The thin flexible device described in a paper titled "Biodegradable and flexible arterial-pulse sensor for the wireless monitoring of blood flow" published in Nature Biomedical Engineering was designed to locally monitor blood flow after complex reconstructive surgeries involving "anastomosis", the suturing of blood vessels, such as would be the case in cardiovascular, vascular and transplantation operations.
So far, commercially existing sensor require careful fixation and also need to be removed after use, which presents an additional surgical risk. The paper describes a thin and flexible pressure sensor made entirely of biodegradable materials, which can be wrapped around arteries as small as 1mm in diameter.
Measuring only a few square millimetres, the whole device consists of a layered fringe-field capacitive sensor sensitive in both contact (the sensor is put in contact with the artery) and non-contact modes, connected to a bilayer coil structure (made of magnesium) used for data transmission through radio-frequency coupling with an external reader coil.
Here, blood flow is indirectly measured through pulse detection as the monitored artery experiences pulsatile changes of vessel diameter which can measured by the capacitive sensor. The change in capacitance results in a shift of the resonant frequency in an inductor–capacitor–resistor circuit, which is monitored wirelessly through the skin via inductive coupling, enabling battery-free operation.