Feasiblity of using printed polymer transducers for mid-air haptic feedback

Recently, there has been considerable interest in the development of ultrasound based mid-air haptic feedback devices. These devices allow for tactile sensations to be induced at any position and time without constraints to human motion, which is useful for virtual user interfaces, augmented/virtual reality and feedback buttons. The haptic feedback mechanism is a combination of acoustic streaming and radiation force. Most work reported in literature induce said effects using matrices of 'standard' single element transducers, which are rigid, bulky and heavy. Our research focuses on the development of printed polymer transducers (PPTs): piezomembranes deposited using a printing process. As PPTs are fully flexible, < 0.25 mm thick and light, they can be easily integrated onto curved surfaces. However, the piezoelectric charge coefficients of P(VDF-TrFE) are low compared to regular PZT5A/H, making it challenging to achieve the required sound pressure. This work investigates the feasibility of using PPTs for haptic feedback using simulations and laser vibrometer- and acoustic measurements. The peak pressure produced by our chosen array design was calculated to amount to radiation forces approximately 10x larger than the tactile radiation force threshold reported in literature. Thus using PPTs for haptic feedback appears feasible.