Stretchable and Highly Sensitive Strain Sensor Based on a 2D MXene and 1D Whisker Carbon Nanotube Binary Composite Film.

We fabricate a 2D MXene and 1D whisker carbon nanotube (WCNT) binary composite, where the MXene layer was sandwiched between two WCNT films, and assemble a flexible resistive-type strain sensor using this composite film. The deformations of the conductive networks trigged by the external mechanical stimuli cause the variations of the number of effective conductive paths, which result in the changes of the electric resistance of composite films. The resistances of the MXene/WCNT composite films that carry the strain information about the external mechanical stimuli are monitored. In addition, we demonstrate the role of the conductive MXene networks and the WCNT networks in responding to the external mechanical stimuli. The MXene networks dominate the variations of the resistance of the strain sensors in the low strain range. In the middle strain range, the deformations of both the MXene networks and the WCNT networks are responsible for the variations of the resistance of the strain sensors. In the high strain range, an "island bridge" like conductive network forms, where MXenes act as islands and WCNTs connect the adjacent MXene islands like bridges. The multiple types of conductive networks lead to the high sensitivity of the MXene/WCNT-based strain sensors over a wide strain range and a wide response window. This stretchable strain sensor exhibits good performances in detecting human muscle motions with a wide strain range and has the potentials of being applicable to wearable electronics.