Search Results (54)

This study presents the development of a proof of concept, functional hydrogel interface designed for the acquisition of physiological signals, such as electrocardiogram (ECG) and electromyography (EMG). The hydrogel is synthesized using chitosan extracted from the shells of Tenebrio molitor larvae through a sustainable acid–alkaline protocol, blended with glycerol, polyvinyl alcohol (PVA), and ionized with NaCl to enhance conductivity. The resulting hydrogel membranes were cast and cut into circular shapes to provide a uniform contact geometry. The fabrication process yielded flexible membranes exhibiting ionic conductivity and partial surface conformity and handling stability. The extracted chitosan was characterized by Fourier-transform infrared spectroscopy (FTIR), degree of deacetylation (DDA), and molecular weight determination. Mechanical characterization included compression and tensile testing, while electrical characterization was performed through impedance spectroscopy and comparison with a commercial hydrogel interface. Functional evaluation was conducted through ECG and EMG signal acquisition under controlled experimental conditions. Preliminary in situ ECG and EMG recordings demonstrated successful signal acquisition using the proposed hydrogel interface. Future work may further investigate the mechanical and electrical behavior of the hydrogel under broader experimental conditions, as well as the optimization of the hydrogel formulation and extended physiological signal acquisition. Studies may help further characterize its potential as a chitosan-based bio interface material for bioelectrical sensing applications. Full article

Background: Anthracycline- and taxane-based chemotherapy regimens are widely used in the treatment of breast cancer; however, their effects on body composition and fluid distribution are not fully elucidated. Conventional assessment methods are often insufficient to distinguish true tissue changes from treatment-related fluid shifts. The primary objective of this study was to evaluate longitudinal changes in body composition and fluid distribution during chemotherapy in breast cancer patients using bioelectrical impedance spectroscopy. The secondary objective was to investigate the impact of anthracycline and docetaxel exposure on these changes and to identify patterns suggestive of masked sarcopenia. Methods: This prospective, single-center, longitudinal observational study was conducted between October 2024 and October 2025. Follow-up assessments at 3 and 6 months were completed by October 2025. A total of 51 female breast cancer patients undergoing systemic chemotherapy were evaluated using multifrequency bioelectrical impedance spectroscopy (BCM^®). Measurements were performed at baseline, 3 months, and 6 months. Changes in total body water (TBW), extracellular water (ECW), intracellular water (ICW), extracellular-to-intracellular water ratio (E/I), lean tissue mass (LTM), adipose tissue mass (ATM), and volume status were analyzed longitudinally and according to treatment exposure. Results: The cohort consisted of 51 women (median age, 55 years), of whom 70.6% were postmenopausal, and the majority had stage II–III disease. While TBW remained stable, significant alterations in fluid distribution and body composition were observed. ECW increased, and ICW decreased, resulting in a significant rise in the E/I ratio. LTM declined significantly, particularly during the first 3 months, whereas ATM showed a gradual increase. Volume status increased progressively over time, indicating fluid accumulation. Anthracycline exposure was associated with greater reductions in LTM, while docetaxel treatment was linked to significant increases in extracellular fluid and volume, especially during the 3–6-month interval. At 6 months, a median increase of +1100 mL in volume was observed alongside a decrease in muscle mass (−1.4 kg), consistent with a pattern of masked sarcopenia. Conclusions: Chemotherapy in breast cancer patients is associated with concurrent muscle loss and fluid redistribution, which may obscure clinically relevant changes in body composition. Bioelectrical impedance spectroscopy enables differentiation between fluid and tissue compartments and provides a more accurate assessment than conventional methods. Early recognition of these changes may facilitate timely nutritional support and appropriate fluid management strategies. Full article

