattered electrical properties. In this work, the GETs 2.0 with the addition of graphene nanoscrolls (GNS) or multilayer (2 L and 3 L) graphene structures exhibit 3.5-fold decreased sheet resistance, 2.5-fold lower skin impedance, and 5-fold reduced standard deviations of these values. In addition, we introduced holes into the tattoo, enabling healthy sweat evaporation without a substantial decrease in electrical properties. Furthermore, we show that microholes allow for advanced biplanar contact with graphene tattoos. Finally, we show that multilayer GETs 2.0 can be used as efficient skin-wearable electronic heaters, exhibiting heating efficiency of ~6 mW/°C.

Lumped Parametric Model for Skin Impedance Data in Patients with Postoperative Pain.

The societal and economic burden of unassessed and unmodeled postoperative pain is high and predicted to rise over the next decade, leading to over-dosing as a result of subjective (NRS-based) over-estimation by the patient. This study identifies how post-surgical trauma alters the parameters of impedance models, to detect and examine acute pain variability. Model identification is performed on clinical data captured from post-anesthetized patients, using Anspec-PRO prototype apriori validated for clinical pain assessment. The multisine excitation of this in-house developed device enables utilizing the complex skin impedance frequency response in data-driven electrical models. The single-dispersion Cole model is proposed to fit the clinical curve in the given frequency range. Changes in identified parameters are analyzed for correlation with the patient's reported pain for the same time moment. The results suggest a significant correlation for the capacitor component. Clinical Relevance- Individual model parameters validated on patients in the post-anesthesia care unit extend the knowledge for objective pain detection to positively influence the outcome of clinical analgesia management.

Penetration Enhancement Strategies for Intradermal Delivery of Cromolyn Sodium.

This study aimed to explore the use of chemical and physical enhancement strategies for the intradermal delivery of cromolyn sodium (CS) for treatment of atopic dermatitis. CS gels were formulated to individually contain 2.5 and 9% salcaprozate sodium (SNAC) as a potential chemical enhancer. The effect of microneedles, alone and in combination with SNAC, was investigated via in vitro permeation studies. Skin impedance and FTIR evaluation of SNAC-treated stratum corneum (SC) was done and compared to the control. The amount of drug delivered in the dermis after 24h by the 2.5% and 9% SNAC gels was 23.29 ± 1.89µg/cm2 and 35.87 ± 2.23µg/cm2, respectively, which were significantly higher than the control (p < 0.05) but were not remarkably different from each other (p > 0.05). Microneedles enhanced permeation in both the control and 2.5% SNAC groups (p < 0.05); however, no synergistic enhancement was observed when microneedle and SNAC treatments were combined (p > 0.05). Over 24h of treating the SC with 2.5% SNAC, FTIR evaluation showed stretches on the CH2 asymmetric and symmetric stretching vibrations observed at 2920.23cm-1 and 2850.79cm-1 respectively in untreated SC, which shifted to higher wavenumbers and indicated some lipid fluidizing effect. However, no significant drop in skin impedance was seen with SNAC as compared to the control (p > 0.05). SNAC was concluded to have skin permeation enhancement effect on CS, while microneedles effectively enhanced CS permeation even in the absence of SNAC.

A New Impedance Sensor Based on Electronically Implemented Chaotic Coupled van der Pol and Damped Duffing Oscillators

The chaotic behaviour of a system depends on the parameter values, and when the system exhibits such a chaotic behaviour, it is sensitive to the initial conditions. This feature can be used for manufacturing high sensitivity sensors. Sensors based on chaotic circuits have already been used for measuring water salinity, inductive effects, and both noise and weak signals. This article investigates an impedance sensor based on the van der Pol and Duffing damped oscillators. The calibration process is a key point and therefore the folding behaviour of signal periods was also explored. A sensitivity of 0.15 kΩ/Period was estimated over a range from 89.5 to 91.6 kΩ. This range can be adjusted according to the application by varying the gain of the operational amplifier used in this implementation. The development of this type of sensor might be used in medical and biological engineering for skin impedance measurements, for example. This type of chaotic impedance sensor has the advantage of sensing small disturbances and then rapidly detecting small impedance changes within biological materials.

