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Proceedings Paper

Selectivity, cycling stability and temperature dependence of touchless finger motion tracking devices based on 1D photonic crystals
Author(s): Katalin Szendrei; Pirmin Ganter; Bettina V. Lotsch
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Paper Abstract

We report on the humidity-induced swelling behavior of thin film devices composed of 2D phosphatoantimonate nanosheets and study their water uptake mechanism by means of ellipsometric porosimetry. Ambient humidity changes cause significant swelling in thin films composed of turbostratically disordered H3Sb3P2O14 nanosheets through water uptake between the nanosheet layers. This phenomenon is exploited to construct humidity responsive colorimetric sensors based on 1D Photonic Crystals. We demonstrate the ultrahigh sensitivity of H3Sb3P2O14/SiO2 Bragg stacks to ambient humidity, as well as reversible transparency switching as a consequence of refractive index matching at high relative humidities. The Photonic Crystals show substantially higher sensitivity to humidity as compared to ethanol vapor, reflecting the less favorable interaction of ethanol with the nanosheet layers as compared to water. Based on their ultrahigh sensitivity to humidity, phosphatoantimonate nanosheet based Bragg stacks can be used to track the motion of a finger by responding to its humidity sheath, without the finger touching the sensor surface. The cycling stability of such optical touchless positioning interfaces as well as the reversibility of the sensing event was demonstrated for more than 100 cycles. While the dew point presents an inherent lower limit to the sensor performance, the sensing ability remains essentially unaffected at elevated temperatures up to 40 °C.

Paper Details

Date Published: 18 April 2016
PDF: 13 pages
Proc. SPIE 9885, Photonic Crystal Materials and Devices XII, 98850Z (18 April 2016); doi: 10.1117/12.2227431
Show Author Affiliations
Katalin Szendrei, Max Planck Institute for Solid State Research (Germany)
Ludwig-Maximilians-Univ. München (Germany)
Nanosystems Initiative Munich (Germany)
Pirmin Ganter, Max-Planck-Institute for Solid State Research (Germany)
Ludwig-Maximilians-Univ. München (Germany)
Bettina V. Lotsch, Max-Planck-Institute for Solid State Research (Germany)
Ludwig-Maximilians-Univ. München (Germany)
Nanosystems Initiative Munich (Germany)


Published in SPIE Proceedings Vol. 9885:
Photonic Crystal Materials and Devices XII
Dario Gerace; Gabriel Lozano; Christelle Monat; Sergei G. Romanov, Editor(s)

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