Total body water (TBW) undergoes substantial physiological expansion during pregnancy, reflecting coordinated cardiovascular, renal, and endocrine adaptations required to support maternal metabolism, uteroplacental perfusion, and fetal growth. These changes involve not only an overall increase in body water but also shifts in the distribution of extracellular water (ECW) and intracellular water (ICW), which influence maternal body composition, the interpretation of biochemical biomarkers affected by hemodilution, and pregnancy-related clinical outcomes. Despite its physiological and clinical relevance, the regulation and assessment of body-water compartments during pregnancy remain insufficiently integrated within nutritional and clinical research. This narrative review synthesizes current knowledge on the physiological regulation of TBW and its compartments across gestation and provides a critical analysis of the methodological approaches used to assess body-water distribution in pregnant populations. We review the mechanisms underlying plasma volume expansion, interstitial fluid accumulation, and tissue hydration, and discuss their implications for fetal growth, hypertensive disorders of pregnancy, and gestational diabetes mellitus. We also examine the principles, strengths, and limitations of the main techniques used to assess TBW and body-water compartments during pregnancy. Isotope dilution using stable isotopes (²H₂O and H₂¹⁸O) remains the reference method for TBW assessment, whereas bioelectrical impedance-based approaches, including bioelectrical impedance analysis (BIA), bioelectrical impedance spectroscopy (BIS), and bioelectrical impedance vector analysis (BIVA), offer practical alternatives for longitudinal monitoring of fluid redistribution during gestation. By integrating physiological and methodological perspectives, this review provides a framework for understanding body-water dynamics during pregnancy and for selecting appropriate approaches to assess maternal body composition and hydration. Full article

Electric fields (EFs) have emerged as effective, non-chemical tools for modulating microbial populations in complex matrices such as wastewater. This review consolidates current advances on EF-induced alterations in microbial structures and functions, focusing on both vegetative cells and spores. Key parameters affected include membrane thickness, transmembrane potential, electrical conductivity, and dielectric permittivity, with downstream impacts on ion homeostasis, metabolic activity, and viability. Such bioelectrical modifications underpin EF-based detection methods—particularly impedance spectroscopy and dielectrophoresis—which enable rapid, label-free, in situ microbial monitoring. Beyond detection, EFs can induce sublethal or lethal effects, enabling selective inactivation without chemical input. This review addresses the influence of field type (DC, AC, pulsed), intensity, and exposure duration, alongside limitations such as species-specific variability, heterogeneous environmental conditions, and challenges in achieving uniform field distribution. Emerging research highlights the integration of EF-based platforms with biosensors, machine learning, and real-time analytics for enhanced environmental surveillance. By linking microbiological mechanisms with engineering solutions, EF technologies present significant potential for sustainable water quality management. Their multidisciplinary applicability positions them as promising components of next-generation wastewater monitoring and treatment systems, supporting global efforts toward efficient, adaptive, and environmentally benign microbial control strategies. Full article

Lipedema is a chronic, progressive adipose connective tissue disorder characterized by symmetrical, disproportionate fat accumulation, typically affecting the lower extremities and arms, accompanied by pain, swelling, and a sensation of heaviness. This study introduces intermediate Stages 1.5 and 2.5 to the established lipedema classification (Stages 1, 2 and 3), and other affected areas, based on physical examination, a questionnaire, and photographic documentation. Bioelectrical Impedance Spectroscopy (BIS) was employed to quantify total body water (TBW) across stages. A significant and linear increase in BMI was observed from Stage 1 to 3, correlating with increased reported pain and heaviness in the thighs, calves, and upper arms. Systemic symptoms of brain fog, debilitating fatigue, and hypothermia were significantly prevalent. TBW demonstrated a significant, stage-dependent increase in the lower extremities. Adipose tissue accumulation over the knees and feet significantly increased with lipedema stage. In contrast, shin involvement was evident in early stages and remained consistently elevated throughout later stages. Skeletal Muscle Mass (SMM) exhibited a significant increase across lipedema stages, positively correlating with fat mass (FM) in Stage 3. This study elucidates previously underrecognized clinical features and distribution patterns of lipedema, offering a refined staging system to improve understanding of its progression and burden. Full article