Graphene-Based Flexible Electrode for Electrocardiogram Signal Monitoring

With the rapidly aging society and increased concern for personal cardiovascular health, novel, flexible electrodes suitable for electrocardiogram (ECG) signal monitoring are in demand. Based on the excellent electrical and mechanical properties of graphene and the rapid development of graphene device fabrication technologies, graphene-based ECG electrodes have recently attracted much attention, and many flexible graphene electrodes with excellent performance have been developed. To understand the current research progress of graphene-based ECG electrodes and help researchers clarify current development conditions and directions, we systematically review the recent advances in graphene-based flexible ECG electrodes. Graphene electrodes are classified as bionic, fabric-based, biodegradable, laser-induced/scribed, modified-graphene, sponge-like, invasive, etc., based on their design concept, structural characteristics, preparation methods, and material properties. Moreover, some categories are further divided into dry or wet electrodes. Then, their performance, including electrode–skin impedance, signal-to-noise ratio, skin compatibility, and stability, is analyzed. Finally, we discuss possible development directions of graphene ECG electrodes and share our views.

Delta-5\xae oil, containing the anti-inflammatory fatty acid sciadonic acid, improves skin barrier function in a skin irritation model in healthy female subjects

BackgroundSciadonic acid (SA) is an anti-inflammatory fatty acid displacing arachidonic acid (ARA) from specific phospholipid pools, thus modulating downstream pro-inflammatory lipid mediators. Its novel anti-inflammatory actions have been studied in vitro, in pre-clinical models, and stemming from testimonials, after topical- and oral application. It has not been tested in a formal clinical study for topical benefits previously. Skin barrier layer was our focus as it has a critically important role in maintaining skin moisture balance.MethodsHerein, forearm skin was left undamaged; or barrier layer was chemically-damaged with 2% sodium lauryl sulfate (SLS) for 24 h. SLS-damaged skin was left untreated or treated with Delta-5® oil containing 24% SA twice daily for 27 days. Barrier function was assessed by open chamber transepidermal water loss (TEWL) and skin surface impedance on days 0 (clear skin), -1 (1-day post-SLS), -2 (2-days post-SLS, 1-day post-Delta-5), -3, -7, and − 28.ResultsRelative to day 1, Delta-5 oil statistically significantly decreased TEWL vs. untreated damaged sites, on days 3 (125% more reduced), -7 (74% more reduced), and − 28 (69% more reduced). Decreases in TEWL following chemical damage indicates improved skin barrier repair and healing. Similar patterns were quantified for skin impedance. There was also reduced redness observed on days 3 and − 7 with Delta-5 oil vs. untreated SLS-damaged skin.ConclusionsDelta-5 oil thus has anti-inflammatory potential in human skin, under controlled clinical conditions, to accelerate irritant-induced healing, and improve skin barrier function. Improvement in barrier function would benefit dermatitis, acne, eczema, and skin scarring. In normal skin, Delta-5 oil has potential to promote healthy, moisturized skin; and improve skin structure, elasticity, and firmness.

Linear, High Dynamic Range Isolated Skin Resistance Transducer Circuit for Neurophysiological Research in Individuals after Spinal Cord Injury

The quantification of skin resistance in individuals after spinal cord injury for the purpose of neurophysiological research is difficult, mainly as a consequence of decreased activity of sweat glands in the injured human organism. In this original work, we propose a custom electrical skin resistance transducer, featuring extremely low patient auxiliary current, linear response and high dynamic range. After the design and fabrication of the prototype device, we conducted preliminary benchmark tests. We found that our prototype transducer was able to linearly report a broad range of resistance presented to its input terminals, which is not usually found in skin resistance research instrumentation. The basic design idea is viable and, following further research, an improved version of presented prototype device may be used for the purpose of neurophysiological research in individuals after spinal cord injury.

