Abstract
We integrated a piezoelectric sensing layer lamina containing liquid crystals (LC) and spiropyran (SP) in a LC/SP mixture to create an optically reconfigurable modal sensor for a cantilever beam. The impedance of this LC/SP lamina was decreased by UV irradiation which constituted the underlying mechanism to modulate the voltage externally applied to the piezoelectric actuating layer. Illuminating a specific pattern onto the LC/SP lamina provided us with a way to spatially modulate the piezoelectric vibration signal. We showed that if an UV illuminated pattern matches the strain distribution of a specific mode, a piezoelectric modal sensor can be created. Since UV illumination can be changed in situ in real-time, our results confirm for the first time since the inception of smart sensors, that an optically tailored modal sensor can be created. Some potential applications of this type of sensor include energy harvesting devices, bio-chips, vibration sensing and actuating devices.
Highlights
Modal sensors were originally developed to eliminate a spillover problem which has its roots in noise induced by high-frequency modes in structural feedback control [1]
For a one-dimensional cantilever beam, the metallic electrode of the traditional mode 1 sensor was made with a specific pattern [1]
We used liquid crystals (LC) as the solvent which was mixed with 3 wt% of the spiropyran powder
Summary
Modal sensors were originally developed to eliminate a spillover problem which has its roots in noise induced by high-frequency modes in structural feedback control [1]. We developed an optical modal sensor system which integrates a lead zirconate titanate (PZT) containing liquid crystals (LC) and spiropyran (SP). The LC/SP lamina was employed to replace the traditional metallic electrode for modal sensor application due to its electrical properties.
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