Multi-responsive and conductive bilayer hydrogel and its application in flexible devices

Yu, Dongyang; Teng, Yanhua; He, Feng; Lin, Xiuling; Li, Jianjun; Wang, Qingping; Xue, Changguo

doi:10.1039/d1ra09232d

Cited by 7 publications

(3 citation statements)

References 40 publications

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“…Poly(N-isopropylacrylamide) (PNI-PAAm), a widely studied thermoresponsive hydrogel, was selected as the stimuli-responsive base material. [32][33][34][35][36][37][38] This hydrogel swells below a lower critical solution temperature (LCST) and shrinks above this temperature. Electrophoresis was performed under varying conditions to generate gradient structures, and subsequent photopolymerization of the N-isopropylacrylamide (NIPAAm) and cross-linker was carried out to obtain an anisotropic thermoresponsive hydrogel with spatiallyfixed CNCs.…”

Section: Doi: 101002/marc202300205mentioning

confidence: 99%

Cellulose Nanocrystal‐Based Gradient Hydrogel Actuators with Controllable Bending Properties

Roopsung,

Sugawara,

Hsu

et al. 2023

Macromol. Rapid Commun.

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Stimuli‐responsive hydrogel actuators are being increasingly used in microtechnology, but typical bilayer hydrogel actuators have significant drawbacks due to weak adhesive interface between the two layers. In this study, thermoresponsive single‐layer hydrogel actuators are produced by generating a gradient distribution of cellulose nanocrystals (CNCs) in a poly(N‐isopropylacrylamide) (PNIPAAm) hydrogel network by electrophoresis. Tunable bending properties of the composite hydrogels, such as the thermoresponsive bending speed and angle, are realized by varying the electrophoresis time, applied voltage, and CNC concentration. By varying these conditions, the gradient distribution of the CNCs can be optimized, leading to fast bending and large bending angles of the hydrogels. Bending properties are attributed to the gradient distribution of CNCs causing different deswelling rates across the hydrogel network owing to reinforcing effects. Bending ability is also influenced by differences in the CNC dimensions based on the sources of cellulose, which determine the rigidity of the CNC‐rich layer of the polymer composite. It is thus shown that thermoresponsive single‐layer gradient hydrogels with tunable bending properties can be realized.

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Section: Doi: 101002/marc202300205mentioning

confidence: 99%

Cellulose Nanocrystal‐Based Gradient Hydrogel Actuators with Controllable Bending Properties

Roopsung,

Sugawara,

Hsu

et al. 2023

Macromol. Rapid Commun.

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“…Therefore, a method for controlling and utilizing the shape-change function via such external stimuli has been devised [4]. For example, hydrogels and reactive polymers are soft materials that can undergo shape changes through deformation in response to external stimuli such as temperature, pH, and electrical fields [5][6][7][8][9][10]. However, recent research is also drawing attention to the creation of shape deformation and shape-memory functions via the external stimulation of commonly available polymers such as those used in various existing industries.…”

Section: Introductionmentioning

confidence: 99%

Development of smart materials with versatile bending capabilities using microcellular foaming process: influence of foaming and desorption time

Lim,

Kim,

Hong

et al. 2024

Smart Mater. Struct.

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Herein, a smart material with versatile bending capability is developed using a microcellular foaming process (MCPs). In contrast to previous hydrogel-based approaches, the bi-layered smart material is fabricated using typical thermoplastics, polyethylene terephthalate glycol (PETG) and polymethyl methacrylate (PMMA), to achieve shape deformation in response to thermal stimuli. Further, the theoretical model for bi-layered smart materials based on the modified Timoshenko’s model is employed to predict and comprehend this thermal response phenomenon. Due to the distinct foaming characteristics of the two polymers, a reversal in the bending direction is achieved by manipulating the foaming and desorption time. The length variation after foaming differs depending on the desorption time for each polymer. PMMA decreases in length after foaming, measuring 56.25 mm at a desorption time of 40 min and 53.16 mm at 80 min. On the other hand, PETG shows an increase in length after foaming, measuring 53.33 mm at 40 min and 58.25 mm at 80 min. Consequently, when the two polymers are bonded and foamed, bending occurs depending on the desorption time, and a reversal in the bending direction is observed at the critical desorption time of around 60 min. Based on this result, the folding direction of a five-leafed flower-shaped object is successfully altered under thermal stimuli. This innovative approach extends the category of smart materials beyond the hydrogels and showcases the potential of the MCPs for the creation of smart materials for various applications that require versatile shape changes in response to temperature.

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“…Recently, functional hydrogels and microgels have been extensively researched in water-related fields. − Because of their high designability in chemical structures, functional hydrogels exhibit responsiveness toward different environmental stimuli such as temperature, pH, light, and electricity. This property could be utilized in drug release, artificial muscles, and other fields. − On the basis of the adsorption sites provided by hydrogels, the spontaneous incorporation of nanoparticles into a soft gel system is a feasible method to further improve the performance. Zhang et al proposed a novel asymmetric bilayer CNT elastomer/poly( N -isopropylacrylamide) (PNIPAM) hydrogel composite with integrated actuating and sensing performances that may provide new insight into the design and fabrication of intelligent biomimetic hydrogel soft robots with integrated self-sensing capacity.…”

Section: Introductionmentioning

confidence: 99%

Carbon Nanomaterials in Temperature-Responsive Poly(N-isopropylacrylamide) Microgels for Controlled Release and Friction Reduction

Cao

Ding

Fan

et al. 2022

ACS Appl. Nano Mater.

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As a type of promising lubricating additive, carbon nanomaterials can realize ultralow friction with diamond-like carbon films in water. However, the long-term dispersion stability of their aqueous solution remains a challenge. Herein, we found that a poly(N-isopropylacrylamide) (PNIPAM) microgel, which has been extensively used in nanodrug delivery, can considerably improve the dispersion stability of graphene oxide and hydroxylated multiwalled carbon nanotubes in aqueous solutions, while achieving an ultralow friction coefficient of 0.02. On the basis of structural characterizations, rheological tests, and molecular dynamics simulations, the mechanism for good collaborative effects is ascribed to the unique hybrid structure formed by the carbon nanomaterials and PNIPAM microgel via the hydrogen bonds between them. Interestingly, on the basis of the temperature sensitivity of the PNIPAM microgel, the hybrid structure can be reversed by varying the temperature, realizing controllable release of carbon nanomaterials. Surface characterizations reveal that a soft polymer tribofilm comprising a microgel and released nanomaterials forms on the wear surface after friction, accounting for the reduced friction and wear. The developed temperature-sensitive nanocomposite microgels are ecofriendly and easy to prepare, exhibiting good application prospects in water lubrication systems.

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Multi-responsive and conductive bilayer hydrogel and its application in flexible devices

Abstract: A multi-stimuli-responsive bilayer hydrogel with conductivity has potential for application as soft robots, multi-stimuli-dependent resistors and human body monitors.

Cited by 7 publications

References 40 publications

Cellulose Nanocrystal‐Based Gradient Hydrogel Actuators with Controllable Bending Properties

Cellulose Nanocrystal‐Based Gradient Hydrogel Actuators with Controllable Bending Properties

Development of smart materials with versatile bending capabilities using microcellular foaming process: influence of foaming and desorption time

Carbon Nanomaterials in Temperature-Responsive Poly(N-isopropylacrylamide) Microgels for Controlled Release and Friction Reduction

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