A CNT-PDMS wearable device for simultaneous measurement of wrist pulse pressure and cardiac electrical activity

Abstract Simultaneous measurement of multi-physiological signals can provide effective diagnosis and therapeutic assessment of diseases. This paper reports a carbon nanotube (CNT) - Polydimethylsiloxane (PDMS) - based wearable device with piezo-resistive and voltage-sensing capabilities for reliably capturing wrist pulse pressure and cardiac electrical signal. The layout of sensing elements in the device was guided by analyzing strain distribution and electric field distribution for minimizing the interference between wrist pulse and cardiac electric activity during measurement. Each device was preconditioned under the strain of 20% until the resistance change of the device reached equilibrium. After preconditioning, the relationship between the resistance change and the pressure was calibrated, which determined the device sensitivity to be 0.01 Pa−1 and the linear pressure range covered by the device to be 0.4 kPa to 14.0 kPa. Mechanisms of CNT-PDMS for sensing strain and sensing electrical pulse were explored by scanning electron microscopy (SEM) and equivalent circuit modeling. The device was applied to monitor the wrist pulse and ECG signals of volunteers during the recovering process after physical exercises.