{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,10]],"date-time":"2026-01-10T03:49:54Z","timestamp":1768016994422,"version":"3.49.0"},"reference-count":34,"publisher":"MDPI AG","issue":"4","license":[{"start":{"date-parts":[[2025,3,25]],"date-time":"2025-03-25T00:00:00Z","timestamp":1742860800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Japan Society for the Promotion of Science (JSPS), KAKENHI","award":["JP18K04047"],"award-info":[{"award-number":["JP18K04047"]}]},{"name":"Japan Society for the Promotion of Science (JSPS), KAKENHI","award":["JP22K04026"],"award-info":[{"award-number":["JP22K04026"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Biomimetics"],"abstract":"<jats:p>In this study, we investigated the thrust enhancement in a bio-inspired underwater propulsion fin using a shear-stiffening gel. Shear-stiffening gels exhibit velocity-dependent stiffness, i.e., they become stiffer during high-speed deformation and softer during low-speed motion, providing adaptive mechanical properties without requiring complex mechanisms. A \u201ccompound joint\u201d incorporating a dilatant compound, a material of shear-stiffening gel, was developed and experimentally evaluated against a \u201crigid joint\u201d and a flexible \u201curethane joint\u201d. A speed-ratio control strategy was employed to assign faster and slower oscillations during positive and negative thrust intervals, respectively. The results demonstrated that the compound joint achieved a balance between high thrust and stable performance. Its adaptive stiffness effectively reduced deformation during high-speed oscillations, enhanced thrust while maintaining flexibility during low-speed intervals, and minimized thrust fluctuations. Compared with the rigid and urethane joints, the compound joint exhibited a superior balance between a high average thrust and low thrust variation.<\/jats:p>","DOI":"10.3390\/biomimetics10040198","type":"journal-article","created":{"date-parts":[[2025,3,25]],"date-time":"2025-03-25T10:48:58Z","timestamp":1742899738000},"page":"198","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":2,"title":["Enhancing Thrust in Underwater Bio-Inspired Propulsion Fin Using Shear-Stiffening Gel"],"prefix":"10.3390","volume":"10","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-6191-1196","authenticated-orcid":false,"given":"Shunichi","family":"Kobayashi","sequence":"first","affiliation":[{"name":"Institute of Textile Science and Technology, Academic Assembly, Shinshu University, Ueda 386-8567, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yusuke","family":"Jonishi","sequence":"additional","affiliation":[{"name":"Graduate School of Science and Technology, Shinshu University, Ueda 386-8567, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2025,3,25]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"118400","DOI":"10.1016\/j.oceaneng.2024.118400","article-title":"CFD simulation and experimental validation of novel cutting device for underwater propeller entanglements","volume":"309","author":"Liu","year":"2024","journal-title":"Ocean Eng."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"265","DOI":"10.1017\/S0022112070001830","article-title":"Aquatic animal propulsion of high hydromechanical efficiency","volume":"44","author":"Lighthill","year":"1970","journal-title":"J. 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