Yixuan "Sean" Chen — 2008-09 Fellow
The project will research on the development of integrated multi-modality sensing systems based on arrays of conducting polymer nanowires (CPNWs) that can be made of different polymer materials and have systematically adjusted electrical/chemical properties. Such a system can potentially provide highly reliable, sensitive, specific gas and solution phase detection of chemical and biological targets which can be used for homeland security, environmental safety, health industry, and even in households for detection of various species (e.g. poisonous species, flammable gases, viruses). On the other hand, such a system requires the fabrication of well defined and organized CPNWs - a very challenging demand that has recently been realized with my newly developed method. In addition, when a large scale multi-degree sensor array is made on a pre-prefabricated CMOS chip that contains specially designed power supply, signal conditioning and monitoring components as well as higher level control, communication and logic circuitries, it will serve as a comprehensive multi-modality multi-target detecting and monitoring stand-alone system-on-a-chip. Different arrays of individually tunable and addressable CPNWs are positioned side by side for cross-checking control and they can be functionalized with different receptors for multiple-target detection.
To realize such systems, I have developed an innovative method with which nanoscale CP materials of arbitrarily designed patterns can be made in parallel. It involves electrochemical polymerization of monomer precursors on a template mold and subsequent transfer of polymer nano-structures onto a substrate of choice. Nano- and micro-scale CP patterns with substantial complexity can be fabricated with this new method. The CP nanowires prepared by this new method show very good electrical properties. The conductivity of a CP nanowire can be controlled by the ion concentration inside the polymer. The new approach has a unique combination of advantages which is ideal to construct a highly reliable, sensitive and selective sensing system. First, it can produce (quasi) one-dimensional CP features (with CD down to the scale of 100nm or less) which interact directly with target species, achieving ultrahigh sensitivity. Second, properly connected and independently addressable nanowires that are made of different conducting materials such as polythiophene, polypyrrole, polyaniline, poly-EDOT as well as their variations with very desirable electrical and chemical properties for chemical/biological sensing purposes can be fabricated and functionalized simultaneously side-by-side on a single substrate. Each target species should have a unique signature as each CP type responds differently to it. The unique combination of response patterns of different CP nanowires constitutes a look-up table for easy identification of the target species. Thus an extremely selective and reliable sensor system can be achieved. Third, it can fabricate precisely designed CP nano-patterns at exactly the expected locations, making interconnections among themselves and to peripheral circuits relatively easy. Fourth, since the method is a parallel technology that is suitable for wafer scale processing, it is extremely efficient.