Nanofabrication/Characterization and Biosensor Development

My research interests cover a broad area closely related to surface chemistry/physics, particularly the surface properties of organic self-assembled films and the fundamental processes at electrode/electrolyte interfaces. In recent years, my research activities have shifted from the investigation of fundamental issues to the fabrication/characterization of nanodevices and the development of biosensors. Current research topics that I am pursuing with my colleagues at Ames Research Center are

(1) the fabrication of nanotube or nanowire assembly as electrodes for the development of ultrasensitive biosensors,
(2) the investigation of the mechanism of transducing DNA hybridization into electronic signals by electrochemical methods,
(3) the integration of nanoelectrodes into genoelectronics based genechips.

Our goal is to study methods to fabricate nanomaterials such as carbon nanotubes and mesoporous catalyst templates and to integrate these materials into useful nanodevices by the combination of nanofabrication and chemical functionalization, particularly nanoelectrode

assembly interfaced with biomolecules for the development of biosensors. Carbon nanotubes are ideal building blocks for the fabrication of nanodevices which are not easily achievable using other materials. The key for this application is to precisely control the growth of carbon nanotube at desired sites with desired structure and orientation. We are pursuing this goal with plasma assisted catalytic CVD in combination with well-defined nanoporous templating methods. Current effect is to grow micropatterned multiwalled carbon nanotube array with controlled density and purity for the application as nanoelectrode assembly.

The essential issue of the development of biosensors is to understand the mechanism that biorecognition processes are transduced into measurable physical signals. We are focusing on investigating systems in which the transduction is by electrochemical mechanisms. DNA molecules are electroactive at certain potentials which can be used to identify the hybridization process. However, the redox signal from DNA itself is very weak to be detected. We are working on the amplification of the signal using metal chelates as well as indicator-free mechanisms in the combination with the design of delicately archetectured nanoelectrodes.

Our ultimate goal is to develop fast, ultrasensitive, high specific, low cost, and miniaturized biosensors using state-of-the-art nanotechnolgoies. These sensors are expected to be integrated into the next-generation genechips. Along this direction, other methods based on molecular electronics are also being pursued at this moment.