Screen-printed highly mechanical and conductive flexible electrodes based on chiral structure with negative Poisson’s ratio

Stretching and bending are the two most prevalent deformations during the service of wearable electronic devices that increase the demand for conductivity. However, the fabrication of fully flexible electronics with both satisfactory mechanical properties and conductivity remains a considerable technological challenge. In this paper, a flexible electrode of polyamide (PA) substrate, with negative Poisson’s ratio structure (NPR), is manufactured based on chiral structure by synergistically combining structural optimization and screen-printed technology. Results from finite element analyses (FEA) and experiment tests demonstrate that flexible electrodes with optimized U-shaped NPR structure can effectively boost mechanical properties (the maximum stretching and bending stresses are reduced by 67 % and 71 % respectively) and conductivity (the resistance is only 4.1 Ω at 180°, 4.5 Ω after 1000 cycles, 20.3 Ω at 20 % strain). Especially, the electrode is still conductive at a strain of 40 %. Comparing recorded electrocardiography (ECG) signals of various electrodes successfully demonstrated the electrode prepared herein has superior accuracy, good stability and great potential in long-term health monitoring (max Signal-to-Noise Ratio (SNR) can reach 34.9 dB). The strategy proposed here is expected to make major contributions to the development and application of flexible electrodes with high properties.