Process for integrating multiple porous silicon membranes with variable characteristics into planar microfluidics

We present a fabrication process based on selective ion implantation to monolithically integrate several porous silicon membranes with different morphologies in the same planar fluidic chip through a single anodization step. By manipulating the dopant concentration of specific zones of a silicon on insulator wafer, the porous silicon elements formed through electrochemical anodization present different characteristics in terms of pore size and porosity. Using this technique, we are able to fabricate both lateral porous silicon membranes and standard porous silicon membranes with vertical pores that can be used in flow-through and flow-over configurations. Achieved mean pore sizes and porosities for the various membranes integrated in the same chip range from 25 nm to 50 nm, and 65–90 %, respectively. Because porous silicon membranes have been used for biosensing and for sample preparation in microfluidics devices, this method is foreseen to enable the use of porous silicon membranes to achieve all the functions involved in the analytical process on a single chip. [Display omitted] •Flow-through/flow-over porous silicon membranes with tailored properties are monolithically integrated in a single chip.•The fabrication process is simple/straightforward as it relies on a single anodization step to create multiple membranes.•This work paves the way towards using porous silicon to perform all analytical steps (sample preparation/sensing) on a chip.