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In a liquid droplet, as the cohesive force of the outermost liquid molecules increases, the net force pulling the liquid molecules inward also increases. This leads to high surface tension, resulting in the liquid droplet reverting to a circular shape from its distorted shape induced by gravitational forces. Similarly, the shape and stiffness of a wheel were controlled by changing the traction force at the outermost smart chain block. As the tension of the wire spokes connected to each chain block increased, the wheel characteristics reflected those of a general circular-rigid wheel, which has an advantage in high-speed locomotion on normal flat ground. Conversely, the modulus of the wheel decreased as the tension of the wire spoke decreased, and the wheel was easily deformed according to the shape of obstacles. This makes the wheel suitable for overcoming obstacles without requiring complex control or sensing systems. On the basis of this mechanism, a wheel was applied to a two-wheeled wheelchair system weighing 120 kilograms, and the state transition between a circular high-modulus state and a deformable low-modulus state was realized in real time when the wheelchair was driven in an outdoor environment.<\/jats:p>","DOI":"10.1126\/scirobotics.adl2067","type":"journal-article","created":{"date-parts":[[2024,8,14]],"date-time":"2024-08-14T17:58:23Z","timestamp":1723658303000},"update-policy":"https:\/\/doi.org\/10.34133\/aaas_crossmark","source":"Crossref","is-referenced-by-count":27,"title":["Variable-stiffness\u2013morphing wheel inspired by the surface tension of a liquid droplet"],"prefix":"10.1126","volume":"9","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-2237-7565","authenticated-orcid":true,"given":"Jae-Young","family":"Lee","sequence":"first","affiliation":[{"name":"Advanced Robotics Research Center, Korea Institute of Machinery and Materials, University of Science and Technology, Daejeon 34103, Korea."},{"name":"School of Mechanical Engineering, Sungkyunkwan University, Suwon 16419, Korea."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1187-2456","authenticated-orcid":true,"given":"Seongji","family":"Han","sequence":"additional","affiliation":[{"name":"Department of Mechanical Engineering (Integrated Engineering), Kyung Hee University, Yongin 17104, Korea."},{"name":"Department of Mechatronics Engineering, Chungnam National University, Daejeon 34134, Korea."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5375-6344","authenticated-orcid":true,"given":"Munyu","family":"Kim","sequence":"additional","affiliation":[{"name":"Department of Control and Instrumentation Engineering, Korea University, Sejeong 30019, 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