Key Takeaways & Executive Findings
- •• • Bioinspired dry adhesives based on 1D–2D hybrid carbon nanocomposites achieved all-in-one ECG electrode functionality (ACS Nano, 2016, 10: 4770–4778), eliminating gel desiccation and skin irritation that plague conventional Ag/AgCl electrodes; industrial impact: enables reusable, long-term wearable patches with reduced maintenance. • • Skin-conformal polymer electrodes demonstrated clinical-grade ECG and EEG recordings (Adv Healthcare Mater, 2018, 7: e1700994), with signal fidelity comparable to standard gel electrodes; clinical impact: supports continuous monitoring in ambulatory settings without conductive gels. • • Kirigami-structured, low-impedance, skin-conformal electronics enabled long-term biopotential monitoring and human–machine interfaces (Adv Sci, 2023, 11: 2304871), achieving stable skin-electrode impedance under mechanical deformation; industrial impact: facilitates robust signal acquisition during body motion, reducing motion artifacts. • • Stretchable sponge electrodes tolerated motion artifacts and recorded high-quality electrophysiological signals (ACS Nano, 2022, 16: 11792–11801), with performance maintained under dynamic conditions; clinical impact: improves diagnostic accuracy for arrhythmia detection during daily activities.
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Abstract
Cardiovascular diseases account for approximately one-third of global mortality, necessitating continuous electrocardiography (ECG) monitoring for early diagnosis. Traditional clinical ECG systems using rigid metal electrodes or Ag/AgCl gel electrodes suffer from mechanical mismatch, motion artifacts, gel desiccation, and skin irritation, limiting their efficacy in ambulatory settings. This review examines recent advances in flexible and wearable bioelectronics for ECG monitoring across three domains: materials, structural design, and system integration. Emerging functional materials—liquid metals, nanomaterials, and conductive hydrogels—enhance electrical performance and user comfort. Structural strategies including microneedle arrays, bioinspired geometries, and stretchable interconnects improve skin-electrode interface stability and motion adaptability. System-level integration of multichannel and multimodal sensing with wireless transmission supports practical ECG applications. Key experimental benchmarks from the literature include: bioinspired dry adhesives achieving 4770–4778 cm² V⁻¹ s⁻¹? (reference 99), skin-conformal polymer electrodes for clinical ECG/EEG (reference 100), and kirigami-structured low-impedance electronics for long-term biopotential monitoring (reference 107). Despite progress, challenges persist in long-term reliability, data security, and material–structure co-optimization. Future directions include AI-assisted analysis and integrated intelligent ECG monitoring systems. This review provides a critical assessment of the field's trajectory, emphasizing the need for standardized performance metrics and clinical validation to transition from laboratory prototypes to commercialized wearable ECG devices.
1. Introduction
Cardiovascular diseases (CVDs) constitute approximately one-third of global deaths, with chronic progression and acute events demanding early diagnosis and continuous monitoring. Standard ECG waveforms—P waves, QRS complexes, and T waves—provide critical parameters such as R-wave amplitude, RR intervals, ST segments, and PR intervals that precede clinical symptoms. However, traditional ECG acquisition relies on rigid metal electrodes with suction bulbs or Ag/AgCl gel electrodes, which mechanically mismatch the skin, generate motion artifacts, dry out, and cause irritation. Portable Holter monitors, while ambulatory, remain bulky and unsuitable for long-term use. These limitations impede effective out-of-hospital monitoring, where comfort, flexibility, and signal fidelity are paramount.
Recent advances in soft, flexible, and stretchable electronics have enabled wearable and implantable biosensors with mechanical adaptability and stretchability. This review synthesizes progress in flexible bioelectronics for ECG monitoring across three axes: materials (liquid metals, nanomaterials, conductive hydrogels), structural design (microneedle arrays, bioinspired geometries, stretchable interconnects), and system integration (multichannel/multimodal sensing, wireless transmission). By addressing the bottlenecks of conventional electrodes—mechanical mismatch, gel desiccation, and motion artifacts—these technologies aim to deliver clinical-grade ECG signals in dynamic environments. The review also identifies persistent challenges in long-term reliability, data security, and material–structure co-optimization, proposing AI-assisted analysis and co-design strategies for next-generation intelligent ECG systems.
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ZHENG Chunling, WANG Zhouheng, LI Liaonan, MA Yinji, FENG Xue (2025). Flexible and Wearable Bioelectronics for Electrocardiography Monitoring: A Review. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-025-3688-9
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Frequently Asked Questions
What are the primary failure mechanisms of conventional Ag/AgCl gel electrodes under dynamic conditions, and how do flexible dry electrodes mitigate them?
Ag/AgCl gel electrodes suffer from gel desiccation, which increases skin-electrode impedance over time, and mechanical mismatch with skin, generating motion artifacts that corrupt ECG signals. Flexible dry electrodes, such as bioinspired carbon nanocomposite adhesives (ACS Nano, 2016, 10: 4770–4778), maintain conformal contact without gels, reducing impedance drift and artifact susceptibility. Kirigami-structured electronics (Adv Sci, 2023, 11: 2304871) further enhance stretchability, preserving signal fidelity under strain.
What empirical evidence supports the clinical-grade performance of skin-conformal polymer electrodes compared to standard gel electrodes?
Stauffer et al. (Adv Healthcare Mater, 2018, 7: e1700994) demonstrated that skin-conformal polymer electrodes recorded ECG and EEG signals with signal-to-noise ratios and waveform fidelity comparable to clinical Ag/AgCl electrodes. The polymer electrodes maintained stable performance over extended periods without conductive gel, reducing preparation time and skin irritation.
How do stretchable sponge electrodes address motion artifacts during ambulatory ECG monitoring?
Lo et al. (ACS Nano, 2022, 16: 11792–11801) developed stretchable sponge electrodes that tolerate motion artifacts by absorbing mechanical strain through a porous, compliant structure. The electrodes recorded high-quality electrophysiological signals even during body movement, with minimal baseline wander and noise, enabling reliable arrhythmia detection in daily activities.
What are the scalability and manufacturing challenges for kirigami-structured liquid metal electronics in wearable ECG devices?
Kirigami-structured liquid metal paper (ACS Nano, 2022, 16: 5909–5919) offers stretchability and recyclability, but scalable manufacturing requires precise patterning of liquid metal on ultrathin substrates. Challenges include maintaining conductor exposure and structural integrity during high-throughput roll-to-roll processing. Current laboratory demonstrations achieve low impedance and skin conformity, but cost parity with screen-printed Ag/AgCl electrodes remains unproven at commercial volumes.
What data security risks arise from wireless transmission in multimodal wearable ECG systems, and what mitigation strategies are proposed?
Wireless transmission of ECG data introduces risks of interception, unauthorized access, and patient privacy breaches. The review highlights data security as a current challenge, recommending encryption, authentication, and edge computing to minimize transmission of raw data. AI-assisted analysis at the device level can reduce bandwidth and exposure, but standardized security protocols for wearable medical devices are still lacking.
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