Nanomanufacturing for biological sensing applications

Abstract

Over the past 10-15 years, there have been tremendous research efforts in the synthesis of nanomaterials with unique electronic properties. Much less work, however, has focused on the incorporation of the nanomaterials into electronic devices. In order for nanomaterials to have a technological impact in electronic devices, nanomanufacturing techniques must be established for the reliable and reproducible creation of devices with nanomaterials as the active component. In this thesis, the incorporation of 3-20 nm diameter ligand coated gold nanoparticles into an electronic device is studied. Ligand coated nanoparticles provide great control over their solubility and electronic properties through the choice of protecting ligand molecule. The use of an isolated nanoparticle in electronic devices presents two major difficulties which are studied in detail in this work. In order to use the electrical properties of a single particle or a few particles, insulating gaps in metallic electrodes must be fabricated with dimensions of 5-50 nm. Several methods including direct patterning with electron beam lithography, physical methods of gap formation, and electrical methods of gap formation are described, studied and evaluated for use in nanomanufacturing.

(cont.) A second major challenge is the specific assembly of nanoparticles into the nanogaps. The use of chemically directed assembly to pattern particles on templates generated by Dip Pen Nanolithography is described using several different surface chemistries. An electrical based method, dielectrophoresis, is found to be better suited for assembly of particles into the gaps and the forces which affect assembly are studied in detail. Electrical characterizations of networks of 10-200 nanoparticles are studied as a function of protecting ligand molecule. Preliminary results on the use of nanomanufactured devices consisting of gold nanoparticles-oglionucleotide conjugates bridging a nano-gap for DNA sensing are presented.