Recently,
concerns over water scarcity are on the rise, leading
to growing research interest in advanced water purification methods.
Solar water purification, which utilizes sustainable energy to separate
water impurities and water through evaporation, is emerging as a promising
strategy for clean water production. Here, we report a novel solar
evaporator based on a carbon nanotube composite polyacrylamide hydrogel
(CAH) with a high solar evaporation rate of 4.3 kg·m–2·h–1 under 1 sun irradiation (1 kW·m–2). Such a highly efficient solar evaporator is achieved
by introducing solar absorbers (carboxyl multi-walled carbon nanotubes)
in the hydrophilic skeleton (polyacrylamide) of hydrophobic association
hydrogel. More importantly, the self-healing properties endowed by
hydrophobic association also provide a simple fabrication route of
double-layer hydrogel-based solar evaporator. By a proper double-layer
structure design, the solar evaporation rate of CAH can be further
increased to a record high value of 5.1 kg·m–2·h–1. In addition, the CAH can effectively
remove salt ions and heavy metal ions in water. The extraordinary
performance along with the simple and low-cost fabrication route of
CAH offers possibilities for practical ultra-fast solar water purification
under natural sunlight.
Flexible
hydrogel strain sensors have received increased attention
due to their potential applications in human–machine interfaces,
soft robotics, and electronic skin. However, it still remains a challenge
to prepare a multifunctional conductive hydrogel integrating high
stretchability, strength, and self-healing property. Here, melanin-inspired
polydopamine–Fe (PDA–Fe) nanoparticles were successfully
incorporated into the hydrogel, with hydrophobic association serving
as dynamic physical cross-linking. The hydrogel exhibited ultrahigh
stretchability (1900%) and toughness (1.24 MPa), rapid recovery, self-healing
property, photothermal effect, and thermal stability. PDA–Fe
enhanced the electrical conductivity of the gel, making it potentially
useful for application in flexible strain sensors. The PDA–Fe
hydrogel strain sensor showed a broad sensing range (350%), high sensitivity
(GF = 3.7), a fast response time, and reliable durability, which could
enable detection of large (bending of the finger, elbow, and knee)
and subtle (pronunciation) human movements. Therefore, the strategy
will shed light on preparation of a multifunctional conductive hydrogel
for broad applications.
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