Silk as a biodegradable resist for field-emission scanning probe lithography

Abstract

The patterning of silk allows for manufacturing various structures with advanced functionalities for optical and tissue engineering and drug delivery applications. Here, we propose a high-resolution nanoscale patterning method based on field-emission scanning probe lithography (FE-SPL) that crosslinks the biomaterial silk on conductive indium tin oxide (ITO) promoting the use of a biodegradable material as resist and water as a developer. During the lithographic process, Fowler-Nordheim electron emission from a sharp tip was used to manipulate the structure of silk fibroin from random coil to beta sheet and the emission formed nanoscale latent patterns with a critical dimension (CD) of similar to 50 nm. To demonstrate the versatility of the method, we patterned standard and complex shapes. This method is particularly attractive due to its ease of operation without relying on a vacuum or a special gaseous environment and without any need for complex electronics or optics. Therefore, this study paves a practical and cost-effective way toward patterning biopolymers at ultra-high level resolution.