Biologically-Inspired Water-Swelling-Driven Fabrication of Centimeter-Level Metallic Nanogaps

Metallic nanogaps have great values in plasmonics devices. However, large-area and low-cost fabrication of such nanogaps is still a huge obstacle, hindering their practical use. In this work, inspired by the cracking behavior of the tomato skin, a water-swelling-driven fabrication method is developed. An Au thinfilm is deposited on a super absorbent polymer (SAP) layer. Once the SAP layer absorbs water and swells, gaps will be created on the surface of the Au thinfilm at a centimeter-scale. Further experimentation indicates that such Au gaps can enhance the Raman scattering signal. In principle, the water-swelling-driven fabrication route can also create gaps on other metallic film and even nonmetallic film in a low-cost way.