Using various nanomanipulating instruments, solvated polymers are simultaneously formed into fibers, adhered to solid supports, and interconnected in real-time to create suspended fiber bridges and networks of specified geometries. Fibers from 50 nm to 20 µm diameter have been drawn individually and in parallel using single tips and tip arrays. The speed and ease of producing suspended three-dimensional structures recommends the method for application to custom fabrication of prototype microfluidic and microoptical devices.

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Cationic photopolymerizations of vinyl ethers were investigated using in situ, time-resolved fluorescence spectroscopy. Due to its short intrinsic time scale, fluorescence spectroscopy provides a means to characterize these polymerizations which are too rapid to be monitored by traditional methods. The fluorescence intensity of the photosensitizer (anthracene or its derivatives) was monitored as a function of time with spectra collected in intervals as short as 2 ms. An observed reduction in fluorescence intensity was attributed to consumption of the photosensitizer, providing a means to monitor the production of active cationic centers. The reaction rate increased as the initiator or photosensitizer concentrations were increased. Also, reactions photosensitized by anthracene and 9,10-dimethylanthracene produced the fastest rates, followed by 9-vinylanthracene. The polymerization rate for 9,10-diphenylanthracene was considerably slower due to steric hindrance or resonance effects. These results illustrate the tremendous potential of in situ, timeresolved fluorescence spectroscopy for monitoring polymerizations.

We report on fabrication and characterization of arrays of bimaterial microcantilevers and discuss their performance as uncooled infrared imagers. An optical readout was used to simultaneously measure deflections of all microcantilevers in the array. The fabricated arrays had an average noise equivalent temperature difference (NETD) and a response time of 1.5K and 6ms, respectively. Some microcantilevers in the array exhibited NETD values below 500mK, approaching our theoretical prediction of 151mK. A unique and valuable feature of the implemented approach is its straightforward scalability to higher resolution arrays, without progressively growing complexity and cost.

The photosensitization mechanism for cationic polymerizations initiated by diaryliodonium salts photosensitized by anthracene was investigated using fluorescence and phosphorescence spectroscopy. In situ photosensitizer fluorescence measurements confirmed that the photosensitization reaction proceeds by an electron transfer process. Transient phosphorescence studies demonstrated that electron transfer occurred from the triplet excited state of anthracene to the initiator, with an intrinsic kinetic rate constant of 2 × 108 L/mol s. Further evidence for the role of the triplet state was provided by an observed seven‐fold decrease in the polymerization rate upon addition of a triplet state quencher. Finally, numerical solution of the photophysical kinetic equations indicated that the triplet state concentration was approximately three orders of magnitude higher than that of the singlet state, and that 94‐96% of the active cationic centers are produced by reaction of the initiator with the triplet state. These results indicate that the electron transfer occurs primarily from the triplet state of anthracene, with the singlet state providing only a minor contribution to the photosensitization reaction. © 1995 John Wiley & Sons, Inc.