A biomimetic skin phantom for characterizing wearable electrodes in the low-frequency regime

Advances in the integration of wearable devices in our daily life have led to the development of new electrode designs for biopotential monitoring. Historically, the development and testing of wearable electrodes for the acquisition of biopotential signals has been empirical, relying on experiments on human volunteers. However, the lack of explicit control on human variables, the intra-, and inter-subject variability complicates the understanding of the performance of these wearable electrodes. Herein, phantom mimicking the electrical properties of the skin in the low-frequency range (1–1000 Hz), which has the potential to be used as a platform for controlled benchtop experiments for testing electrode functionality, is demonstrated. The fabricated phantom comprises two layers representing the deeper tissues and stratum corneum. The lower layer of the phantom mimicking deeper tissues was realized using polyvinyl alcohol cryogel (PVA-c) prepared with 0.9% W/W saline solution by a freeze-thaw technique. The properties of the upper layer representing the stratum corneum were simulated using a 100 µm thick layer fabricated by spin-coating a mixture of polydimethylsiloxane (PDMS), 2.5% W/W carbon black (CB) for conductance, and 40% W/W barium titanate (BaTiO3) as a dielectric. The hydration of the stratum corneum was modeled in a controlled way by varying porosity of the phantom’s upper layer. Impedance spectroscopy measurements were carried out to investigate the electrical performance of the fabricated phantom and validated against the impedance response obtained across a physiological skin impedance range of five human subjects. The results indicated that the Bode plot depicting the impedance response obtained on the phantom was found to lie in the human skin range. Moreover, it was observed that the change of porosity provides control over the hydration and the phantom can be tuned as per the skin ranges among different individuals. Also, the phantom was able to mimic the impact of dry and hydrated skin on a simulated ECG signal in the time domain. The developed skin phantom is affordable, fairly easy to manufacture, stable over time, and can be used as a platform for benchtop testing of new electrode designs.

Clinical evaluation of anaesthetic‐like effect of two dermocosmetic formulations containing Aquaphilus dolomiae extract‐G3 in subjects with sensitive facial skin

Sensitive skin is a common condition of hyper-reactivity to external stimuli, e.g. heat or abrasion. The symptoms are subjective but can be measured using validated emotional and technical methods. Avène water has several beneficial effects on the skin. In vitro studies indicated that the active component of this natural spring water, Aquaphilus dolomiae extract-G3 (ADE-G3), modulates cutaneous sensitivity via an anaesthetic-like mechanism. To assess facial skin reactivity after repeated application of two formulations containing ADE-G3. In open-label studies, healthy subjects with sensitive facial skin applied cream or balm twice daily for 84 days. The severity of skin sensitivity was measured using the Sensitive Scale (based on quantifying visible or subjective signs). Subjective responses associated with pain or uncomfortable feeling were assessed by measuring electrodermal response (EDR). This involves measuring variations in skin electrical resistance due to non-conscious physiological changes in activity of the sympathetic nervous system. Subjects were also evaluated for beneficial effects according to a quantitative approach using semantic assessment of a question regarding their skin quality. Evaluations were performed before and after the first application, and after 29/30, 56 and 84 days of twice daily use. There was a significant decrease in the EDR after stimuli immediately after the application of both ADE-G3 formulations, which continued to decrease over 84 days (40-50% decrease by D85). Likewise, all physical and functional signs of the Sensitive Scale were significantly decreased immediately after the first application and at all time points tested after treatment. Verbatim analysis revealed a semantic shift, from mainly negative terms on D1 to mainly positive terms at D85 for both tested products. These results demonstrated that two formulations containing ADE-G3 reduced skin sensitivity, indicating a decreased activation of the sympathetic nervous system associated with this condition.

EmteqPRO—Fully Integrated Biometric Sensing Array for Non-Invasive Biomedical Research in Virtual Reality

Virtual Reality (VR) enables the simulation of ecologically validated scenarios, which are ideal for studying behaviour in controllable conditions. Physiological measures captured in these studies provide a deeper insight into how an individual responds to a given scenario. However, the combination of the various biosensing devices presents several challenges, such as efficient time synchronisation between multiple devices, replication between participants and settings, as well as managing cumbersome setups. Additionally, important salient facial information is typically covered by the VR headset, requiring a different approach to facial muscle measurement. These challenges can restrict the use of these devices in laboratory settings. This paper describes a solution to this problem. More specifically, we introduce the emteqPRO system which provides an all-in-one solution for the collection of physiological data through a multi-sensor array built into the VR headset. EmteqPRO is a ready to use, flexible sensor platform enabling convenient, heterogenous, and multimodal emotional research in VR. It enables the capture of facial muscle activations, heart rate features, skin impedance, and movement data—important factors for the study of emotion and behaviour. The platform provides researchers with the ability to monitor data from users in real-time, in co-located and remote set-ups, and to detect activations in physiology that are linked to arousal and valence changes. The SDK (Software Development Kit), developed specifically for the Unity game engine enables easy integration of the emteqPRO features into VR environments.Code available at: (https://github.com/emteqlabs/emteqvr-unity/releases)

Highly Precise, Continuous, Long-Term Monitoring of Skin Electrical Resistance by Nanomesh Electrodes.

