Fully Transparent Friction‐Modulation Haptic Device Based on Piezoelectric Thin Film

Standing Lamb waves in vibrating plates enable haptic interfaces. If the out-of-plane displacement of these waves exceeds 1 mu m at frequencies above 25 kHz, a silent friction modulation can be created between a human finger and a vibrating plate. A fully transparent friction-modulation haptic device based on a piezoelectric thin film is demonstrated. The antisymmetric Lamb mode induced at 73 kHz allows for a functional performance that fulfills all conditions for practical use. Out-of-plane displacement reaches 2.9 mu m when 150 V unipolar voltage is applied. The average transmittance of the whole transducer reaches 75%. The key points of this technology are: 1) a thin HfO(2)layer between lead zirconate titanate film and substrate that prevents chemical reaction between them; 2) the efficient integration of transparent indium tin oxide electrodes and solution-derived piezoelectric lead zirconate titanate thin film onto optical-grade fused silica; and 3) the use of a transparent insulating layer made of SU-8 photoresist.