Printable Strain Sensing Ink with Ultra‐Low Detection Limit

ABSTRACT The preparation of flexible resistive strain sensors based on polymer composites faces significant challenges in achieving a low strain detection limit, high sensitivity and printability. Herein, a conductive polymer composite ink was developed via high‐shear mechanical dispersion of carbon black (CB) in an epoxy matrix with semiconductive aluminum‐doped zinc oxide (AZO) incorporated to reduce local carrier scattering within the conductive filler network. The formulation strategy focuses on elucidating the effects of dispersant and dispersion conditions on filler distribution and correlating the dispersion state with the rheological behavior and printability of the ink. By adjusting the composition of the conductive phases within the epoxy matrix, a synergistic percolation network is established, which effectively suppresses carrier scattering and enables stable, repeatable electrical responses under small deformation. The resulting ink exhibits reliable resistance response (∼10 με), demonstrating excellent micro‐strain sensitivity (gauge factor ∼5.6). Finite element simulations further validate the experimentally observed micro‐strain distribution in the sensing layer. Moreover, the ink could be conformally printed onto diverse substrates with excellent adhesion, highlighting its versatility and practical potential for flexible sensing. This study presents a robust micro‐strain sensing strategy based on modulating the percolating network, offering new insights for the design of high‐performance flexible strain sensors.