The transepidermal water loss has been widely used as a method for directly evaluating the barrier function of the stratum corneum of the skin. However, transepidermal water loss could not be measured continuously for a long period of time, and there were no reports of continuous monitoring of skin barrier functions. Here, a method is reported to continuously monitor the skin electrical resistance by nanomesh electrodes for a long period of time while maintaining the natural skin condition that does not inhibit water evaporation. Simultaneous measurements of the skin electrical resistance by nanomesh electrodes and transepidermal water loss exhibits a linear fit with a high negative correlation. Furthermore, dynamics of skin physiological functions are successfully visualized by monitoring of the skin electrical resistance by nanomesh electrodes for 30 h in daily life.

Garment embedded sweat-activated batteries in wearable electronics for continuous sweat monitoring

Thin, soft, and skin-integrated electronic system has great advantages for realizing continuous human healthcare monitoring. Here, we report an ultra-thin, flexible, and garment-based microelectronics powered by sweat-activated batteries (SABs) and applications of powering biosensors and microelectronic systems for real time sweat monitoring. The SAB cell is ultra-thin (1.25 mm) with excellent biocompatibility. The SAB has good electricity output with high capacity (14.33 mAh) and maximum power density (3.17 mW cm−2) after being activated by the sweat volume of 0.045 mL cm−2, which could continuously power 120 light emitting diodes over 3 h. The outputs could maintain stable after repeatable bending. Wireless microelectronics system could be continuously powered by the SABs for 3 h to monitor sweat and physiological information, including sweat Na+ concentration, pH, and skin impedance. The reported integrated system provides a potential for solving the power issues of flexible wearable electronics and realizing personalized medicine.

Analgesic Effects of Interferential Current Therapy: A Narrative Review.

Background and Objectives: Transcutaneous electrical stimulation of low- and medium-frequency currents is commonly used in pain management. Interferential current (IFC) therapy, a medium frequency alternating current therapy that reportedly reduces skin impedance, can reach deeper tissues. IFC therapy can provide several different treatment possibilities by adjusting its parameters (carrier frequency, amplitudemodulated frequency, sweep frequency, sweep mode or swing pattern, type of application (bipolar or quadripolar), time of application and intensity). The objective of this review article is to discuss the literature findings on the analgesic efficacy of IFC therapy. Conclusions: According to the literature, IFC therapy shows significant analgesic effects in patients with neck pain, low back pain, knee osteoarthritis and post-operative knee pain. Most of the IFC parameters seem not to influence its analgesic effects. We encourage further studies to investigate the mechanism of action of IFC therapy.

Measurement of Skin Impedance, Using ECG Electrodes, to Monitor Skin Barrier Function of Skin Subjected to Static Pressure

Measurement of Skin Impedance, Using ECG Electrodes, to Monitor Skin Barrier Function of Skin Subjected to Static Pressure

Testing and analysis of nanoparticles-based textrodes for physiological signals

The different kinds of electrodes to monitor the physiological parameters like heart rate, respiration rate, blood pressure, temperature etc. have become inevitable in the healthcare sector. The use of surface electrodes may be allergic to the skin, and the glue used here gets dehydrated over some time. Moreover, surface degradation of electrodes leads to poor acquisition of signal. Hence, the present-day monitoring systems fail to provide a high level of comfort to the users. To make the continuous monitoring system to be more reliable, textile-based wearable electrodes (textrodes) for ECG measurement device is proposed. The fabric in the textile electrode must be conductive to acquire the biosignals. The textiles are made conductive by coating them with a silver (Ag) and copper (Cu) nanoparticles. The poly (3,4-ethylene dioxythiophene) polystyrene sulfonate (PEDOT: PSS) solution is also used to make the fabric conductive. Both are blended at certain ratios to enhance better conductivity. Silver nanoparticles and copper nanoparticles are produced by chemical reduction and solution reduction methods respectively. In both processes, sodium borohydride is used as a reducing agent. The presence of Ag and Cu nanoparticles is confirmed by UV and XRD analysis. The obtained UV range for silver and copper nanoparticles are 405 nm and 545 nm respectively. The skin impedance of the commercially available disposable electrodes offers 4KΩ. Based on experimentation, PEDOT: PSS coated cotton fabric offers the lowest impedance; thereby low signal to noise ratio (SNR) is achieved while acquiring ECG signal in a real-time environment. Followed by PEDOT: PSS, Ag and Cu coated cotton fabrics offer better impedance and SNR. The application of textrodes can be expanded continuously to meet people’s activity where the electronic product is expected to be integrated with garments as so thin and lightweight.

