Ultralight graphene-based cellular elastomers are found to exhibit nearly frequency-independent piezoresistive behaviors. Surpassing the mechanoreceptors in the human skin, these graphene elastomers can provide an instantaneous and high-fidelity electrical response to dynamic pressures ranging from quasi-static up to 2000 Hz, and are capable of detecting ultralow pressures as small as 0.082 Pa.
The architecture of the nanofiller phase in polymer nanocomposites matters! Polymer hydrogels that can combine stimuli-responsiveness with excellent electrically conductivity and mechanical strength can be fabricated by incorporation of the polymer into an ultralight and superelastic graphene aerogel to form a binary network.
The actuation of a single-wall carbon nanotube (CNT) mat, an
electrically conducting polyaniline (PAn) film and a composite of
these two materials has been investigated in NaNO3 (1
M), NaCl (1 and 3 M) and HCl (1 M) solutions. The expansion and contraction
patterns of the PAn, CNT and CNT/PAn samples are similar in these solutions.
Fabrication of the CNT/PAn samples by coating PAn (CNT:PAn = 3:1
by weight) substantially enhanced the actuation strain (0.2–0.5%) of the
CNT/PAn composite compared to the low actuation strain (0.06%) of the pure
CNT mat. The actuation of PAn and CNT operates via different mechanisms.
Non-Faradaic electrochemical charging of the CNT bundles is the main factor
behind the expansion of CNT, while the expansion/contraction of PAn is
dependent on the redox reactions of the polymer. The displacement pattern of the
composite is dominated by the PAn component. However, when a load is applied
to the sample (up to 1.2 MPa) the CNT/PAn sample behaves similarly
to CNT samples, i.e. the actuation strain is almost independent of the
applied loads in contrast to pure conducting polymers. This implies that the
reinforcing effect of the CNT component is possibly due to the inherent high
Young’s modulus of the CNT bundles (∼640 GPa).
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