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 struc-ture 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 af-ter 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.