Saltwater-responsive bubble artificial muscles using superabsorbent polymers
Robots operating in changing underwater environments may be required to adapt to these varying conditions. In tidal estuaries, for example, where the degree of salinity cycles in step with the level of the water, a robot may need to adapt its behaviour depending on the position of the tide. In fresh...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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Frontiers Media S.A.
2022-08-01
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| Series: | Frontiers in Robotics and AI |
| Subjects: | |
| Online Access: | https://www.frontiersin.org/articles/10.3389/frobt.2022.960372/full |
| _version_ | 1817996261341528064 |
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| author | Daniel Gosden Richard Suphapol Diteesawat Matthew Studley Jonathan Rossiter |
| author_facet | Daniel Gosden Richard Suphapol Diteesawat Matthew Studley Jonathan Rossiter |
| author_sort | Daniel Gosden |
| collection | DOAJ |
| description | Robots operating in changing underwater environments may be required to adapt to these varying conditions. In tidal estuaries, for example, where the degree of salinity cycles in step with the level of the water, a robot may need to adapt its behaviour depending on the position of the tide. In freshwater bodies, the unexpected presence of a pollutant may also require the robot to respond by altering its behaviour. Embodying this sensing and response in the body of the robot means that adaptivity to the environment can be achieved without resorting to centralised control. This can also allow direct responsivity using ‘free’ environmental energy, actuating without requiring stored onboard energy. In this work we present a soft artificial muscle, the contraction of which varies in response to the salinity the water surrounding it. The novel actuator uses a super-absorbent polymer gel encapsulated within a series of discrete cells. This gel readily absorbs water through the membrane wall of the actuator, and can swell to over 300 times its initial volume. This swelling generates significant pressure, changing the shape of the cells and driving the contraction of the muscle. The degree of swelling is significantly reduced by the presence of salts and pollutants in the surrounding water, so transitioning from a freshwater to a saltwater environment causes the muscle to relax. In this paper, we discuss the design and fabrication of these superabsorbent polymer-based Bubble Artificial Muscle (SAP-BAM) actuators. The tensile properties of the muscle under actuated (fresh water) and relaxed (salt water) conditions are characterised, showing a maximum generated force of 10.96N. The length response under constant load for a full actuation cycle is given, showing a maximum contraction of 27.5% of the initial length at 1N load, and the performance over repeated actuation and relaxation cycles is shown. The SAP-BAM muscles are straightforward to fabricate and are composed of low-cost, freely-available materials. Many existing pneumatically-actuated muscles can be modified to use the approach taken for this muscle. The muscle presented in this work represents the first example of a new class of super-absorbent polymer-driven environmental soft artificial muscles. |
| first_indexed | 2024-04-14T02:19:33Z |
| format | Article |
| id | doaj.art-3028ac1b2079416ab882f19b72b44820 |
| institution | Directory Open Access Journal |
| issn | 2296-9144 |
| language | English |
| last_indexed | 2024-04-14T02:19:33Z |
| publishDate | 2022-08-01 |
| publisher | Frontiers Media S.A. |
| record_format | Article |
| series | Frontiers in Robotics and AI |
| spelling | doaj.art-3028ac1b2079416ab882f19b72b448202022-12-22T02:18:04ZengFrontiers Media S.A.Frontiers in Robotics and AI2296-91442022-08-01910.3389/frobt.2022.960372960372Saltwater-responsive bubble artificial muscles using superabsorbent polymersDaniel Gosden0Richard Suphapol Diteesawat1Matthew Studley2Jonathan Rossiter3Department of Engineering Mathematics, University of Bristol, Bristol, United KingdomDepartment of Engineering Mathematics, University of Bristol, Bristol, United KingdomDepartment of Engineering Design and Mathematics, University of the West of England, Bristol, United KingdomDepartment of Engineering Mathematics, University of Bristol, Bristol, United KingdomRobots operating in changing underwater environments may be required to adapt to these varying conditions. In tidal estuaries, for example, where the degree of salinity cycles in step with the level of the water, a robot may need to adapt its behaviour depending on the position of the tide. In freshwater bodies, the unexpected presence of a pollutant may also require the robot to respond by altering its behaviour. Embodying this sensing and response in the body of the robot means that adaptivity to the environment can be achieved without resorting to centralised control. This can also allow direct responsivity using ‘free’ environmental energy, actuating without requiring stored onboard energy. In this work we present a soft artificial muscle, the contraction of which varies in response to the salinity the water surrounding it. The novel actuator uses a super-absorbent polymer gel encapsulated within a series of discrete cells. This gel readily absorbs water through the membrane wall of the actuator, and can swell to over 300 times its initial volume. This swelling generates significant pressure, changing the shape of the cells and driving the contraction of the muscle. The degree of swelling is significantly reduced by the presence of salts and pollutants in the surrounding water, so transitioning from a freshwater to a saltwater environment causes the muscle to relax. In this paper, we discuss the design and fabrication of these superabsorbent polymer-based Bubble Artificial Muscle (SAP-BAM) actuators. The tensile properties of the muscle under actuated (fresh water) and relaxed (salt water) conditions are characterised, showing a maximum generated force of 10.96N. The length response under constant load for a full actuation cycle is given, showing a maximum contraction of 27.5% of the initial length at 1N load, and the performance over repeated actuation and relaxation cycles is shown. The SAP-BAM muscles are straightforward to fabricate and are composed of low-cost, freely-available materials. Many existing pneumatically-actuated muscles can be modified to use the approach taken for this muscle. The muscle presented in this work represents the first example of a new class of super-absorbent polymer-driven environmental soft artificial muscles.https://www.frontiersin.org/articles/10.3389/frobt.2022.960372/fullartificial musclesuperabsorbent polymerhydrogelsodium polyacrylatesoft robotics |
| spellingShingle | Daniel Gosden Richard Suphapol Diteesawat Matthew Studley Jonathan Rossiter Saltwater-responsive bubble artificial muscles using superabsorbent polymers Frontiers in Robotics and AI artificial muscle superabsorbent polymer hydrogel sodium polyacrylate soft robotics |
| title | Saltwater-responsive bubble artificial muscles using superabsorbent polymers |
| title_full | Saltwater-responsive bubble artificial muscles using superabsorbent polymers |
| title_fullStr | Saltwater-responsive bubble artificial muscles using superabsorbent polymers |
| title_full_unstemmed | Saltwater-responsive bubble artificial muscles using superabsorbent polymers |
| title_short | Saltwater-responsive bubble artificial muscles using superabsorbent polymers |
| title_sort | saltwater responsive bubble artificial muscles using superabsorbent polymers |
| topic | artificial muscle superabsorbent polymer hydrogel sodium polyacrylate soft robotics |
| url | https://www.frontiersin.org/articles/10.3389/frobt.2022.960372/full |
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