The Beckman Institute Graduate Student Seminar Series presents the work of outstanding graduate students working in Beckman research groups. The seminars are open to the UIUC campus.

The first seminar in the Fall 2006 series takes place on Wednesday, September 6, 2006 at noon in Room 1005 of the Beckman Institute. Speakers and abstracts are listed below:

Self-Healing Materials Using Microvascular Networks
Kathleen Toohey (ACS)

The first generation of self-healing composites incorporates healing agent filled microcapsules and solid catalyst particles in an epoxy matrix. A limitation of this concept is that after healing occurs, the supply of healing agent at the crack has been consumed. If the same crack were to open again, a second healing would not be possible. To approach this problem, the next generation of self-healing composites will utilize an interconnected microvascular network to flow healing agent throughout the matrix. Here, this concept is applied to heal a coating on a substrate containing a network of microchannels. The beam will consist of a brittle epoxy coating with catalyst particles attached to a more compliant substrate which encloses microchannels with healing agent. When loaded in bending, the coating will crack and healing agent will flow into the crack plane. Catalyst in the coating will react with the healing agent and will seal the faces of the crack closed. Cracks in the brittle coating have been shown to heal up to seven times for a single specimen.

Synthesis of Mono-Chiral and Narrow Chirality Distributions of Single-Walled Carbon Nanotubes
Noureddine Tayebi (NB)

Single-walled carbon nanotube (SWNT) field-effect transistors with very promising characteristics have already been demonstrated.
However, batch fabrication of identical devices is not yet possible. This is mainly due to the fact that the SWNT chirality, which not only determines whether the SWNT will be metallic or semiconducting but also its diameter, is not controlled. This is crucial for equal performance of SWNT transistors across a chip. Another issue is the controllable growth location of monodispersed SWNTs on the chip surface, which would enable the placement of devices in well defined positions. Here we report a simple and inexpensive technique that controls both the chirality and surface location of SWNTs. This technique is based on nanosphere lithography, which allows for the fabrication of periodically-spaced and monodispersed metal particles of equal size from which the chemical-vapor-deposition (CVD) synthesis of monodispersed SWNTs is achieved. The particle diameter, and thus that of the SWNTs, is controlled down to 7 A, with an interparticle spacing down to 5 nm. Raman spectroscopy analysis reveals that a single chirality is achieved for all 7 A SWNTs. Transmission electron microscopy analysis reveals that the 7 A particles are crystallographically identical, which could be the origin of the mono-chiral SWNTs.