Macroscopic porous membranes with pore diameter uniformity approaching the nanometer scale have great potential to significantly increase the speed, selectivity, and efficiency of molecular separations. We present fabrication, characterization, and molecular transport evaluation of nanoporous thin silicon-based sieves created by laser interferometric lithography (LIL). This fabrication approach is ideally suited for the integration of nanostructured pore arrays into larger microfluidic processing systems, using a simple all-silicon lithographic process. Submilli-meter-scale planar arrays of uniform cylindrical and pyramidal nanopores are created in silicon nitride and silicon, respectively, with average pore diameters below 250 nm and significantly smaller standard error than commercial polycarbonate track etched (PCTE) membranes. Molecular transport properties of short cylindrical pores fabricated by LIL are compared to those of thicker commercial PCTE membranes for the first time. A 10-fold increase in pyridine pore flux is achieved with thin membranes relative to commercial sieves, without any modification of the membrane surface.
The central goal of our work is to combine semiconductor nanotechnology and surface functionalization in order to
build platforms for the selective detection of bio-organisms ranging in size from bacteria (micron range) down to
viruses, as well as for the detection of chemical agents (nanometer range). We will show on three porous silicon
platforms how pore geometry and pore wall chemistry can be combined and optimized to capture and detect specific
targets.
We developed a synthetic route allowing to directly anchor proteins on silicon surfaces and illustrated the relevance of
this technique by immobilizing live enzymes onto electrochemically etched luminescent nano-porous silicon. The
powerful association of the specific enzymes with the transducing matrix led to a selective hybrid platform for chemical
sensing.
We also used light-assisted electrochemistry to produce periodic arrays of through pores on pre-patterned silicon
membranes with controlled diameters ranging from many microns down to tens of nanometers. We demonstrated the
first covalently functionalized silicon membranes and illustrated their selective capture abilities with antibody-coated
micro-beads. These engineered membranes are extremely versatile and could be adapted to specifically recognize the
external fingerprints (size and coat composition) of target bio-organisms.
Finally, we fabricated locally functionalized single nanopores using a combination of focused ion beam drilling and ion
beam assisted oxide deposition. We showed how a silicon oxide ring can be grown around a single nanopore and how it
can be functionalized with DNA probes to detect single viral-sized beads. The next step for this platform is the detection
of whole viruses and bacteria.
Conference Committee Involvement (3)
Frontiers in Pathogen Detection: From Nanosensors to Systems
23 January 2010 | San Francisco, California, United States
Frontiers in Pathogen Detection: From Nanosensors to Systems
24 January 2009 | San Jose, California, United States
Micro (MEMS) and Nanotechnologies for Defense and Security
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