A MACEing Silicon: Towards single-step etching of defined porous nanostructures for biomedicine

Publication date: Available online 26 December 2019Source: Progress in Materials ScienceAuthor(s): Hashim Alhmoud, Daniel Brodoceanu, Roey Elnathan, Tobias Kraus, Nicolas H. VoelckerAbstractMetal-assisted chemical etching (MACE) affords porous silicon nanostructures control over size, shape, and porosity in a single step. Simplicity and flexibility are potential advantages over more traditional silicon bulk micromachining techniques. MACE porous micro- and nanostructures are suitable as biomaterials through their length scales and biocompatibility.This work provides a comprehensive overview of the MACE reaction mechanism that yields biomedically relevant silicon nanostructures – from nanowires, nanopillars, to sub-micrometer holes and pores. We discuss their biomedical applications in biosensors, cell capture and transfection arrays, and drug delivery vectors. We assess the reported benefits of the various nanostructures and discuss whether MACE provides clear and distinct advantages over other techniques.The flexibility and simplicity of MACE comes at a cost. The reaction parameters are many and inter-related, and we lack a full model of the etching mechanism. While the cathode reaction is well understood, the anode reaction involving dissolution of the silicon remains controversial. Such uncertainties impede rational design of specific structures that address biomedical requirements. We summarize current understanding to provide design guidelines for structures used in bi...
Source: Progress in Materials Science - Category: Materials Science Source Type: research