Abstract
Soft actuators based on hydrogel materials, which can convert light energy directly into mechanical energy, are of the utmost importance, especially with enhancements in device development. However, the hunt for specific photothermal nanomaterials with distinct performance remains challenging. In this study, we successfully fabricated a bilayer hydrogel actuator consisting of an active photothermal layer from incorporated Ti3C2Tx MXene in poly(N-isopropylacrylamide) p(NIPAm)hydrogel structure and a passive layer from the N-(2-hydroxylethylpropyl)acrylamide (HEAA) hydrogel structure. The uniform and effective incorporation of MXene into the NIPAm hydrogel structures were characterized by a battery of techniques. The light responsive swelling properties of the MXene-embedded NIPAm-based hydrogel demonstrated fully reversible and repeatable behavior in the light on–off regime for up to ten consecutive cycles. The effect of MXene loading, the shape of the actuator, and the light source effects on the bilayer NIPAm-HEAA hydrogel structure were investigated. The bilayer hydrogel with MXene loading of 0.3% in the NIPAm hydrogel exhibited a 200% change of the bending angle in terms of its bidirectional shape/volume after 100 s exposure to white light at an intensity of 70 mW cm−2. Additionally, the bending behavior under real sunlight was evaluated, showing the material’s potential applicability in practical environments.
Highlights
Actuators show changes in their behaviors, shapes, structures, or properties upon exposure to external stimuli such as heat [1,2], light [3,4], pH [5,6], ionic strength [7], and magnetic or electric fields [8]
We successfully fabricated a bilayer hydrogel actuator consisting of an active photothermal layer from incorporated Ti3C2Tx MXene in poly(N-isopropylacrylamide) p(NIPAm)hydrogel structure and a passive layer from the N-(2-hydroxylethylpropyl)acrylamide (HEAA) hydrogel structure
Considering the photothermal efficiency of the nanomaterial properties of MXene, we focused on the fabrication process [39] and application of nanocomposite hydrogels possessing Ti3C2Tx MXene [40,41] to exploit the volume shrinkage promoted by light in NIPAm-based hydrogel materials [42,43]
Summary
Actuators show changes in their behaviors, shapes, structures, or properties upon exposure to external stimuli such as heat [1,2], light [3,4], pH [5,6], ionic strength [7], and magnetic or electric fields [8]. MXene is a relatively new type of 2D material derived from the MAX phase (two-dimensional closely packed layered structure of M transition metal, A is an A-group element and X is C and/or N) etching of the A phase by a selective method [24,25] Such materials possess interesting properties such as high electrical conductivity and thermal stability, hydrophilic characteristics, and a high surface area [26]. Considering the photothermal efficiency of the nanomaterial properties of MXene, we focused on the fabrication process [39] and application of nanocomposite hydrogels possessing Ti3C2Tx MXene [40,41] to exploit the volume shrinkage promoted by light in NIPAm-based hydrogel materials [42,43].
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