Physics

Doppler effect

Waveform

Astronomy

Wearable computer

Engineering

Biomedical engineering

Ultrasonic testing

Ultrasound

Embedded system

Antenna (radio)

Acoustics

Materials science

Programming language

Operations management

Continuous monitoring

SIGNAL (programming language)

Computer science

Radar

Phased array

Medicine

Telecommunications

Ultrasonic sensor

Nature Biomedical Engineering

Stretchable wearable devices for the continuous monitoring of physiological signals from deep tissues are constrained by the depth of signal penetration and by difficulties in resolving signals from specific tissues. Here, we report the development and testing of a prototype skin-conformal ultrasonic phased array for the monitoring of haemodynamic signals from tissues up to 14 cm beneath the skin. The device allows for active focusing and steering of ultrasound beams over a range of incident angles so as to target regions of interest. In healthy volunteers, we show that the phased array can be used to monitor Doppler spectra from cardiac tissues, record central blood flow waveforms and estimate cerebral blood supply in real time. Stretchable and conformal skin-worn ultrasonic phased arrays may open up opportunities for wearable diagnostics. A prototype skin-conformal ultrasonic phased array enables the monitoring of physiological signals from deep tissues, as shown for the measurements of cardiac Doppler waveforms and central and cerebral blood flows.

Continuous monitoring of deep-tissue haemodynamics with stretchable ultrasonic phased arrays