Background: Bioelectrical impedance measurement is a technique used in engineering (development of different wearable biosensors with diverse applications), in the medical field (health monitoring and diagnosis), and in biomedical research (fundamental and applied). Problem: despite its long history and existence of standardized techniques, measurement results can often be unreliable and plagued by high variance (intra- and inter-subject measurement), which can distort the correct interpretation of the results. Methods: we have reviewed bioelectrical impedance measurements from both engineering and medical research teams over the past 60 years, with a focus on factors that might influence the skin–electrode interface. Results: We identified 40 confounding factors in 10 different categories, some of which are sometimes overlooked in applied research, and we propose mitigation strategies for each one. Full article

Based on the photoconductive effect of photosensitive films, a designed light pattern was projected onto a hydrogenated amorphous silicon (a-Si:H) photosensitive chip to generate virtual light-induced electrodes for cellular electrical detection. To obtain high-quality cellular signals, this study aims to explore the effect of electrical excitation on a-Si:H photosensitive chip. Firstly, the electrochemical impedance spectroscopy (EIS) and volt-ampere characteristics of the a-Si:H photosensitive chip were characterized. EIS data were fitted to extract equivalent circuit models (ECMs) for both the chip and system. Then analog experiments were performed to verify the ECMs, and the results were consistent with the circuit simulation. Finally, applied alternating current (AC) or direct current (DC) signals to the chip and recorded the electrical signals of the cultured cardiomyocytes on the a-Si:H photosensitive chip. The results demonstrated that applying a high-frequency small AC signal to the chip reduced the background noise of the system by approximately 85.1%, and applying a DC bias increased the amplitude of the detection signal by approximately 142.7%. Consequently, the detection performance of the a-Si:H photosensitive chip for weak bioelectrical signals was significantly enhanced, advancing its applicability in cellular electrophysiological studies. Full article

Strawberry post-harvest losses are estimated at 50%, due to improper handling and harvest timing, necessitating the use of non-invasive methods. This study develops a non-invasive in situ bioelectrical spectroscopy for strawberry peduncles. Based on traditional assessments and invasive metrics, 100 physiologically ripe (PR) and 100 commercially mature (CM) strawberries were distinguished. Spectra from their peduncles were measured from 1 kHz to 1 MHz, collecting four parameters (magnitude (Z(f)), phase angle (θ(f)), resistance (R(f)), and reactance (X(f))), resulting in 80,000 raw data points. Through systematic spectral preprocessing, Bode and Cole–Cole plots revealed a distinction between PR and CM strawberries. Frequency selection identified seven key frequencies (1, 5, 50, 75, 100, 250, 500 kHz) for deriving 37 engineered features from spectral, extrema, and derivative parameters. Feature selection reduced these to 6 parameters: phase angle at 50 kHz (θ (50 kHz)); relaxation time (τ); impedance ratio (|Z_1k/Z_250k|); dispersion coefficient (α); membrane capacitance (Cm); and intracellular resistivity (ρi). Four algorithms (TabPFN, CatBoost, GPC, EBM) were evaluated with Monte Carlo cross-validation with five iterations, ensuring robust evaluation. CatBoost achieved the highest accuracy at 93.3% ± 2.4%. Invasive reference metrics showed strong correlations with bioelectrical parameters (r = 0.74 for firmness, r = −0.71 for soluble solids). These results demonstrate a solution for precise harvest classification, reducing post-harvest losses without compromising marketability. Full article

The aim of this study was to enhance and maintain bioelectricity generation from distillery spent wash using a microbial fuel cell (MFC). Electrode materials play a critical role in the generation of bioelectricity in MFCs. Utilizing double oxidant-treated carbon felts in MFC applications increased current density to 749.56 mA/m² and increased peak power density to 125.23 mW/m². Electrochemical impedance spectroscopy (EIS) analysis further verified the improved electrocatalytic activity observed in the oxidized carbon felt, consistent with the findings from cyclic voltammetry (CV) and polarization curves, thereby confirming the enhanced performance of the oxidized carbon felt electrode. Overall, the study highlights the significance of electrode morphology and surface modifications in influencing microbial adhesion, electron transport, and the overall efficiency of fuel cells using distillery spent wash as a substrate. Full article

