A new approach to optical monitors for gases is introduced using cholesteric liquid crystals doped with reactive chiral compounds. The approach is based on cholesteric pitch length changes caused by a change in helical twisting power (HTP) of the chiral dopants upon reaction with the analyte. The concept is demonstrated for monitoring carbon dioxide via reversible carbamate formation and for oxygen using the irreversible oxidation of a chiral dithiol to a disulfide. Monitoring of CO(2) was achieved by doping a commercial cholesteric liquid crystalline mixture (E7) with 1.6% mol of the 1:1 complex of an optically pure diamine with a TADDOL derivative. Upon exposure to carbon dioxide, the reflection band of a thin film of the mixture shifted from 637 to 495 nm as a consequence of dissociation of the complex after carbamate formation of the diamine. An O(2) monitor was obtained by doping E7 with a chiral binaphthyl dithiol derivative and a nonresponsive codopant. The reflection band of the oxygen monitor film changed from 542 to 600 nm, due to the conformational change accompanying oxidation of the dithiol to disulfide. These monitoring mechanisms hold promise for application in smart packaging, where carbon dioxide and oxygen are of special interest because of their roles in food preservation.

Integration of electronic functionalities into textiles adds to the value of textiles. It allows measuring, detecting, actuating and treating or communicating with a body or object. These added values can render the smart textiles very useful, fun, supporting, protecting or even lifesaving. It is, however, important for the comfort, acceptance and functionality to have integration of electronics as unobtrusive as possible. One elegant unobtrusive method of integration is to have circuitry included in the textile and mount components to this circuitry. Conducting yarns introduced by weaving, knitting or embroidery are attractive candidates to compose the circuitry as they do not disturb the textile nature of the system and are processable by the mentioned conventional textile technologies. In the case that these smart textiles are worn by humans under dynamic circumstances, the system is exposed to mechanical stress. In this paper we report the results of studies on the failure modes of Ag-coated nylon yarns, which are applied on textile carriers by means of stitching or soutache embroidery. The test methods varied in combinations of mechanical stress, such as shearing, bending and tension, and support to better understand the process of deterioration of the yarns when these are mechanically stressed. The delamination of the Ag coating from the yarns leads to unstable resistance values in non-static conditions. The mechanical forces, such as shearing, bending and tension, cause progressively more damage to the filaments of the yarns. This leads to a reduction of the electrical conductivity.

High (2 eV) and low kinetic energy supersonic jets of disilane as well as ultrahigh vacuum chemical vapor deposition have been employed to grow epitaxial silicon thin films on Si(100) wafers at temperatures ranging from 500 to 650 °C. The growth properties and film uniformity are compared in order to characterize the high energy technique. High translational energy disilane supersonic jets increase the efficiency of deposition by increasing the disilane reaction probability. The growth profiles from the high energy jet are sharply peaked due to a focusing of the precursor along the jet centerline.

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