Metallic micro/nanostructured surfaces exhibit significant application potential due to their distinctive physicochemical properties. However, conventional fabrication techniques often suffer from a trade-off between production throughput and struc-tural accuracy. To address this challenge, this study presents a novel shock imprinting method based on underwater pulsed spark discharge (UPSD) induced shock waves. In this method, a DVD polycarbonate (PC) film with nano structures on its surface serves as the mold, and an aluminum foil acts as the workpiece. During the shock imprinting process, the foil is compressed into the mold via the shock wave of ultra high strain rate (~10⁷ Pa·s^-1) generated by UPSD, thereby fabricating nano structures onto the foil. Experimental results confirm the successful fabrication of micro/nano structures on aluminum foil using the proposed method.
To systematically evaluate the imprinting performance (characterized by structural fidelity and imprinting area), the influence of the water gap distance was first inves-tigated. At a fixed charging voltage of 30 kV, both imprinting area and fidelity ex-hibit a non-monotonic trend with increasing gap distance, peaking at 3 mm. Under optima conditions, the proposed method can achieve large-area imprinting (20 mm diameter) with a maximum fidelity of 0.7. Meanwhile, repeated experiments under identical conditions reveal stochastic variation in imprinted height, attributed to the randomness of the discharge dynamics, likely associated with the stochastic streamer initiation and propagation. To further elucidate the dominant factors governing the imprinting fidelity, the correlation between fidelity and deposited energy was ana-lyzed derived from experiments with varying gap distances and charging voltages. Results indicate that the imprinting fidelity correlates more strongly with the first half-cycle deposited energy than with the total deposited energy. Furthermore, the imprinting fidelity exhibits a piecewise-linear rule as the first half-cycle deposited energy increased: below a threshold energy (~280 J), the imprinted height remains negligible (< 0.2) and beyond a saturation energy (~380 J), the fidelity plateaus at ~0.7 despite the deposited energy increased. Maintaining the deposited energy slightly above the saturation values is essential to achieve high-fidelity imprinting with enhanced energy efficiency.