Perfectly Spatial and Shape-Controllable Nanocrack Lithography via Localized Compressive-Shear Stress Coupling.

Cracking-assisted nanofabrication techniques have gained widespread applications across diverse engineering fields for the creation of nanoscale features, valued for their simplicity, cost-effectiveness, and high resolution. However, conventional methods often struggle to control the density, shape, and uniformity of nanocracks due to random stress concentrations caused by material defects and uncontrolled mechanical stress distribution during nanocrack formation. To address these limitations, we developed a highly reliable and reproducible nanocrack patterning method capable of creating large-scale, customizable nanocrack patterns on flexible substrates via the compressive-shear stress coupling effect. Our approach utilizes photolithography-based microphotoresist structures and simultaneous bending and pressing to induce highly localized stresses at the corners of the structures, facilitating the formation of nanocracks. This method enables precise spatial and shape control of nanocrack patterns in functional materials on flexible substrates. For example, in platinum films on polymer substrates, we achieved a uniform and consistent average nanocrack spacing of 40 μm with a standard deviation as low as 0.1 μm across 100 parallel nanocracks. The technique is versatile and can be applied to various functional materials, such as copper and indium tin oxide. We further showed the creation of diverse curved and closed-shape nanocracks, including zigzag, wave, square, circle, parallelogram, and cross shapes, in copper thin films. Finally, we applied this method to various engineering fields to demonstrate its efficacy, including strain sensors with gauge factors of approximately 380, a three-dimensional pressure sensor array capable of reliably measuring pressures below 0.1 N, and nanowire patterning with highly uniform spacing (40 ± 0.5 μm) on polymer substrates that offered both flexibility and transparency.