Congestive heart failure (CHF) is a progressive condition wherein the heart is unable to adequately pump blood to meet the metabolic demands of the body, is a leading cause of hospitalization and mortality, and substantially degrades the quality of life of affected individuals. An effective strategy to improve survival rate is to detect early physiological changes, such as abnormal heart sounds, associated with CHF and implement treatments proactively to slow its progression. However, early CHF is highly underdiagnosed and general screening of the population remains a major challenge.
In this paper, our research team focuses on tackling this issue by developing a micro-sensor for capturing the body’s mechano-acoustic signals in a wide frequency range of DC-12 kHz and enable longitudinal study and monitoring of the cardiopulmonary system. The 2 mm × 2 mm encapsulated microsensor chip can record a wide range of vibrations on human skin, ranging from very low frequency (below 1 Hz) movements associated with the chest wall and body position to high frequency acoustic signals (up to 12 kHz) emanating from the heart and lungs. The sensor are fabricated using a unique and high-precision fabrication technique, the high aspect-ratio combined poly- and single-crystal silicon micromachining technology (HARPSS), to achieve an ultrasensitive, wideband capacitive vibration transducer. The performance of these hermetically-encapsulated sensors is not compromised by body sweat and environmental effects. Moreover, the sensor only responds to vibrations on the surface and is not susceptible to airborne acoustic noise in the environment.
We apply the sensor to demonstrate that heart rate, heart sounds, respiratory rate, lung sounds, and body motion of an individual can be simultaneously recorded in a continuous and unobtrusive manner using a single integrated sensor. Proof-of-concept studies were conducted on healthy control subjects as well as patients with preexisting conditions to monitor physiological and pathological mechano-acoustic signals emanating from the heart and lungs.
Development of such high precision sensors with a small footprint will enable us to replace bulky stethoscopes with ergonomic wearable auscultation systems in the future, that can precisely measure cardiopulmonary signals, and hence open new gateways in telemedicine and remote health monitoring. Such an integrated solution will significantly reduce fabrication cost of wearable technology, making it more accessible and affordable to the masses.