3D Printing of Stretchable Strain Sensor Based on Continuous Fiber Reinforced Auxetic Structure

Stretchable strain sensors play a key role in motion detection and human-machine interface functionality, and deformation control. However, their sensitivity is often limited by the Poisson effect of elastic substrates. In this study, a stretchable strain sensor based on a continuous-fiber-reinforced auxetic structure was proposed and fabricated using a direct ink writing (DIW) 3D printing process. The application of multi-material DIW greatly simplifies the fabrication process of a sensor with an auxetic structure (auxetic sensor). The auxiliary auxetic structure was innovatively printed using a continuous-fiber-reinforced polydimethylsiloxane composite (Fiber-PDMS) to balance the rigidity and flexibility of the composite. The increase in stiffness enhances the negative Poisson's ratio effect of the auxetic structure, which can support the carbon nanotube-polydimethylsiloxane composite (CNT-PDMS) stretchable sensor to produce a significant lateral expansion when stretched. It is shown that the structural Poisson's ratio of the sensor decreased from 0.42 to −0.33 at 20% tensile strain, and the bidirectional tensile strain increases the sensor sensitivity by 2.52 times (gage factor to 18.23). The Fiber-PDMS composite maintains the excellent flexibility of the matrix material. The auxetic sensor exhibited no structural damage after 150 cycles of tension and the signal output exhibited high stability. In addition, this study demonstrates the significant potential of auxetic sensors in the field of deformation control.