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Research Highlights

Patterning Organic Semiconductor Single Crystal Field-Effect Transistors

Single-crystal organic field-effect transistors (OFETs) are ideal device structures for studying fundamental science associated with charge transport in organic materials and have demonstrated outstanding electrical characteristics. However, it remains a technical challenge to integrate single-crystal devices into practical electronic applications. A key difficulty is that organic single-crystal devices are usually fabricated one device at a time through manual selection and placing individual crystals. To overcome this difficulty, Bao et al. successfully developed two high-throughput approaches to pattern organic single crystal arrays.

Flow-Enhanced Single Molecule DNA Hybridization Studies

Objective: To develop novel microfluidic flow cells that allow trapping of single DNA molecules and studies of the binding of sequence-specific probes to the trapped DNA.

Fig. 2
Approach: Two different devices have been designed and fabricated: a cross-slot that uses flow focusing to direct probes to the trapped DNA and a microfluidic “four roll mill” that allows the flow type to be varied from extension to shear to rotation near the trapped DNA (fig. 2).

Education Highlight

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%).

Facility Highlight

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.