Aluminum-Based Multiscale 3D Structures for Customizable Flexible Sensing

Over millions of years, biological systems have evolved optimized functions based on the beneficial size and material effects of their unit cells, which contribute to favourable mechanical and physical properties. For example, micro- and nanoscale two-tier structures play a crucial role in enabling lotus leaves to achieve both high apparent contact angles and low adhesion. Inspired by these natural systems, researchers have employed various trial-and-error reverse-engineering and computational methods to mimic these complex structures for a wide range of applications, such as light management, flexible sensing, wetting control, adhesion, and electrocatalysis. However, manufacturing man-made structures with controllable features across multiple length scales, particularly down to the nanoscale, remains a significant challenge, which can adversely affect their collective properties.<br/>In this work, we introduce an aluminum-based 3D lithography (AL-3DLitho) technique that combines sequential nano-micro-macro-imprinting and anodization of multiscale anodic aluminum oxide templates to fabricate well-defined multiscale structures using various materials. The high-fidelity nano- and micropatterns are achieved through the surface work hardening phenomenon, with nanopatterns further refined by anodization to obtain high aspect ratios and tunable nanoholes. Using AL-3DLitho, we successfully fabricated multiscale materials across at least 10⁷ length scales, including carbon, semiconductors, and metals. As a proof-of-concept, we developed homogeneous multiscale carbon network-based pressure sensors by integrating arrayed nanofibers, micropyramids, and macrodomes. These sensors demonstrate a low detection limit (0.09 Pa), a wide linearity range (0-150 kPa), and excellent stability (over 10⁵ cycles). Furthermore, we integrated two multiscale carbon networks back-to-back to create “on-chip” pressure and biosensors with customizable performance, fully utilizing the strengths of multiscale carbon networks across different length scales. This work provides a versatile technique for prototyping on-demand multiscale structures and materials, enabling the exploration of desirable mechanical and physical properties.