This paper presents a highly efficient, low-power, compact mixed-signal sinusoidal current generator (CG) integrated circuit (IC) designed for bioelectrical impedance spectroscopy (BIS) with low total harmonic distortion (THD). The proposed system employs a 9-bit sine wave lookup table (LUT) which is simplified to a 4-bit data stream through a third-order digital delta–sigma modulator (ΔΣM). Unlike conventional analog low-pass filters (LPF), which statically limit bandwidth, the finite impulse response (FIR) filter attenuates high-frequency noise according to the operating frequency, allowing the frequency range of the sinusoidal signal to vary. Additionally, the output of the FIR filter is applied to a 6-bit capacitive digital-to-analog converter (CDAC) with data-weighted averaging (DWA), enabling dynamic capacitor matching and seamless interfacing. The sinusoidal CG IC, fabricated using a 65 nm CMOS process, produces a 5 μA amplitude and operates over a wide frequency range of 0.6 to 20 kHz. This highly synthesizable CG achieves a THD of 0.04%, consumes 19.2 μW of power, and occupies an area of 0.0798 mm². These attributes make the CG IC highly suitable for compact, low-power bio-impedance applications. Full article

This paper proposes a method for localized damage detection in tomato, with the objective of enabling the detection of bruises prior to sorting. Bioimpedance spectroscopy technology is employed to assess the extent of localized damage in tomato. An equivalent circuit model is constructed, and the impedance spectroscopy data are obtained by developing a local damage measurement platform for tomatoes using a self-designed circular four-electrode BIS sensor. The electrical parameters are then extracted by fitting the constructed equivalent circuit model to the tomato data. Subsequently, we analyze the variation rules of the electrical parameters in different damage levels. To reduce the dimensionality of the features, including biological variables, fitted electrical parameters, and tomato ripeness, we employ Spearman feature selection. We then classify the reduced features by combining the advantages of the support vector machine and the artificial neural network. The results demonstrate that the designed circular four-electrode BIS sensor can non-destructively measure localized damage conditions in tomato. A localized damage measurement platform for tomatoes has been constructed using this sensor. A comparison of the impedance measurements obtained using the designed circular four-electrode BIS sensor with those obtained using a needle sensor proposed by previous scholars revealed that both sensors exhibited a decrease in impedance with increasing damage degree. This finding indicates that the designed circular four-electrode BIS sensor is an effective tool for characterizing damage conditions in tomatoes. The design of the tomato circular four-electrode BIS sensor is an effective means of characterizing tomato damage. The Spearman-SVM-ANN damage classification algorithm, based on the Spearman feature selection, effectively classified tomato damage with a 98.765% accuracy rate. The findings of this study provide a reference for the grading and transportation of tomatoes after harvest. Full article

The pitting qualities of lymphoedema tissue change with disease progression. However, little is known about the underlying tissue response to the pitting test or the tissue characteristics that enhance or resist indentation. The pitting test is currently unstandardised, and the influence of test technique on pitting outcomes is unknown. Understanding how tissue reacts to applied pressure will build evidence for the standardisation of the pitting test. Ninety pitting test sites from fifteen women with unilateral breast cancer-related lymphoedema were evaluated using high-frequency ultrasound (HFUS), bioelectrical impedance spectroscopy (BIS), and limb volume measures. Three sites on each lymphoedema and non-lymphoedema arm were subject to a 60-s (s) staged pitting test, with changes in tissue features captured with ultrasound imaging before, throughout, and after the pitting test. Pitting qualities of tissues varied greatly, with lymphoedema sites pitting more frequently (p < 0.001) with greater depth (p < 0.001) and requiring a longer recovery time (p = 0.002) than contralateral unaffected tissue. Pitting is not solely attributable to oedema volume. Non-structural and structural characteristics of dermal and subcutaneous layers also influence tissue responses to sustained pressure. To enhance the validity and reliability of pitting assessment, a 60 s staged pitting test with an observation of tissue recovery is recommended for lymphoedema presentations. Full article

