Hybrid Ori/Kirigami Structured Pizeoelectric Thin-Film Sensors Covered by Elastomer with Highly Directional Stretch Sensing Ability for Heartbeat Motion Monitoring

This paper proposes the cross-directional coupling negligible stretch sensor with large-area, microfeature-patterned Ori-kirigami hybrid structures embedded in the 3-dimensional elastomer layers. The key 3D Ori-kirigami features of the sensor is superior to the common planar elastomer sensors with inherently lateral deformation affected by the other orthogonal direction as a single direction stress is applied due to inherent material property. This unique sensor exhibits an almost-zero Poisson ratio and enhances the directional strain sensitivity and stretchability capabilities. The PZT thin films of the sensor core are deposited on a rigid titanium sheet with top electrodes in the X and Y directions on both sides of this rigid sheet, which gives an output corresponding to the directional stretch level. This rigid titanium sheet effectively contributes large-scale flexibility and local-scale stiffness for maintaining the resistance of the top and bottom electrodes while stretching the sensor. These origami structures can be stretched by more than 25% of its original size, while the kirigami structure increased the strain by 40%. The sensing core, comprising a thin titanium film packaged with an elastomer, offers improved isolation and elastic support to the sensor.