3D Printed, Solid-State Conductive Ionoelastomer as a Generic Building Block for Tactile Applications

Shaping soft and conductive materials into preferential architectures via 3D printing is highly attractive for numerous applications ranging from tactile devices to bioelectronics. A landmark type of soft and conductive materials is hydrogels/ionogels. However, 3D-printed hydrogels/ionogels still suffer from a fundamental bottleneck: limited stability in their electrical-mechanical properties caused by the evaporation and leakage of liquid within hydrogels/ionogels. Although photocurable liquid-free ion-conducting elastomers can circumvent these limitations, the associated photocurable process is cumbersome and hence the printing quality is relatively poor. Herein, a fast photocurable, solid-state conductive ionoelastomer (SCIE) is developed that enables high-resolution 3D printing of arbitrary architectures. The printed building blocks possess many promising features over the conventional ion-conducting materials, including high resolution architectures (even ≈50 µm overhanging lattices), good Young's modulus (up to ≈6.2 MPa), and stretchability (fracture strain of ≈292%), excellent conductivity tolerance in a wide range of temperatures (from -30 to 80 °C), as well as fine elasticity and antifatigue ability even after 10 000 loading-unloading cycles. It is further demonstrated that the printed building blocks can be programmed into 3D flexible tactile sensors such as gyroid-based piezoresistive sensor and gap-based capacitive sensor, both of which exhibit several times higher in sensitivity than their bulky counterparts.