Electrohydrodynamic Printing of High‐Resolution Self‐Reduced Soldered Silver Nanowire Pattern for Wearable Flexible Strain Sensors

Abstract As an indispensable aspect of flexible and printed electronics, flexible strain sensors composed of silver nanowires (AgNWs) have attracted significant attention recently. However, low resolution and large wire‐wire contact resistance still impede the stability and sensitivity of AgNW‐based flexible strain sensors. Herein, self‐reduced soldered AgNW pattern is fabricated by combining the high‐resolution electrohydrodynamic (EHD) printing and joining of AgNWs. The resolution achieved by EHD printing is up to ≈20 µm. The contact resistance between AgNWs is greatly reduced by depositing Ag atoms at the AgNW junctions while EHD printing Ag ion ink on as‐prepared AgNW pattern. After self‐reduced soldering process, the sheet resistance decreases from 14.8 to 2.13 Ω sq⁻¹. This process can be conducted under room temperature and ambient conditions and requires no external assistance from heat, light, or mechanical pressing. Furthermore, the deposited Ag atoms at the junctions remarkably improve the sensitivity (gauge factor 14.5–37.9) and stability (over 5000 stretching cycles with 25% strain). This superior sensitivity and stability occur because nano‐junctions induced by the self‐reduced soldering process significantly reduce the initial resistance and enable a robust network structure. This EHD‐based technique for nanojoining of AgNWs demonstrates its potential for flexible and wearable electronics.