Emerging strategies for controllable mechanical exfoliation of crystalline thin films and nanomembranes

Building crystalline heterostructures with arbitrary material combinations, which has been often referred to as "anything-on-anything" integration, has remained a central challenge in materials science and device platforms. Membrane-based technologies provide a viable pathway toward this goal by decoupling thin-film growth from the resulting heterostructures. By isolating high-quality single-crystal layers from their host substrates, lift-off techniques bypass the intrinsic constraints imposed by substrate properties and enable the production of freestanding films and nanomembranes as previously inaccessible material building blocks. Among various lift-off strategies, mechanical lift-off is particularly attractive due to its wide applicability to virtually any material systems. However, the difficulty in manipulating cracks during mechanical lift-off, which determines the properties of exfoliated membranes, has limited the widespread adoption of the technology. Here, we provide key insights into the fundamental mechanics governing mechanical lift-off and discuss how recent breakthroughs in interface design, epitaxy techniques, and crack-guiding principles have enabled highly controlled spalling with atomic precision, scalability, and throughput. We then highlight how such innovations in mechanical lift-off technology, along with other emerging lift-off methods, have advanced membrane-based technologies and have opened new application spaces. Finally, we discuss remaining challenges not only in the lift-off processes themselves but also across the full process flow, outlining pathways toward the broader adoption of lift-off technologies for both fundamental scientific studies and advanced device platforms.