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Humidity-responsive fiber actuators based on cellulose nanofibrils
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).ORCID iD: 0000-0003-3334-9076
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

Fiber actuators, particularly valuable in soft robotics and environmental sensing, are at the forefront of smart materials and materials innovation. Torsional and tensile biofiber actuators, notable for their cost-effectiveness and biodegradability, mark a critical gap in the development of next-generation functional materials and devices. To address this gap, this study showcases moisture-responsive actuators made from cellulose nanofibrils (CNFs). It introduces a pioneering torsional actuator, leveraging the hydrophilic nature of CNFs filaments produced through wet-spinning processes. These robust filaments exhibit a mechanical strength of 237.0 MPa, and are twisted to form the high-performance torsional actuator. This torsional actuator demonstrates rapid rotations, achieving up to 1180 revolutions per minute (rpm) within merely 10 seconds of moisture exposure and being durable across multiple cycles. The research here further explores critical factors such as filament morphology and twist density, which significantly impact the performance of this torsional actuator. Additionally, a sheath-run tensile actuator is unveiled, ingeniously combining a moisture-sensitive CNFs layer with a supercoiled nylon core to enhance structural support. 

Keywords [en]
fiber actuator, tensile actuator, tensile actuator, Wet spinning, cellulose nanofibrils
National Category
Materials Chemistry
Research subject
Materials Chemistry
Identifiers
URN: urn:nbn:se:su:diva-224539OAI: oai:DiVA.org:su-224539DiVA, id: diva2:1820191
Available from: 2023-12-16 Created: 2023-12-16 Last updated: 2023-12-17
In thesis
1. Stimuli-Responsive Materials Derived from Cellulose Nanofibrils: Synthesis, characterization, and performance evaluation
Open this publication in new window or tab >>Stimuli-Responsive Materials Derived from Cellulose Nanofibrils: Synthesis, characterization, and performance evaluation
2024 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis presents a comprehensive study on stimuli-responsive materials derived from cellulose nanofibrils (CNFs), focusing on their synthesis, characterization, and performance evaluation in various applications. Renowned for their biodegradability, renewability, and robust mechanical properties, CNFs are explored in three primary contexts: moisture-responsive actuators, voltage-responsive actuators, and CO2-responsive sensors.

The unique properties of CNFs, such as high tensile strength and surface area, are leveraged to achieve effective motion in response to moisture exposure. Specifically, CNFs are utilized to create bilayer, torsional, and tensile actuators. These actuators exhibit controllable and dynamic responses, making them suitable for applications in soft robotics and wearable technology.

In the realm of voltage-responsive actuators, this study investigates the impact of various electrolytes and counteranions on positively charged CNFs. It uncovers the critical role of electrolyte choice, ion migration and the plasticization effect within the CNFs matrix, resulting in volumetric expansion, which is pivotal to the actuation mechanism. These insights pave the way for CNFs applications requiring precise control of motion and flexibility in shape, such as in soft robotics.

The third area of application involves the development of a capacitive CO2 sensor using CNFs-based foams functionalized with primary amines to enhance CO2 capture through chemisorption. This functionalization turns the CNFs-based foam into an efficient dielectric layer (DE) for sensor applications. The addition of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) to the DE further expands the scope of sensor's capacitance change in response to CO2 exposure, underscoring its potential in environmental monitoring and CO2 detection.

Overall, this thesis emphasizes the versatility and adaptability of CNFs as a sustainable biomaterial for developing stimuli-responsive devices. The insights gained from studying CNFs in these varied applications contribute significantly to materials science and open new avenues for research in sustainable, bio-based materials.

Place, publisher, year, edition, pages
Stockholm: Department of Materials and Environmental Chemistry, Stockholm University, 2024. p. 45
Keywords
bio-based materials, cellulose nanofibrils, CO2 sorption, soft actuators, stimuli-responsive materials
National Category
Materials Chemistry Biomaterials Science
Research subject
Materials Chemistry
Identifiers
urn:nbn:se:su:diva-224538 (URN)978-91-8014-627-2 (ISBN)978-91-8014-628-9 (ISBN)
Public defence
2024-02-16, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 13:00 (English)
Opponent
Supervisors
Available from: 2024-01-24 Created: 2023-12-17 Last updated: 2024-01-16Bibliographically approved

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