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Addressing these issues is challenging due to three key factors: (1) Difficulty in finding a universal method to control deformation across different materials; (2) Variability in deformation influenced by factors such as printing speed, layer thickness, and heating temperature; (3) Environmental factors affecting the deformation process. To overcome these challenges, we introduce FreeShell, a robust 4D printing technique that uses thermal shrinkage to create precise 3D shells. This method prints triangular tiles connected by shrinkable connectors using a single material. Upon heating, the connectors shrink, moving the tiles to form the desired 3D shape, simplifying fabrication and reducing material and environment dependency. An optimized mesh layout algorithm computes suitable printing structures that satisfy the defined structural objectives. FreeShell demonstrates its effectiveness through various examples and experiments, showcasing precision, robustness, and strength, representing advancement in fabricating complex freeform surfaces.<\/jats:p>","DOI":"10.1145\/3778349","type":"journal-article","created":{"date-parts":[[2026,1,24]],"date-time":"2026-01-24T18:31:53Z","timestamp":1769279513000},"page":"1-12","update-policy":"https:\/\/doi.org\/10.1145\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["FreeShell: A Context-Free 4D Printing Technique for Fabricating Complex 3D Triangle Mesh Shells"],"prefix":"10.1145","volume":"45","author":[{"ORCID":"https:\/\/orcid.org\/0009-0002-1864-2792","authenticated-orcid":false,"given":"Chao","family":"Yuan","sequence":"first","affiliation":[{"name":"Shanghai Research Institute for Intelligent Autonomous Systems, Tongji University","place":["Shanghai, China"]}]},{"ORCID":"https:\/\/orcid.org\/0009-0005-5301-884X","authenticated-orcid":false,"given":"Shengqi","family":"Dang","sequence":"additional","affiliation":[{"name":"Shanghai Research Institute for Intelligent Autonomous Systems, Tongji University","place":["Shanghai, China"]}]},{"ORCID":"https:\/\/orcid.org\/0009-0006-6225-0445","authenticated-orcid":false,"given":"Xuejiao","family":"Ma","sequence":"additional","affiliation":[{"name":"Intelligent Big Data Visualization Lab, Tongji University","place":["Shanghai, China"]}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1316-7515","authenticated-orcid":false,"given":"Nan","family":"Cao","sequence":"additional","affiliation":[{"name":"Shanghai Research Institute for Intelligent Autonomous Systems, Tongji University","place":["Shanghai, China"]}]}],"member":"320","published-online":{"date-parts":[[2026,1,27]]},"reference":[{"key":"e_1_3_1_2_1","doi-asserted-by":"publisher","DOI":"10.1073\/pnas.1804702115"},{"key":"e_1_3_1_3_1","first-page":"1","volume-title":"Proceedings of the 2018 CHI Conference on Human Factors in Computing Systems","author":"An Byoungkwon","year":"2018","unstructured":"Byoungkwon An, Ye Tao, Jianzhe Gu, Tingyu Cheng, Xiang \u2019Anthony\u2019 Chen, Xiaoxiao Zhang, Wei Zhao, Youngwook Do, Shigeo Takahashi, Hsiang-Yun Wu, et\u00a0al. 2018. 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