A Directional Chitosan Sound Sensor Based on Piezoelectric–Triboelectric Sensing

Abstract

Herein, we have constructed a directional sound sensor based on an anisotropic chitosan aerogel. Because of the lamellar porous structure, this chitosan aerogel exhibits a distinct anisotropic behavior, featuring the compressive stress along the direction of the parallel laminate structure, being approximately 2.6 times that in the orthogonal direction. Simultaneously, the chitosan aerogel is used as a directional sound-sensing material, which exhibits excellent acoustic–electric conversion performance with a marked difference in the direction perpendicular to the laminate structure than in the parallel direction. The CSANG has an optimum electrical output of 66 V and 9.2 μA under a sound stimulation of 150 Hz and 120 dB in the orthogonal direction of the laminate structure. Therefore, this directional chitosan sound sensor with excellent biocompatibility and sound sensitivity demonstrates promising application potential in the field of intelligent sensing and artificial cochlea.

Glycine/alginate-based piezoelectric film consisting of a single, monolithic β-glycine spherulite towards flexible and biodegradable force sensor

“…Moreover, the position and intensity of the voltage waveform precisely matched with the waveform of the sound source. This result indicates that the Gly-Alg-Glycerol piezoelectric film developed here has potential for application in artificial cochlea [ 48 ].…”

Directional freezing-induced self-poled piezoelectric nylon 11 aerogels as high-performance mechanical energy harvesters

“…In this regard, the easy processability, flexibility, biocompatibility, and chemical robustness of piezoelectric polymers render them excellent candidates to be integrated into small and lightweight devices for energy harvesting applications. 10–14 Though polymers such as polyvinylidene fluoride (PVDF) and their copolymers such as polyvinylidene fluoride trifluoroethylene (PVDF-TrFE) and poly(vinylidene fluoride-co-hexafluoropropene) (PVDF-HFP), 15,16 odd nylons, 1,2,17–20 poly (lactic acid), 4 cellulose, 21,22 chitosan, 23 polyhydroxybutyrate, 24 etc. , are known to exhibit the piezoelectric effect, most of the earlier studies were focussed on PVDF and their copolymers, as they exhibit superior piezoelectric performance.…”

“…40 Recently, many groups have focussed on the design and fabrication of three-dimensional porous ceramics, polymers and composite-based piezoelectric devices. 12,23,41–46 Porous piezoelectric materials were reported to show high output sensitivity and a higher piezoelectric harvesting figure of merit over dense materials. 47 Previous studies demonstrated that porous materials featuring a lower modulus have improved compression deformation and also the emergence of local stress hot spots improved the output performance.…”

“…50 However, only a few reports are available on the preparation of anisotropic aerogels for piezoelectric applications. 23,43,44,51,52 Though there are reports on aromatic polyamide aerogels, no attempts were made to prepare aliphatic polyamide aerogels. 53,54 Furthermore, the orientation of the polymer crystals by the directional freezing technique is rarely reported, and the understanding of the piezoelectric properties with respect to the orientation of polar piezoelectric γ crystals in aerogels is not yet reported.…”

Porous Polymer Materials in Triboelectric Nanogenerators: A Review

“…Abundant evidence has shown that the number and size of pores are crucial for defining the behavior of materials. Additionally, the porous structure of PPMs not only creates a rough surface but also offers an immense internal surface area, which might be beneficial for generating additional charges [44,45].…”