Flexible Piezoelectric Touch Sensor by Alignment of Lead‐Free Alkaline Niobate Microcubes in PDMS. (24th April 2017)

• Record Type: Journal Article
• Authors: Deutz, Daniella B.; Mascarenhas, Neola T.; Schelen, J. Ben J.; de Leeuw, Dago M.; van der Zwaag, Sybrand; Groen, Pim
• Is Part Of: Advanced functional materials. Volume 27:Number 24(2017)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2017-04-24
• Subjects: alkaline niobates -- energy harvesting -- functional composites -- piezoelectric materials -- touch sensors; Materials -- Periodicals; Chemical vapor deposition -- Periodicals; 620.11
• DOI: 10.1002/adfm.201700728
• Languages: English
• ISSNs: 1616-301X

Abstract

Abstract : A highly sensitive, lead‐free, and flexible piezoelectric touch sensor is reported based on composite films of alkaline niobate K0.485 Na0.485 Li0.03 NbO3 (KNLN) powders aligned in a polydimethylsiloxane (PDMS) matrix. KNLN powder is fabricated by solid‐state sintering and consists of microcubes. The particles are dispersed in uncured PDMS and oriented by application of an oscillating dielectrophoretic alignment field. The dielectric constant of the composite film is almost independent of the microstructure, while upon alignment the piezoelectric charge coefficient increases more than tenfold up to 17 pC N −1 . A quantitative analysis shows that the origin is a reduction of the interparticle distance to under 1.0 µm in the aligned bicontinuous KNLN chains. The temperature stable piezoelectric voltage coefficient exhibits a maximum value of 220 mV m N −1, at a volume fraction of only 10%. This state‐of‐the‐art value outperforms bulk piezoelectric ceramics and composites with randomly dispersed particles, and is comparable to the values reported for the piezoelectric polymers polyvinylidenefluoride and its random copolymer with trifluoroethylene. Optimized composite films are incorporated in flexible piezoelectric touch sensors. The high sensitivity is analyzed and discussed. As the fabrication technology is straightforward and easy to implement, applications are foreseen in flexible electronics such as wireless sensor networks and biodiagnostics. Abstract : Composite films of aligned K0.485 Na0.485 Li0.03 NbO3 piezoelectric particles in a polydimethylsiloxane matrix are presented. The lead‐free microcubes are dispersed in the uncured matrix and oriented by application of an oscillating dielectrophoretic alignment field. The state‐of‐the‐art piezoelectric constants are measured and quantitatively interpreted. Aligned films are implemented in a flexible touch sensor. The technology will enable the next‐generation "3D touch" sensor.