3D-printed flexible, multilayered ceramic-polymer composite grid with integrated structural-self-sensing function

Piezo-polymer is widely used for pressure sensors or electromechanical transducers; and normally, it is simply designed and prepared into thin film as a force-sensing element integrated in smart structures or robots. In this paper, we report a flexible, three-dimensional multilayer composite grid complex structure containing inside electrode layers prepared totally based on direct-writing 3D printing method. The composite material is composed of a polydimethylsiloxane (PDMS) elastomer matrix and 0.55Pb (Ni1/3Nb2/3) O3-0.135PbZrO3- 0.315PbTiO3 (PNN-PZT) piezoelectric ceramic particles coated with Ag and multi-walled carbon nanotubes (1 wt% of the [email protected] ceramic powders). The 3D-printed composite grid exhibits both large piezoelectric effect (with an effect piezoelectric coefficient (d33) of 21 pC/N) and qualified mechanical performances, such as a large failure tensile strain of 150% and tensile stress of 2.2 MPa. Under a dynamic compression stress of 0.125 MPa at 3.5 Hz, a 3D-printed 7-layer composite grid (550 μm in thickness) with internal electrode layers inside could produce output voltage peak of 3 V accompanying with a peak current of 0.7 μA. In comparison with a single layer composite grid, its peak output current shows a 7-time increase, although its peak output voltage keeps unchanged under the same compression stress. This work shows that the 3D-printed multilayer composite grid exhibits the integrated structural-self-sensing function, which will bring great benefits to future artificial muscle in robots and other flexible intelligent structures.