Page 345 - IJB-9-1

International Journal of Bioprinting High-performance electrospun PVDF/AgNP/Mxene fiber

1. Introduction than the β-phase . Since the piezoelectric coefficients
[33]
of PVDF materials are substantially lower than those of
The internet of things (IoT) will benefit from the piezoelectric ceramics, PVDF materials have not been
ubiquitous use of sensor networks in our daily lives, employed as self-powered sensors in actual applications.
such that each person and everything will be connected. In order to enhance the piezoelectric capabilities of
Wearable electronics, for example, can be positioned on PVDF and its copolymers, two techniques have been
skin, clothes, or accessories, allowing users to monitor and employed: increasing the piezoelectric phase content
receive feedback on their health and physical activities [1–3] . and enhancing the residual polarization . It is generally
[34]
While being an essential aspect of the IoT, these devices difficult to achieve a high content of the β-phase through
would likely function as personal assistants [4–8] . Wearable solution processing and conventional melting , but there
[35]
electronics should be light in weight, inexpensive, small, are several strategies to do so, including incorporating
flexible, and sustainably powered . These requirements fillers , mechanical stretching, heat treatment, and
[9]
[36]
cannot be met by existing batteries, as they are too polarizing [37,38] . Electrospinning has been recognized as
bulky and have relatively short lifespan. Nevertheless, a feasible approach to converting the non-electroactive
various pressure sensors, including resistive, capacitive, phase into the electroactive phase (γ- and β-phase). The
piezoresistive, and piezoelectric sensors, are available electrospinning of a PVDF solution allows the conversion
in the market [10–12] . In most cases, the output of these of the nonpolar α-phase into the polar β-phase.
sensors is an electrical signal that varies depending on the
amount of force or pressure applied [13–15] . Practical sensing Near- and far-field electrospinning can be used
applications require not only the conversion of mechanical to enhance the piezoelectric characteristics of PVDF.
signals into electrical signals but also an instantaneous, Electrospinning, as an excellent approach for fabricating
linear, and stable response. It is generally difficult to polymer fibers, was first patented in the United States
achieve an instantaneous, linear, and stable response with in 1902 . Until the 1990s, this technique was often
[39]
piezoresistive pressure sensors; moreover, in the interest of neglected, but it re-emerged as a leading technique
energy and environmental sustainability, renewable energy following the rapid development and applications of
sources should ideally be used to power such devices. nanofibers. It is possible to control the diameters and
Piezoelectric materials have been extensively researched on morphologies of electrospun fibers by modifying the
in recent years for their capacity to transform mechanical process parameters, particularly the molecular weight,
energy into electrical energy, and vice versa. In particular, solution properties (e.g., surface tension, conductivity,
there has been a great deal of interest in the use of organic and viscosity), flow rate, electric voltage, and distance
piezoelectric materials for fabricating flexible and wearable between the needle and the collection plate. In this study,
electronics due to their low density, high sensitivity, the parameters of near-field electrospinning (NFES)
biocompatibility, stretchability, wide detection range, low [40–42] were optimized to develop flexible, dynamic, and
to zero power consumption, high output, rapid response, soft sensing elements of PVDF piezoelectric fibers
flexibility, and ease of processing [16–20] .
incorporating silver nanoparticles (AgNPs) and transition
Piezoelectricity is a phenomenon of electromechanical metal carbide/nitride (MXene). NFES was performed in
conversion between mechanical and electrical energy. conjunction with a rolling collection system and its XY-
Although non-centrosymmetric material is not a sufficient axis digital control platform. In order to optimize the
requirement, it is necessary to display this effect [21–24] . With piezoelectric fibers, the needle and rotating collector
the exception of cubic class 432, all non-centrosymmetric were vertically aligned to collect the fibers produced by
crystallographic classes display piezoelectricity . Pierre electrospinning. The stainless-steel needle was connected
[25]
and Jacques Curie were the first to discover that the to a positive high-voltage source. Under the effects of
asymmetric movement of ions or charges in piezoelectric gravity, the vertical collection method makes it easy to
materials is caused by deformation via the changes break through the spinneret to collector surface. With
in electrical polarization [26–28] . Due to their relatively the software-controlled platform moving back and forth,
high piezoelectric coefficients and natural flexibility, continuous piezoelectric fibers were obtained through
poly(vinylidene fluoride) (PVDF) and its copolymers electrospinning. Through the combined effects of the
have been widely used in the production of organic conductivity, viscosity, and contact angle of the best
piezoelectric materials [29–32] . Kawai et al. discovered that precursor solution, a Taylor cone was formed, when the
PVDF has five main phases: alpha (α), beta (β), gamma (γ), electrostatic force, provided by the electric field, was
epsilon (ε), and delta (δ) . The main electroactivity of greater than the droplet surface tension, resulting in a
[32]
PVDF arises from its crystalline ferroelectric phases (γ- large amount of orderly material collected on the rotating
and β-phase), with the γ-phase being less electroactive collector with parallel electrospinning [43–46] .

Volume 9 Issue 1 (2023)olume 9 Issue 1 (2023) 337 https://doi.org/10.18063/ijb.v9i1.647
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