Researchers report a liquid crystal gel capable of generating underwater movement in response to light. The locomotion of soft-bodied aquatic organisms, such as sea slugs and snails, has inspired efforts to develop soft-bodied robots that can operate underwater. Difficulties in precisely controlling shape changes and an inability to overcome underwater drag forces hinder the use of existing materials for such robots. Metin Sitti and colleagues developed liquid crystalline gels capable of underwater photothermal actuation. The gels were designed so that light-driven heating would cause a change in the liquid crystal molecular alignment, leading to macroscopic shape changes that could drive locomotion. The material exhibited a sharp ordered-to-disordered phase transition at temperatures in the desired range, above ambient temperature but below the boiling point of water, thus causing the material to bend with increasing temperature at approximately 30-60 °C. Laser illumination of the gels in water induced localized bending of the gel at the point of illumination, and pulsed illumination led to oscillation between bent and relaxed conformations. By controlling the position and timing of illumination, the authors were able to induce various types of underwater locomotion, including crawling, walking, jumping, and swimming. The liquid crystalline gels could be used to design light-fueled aquatic soft robots, according to the authors.
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Article #19-17952: "Bioinspired underwater locomotion of light-driven liquid crystal gels," by Hamed Shahsavan et al.
MEDIA CONTACT: Metin Sitti, Max Planck Institute for Intelligent Systems, Stuttgart, GERMANY; tel: +49-7116893401; e-mail: <sitti@is.mpg.de>
Videos: Movie courtesy of Hamed Shahsavan.
DOWNLOAD MOVIE_S01: Photothermal actuation of planar liquid crystal network and liquid crystal gel constructs. https://www.eurekalert.org/file/jrnls/pnas/si/pnas.201917952.sm01.mp4
DOWNLOAD MOVIE_S02: Photothermal bending oscillation of LCN and LCG cantilevers. https://www.eurekalert.org/file/jrnls/pnas/si/pnas.201917952.sm02.mp4
DOWNLOAD MOVIE_S03: Making waves by constant illumination of LCN and LCG constructs. https://www.eurekalert.org/file/jrnls/pnas/si/pnas.201917952.sm03.mp4
DOWNLOAD MOVIE_S04: Framed locomotion of the LCG-50 construct. https://www.eurekalert.org/file/jrnls/pnas/si/pnas.201917952.sm04.mp4
DOWNLOAD MOVIE_S05: Underwater walking of the LCG-50 construct on a ratchet surface. https://www.eurekalert.org/file/jrnls/pnas/si/pnas.201917952.sm05.mp4
DOWNLOAD MOVIE_S06: Underwater jumping of the LCG-70 construct on a ratchet surface. https://www.eurekalert.org/file/jrnls/pnas/si/pnas.201917952.sm06.mp4
DOWNLOAD MOVIE_S07: Underwater jumping of the LCG-70 construct on a smooth surface. https://www.eurekalert.org/file/jrnls/pnas/si/pnas.201917952.sm07.mp4
DOWNLOAD MOVIE_S08: Underwater swimming of the LCG-70 construct. https://www.eurekalert.org/file/jrnls/pnas/si/pnas.201917952.sm08.mp4
Journal
Proceedings of the National Academy of Sciences