Direct ink writing combined with metal-assisted chemical etching of microchannels for the microfluidic system applications

Abstract

Microchannels are critical components of the microfluidic systems. But the low efficiency and high cost of conventional machining methods severely hinder the wide applications of microchannels. Here, we have reported a facile and low-cost strategy for the fabrication of microchannels on silicon substrate based on direct marker pen ink writing (DIW) and metal-assisted chemical etching (MaCE). Firstly, ink patterns were directly written on the bare silicon substrate by DIW without any polymer resist. They were utilized as stable mask in subsequent step, and can be easily removed by ethanol when not needed. Then, Ag nanofilms were deposited on the spaces between ink patterns by electroless deposition. Finally, silicon microchannels were fabricated by MaCE. During MaCE process, the Ag nanofilm was acted as catalyst and hydrogen peroxide-hydrofluoric acid solution was used as etching solution. The mask effect of ink patterns in the DIW-MaCE fabrication strategy was studied, and the effects of etching time, Ag nanofilm thickness, and etchant concentration on the formation of microchannels structures were also investigated. The microchannels structures were also fabricated to demonstrate the applications in microfluidics. We have introduced diamond tips of multi-probe microfabrication equipment to control the geometry and size of ink patterns in this study, and thus the final microchannels structures can be optimized during MaCE. The proposed DIW-MaCE strategy is facile and cost-effective for the fabrication of microchannels, and the microchannels structures are promising for extending the microfluidics and microsensors devices applications.