Intelligent skinlike materials have
recently attracted tremendous
research interests for employing in electronic skin, soft robotics,
and wearable devices. Because the traditional soft matters are restricted
in unsatisfactory mechanical performances or short-term usage, these
materials are adverse to practical applications. Here, intriguing
conductive hydrogel materials with multifunctionality (MFHs) are fabricated
by using poly(acrylic acid) (PAA), dopamine-functionalized hyaluronic
acid (DHA), and Fe3+ as ionic cross-linker. The mussel-inspired
networks with delicate combination of physical and chemical cross-linking
possess synergistic features of inherent viscoelasticity, high stretchability
(800%), and durable self-adhesiveness to various substrates. Owing
to the abundant hydrogen bonds and multiple metal coordination interactions
between Fe3+, catechol, and carboxylic groups, the matrix
reveals repeatable thermoplasticity and autonomous self-healing property
both mechanically and electrically (98% recovery in 2 s). When served
as strain sensors, the MFHs can distinctly perceive complex body motions
from tiny physiological signal (breathing) to large movements (knee
bending) as human motion detecting devices. Moreover, the MFHs were
explored as ideal material for circuit repairing, programming, and
switches constructing because of their excellent properties. Consequently,
these eco-friendly hydrogel ionotronic devices can be promising candidates
for next-generation intelligent wearable devices and human–machine
interfaces.
The constant and
noninvasive tracking of the distribution and degradation of engineered
hydrogel scaffolds using fluorescent probes is considered to be one
of the important research studies. Conventional fluorophores were
simply mixed into hydrogels by physical doping, and they suffered
from photoinstability or UV–vis light excitation, which usually
led to the potential leak of the fluorescent tag and imprecise tracking
results. In this article, upconversion nanoparticles, NaGdF4:Yb3+,Er3+@NaGdF4 (UCNPs) with near-infrared
light (NIR) excitation, were synthesized and were coated with polydopamine
(PDA). A biodegradable composite hydrogel OSA-I-CMCS-I-UCNPs@PDA (“I”
means “linked-by”) was constructed by the UCNPs@PDA,
serving as both the construction unit and NIR-excited fluorescent
probe, where carboxymethyl chitosan (CMCS) was used as the cross-linker
to chemically cross-link UCNPs@PDA and oxidized sodium alginate (OSA)
based on dynamic covalent Schiff-base linkages. It is demonstrated
that the composite hydrogels possess enhanced mechanical strength,
excellent self-healing capacity, injectable performance, and good
biocompatibility with the tissue. In addition, the composite hydrogels
possess a deep penetrating ability from UCNPs@PDA in vitro through
about 10 mm thick chicken strips. A mimetic lysozyme biodegradation
test was performed for 108 h in vitro for evaluating the feasibility
and accuracy of UCNPs@PDA in tracking the hydrogel degradation. The
degradation signals were obtained by the decrease in fluorescence
intensity, which were well consistent with the weight changes in composite
hydrogels, suggesting the accuracy of the UCNPs@PDA in consecutively
monitoring the hydrogel degradation in vitro. With these superior
properties, the composite hydrogels are expected to be promising candidates
for various biomedical fields, for example, as tissue engineering
or delivery carriers in vivo.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.