Highly Stretchable and Wearable Strain Sensor Based on Printable Carbon Nanotube Layers/Polydimethylsiloxane Composites with Adjustable Sensitivity

Strain sensors that are capable of monitoring complex human motions with high accuracy are highly desirable for developing wearable electronics. This paper reports the fabrication of highly stretchable and sensitive multidirectional strain sensors with tunable strain gauge factors by employing a digitally controlled printer to incorporate carbon nanotube (CNT) layers into polydimethylsiloxane (PDMS) substrates. The fabricated sensors exhibit a high stretchability (up to 45%) and sensitivity with a gauge factor of 35.75. The gauge factors could be easily modulated by tuning the number of CNT printing cycles to accommodate diverse requirements. The cyclic loading-unloading test results revealed that the composite strain sensors exhibited excellent long-term durability. Particularly, in this work, for the first time, human-motion-induced strain was measured by a motion capture system and compared with the strain data obtained from the fabricated strain sensors. The deviation of strains measured by composite sensors is less than 20%, indicating the great accuracy of CNT/PDMS sensors to quantify the amount of motion-induced strain. Of significant importance is that due to the flexibility of the printing technique used, rosette-type sensors were fabricated to simultaneously measure strains along multiple axes. These superior sensing capabilities of the fabricated CNT/PDMS strain sensors give them great application potential in motion-detecting systems.