To provide tactile feedback on flexible touch screens, transparent relaxor ferroelectric polymer film vibrators were designed and fabricated in this study. The film vibrator can be integrated underneath a transparent cover film or glass, and can also produce acoustic waves that cause a tactile sensation on human fingertips. Poly(vinylidene fluoride-trifluoroethylenechlorotrifluoroethylene) [P(VDF-TrFE-CTFE)] polymer was used as the relaxor ferroelectric polymer because it produces a large strain under applied electric fields, shows a fast response, and has excellent optical transparency. The natural frequency of this tactile-feedback touch screen was designed to be around 200-240 Hz, at which the haptic perception of human fingertips is the most sensitive; therefore, the resonance of the touch screen at its natural frequency provides maximum haptic sensation. A multilayered relaxor ferroelectric polymer film vibrator was also demonstrated to provide the same vibration power at reduced voltage. The flexible P(VDF-TrFE-CTFE) film vibrators developed in this study are expected to provide tactile sensation not only in large-area flat panel displays, but also in flexible displays and touch screens.
A novel method to drill stepwise vias on a multilayered metal/polymer structure by using a CO2 laser percussion drilling process is developed, in which the Gaussian intensity distribution of the CO2 laser and the differences in CO2 laser absorption and melting characteristics between the metal and polymer layers are understood to be the key factors. As a model device, gold and poly(vinylidene fluoride-trifluoroethylene-clorotrifluoroethylene) [P(VDF-TrFE-CTFE)] films were alternatively stacked to form a multilayer structure, and the CO2 laser percussion drilling process was optimized to produce stepwise vias on the gold/P(VDF-TrFE-CTFE) multilayer structure. After the deposition of an interconnection metal on the stepwise vias, the electrical resistance of the stepwise vias was measured and confirmed that the stepwise vias produced by the present method could provide a good electrical interconnection for multilayered metal/polymer electronic devices.
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