Lateral porous silicon membranes with size and charge selectivity

In this work, we present methods for the fabrication of lateral porous silicon membranes with size and charge selectivity, and their monolithic integration into planar microfluidics as opposed to classical porous silicon membranes with perpendicular pores that are used in hybrid 3D fluidic systems. Our approach is based on the use of locally patterned electrodes to guide pore formation horizontally within the membrane in combination with locally doped substrates to spatially localize the porous silicon within the channel depth. Membranes with lateral pores and tunable porosity were successfully fabricated by these methods. The dead-end filtration capability and the cation perm-selectivity of the fabricated membranes were also demonstrated, thus enabling on-chip size- and charge-based separation.