Deterministic roll-contact printing of ultradense aligned nanowire arrays for high-performance flexible electronics

Semiconducting nanowires (NWs) are versatile building blocks for mechanically compliant electronics, with applications spanning sensing, displays, and neuromorphic computing. However, translating their exceptional one-dimensional transport properties into large-area device arrays requires scalable assembly methods capable of simultaneously controlling NW density, alignment, and material purity - a combination that has remained elusive. Here we report a deterministic contact roll-printing approach that overcomes this barrier, enabling highly aligned ZnO NWs arrays at record densities of up to 14 NWs/µm on flexible substrates. Replacing conventional area contact with a travelling line contact reduces mechanical stress on individual NWs while enabling continuous, large-area transfer. Parametric studies reveal the governing mechanisms of high-fidelity NW assembly, including the roles of applied force and velocity ratio in controlling density, transfer length, alignment uniformity, and suppression of donor-derived contamination. Flexible ultraviolet photodetectors fabricated across a controlled range of NW densities show that performance scales systematically with printed density. Highest-density devices achieve responsivity of up to 4000 A W⁻¹ and retain full functionality after 5000 bending cycles at 10 mm radius and 5000 twisting cycles at ±25°. This work established both a fundamental understanding of roll-contact NW assembly mechanics and a manufacturable, resource-efficient route to high-performance large-area flexible electronics.