Achieving
a high-strength piezoresistive foam with high sensitivity
and a large workable range remains a major challenge. To realize these
goals, we developed a facile, novel, and eco-friendly strategy for
constructing segregated microcellular structures fabricated using
coating, heat compression molding, and supercritical CO2 (ScCO2) foaming. The segregated poly(ether block amide)
(PEBA)/carbon nanostructure (CNS) composites were fabricated via compression
molding. This effectively improved the foamability and cell morphology
of PEBA/CNS composites. Moreover, compared with the randomly distributed
structure, the segregated structure also endowed the foams with better
conductivity and sensing capability. Subsequently, the ScCO2 foaming was employed to fabricate segregated PEBA/CNS composite
foams. The foaming gave composites a large compressibility and reduced
their percolation threshold. Under 1 wt % CNS loading, via tuning
the expansion ratio of foam from ∼2.1 to 4.1, the compression
stress at 50% compression strain of foam varied from ∼3.3 to
0.5 MPa, and the conductivity changed from 4.89 × 10–3 to 1.93 × 10–6 s/m, implying a tunable conductivity.
Additionally, the adjustable conductivity enabled the sensitivity
of segregated composite foams to be regulated. The segregated PEBA/CNS
foam (FCNS1–4.1) exhibited a good combination of high sensitivity
(GF = 3.5), large work range (80% strain), and high compression strength
(∼0.5 MPa at 50% strain) as well as a stable, reproducible,
and durable sensing response under a low CNS content (∼0.11
vol %). Furthermore, the ΔI/I0 of FCNS1–4.1 (75.6% porosity) reached a high
value of ∼810 and exhibited an ultrahigh sensitivity of ∼3706
(ΔI/I0ε) from 60 to 80% strain. Moreover,
the foam
sensor could be used as a sensing function sole for monitoring diverse
human motions. Therefore, the segregated PEBA/CNS composite foams
with outstanding piezoresistive performances show promising potential
applications in monitoring human motions as wearable electronics and
provides a new design strategy for a new generation of foam sensors
with high performance.