Towards Fabrication of Solid-State Mimics of Biological Nanopores

Brian J. Polk, Michael Gaitan,

Device Technology Group, Semiconductor Electronics Division

Electronics and Electrical Engineering Laboratory

Martin Misakian, John J. Kasianowicz

Biomolecular Materials Group, Biotechnology Division

Chemical Science and Technology Laboratory

Biological nanopores are complex protein assemblies that span cell membranes and allow ionic transport across the otherwise impermeable lipid bilayer.  Nanopores are important because while some pores help maintain cell homeostasis, others disrupt cell function.  Unfortunately, functioning bio-nanopores are difficult to study because of the fragility of the supporting lipid bilayer and the mobility of the pore itself.  A stable, robust solid-state mimic would facilitate understanding of bio-nanopores by allowing control of the location, dimension, and composition of the pores.  However, reproducibly matching the exceedingly small inner diameter (1-2 nm) of the bio-nanopore in a solid-state device is experimentally challenging.

The first steps towards creation of a solid-state nanopore are evaluating fabrication strategies.  In the top-down approach, pores are etched in solid-state materials such as silicon using industry standard lithographic techniques.  While lithography provides tight control over the location and composition of structures, it is unclear that the dimensions can be made small enough to fabricate a bio-nanopore mimic.  This limitation can be overcome by creating a hole larger than desired, then back filling it with another layer of material.  Preliminary experiments have reduced an opening lithographically etched in silicon from 1600_mm2 to less than 1_mm2 by electroplating silver into the opening.  Further size reductions are foreseeable.  Future work will explore bottom-up fabrication strategies with emphasis on self-assembly.

The fabrication of solid-state nanopores is conducted at the interface of biology, chemistry, and engineering and holds exciting prospects for fundamental research with the potential for diverse applications.