Micromachined nanofiltration modules for lab-on-a-chip applications

In this paper, we present a new concept of particle filtration modules for lab-on-a-chip (LOC) devices. The modules are designed as vertical walls that separate fluidic micro channels. In these walls, nano channels that connect the two adjacent micro channels are embedded. Fluid and small particles can penetrate the walls through the embedded nano channels, while particles larger than the nano channels size will be stopped. By keeping the fluid in the surface plane of the LOC, the module can be easily integrated with other LOC modules. To fabricate these modules, we use chemical vapor deposition to deposit nanometer thick sacrificial layers and embed them into the wall structure. Wet chemical enchants are used to remove the sacrificial layers and form the nano channels. This fabrication process can generate 100 nm⁻¹ μm high nano channels with high accuracy and uniformity with well-established micromachining techniques. Two types of modules, surface micromachining design for more flexibility in the choice of substrate material and bulk micromachining design for higher porosity without increasing footprint, are fabricated and successfully tested. (paper)