Wearable Kirigami‐Apertured Capacitive Sensors for Continuous Cardiac Volumetric Monitoring

Continuous cardiac volumetric monitoring remains challenging because clinical imaging is not readily accessible and most wearable sensors estimate cardiac volume indirectly through proxy measurements rather than direct measurement. Wearable ultrasound enables direct cardiac monitoring but is constrained by its form factor and power demands. This study introduces a wearable kirigami‐apertured carbon nanotube‐paper composite (K‐CPC) capacitive sensor for cardiac volumetric monitoring. A novel kirigami process creates a central aperture in the nanocomposite electrode, forming cantilever‐like conductive fibers along the aperture rim. This aperture concentrates and confines the electric fields, enhancing sensitivity and lateral resolution. The enhanced sensing performance enables detection of localized subsurface cardiac boundary displacements driven by volumetric changes. When configured as an array, the K‐CPC sensors provide spatially and depth‐resolved mapping of a cardiac chamber, such as changes in left ventricular (LV) volume. Integrated with a machine learning (ML) model, the system continuously estimates LV volume with a mean absolute error of 9.4 mL. It further derives key cardiac parameters, including stroke volume, cardiac output, and ejection fraction during motion. This work establishes an electrode engineering strategy for wearable, low‐power, and motion‐tolerant cardiac volumetric monitoring, providing a pathway toward continuous hemodynamic assessment beyond clinical settings.