Micropiezoelectric devices have become one of the most competitive candidates for use in self-powered flexible and portable electronic products because of their instant response and mechanic−electric conversion ability. However, achievement of high output performance of micropiezoelectric devices is still a significant and challenging task. In this study, a poly(vinylidene fluoride) (PVDF)/MXene piezoelectric microdevice was fabricated through a microinjection molding process. The synergistic effect of both an intense shear rate (>10 4 s −1 ) as well as numerous polar C−F functional groups in MXene flakes promoted the formation of β-form crystals of PVDF in which the crystallinity of β-form could reach as high as 59.9%. Moreover, the shear-induced shish-kebab crystal structure with a high orientation degree (f h = ∼0.9) and the stacked MXene acted as the driving force for the dipoles to regularly arrange and produce a self-polarizing effect. Without further polarization, the fabricated piezoelectric microdevices exhibited an open-circuit voltage of 15.2 V and a short-circuit current of 497.3 nA, under optimal conditions (400 mm s −1 and 1 wt % MXene). Impressively, such piezoelectric microdevices can be used for energy storage and for sensing body motion to monitor exercise, and this may have a positive impact on next-generation smart sports equipment.
With rapid consumption of fossil energy and its impact
on the environment,
the desire for clean energy is gradually increasing around the world,
and piezoelectric polymers have received extensive attention owing
to their capability to harvest discrete mechanical energy in the environment.
However, the existing piezoelectric devices are mostly low-dimensional
fibers or films, making it difficult to achieve a good balance between
mechanical robustness and piezoelectric output. Herein, a polyvinylidene
fluoride (PVDF)/multiwalled carbon nanotube (MWCNT) scaffold with
a hierarchical porous structure and geometry was fabricated by chemical-foaming-assisted
fused deposition modeling (FDM). Chemical foaming was triggered by
the heat accompanied during FDM molding, where a microporous structure
was formed inside the part without affecting the geometric design
to realize strain accumulation in normal space. Moreover, the conductive
MWCNT formed discontinuous and parallel morphology around the pores,
which not only promotes the polling process and formation of electrets,
but also avoids the electrical breakdown caused by the formation of
the conductive network. Accordingly, the combined effect of hierarchical
structure and incorporation of MWCNT leads to a balanced piezoelectric
(open circuit voltage of 8.46 V and short circuit current of 157 nA)
and mechanical performance (compressive modulus of 14.07 MPa). These
excellent properties all demonstrate the potential capabilities of
the developed piezoelectric nanogenerators in the field of self-powered
nanosensors and portable devices.
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