High‐performance flexible loudspeakers have the potential to revolutionize the future of flexible/wearable electronics by providing this long‐sought function. Here, a novel method is developed to produce large‐area, flexible, and transparent piezoelectric loudspeakers, where both piezoelectric lead zirconate titanate (PZT) nanoparticles and graphene nanoplatelets (GNPs) are simultaneously aligned in the thickness direction forming dense “nanocolumn forests.” The preferential alignment of the particles not only reduces filler concentration and improves the piezoelectric performance, but also provides transparency to the film by enabling light to travel with little scattering or absorption in the thickness direction. Its potential applications, such as wearable and portable personal audio systems, along with a 9‐ft‐tall immersive walk‐through soundscape structure, are also demonstrated. The performance and the directivity of each loudspeaker are characterized through sound pressure level (SPL) versus frequency measurements over human audio spectrum (20 Hz–20 kHz) in an anechoic chamber. Furthermore, scalability of this unique roll‐to‐roll process is demonstrated on a 44‐ft‐long custom designed roll‐to‐roll (R2R) manufacturing line that can produce these six‐inch‐wide multifunctional films continuously.
Three-dimensional (3D) printing allows for complex or physiologically realistic phantoms, useful, for example, in developing biomedical imaging methods and for calibrating measured data. However, available 3D printing materials provide a limited range of static optical properties. We overcome this limitation with a new method using stereolithography that allows tuning of the printed phantom’s optical properties to match that of target tissues, accomplished by printing a mixture of polystyrene microspheres and clear photopolymer resin. We show that Mie theory can be used to design the optical properties, and demonstrate the method by fabricating a mouse phantom and imaging it using fluorescence optical diffusion tomography.
This note points out a number of corrections that were omitted from the published version of the article [Opt. Lett.41, 5230 (2016)OPLEDP0146-959210.1364/OL.41.005230].
The unusual acoustical properties of a particular landscape architecture feature of Academy Park on the Purdue University campus have been the subject of speculation for years. The feature, known informally as the “clapping circle,” consists of sixty-six concentric rings of stone tiles. When someone claps while standing at the middle of the circle, they hear a high-pitched squeak immediately afterwards. Experiments were conducted by the Purdue student chapters of the Acoustical Society of America and the Audio Engineering Society to characterize this effect. The response to a clap played from an omnidirectional speaker placed at the center of the circle was recorded using a microphone positioned above the loudspeaker. Spectrograms of the recorded responses revealed the squeak to consist of a descending tone at around 1500 Hz, and its harmonics. This tone disappeared from the spectrogram when the tile rings were covered with absorbing blankets. A mathematical model based on scattering from the gaps between the tile rings reproduced the descending frequency of the squeak, and reproduced the effect of the source and receiver height on the rate of change of frequency. Thus, it was concluded that the squeak is an example of repetition pitch produced by the tile formation.
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