Controllable Bending of Bi-hydrogel Strips with Differential Swelling

  • Yi Wu
  • Xingpeng Hao
  • Rui Xiao
  • Ji Lin
  • Zi Liang Wu
  • Jun Yin
  • Jin QianEmail author


Bi-hydrogel strips consisting of a highly swelling layer and a non-swelling layer are investigated in this study, in which the differential swelling capabilities and mismatch strain in the composite structure drive the strips into a bending configuration when being exposed to solvents. A modified analytical model originated from Timoshenko theory on bi-material beam is proposed to predict the swelling-induced bending shape of the bi-hydrogel strips, with explicit relations of bending curvature and mid-span deflection versus mismatch strain. Different sets of experiments were performed to verify the analytical model and its solutions, in which the swelling-induced mismatch strain was systematically tuned by the selection of saline concentration. The broad agreements between the theoretical and experimental results indicate that the modified analytical model can be used to guide the design of morphing elements by modulating layer-by-layer mismatches in gel composites to produce precise and complex shape transformations for practical applications.


Bi-hydrogel strip Hydrogel swelling Mismatch strain Shape morphing Analytical model 



This work was supported by the National Natural Science Foundation of China (91748209, 11672268 and 11621062), the Zhejiang Provincial Natural Science Foundation of China (LR16A020001) and the Fundamental Research Funds for Central Universities of China.


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Copyright information

© The Chinese Society of Theoretical and Applied Mechanics 2019

Authors and Affiliations

  • Yi Wu
    • 1
  • Xingpeng Hao
    • 2
  • Rui Xiao
    • 1
  • Ji Lin
    • 1
  • Zi Liang Wu
    • 2
  • Jun Yin
    • 3
  • Jin Qian
    • 1
    Email author
  1. 1.Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province, Department of Engineering MechanicsZhejiang UniversityHangzhouChina
  2. 2.MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and EngineeringZhejiang UniversityHangzhouChina
  3. 3.State Key Laboratory of Fluid Power and Mechatronic Systems, Key Laboratory of 3D Printing Process and Equipment of Zhejiang Province, School of Mechanical EngineeringZhejiang UniversityHangzhouChina

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