The stiffness of a plant cell in response to an applied force is determined not only by the elasticity of the cell wall but also by turgor pressure and cell geometry, which affect the tension of the cell wall. Although stiffness has been investigated using atomic force microscopy (AFM) and Young’s modulus of the cell wall has occasionally been estimated using the contact-stress theory (Hertz theory), the existence of tension has made the study of stiffness more complex. Elastic shell theory has been proposed as an alternative method; however, the estimation of elasticity remains ambiguous. Here, we used finite element method simulations to verify the formula of the elastic shell theory for onion (Allium cepa) cells. We applied the formula and simulations to successfully quantify the turgor pressure and elasticity of a cell in the plane direction using the cell curvature and apparent stiffness measured by AFM. We conclude that tension resulting from turgor pressure regulates cell stiffness, which can be modified by a slight adjustment of turgor pressure in the order of 0.1 MPa. This theoretical analysis reveals a path for understanding forces inherent in plant cells.

This study proposes a concept of a single-layer deployable truss structure driven by elastic components which is applicable to small satellites. The structure is self-deployable from its stowed state to a planar regular hexagon configuration, and the concept is compared with other three competing concepts in terms of some geometric metrics. The deployability and serviceability of the model are verified through both numerical analyses and experiments. The deployment process of the structure is investigated and demonstrated by a deployment test. Robustness and stability analyses for the deployment are also conducted by considering failure of some elastic components. Flatness of the deployed structure is analyzed and measured. Modal analysis and frequency identification tests reveal that the fundamental frequency of the deployed structure is around 2.3 Hz. It is concluded that the proposed single-layer deployable truss structure is valid and has high potential application to small satellites.

Movable bridges are interesting and feasible solutions at the crossover point of transportations, providing fascinating landscapes and significant engineering challenges. This paper presents a new structural system applied to a movable cable-stayed footbridge. It is an S-shaped curved bridge suspended by cables, and can be opened with a moving mechanism coupled with the torsional deformation. In this paper, we clarify the mechanical behavior of the structural system through a preliminary analysis. We propose novel concepts of the twistable deck, aiming to improve the dynamic performance of the structural system. We trace the moving process of the structure by decoupling the elastic deformation and the rigid displacement. We confirm the validity and versatility of the proposed structural system through the optimal shapes for the footbridges in different cases with respect to the symmetricity and serviceability. The concept of the movable structural system proposed herein is believed to be feasible for application to the design of movable footbridges based on the preliminary analysis.