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Localized surface-tension-driven forces (microscale Marangoni effect) caused by a temperature inhomogeneity from the decay of optically excited surface plasmons into phonons have been engaged in the actuation of adsorbed and applied liquid on a thin metal film. Microfluidic operations of transport, separation, mixing, and sorting have been experimentally and theoretically demonstrated using this all-optical modulation scheme.

Despite its immediate applications, selective detection of trace quantities of surface adsorbed chemicals, such as explosives, without physically collecting the sample molecules is a challenging task. Standoff spectroscopic techniques offer an ideal method of detecting chemicals without using a sample collection step. Though standoff spectroscopic techniques are capable of providing high selectivity, their demonstrated sensitivities are poor. Here we describe standoff detection of trace quantities of surface adsorbed chemicals using two quantum cascade lasers operated simultaneously, with tunable wavelength windows that match with absorption peaks of the analytes. This standoff method is a variation of photoacoustic spectroscopy, where scattered light from the sample surface is used for exciting acoustic resonance of the detector. We demonstrate a sensitivity of 100 ng/[cm.sup.2] and a standoff detection distance of 20 m for surface adsorbed analytes such as explosives and tributyl phosphate.

Recent advances in our understanding of 1D nanomaterials are paving the way for developing novel platforms for sensors and devices based on multi-physics, multi-modal approaches. Here, we report a new way of detecting volatile organic compounds (VOC) using electrical resonance of a single platinum nanowire. The adsorption of molecular dipoles on a nanowire causes a measurable change in the dissipation and frequency of the electrical resonance. The dissipation at the resonance shows enhanced variations depending on the dipole moments of the adsorbates. Experimental results show the limit of detection (LOD) for sensing acetone, methanol, and ethanol by a nanowire sensor in the range of a few ppm. The LOD, however, can be improved by optimizing the electrical parameters of the nanowire. Furthermore, monitoring the dissipation variations at resonance as a function of temperature provides information on thermally induced polarization or depolarization of adsorbed chemical species. The temperature response of the nanowire at resonance could potentially be used to discriminate different vapor molecules based on differential calorimetry. [ABSTRACT FROM AUTHOR]

A scanned probe above a charged surface was investigated to determine electrostatic force density.

Microcantilever sensors were used to examine adsorption and absorption-induced stresses.

The enhancing of the small amplitude of thermal vibrations of cantilevers uses for atomic force microscopy using feedback mechanism is discussed.

Continuously illuminated single europium ions incorporated in d [Eu (super 3+): Y2O3] nanocrystals (5-15 nm diameter) undergo on-off blinking on a variable time scale ranging from hundreds of milliseconds to several seconds. The study indicates the first report of fluorescence imaging of single rare-earth ions in metal oxide nanoparticles, and the first observation of multiple bright states in the luminescence of a single chromophore.

A study was conducted to analyze the amorphous phase of platinum dioxide films. Nanoindentation determinations were carried out to determine the hardness and Young modulus of the films deposited on fused silica. Results indicated that the interatomic coordinates of the precursor are intermediate of the crystalline phases. Findings also showed that the phase resulting from the amorphous form is unpredictable and depend on various effects such as film stress.

A change of spring constant due to adsorption of chemicals on the surface and mass loading can combine to change the resonance frequency of a cantilever. Differential surface stresses can produce static bending in the cantilevers, and chemical properties of the surface and the amount of material adsorbed on the surface both control the magnitude of the stresses. Novel chemical sensors can be built to measure cantilever deflection and resonance frequency change.