Study the Changes of Bioelectrical Skin Impedance of Human body Associated with Different Physiological Parameters

Bioelectrical Impedance Plethysmography, in other hand Galvanic Skin Response (GSR) of living system specially for human body is deal with great importance as it changes with different physiological parameters and help to predict the different kind of disease like diabetes mellitus, human mental stress etc. This changing pattern also varies with the human ages and life styles. In this study we have collected the GSR values of two groups of people one is young generation under 20-25 years old and group is middle age under 40-50 years old. The GSR values were collected by using Grove-GSR Sensor with Arduino Uno. The individual’s data was analysed in Mat-lab and the statistical parameters like standard deviation and mean of the extracted datasets was calculated respectively and documented. The statistical parameters from the changing pattern of GSR clearly indicate that this changing is fully associated with the different physiological parameters and different ages which indirectly deal with great significance for pre identification of human diseases.

Me-Doped Ti-Me Intermetallic Thin Films Used for Dry Biopotential Electrodes: A Comparative Case Study.

In a new era for digital health, dry electrodes for biopotential measurement enable the monitoring of essential vital functions outside of specialized healthcare centers. In this paper, a new type of nanostructured titanium-based thin film is proposed, revealing improved biopotential sensing performance and overcoming several of the limitations of conventional gel-based electrodes such as reusability, durability, biocompatibility, and comfort. The thin films were deposited on stainless steel (SS) discs and polyurethane (PU) substrates to be used as dry electrodes, for non-invasive monitoring of body surface biopotentials. Four different Ti–Me (Me = Al, Cu, Ag, or Au) metallic binary systems were prepared by magnetron sputtering. The morphology of the resulting Ti–Me systems was found to be dependent on the chemical composition of the films, specifically on the type and amount of Me. The existence of crystalline intermetallic phases or glassy amorphous structures also revealed a strong influence on the morphological features developed by the different systems. The electrodes were tested in an in-vivo study on 20 volunteers during sports activity, allowing study of the application-specific characteristics of the dry electrodes, based on Ti–Me intermetallic thin films, and evaluation of the impact of the electrode–skin impedance on biopotential sensing. The electrode–skin impedance results support the reusability and the high degree of reliability of the Ti–Me dry electrodes. The Ti–Al films revealed the least performance as biopotential electrodes, while the Ti–Au system provided excellent results very close to the Ag/AgCl reference electrodes.

A Novel Biosensor and Algorithm to Predict Vitamin D Status by Measuring Skin Impedance.

The deficiency and excess of vitamin D cause various diseases, necessitating continuous management; but it is not easy to accurately measure the serum vitamin D level in the body using a non-invasive method. The aim of this study is to investigate the correlation between vitamin D levels, body information obtained by an InBody scan, and blood parameters obtained during health checkups, to determine the optimum frequency of vitamin D quantification in the skin and to propose a vitamin D measurement method based on impedance. We assessed body composition, arm impedance, and blood vitamin D concentrations to determine the correlation between each element using multiple machine learning analyses and an algorithm which predicted the concentration of vitamin D in the body using the impedance value developed. Body fat percentage obtained from the InBody device and blood parameters albumin and lactate dehydrogenase correlated with vitamin D level. An impedance measurement frequency of 21.1 Hz was reflected in the blood vitamin D concentration at optimum levels, and a confidence level of about 75% for vitamin D in the body was confirmed. These data demonstrate that the concentration of vitamin D in the body can be predicted using impedance measurement values. This method can be used for predicting and monitoring vitamin D-related diseases and may be incorporated in wearable health measurement devices.