Regioregular polythiophene-based conductive copolymers with highly crystalline nanostructures are shown to hold considerable promise as the active layer in volatile organic compound (VOC) chemresistor sensors. While the regioregular polythiophene polymer chain provides a charge conduction path, its chemical sensing selectivity and sensitivity can be altered either by incorporating a second polymer to form a block copolymer or by making a random copolymer of polythiophene with different alkyl side chains. The copolymers were exposed to a variety of VOC vapors, and the electrical conductivity of these copolymers increased or decreased depending upon the polymer composition and the specific analytes. Measurements were made at room temperature, and the responses were found to be fast and appeared to be completely reversible. Using various copolymers of polythiophene in a sensor array can provide much better discrimination to various analytes than existing solid state sensors. Our data strongly indicate that several sensing mechanisms are at play simultaneously, and we briefly discuss some of them.

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This article describes an approach for implementing a complete computer system ͑CPU, RAM, I/O, and nonvolatile mass memory͒ on a single integrated-circuit substrate ͑a chip͒-hence, the name ''single-chip computer.'' The approach presented combines advances in the field of microelectromechanical systems ͑MEMS͒ and micromagnetics with traditional low-cost very-large-scale integrated circuit style parallel lithographic manufacturing. The primary barrier to the creation of a computer on a chip is the incorporation of a high-capacity ͓many gigabytes ͑GB͔͒ re-writable nonvolatile memory ͑in today's terminology, a disk drive͒ into an integrated circuit ͑IC͒ manufacturing process. This article presents the following design example: a MEMS-based magnetic memory that can store over 2 GB of data in 2 cm 2 of die area and whose fabrication is compatible with a standard IC manufacturing process.

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