Two-Dimensional MOF Modulated Fiber Nanogenerator for Effective Acoustoelectric Conversion and Human Motion Detection

Abstract

The real-time application of piezoelectric nanogenerators (PNGs) under a harsh environment remains a challenge due to lower output performance and poor durability. Thus, the development of flexible, sensitive, and stable PNGs became a topic of interest to capture different human motions including gesture monitoring to speech recognition. Herein, a scalable approach is adapted where naphthylamine bridging a [Cd­(II)-μ-I4] two-dimensional (2D) metal–organic framework (MOF)-reinforced poly­(vinylidene fluoride) (PVDF) composite nanofibers mat is prepared to fabricate a flexible and sensitive composite piezoelectric nanogenerator (C-PNG). The needle-shaped MOF was successfully synthesized by the layering and diffusion of two different solutions. The incorporation of single-crystalline 2D MOF ensures a large content of electroactive phases (98%) with a resultant high-magnitude piezoelectric coefficient of 41 pC/N in a composite nanofibers mat due to the interfacial specific interaction with −CH2–/–CF2– dipoles of PVDF. As an outcome, C-PNG generates high electrical output (open-circuit voltage of 22 V and maximum power density of 24 μW/cm2) with a very fast response time (t r ≈ 5 ms) under periodic pressure imparting stimuli. Benefiting from bending and twisting functionality, C-PNG is capable of scavenging biomechanical energy by mimicking complex musculoskeletal motions that broaden its application in wearable electronics and fabric integrated medical devices. In addition, C-PNG also demonstrates an efficient acoustic vibration to electric energy conversion capability with an improved power density and acoustic sensitivity of 6.25 μW and 0.95 V/Pa, respectively. The overall energy conversion efficiency is sufficient to operate several consumer electronics without any energy storage unit. This acoustic observation is further validated by the finite element method-based theoretical simulation. Overall, the 2D MOF-based device design strategy opens up a new possibility to develop a human-motion compatible energy generator and a self-powered acoustic sensor to power up electronic gadgets as well as low-frequency noise detection.

Lead-Free Perovskite Cs3Bi2I9-Derived Electroactive PVDF Composite-Based Piezoelectric Nanogenerators for Physiological Signal Monitoring and Piezo-Phototronic-Aided Strain Modulated Photodetectors

“…To explore the versatile applications of the PNG for human physiological motion sensing, the PNG was conformally affixed to various parts of the body to provide body-wide physiological signal and joint movement monitoring. ,, While PNG is attached to the human skin, the subtle deformation of the PNG generates an electrical signal due to movement of the human body. The various regions of the human body movement are illustrated in Figure a to accomplish health-care monitoring .…”

Processes of Electrospun Polyvinylidene Fluoride-Based Nanofibers, Their Piezoelectric Properties, and Several Fantastic Applications

“…In addition, Zr-based MOF can also be used for SO 2 detection, and the results show that it has high sensitivity and excellent flexibility [ 125 ]. Roy et al [ 126 ] incorporated 2D MOF into PVDF, and the structure of MOF is shown in Figure 7 (1). The composite fiber-based piezoelectric nanogenerator (C-PNG) was prepared by the electrospinning method.…”

“…Reprinted with permission from Ref. [ 126 ], copyright 2021, American Chemical Society. ( 2 ) Analysis of piezoelectric properties during human movement, ( a ) voltage responses of C−PNGs attached to a wrist, ( b ) elbow, ( c ) neck, ( d ) knee, ( e ) toe, and ( f ) heel movements, the arrows represent pressure and release.…”

Self-Powered Sensors: New Opportunities and Challenges from Two-Dimensional Nanomaterials

“…The flexible and transparent 4 mm 2 ACEL display arrays successfully exhibited pattern Z (Figure 14e). In 2021, a 2D metal-organic framework (MOF) and polyvinylidene fluoride (PVDF)based piezoelectric nanogenerators were presented by Sinha and Mandal et al [79]. In addition to the excellent piezoelectric output at as high a power density as 24 µW•cm −2 , an acoustoelectric application was demonstrated (Figure 15a).…”