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2007 Highlights

Closing the Loop on Recycling: Can We Stop the oil-to-Landfill Treadmill?

Waste PET Processing Poly(ethylene terephthalate) (PET), a widely used engineering thermoplastic for carpet, clothing (fibers), tire cords, soda bottles and other containers, film, automotive, electronics, displays etc., will contribute several billion pounds of waste to landfills this year alone! According to the American Plastics Council, PET packaging was originally used for soft drinks, but packing applications today include other beverages such as water, juice, beer, in addition to other foods such as peanut butter and ketchup and a variety of other household products.

CPIMA SURE Student Highlight: Vivian Trang

Scanning electron micrograph Vivian Trang joined CPIMA scientists at Stanford and IBM working to develop novel synthesis methods to control the porosity of hydrogels. She used an organocatalytic living polymerization method to make the systems. Cyclic carbonate functional macromolecules were ring-opened using an alcoholic initiator in the presence of an organic catalyst. A model reaction for the cross-linking identified the critical monomer concentration dependent reaction regimes, and enhanced kinetic control was demonstrated by introducing a co-monomer which facilitated near quantitative conversion of monomer to polymer (>96%).

Quartz Crystal Microbalance Sensor

The quartz crystal microbalance (QCM) sensor has recently been put into place in the Stanford CPIMA Shared Facilities and is experiencing a surge of use. This sensor is extraordinarily sensitive to mass changes associated with the deposition of material onto the surface of a quartz crystal. These changes are sensed as changes in the natural resonant frequency of the QCM.

The QCM is also sensitive to the mechanical losses in the film, which give rise to increasing resonance widths. This increasing width or decreasing quality factor (Q) is measured as an increase in the equivalent circuit resistance.

Microfluidic Device for DNA Dynamics in Mixed Flows

DNA tumbling in mixed flows that vary from shear to rotation.Lab-on-a-chip devices that are capable of performing microanalytical testing must have the capacity to precisely control the flow of very small volumes of fluid. The typical approach to this involves microfluidic devices in which the flow channels are of the order of 50 to 100 microns in diameter. Of particular interest in CPIMA has been the use of microfluidic devices that could be used to create flow conditions for capturing and orienting biomolecules that are sufficiently long that they may be visualized with optical microscopy. The prime model system for such experiments has been double-stranded DNA, which could achieve lengths of the order of tens of microns. In recent work, Muller and Shaqfeh have developed microfluidic devices and sequence-specific probes for studies of DNA hybridization kinetics that may also allow DNA genotyping with unprecedented read lengths.

Verticle Nanopore Bulk Heterojunction Solar Cells

A major effort in CPIMA has been to control and characterize interfacial charge transport in directed nanoassemblies. Such research is motivated by basic issues that relate to the performance of organic electronic devices, including photovoltaics, field-effect transistors, biological sensors, and memory elements. This highlight focuses on recent activity in photovoltaics. Prior work in CPIMA by McGehee in collaboration with Miller has demonstrated that poly(3-hexylthiophene) (P3HT) has much larger charge carrier mobility when confined in straight nanopores than when confined in disordered nanopores.