Hydrogel-based
wearable sensors have experienced an explosive development,
whereas functional integration to mimic the multisignal responsiveness
of skin especially for pressure and temperature remained a challenge.
Herein, a functional ionic hydrogel-base flexible sensor was successfully
prepared by integrating the thermal-sensitive N-isopropylacrylamide
(NIPAAm) into another conductive double-network hydrogel based on
polyvinyl alcohol–graphene oxide (PVA–GO) and polyacrylic
acid–Fe3+ (PAA–Fe3+). Because
of the multisynergistic network design, the triple-network hydrogel
was endowed with excellent conductivity (∼170 Ω/mm),
mechanical tolerance (1.1 MPa), and rapid recoverability (within 0.5
s), which demonstrated the potential use in pressure monitoring. Moreover,
the introduction of a thermal-sensitive network allowed it to capture
the changes in the human body temperature accurately simultaneously
and to be further developed as a flexible temperature sensor. In particular,
the unsynchronization of pressure and temperature strain (straining
to stability within 0.5 s and more than 50 s, respectively) caused
the two electrical signals to be automatically separated. Intuitive
reading of data without involving complex parameter separation calculations
allowed the hydrogel to be developed as an integrated dual temperature–pressure-sensitive
flexible sensor. In addition, all above properties demonstrated that
the as-prepared functional hydrogel could be extended to the practical
application in human–machine interactions and personalized
multisignal monitoring.
Effective
emulsions’ separation is greatly significant for
human health and environmental remediation. In this work, a Janus cellulose membrane
(JCM) with asymmetric wettability and strong antibacterial activity
was successfully fabricated by facile in situ immobilization and single
side modification method. During the typical preparation process,
Ag nanoparticles were first immobilized on the CM surface, and then
one side of the CM was protected using adhesive tape for subsequent
hydrophobic modification. The obtained JCM possessed superhydrophobic
property on one side, whereas the other side was superhydrophilic.
More importantly, the JCM exhibited excellent separation performance
for various oil-in-water and water-in-oil emulsions without external
energy and the separation efficiency was more than 96.0%. Meanwhile,
the separation efficiency and flux had no dramatic fluctuations after
10 separation cycles, indicating fabulous separation recyclability
of the JCM. In addition, both sides of the JCM exhibited strong antibacterial
activity against Escherichia coli and Staphylococcus aureus, and the antibacterial phenomenon
was attributed to the intrinsic antibacterial capability of Ag nanoparticles
on the hydrophilic side and the noncontact effect of the hydrophobic
side. The facile preparation process and exceptional separation performance
of the JCM will provide more enlightenment for the design and preparation
of Janus separation materials for potential industrial applications.
Artificial flexible skin materials with high sensitivity,
different roughness surface recognition, and a wide range of pressure
sensing properties are urgent needs of artificial intelligence and
wearable devices. Inspired by the identification ability between different
rough objects of human skin, the novel flexible sensor device was
developed to improve pressure sensitivity and surface roughness identification,
consisting of silver nanowires, graphene, and biomineral hydrogels.
Here, the prepared flexible skin has a wide range of high sensitivities
including high-pressure sensitivity (0.9–5 KPa) and low-pressure
sensitivity, which can detect the pressure of the rice size. Since
graphene loaded with silver nanowires easily forms the sheet structure,
it can undergo slight changes in pressure such as sphygmus rhythm,
sound vibration, and joint bending. The flexible skin detects changes
in electrical resistance caused by dynamic interaction between the
sensor and the surface of the material being tested, distinguishing
various fruit surfaces. The flexible skin containing silver nanowires
has obvious antibacterial properties against Escherichia
coli and Staphylococcus aureus. Furthermore, the prepared flexible skin can be applied to various
fields such as artificial intelligence, tactile perception, and personal
medical equipment, demonstrating its great potential in smart skin.
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