1 research outputs found
High Strength Magnetic/Temperature Dual-Response Hydrogels for Applications as Actuators
Anisotropically structured magnetic/temperature dual-response
hydrogels
have great application prospects as actuators because they can exhibit
controlled, complex behaviors. However, one key issue hindering the
application of such hydrogels is the imbalance of the mechanical and
response properties. This study used a combination of flexible chain
polymers such as poly(N-isopropylacrylamide) (PNIPAM),
poly(vinyl alcohol) (PVA), and polyacrylamide (PAM) to build a multinetwork
structure. The introduction of TEMPO-oxidized cellulose nanofibrils
(TOCNF) as a nanofiber reinforcement agent led to a key improvement
to ensure a high mechanical strength by creating additional hydrogen
bonding. The cross-linking density was further increased through a
salting out treatment to obtain a greater mechanical strength while
improving the dissipation of energy applied by external sources. The
obtained temperature responsive layer featured a high tensile strength
(1.97 MPa) while the magnetically responsive layer showed a high magnetization
(6.1 emu/g) with a good tensile strength (0.47 MPa). The main idea
of this study was in combining two hydrogel layers with different
polymer network structures, with magnetic nanoparticles being dispersed
within one layer, whereas the other layer was designed as temperature-sensitive.
The obtained bilayer hydrogel had suitable mechanical properties (the
tensile strength reaching 0.81 MPa) coupled with strong dissipation
of the applied external energy and could rapidly and reversibly undergo
bending deformations upon a temperature change within a narrow range,
25–37 °C (bending angle up to 160° within 5 min).
With high magnetization characteristics for the magnetically responsive
layer, the bilayer hydrogel could easily be driven by an external
magnetic field to transport a target object, which was “grabbed”
due to the gel bending. It also showed good biocompatibility, thus
enabling applications in the field of invasive medical actuators