Lymphoedema tissue is characterised by excess free fluid and structural changes to the extracellular matrix (ECM) in the form of fibrotic and fatty deposition. These tissue characteristics are integral to the assessment of lymphoedema progression; however, clinicians and researchers often focus on changes in the free fluid, volume and function of lymphatic vasculature to inform practice. Subsequently, little is known about the effect of clinical interventions on lymphoedema tissue composition. This article presents a novel approach to classify lymphoedema tissue. The Localised Objective Characterisation Assessment of Lymphoedema (LOCAL) classification combines diagnostic and clinically meaningful objective assessment thresholds to infer lymphoedema pathophysiological changes in tissue layers. The LOCAL classification method was verified using data from fifteen women with unilateral breast cancer-related lymphoedema who were evaluated at three sites on each arm using high-frequency ultrasound (HFUS), bio-electrical impedance spectroscopy (BIS) and volume measurements. Participants exhibited an uneven distribution of volume between the proximal and distal segments of the arm (p = 0.023), with multiple tissue compositional categories observed across sites on the same limb (p < 0.001). The LOCAL method demonstrated utility in categorising a diverse range of lymphoedema tissue layer changes beyond what can be ascertained from whole-limb measures. Full article

Bioimpedance is a diagnostic sensing method used in medical applications, ranging from body composition assessment to detecting skin cancer. Commonly, discrete-component (and at times integrated) circuit variants of the Howland Current Source (HCS) topology are employed for injection of an AC current. Ideally, its amplitude should remain within 1% of its nominal value across a frequency range, and that nominal value should be programmable. However, the method’s applicability and accuracy are hindered due to the current amplitude diminishing at frequencies above 100 kHz, with very few designs accomplishing 1 MHz, and only at a single nominal amplitude. This paper presents the design and implementation of an adaptive current source for bioimpedance applications employing automatic gain control (AGC). The “Adaptive Howland Current Source” (AHCS) was experimentally tested, and the results indicate that the design can achieve less than 1% amplitude error for both 1 mA and 100 µA currents for bandwidths up to 3 MHz. Simulations also indicate that the system can be designed to achieve up to 19% noise reduction relative to the most common HCS design. AHCS addresses the need for high bandwidth AC current sources in bioimpedance spectroscopy, offering automatic output current compensation without constant recalibration. The novel structure of AHCS proves crucial in applications requiring higher β-dispersion frequencies exceeding 1 MHz, where greater penetration depths and better cell status assessment can be achieved, e.g., in the detection of skin or breast cancer. Full article

Bioimpedance sensing is widely used across a spectrum of biomedical applications. Among the different system architectures for measuring tissue impedance, synchronous detection or demodulation (SD) stands out for its lock-in amplifier utilising in-phase (I) and quadrature (Q) demodulation signals to derive real and imaginary impedance components. Typically, the current injected into the tissue is controlled by a voltage-controlled current source (VCCS). However, the VCCS can introduce phase shifts leading to discrepancies in real/imaginary outputs, especially at the highest end of the operating frequency bandwidth. Such discrepancies can significantly impact diagnostic accuracy in applications reliant on precise tissue phase profiling, such as cancer and neuromuscular evaluations. In the present work, we propose an automatic phase error compensation stage for bioimpedance measurement systems to minimise this systematic error. Our experimental findings demonstrated a considerable reduction in phase error, with the Phase Error Compensated Synchronous Detection (PECSD) system exhibiting a maximum phase error of 2° (≤5% error) compared with the uncompensated SD system where error exceeded 20%. The improvements made by our proposed SD system hold great potential for enhancing the accuracy of impedance measurements, particularly in clinical diagnosis and disease detection. Full article