Alignment-free knitted sleeve for comprehensive cardiovascular monitoring

Cardiovascular diseases remain the leading global cause of mortality, claiming nearly 18 million lives each year. Early detection and continuous monitoring of blood pressure, vascular resistance, and cardiac performance are essential for managing chronic heart conditions. However, current consumer wearables rely heavily on optical sensors that must be placed precisely over arteries, making them highly susceptible to motion interference and misalignment. Even clinical-grade systems often depend on bulky devices or require repeated calibration. Moreover, key hemodynamic metrics such as stroke volume and systemic vascular resistance are rarely accessible outside clinical settings. Due to these challenges, there is an urgent need to develop reliable, alignment-free wearable technologies for comprehensive cardiovascular monitoring.

Researchers from The Chinese University of Hong Kong and collaborating institutes have developed a textile-based alignment-free electrophysiological sensing sleeve (TAESS), published (DOI: 10.1038/s41378-025-01088-x) in Microsystems & Nanoengineering in 2025. The study presents a knitted wearable system that integrates electrocardiography (ECG) and impedance plethysmography (IPG) to measure core cardiovascular parameters continuously. Unlike optical devices, the TAESS captures high-fidelity electrical and blood-flow signals from the upper arm without requiring precise placement, enabling simultaneous monitoring of blood pressure, stroke volume, systemic vascular resistance, and heart rate during daily activities.

The TAESS system is engineered with silver-coated conductive yarn seamlessly knitted into a breathable and stretchable textile sleeve. Its design incorporates two ECG electrodes and four IPG electrodes arranged around the upper arm to capture cardiac electrical activity and blood-flow-driven impedance changes. The textile's porous architecture ensures superior sweat permeability (37.5 mg·cm⁻²·h⁻¹), heat dissipation, and elasticity exceeding 45%, outperforming commercial electrodes. Signal-level parameters—including RR interval, QTc, pulse transit time, dZ/dt, stroke volume, and vascular resistance—are extracted through synchronized ECG-IPG waveforms.

Critically, the sleeve remains insensitive to radial rotation or axial displacement, unlike photoplethysmography devices that lose signal when not perfectly aligned with arteries. Experiments demonstrated robust ECG and IPG signal-to-noise ratios across dry, wet, stretched, and motion conditions. During controlled breathing tasks, the system accurately tracked beat-by-beat blood pressure, stroke volume, and systemic vascular resistance, achieving systolic and diastolic blood-pressure prediction RMSEs of 7.05 mmHg and 5.93 mmHg, surpassing pulse-wave-velocity and zero-baseline methods. Across 10 participants, the device maintained a mean absolute error of ~4 mmHg even after re-wearing. These capabilities establish the TAESS as a practical, alignment-free solution for comprehensive haemodynamic monitoring in real-world environments.

"Our work demonstrates that precise cardiovascular monitoring no longer requires rigid hardware or perfect sensor positioning," the study's corresponding author noted. "By integrating ECG and impedance plethysmography into a soft knitted sleeve, we enable accurate measurement of blood pressure and haemodynamic parameters even during movement, sweating, or re-wearing. This system captures fundamental physiological signals that current optical wearables cannot reliably obtain. The TAESS offers a scalable path toward continuous cardiovascular assessment, laying essential groundwork for personalized, preventive healthcare in everyday life."

The TAESS represents a major step toward next-generation wearable health technologies capable of continuous and clinically meaningful cardiovascular monitoring. Its alignment-free operation, low manufacturing cost, and textile-grade comfort make it suitable for long-term home use, chronic disease management, remote patient monitoring, and integration into smart clothing. The dual-modal physiological modeling also opens opportunities for detecting arrhythmias, assessing vascular stiffness, and tracking recovery in heart-failure patients. As future studies expand sampling rates and clinical testing, this textile-based platform could transform how blood pressure, cardiac output, and vascular dynamics are monitored, enabling more proactive and personalized cardiovascular care.