(Invited) Tunable Large-Scale Compressive Strain Sensor Based on Carbon Nanotubes/PDMS Foam Composites By Additive Manufacturing

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The compressive strain sensor is widely used as stretchable electronic, human motion detector, and health monitor due to its ability to convert large-scale mechanical deformation to the electrical signal. Carbon material reinforced polymer matrix composites are extensively studied to fabricate the strain sensor. However, there is a challenge to tune the performance of the strain sensor due to the fixed composition of the composite. In this work, we fabricated a carbon nanotube (CNT)/ polydimethylsiloxane (PDMS) compressive strain sensor with tunable mechanical and electrical performance. CNT was used as the reinforcement material due to its excellent electrical conductivity. PDMS was used as the matrix material because of its non-toxicity and flexibility. The foam structure created by the sacrificial sodium chloride (NaCl) allowed the compressive strain sensor to obtain at least 50% strain deformation. The material extrusion 3D printing (ME3DP) method was used to fabricate the complex scaffold structure due to its advantage of free design. The compressive strain sensor had a maximum gauge factor of 17.4 and work stably for at least 10000 cycles. The strain sensor was used to detect both large- and small-scale human motions due to its adjustable composition and sensitivity. We believe our method of building CNT/PDMS strain sensor with tunable performance broadens the potential on the fabrication of flexible electronic devices. Our method of using additive manufacturing to form the model also expends the routes of fabrication in a more flexible design and cost-saving method.