Microstructured single-layer electrodes embedded in P(VDF-TrFE) for flexible and self-powered direction-sensitive strain sensors. (15th July 2020)

• Record Type: Journal Article
• Authors: Schäffner, Philipp; Zirkl, Martin; Schider, Gerburg; Groten, Jonas; Belegratis, Maria Regina; Knoll, Peter; Stadlober, Barbara
• Is Part Of: Smart materials and structures. Volume 29:Number 8(2020)
• Publication Date: 2020-07-15
• Subjects: ferroelectrics -- piezoelectric sensors -- strain sensors -- microfluidics; Smart materials -- Periodicals; Strucural design -- Periodicals; 620.11
• DOI: 10.1088/1361-665X/ab9f4c
• Languages: English
• ISSNs: 0964-1726

Abstract

Abstract: Most flexible piezoelectric transducers have a vertical setup with top and bottom electrodes, which does not enable the selective, directional detection of mechanical stimuli. Here we present a paradigm shift in the design of such transducers by placing the electrodes in a single layer and fully embedding them in a ferroelectric layer. This approach enables a selective detection of in-plane strains with a linear, orientation-dependent response. Our transducers feature microstructured, densely interdigitated electrodes embedded in the ferroelectric copolymer P(VDF-TrFE) and show an in-plane strain sensitivity of up to 8.3 nC % −1 (21.3 V % −1 ), while being 23 times less sensitive to transversal loading, compared to vertical setup devices. The embedded electrodes cause a strong anisotropy for in-plane strain coupling and make it possible to distinguish both the bending orientation and the bending intensity on a time-variable curvilinear surface. A high power density of 2.3 mW cm −3 was achieved during a periodic bending movement at 90 Hz. In addition to a photolithography and electroplating-assisted method, we present an alignment-free, elegant microcapillary force-based process for scalable fabrication of embedded electrodes. The presented transducers have a high potential for application as energy-autonomous sensors for condition monitoring, robotics and wearables.