Nanotechnology can be simply defined as the ability to manipulate molecules and atoms to produce engineered products. By even the most conservative estimation, this field is believed to usher in the new industrial age. At Drexel University, the RET research program in nanotechnology will be built on the strengths and resources of the Nanotechnology Institute (NTI). NTI, funded by the Commonwealth of Pennsylvania at a level of $10.5M, is a partnership between Drexel University and the University of Pennsylvania. Its mission is to conduct basic and applied research in the field of Nanotechnology, with a particular emphasis on applications to biology and medicine, and to commercialize those discoveries, which have application to and viability in the international technology marketplace.
1) Synthesis, Characterization and Modification of Carbon Nanotubes - (Dr. Yury Gogotsi – NSF Career Awardee and Alexander Von Humboldt Fellow)
Carbon nanotubes exhibit spectacular properties (mechanical, electrical, and thermal) when measured parallel to the tube axis. They show great promise in many biomedical and electronics applications. They can be used as a part of multifunctional materials wherein they may be designed to impart improved structural performance, controlled electrical conductivity, and could be used as building blocks for integrated sensing and control systems. Dr. Gogotsi develops novel synthesis techniques such as hydrothermal synthesis of nanotubes, synthesis of giant nanotubes and fullerene-filled peapods. As with other nanoparticles, the dispersion of nanotubes in a second phase can be challenging. Particularly, chemical modification of the tube surfaces is difficult because typical chemical treatments used to add functionality to the relatively inert carbon nanotube surfaces are harsh and can result in the destruction of the delicate thin-walled structure. Teachers will work with Dr. Gogotsi and his graduate students to participate in synthesizing carbon nanotubes using hydrothermal processes. Qualified professionals will train teachers in Raman Spectroscopy and X-Ray analysis techniques. An example of azimuth-dependent Bragg intensity from a magnetically-aligned single wall nanotube (SWNT) foil is shown in Fig. 10. Through these interactions, teachers will gain experience in some of the enabling technologies in materials research and nanotechnology. Drexel personnel will work with the teachers to develop lesson plans describing the importance of nanotechnology to many aspects of our lives and to provide a tutorial of the characterization techniques of observations using light microscopy and electron microscopy.
2) Tailoring Dispersion via Electron Beam Induced Chemical Grafting onto Carbon Nanotube Surfaces - (Dr. Giuseppe R. Palmese)
Control over the dispersion of single wall nanotubes (SWNT) in liquid media is necessary for being able to form ordered materials with tailored structures. Attempts have been made to fabricate SWNT polymer composites by blending with various polymers and by in-situ reaction of monomers to form epoxy-amine, urethane acrylates, and PMMA matrices. In all cases, a limiting factor in producing good composites is the dispersion of the SWNT. SWNT will not readily disperse in water or in solvents like toluene but rather form aggregates that limit their potential usefulness. The surface chemistry of the nanotube can be modified and surfactant molecules can be used to aid the dispersion. In the laboratory of Dr. Giuseppe Palmese, a fundamental understanding of factors that influence the dispersion of nanotubes in solvent and polymer systems will be investigated. Teachers with the assistance of graduate assistants and Dr. Palmese will use electron-beam irradiation to exploit the high dose rates and therefore high graft density that can be achieved. Dr. Palmese’s laboratory personnel possess significant experience and facility using this processing technique as applied to curing of thermosetting systems. Results of this investigation will be used to guide the design of SWNT surface modifications for dispersion in practical devices. A qualified professional will train teachers in the operation of the electron beam apparatus. Drexel personnel will work with the teachers to provide lesson plans on manufacturing technologies using “bottom-up” approaches and to illuminate the differences among the various nanomanufacturing techniques.
3) Hydrogels for Disc Replacement - (Dr. Michele Marcolongo)
Over five million Americans suffer from chronic lower back pain making it the number one cause of lost work days in the United States. With over 20 billion dollars spent each year for the treatment of lower back pain it is one of the most expensive health care issues today. While the causes of lower back pain remain unclear, it is believed that 75% of the cases are associated with degenerative disc disease, where the intervertebral disc of the spine suffers reduced mechanical functionality due to dehydration of the nucleus pulposus. The reduction in the ability of the disc to transmit loads evenly and efficiently between vertebral bodies leads to damage in the annulus fibrosus region of the disc.
The general premise of the research being performed in Dr. Michele Marcolongo’s laboratory is that if the initial dehydration of the degenerated nucleus can be arrested and a fully hydrated state returned to the disc, then the degenerative process (including the associated pain) would be postponed or prevented and that mechanical function would be restored to the vertebral segment. To facilitate this approach, teachers and graduate assistants will investigate replacement of the nucleus with a biocompatible, nano-scale, hydrogel polymer (See Figure 11). For this project, teachers will synthesize hydrogels of three different polymer concentrations and perform a dehydration/rehydration protocol to establish the equilibrium water content and the mechanical properties changes and surface chemical changes associated with the dehydration history of the gels. Laboratory work will be complimented with diffusional studies of the dehydration process which may lead to a better understanding of the shape memory properties of the biomaterials. Drexel personnel will develop lesson plans on biomaterials describing processing, introduction into the body, bodily-acceptance, and various regulatory issues involved in their development.
4) Block Copolymer Templated Self-Assembly at Nano- and Micro- Scales - (Dr. Christopher Li)
Self-Assembly, as an essential part of nanotechnology, is one of the few practical strategies for making ensembles of nanostructures. Self-assembly of polymeric supermolecules is a powerful tool for producing (a) Chemical structures of liquid crystalline block copolymers. R is the disc mesogen, and polystyrene acts as amorphous block. (b) Schematic diagram of block
co-polymer. (c) Cylinder structure of block copolymers. (d) Within each cylinder, nano-scale columnar phase can be formed. functional materials that combine several properties and may respond to external condition. In order to achieve this goal, specific copolymers have been designed as shown in Figure 12. Discotic liquid crystalline (LC, shown in Figure 12b) molecules are well known for their so-called discotic columnar phases in which molecular discs stack together forming columns, and the columns further assemble together to form two-dimensional ordered structure. The size of the LC columns can be controlled by the size of the “disc” (normally 1 to 3 nanometers). Figure 12 shows the cylinder structure as an example. The self-assembly of LC phase and block copolymers fall into two length scales: 1-3 nanometers for LC and 20-200 nanometers for block copolymers. Research in this field is expected to shed light on hierarchical control of structures at different length scales and lead to possible means to transfer regular nanostructures into mesoscopic level. Teachers will perform research on the structural complexity to serve as a platform for further functionalizing both LC molecules and block copolymers to combine different functionalities with in a single material. Teachers will be trained in polymeric material synthesis techniques and characterization using electron microscopy.
In order to extend nano-technology education to the high school level, high school teachers will be invited to work with Dr. Li's group in designing and developing this novel hierarchical self-assembled nanomaterial. Self-assembly principles will be demonstrated using common amphiphilic materials such as soap. By using Transmission Electron Microscopy technique, Dr. Li will demonstrate the image of nano-scale assembled materials to schoolteachers. Differential Scanning Calorimetry will be used to show the transition temperature change of liquid crystals as the size goes down to nanometers, which is a typical phenomenon in nanoscale physics.
