Integration of CCTAO/PDMS composite films into proximity capacitive sensor devices

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dc.contributor.authorBongkarn, Theerachai
dc.contributor.authorPanpho, Phakakorn
dc.contributor.authorCharoonsuk, Thitirat
dc.contributor.authorVittayakorn, Naratip
dc.contributor.authorPakawanit, Phakkhananan
dc.contributor.authorSumang, Rattiphorn
dc.date.accessioned2026-08-06T10:56:26Z
dc.date.available2026-08-06T10:56:26Z
dc.date.issued2026-12-01
dc.description.abstractFlexible capacitive proximity sensors are promising for contactless sensing applications, but their performance is strongly influenced by the dielectric properties and microstructure of the sensing layer. In this work, CaCu<inf>3</inf>Ti<inf>4-x</inf>A<inf>x</inf>O<inf>12</inf>/polydimethylsiloxane (CCTAO/PDMS, A = Nd<sup>3+</sup> or Gd<sup>3+</sup>) composite films were developed as flexible dielectric layers for interdigitated capacitive proximity sensors. Nd- and Gd-doped CCTO ceramics were synthesized by a solid-state reaction method and incorporated into a PDMS matrix at different filler loadings. Structural analysis confirmed that the CCTAO ceramics retained the cubic CCTO phase after rare-earth substitution, while the composite films preserved the characteristic amorphous structure of PDMS with embedded ceramic fillers. The FESEM, EDS mapping and X-ray tomographic microscopy analyses showed that the CCTNdO/PDMS composite had a more uniform distribution of ceramic particles than the CCTO/PDMS system. The dielectric measurements demonstrated the improvement in the dielectric constant of the PDMS-based composites upon CCTNdO incorporation and also indicated that the composites did not exhibit any significant changes in their dielectric properties across the range of frequencies examined. The CCTNdO/PDMS films were found to show the negative capacitance response as a function of distance due to the electric-field shunting mechanism when used in an interdigitated capacitor sensor. The sensor with composition 10 wt% CCTNdO/PDMS had excellent performance with a maximum normalized capacitance change equal to −8.70%, which corresponds to a proximity sensitivity of around 0.42%/mm and an effective sensing range of around 20 mm. It is concluded that the optimization of the loading of the rare-earth material in a flexible PDMS matrix is an effective approach to achieve a compromise between the dielectric enhancement of the sensor and the dispersion of the filler and fringing-field interaction in the contactless capacitive proximity sensor.
dc.identifier.citationRadiation Physics and Chemistry, 249, 2026
dc.identifier.doi10.1016/j.radphyschem.2026.114229
dc.identifier.issn0969806X
dc.identifier.other2-s2.0-105044389771
dc.identifier.urihttps://dspace.kmitl.ac.th/handle/123456789/18341
dc.sourceRadiation Physics and Chemistry
dc.subjectCapacitive sensor
dc.subjectCCTAO
dc.subjectComposite film
dc.subjectPDMS
dc.subjectProximity sensing
dc.titleIntegration of CCTAO/PDMS composite films into proximity capacitive sensor devices
dc.typeArticle

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