Enhanced pseudo-piezoelectric dynamic force sensors based on inkjet-printed electrostrictive terpolymer
Résumé
Printed electromechanical devices are an alternative approach for the fabrication of integrated force sensor networks on large-area flexible polymer foils. In the present contribution, we report on a novel parallel-plates capacitive force sensor device based on an electrostrictive poly(vinylidenefluoride-trifluoroethylene-chlorotrifluoroethylene) (P(VDF-TrFE-CTFE)) terpolymer that exhibited the best electromechanical coupling effect through the drop-on-demand (DoD) inkjet printing technology. Since the ejection of a printable ink droplet is one of the most essential steps for inkjet printing, the adaptable printing parameters depending on the ink delivery system as well as ink formula rheology were first investigated. Successfully printed patterns rely on a controlled drying process of the inks deposited on the flexible polyimide foil, which was also discussed. The substrate temperature was increased for achieving homogeneous polymer patterns. Such a printing technique eventually made it possible to obtain flawless polymer thin layers of several microns, preventing the devices from the risk of electrical failure due to short-circuiting. The capacitive devices were evaluated by proposition of a dynamic force sensor. Sensor devices based on an electrostrictive terpolymer were induced to yield significant polarization thanks to a bias voltage whereas a sensor device of poly(vinylidenefluoride-trifluoroethylene) P (VDF-TrFE) copolymer must be poled under a high electric field with a very high risk of breakdown failure. The pseudo-piezoelectric coefficient d(33)(eq) was a strict function of the applied electric field and reached as high as 81.6 pC N-1 under 33.33 V/mu m. The fabrication process in the present study holds high potential in large-area printed terpolymer sensor networks without a poling process as each sensor corresponds to a pixel of the sensing array.
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