Wearable sensors for monitoring heart beats, blood pressure
doi:10.1038/nindia.2021.43 Published online 22 March 2021
Researchers have fabricated ultrasensitive wearable sensors that can detect delicate human motions such as frowning, gentle tapping, and bending of fingers and the wrist1.
The sensors could even monitor heart beats and blood pressure in real time, researchers from the CSIR-National Physical Laboratory in New Delhi have shown in experiments.
The sensors, they say, could potentially be used in e-skin and wearable electronics.
The scientists, led by Bipin Kumar Gupta, designed the sensors by vertically aligning carbon nanotubes in a matrix of a specific polymer on a silicon-based substrate. They then peeled off the sensors from the substrate and tested their sensing efficiency by exposing them to various strain-producing human movements.
The researchers found that the sensors could tolerate strain-induced deformations of up to 30 per cent. Under strain, the sensors stretched and their networks of carbon nanotubes broke down. Releasing the strain allowed the nanotubes to restore their original network pattern. Such deformation causes a change in electrical resistance of the sensors. This is a measurable electrical signal.
Sensitivity of the sensors increased with increases in their resistance. The sensors responded within 12 milliseconds. They retained their stability and efficiency over 10,000 cycles of strain measurement.
The sensors, when attached to a healthy young adult male, measured precisely his heart rates before and after exercise. Since the sensors could detect muscle convulsions generated by bending and relaxing the wrist, they could be used to monitor and measure hand tremors of a patient suffering from Parkinson's disease, says Gupta.
1. Paul, S. J. et al. Ultrasensitive wearable strain sensors based on a VACNT/PDMS thin film for a wide range of human motion monitoring. ACS. Appl. Mater. Interfaces. (2021) doi: https://dx.doi.org/10.1021/acsami.1c00946