The origami waterbomb base is a single-vertex bistable origami mechanism that has unique properties which may prove useful in a variety of applications. It also shows promise as a test bed for smart materials and actuation because of its straightforward geometry and multiple phases of motion, ranging from simple to more complex. This study develops a quantitative understanding of the symmetric waterbomb baseʼs kinetic behavior. This is done by completing kinematic and potential energy analyses to understand and predict bistable behavior. A physical prototype is constructed and tested to validate the results of the analyses. Finite element and virtual work analyses based on the prototype are used to explore the locations of the stable equilibrium positions and the force–deflection response. The model results are verified through comparisons to measurements on a physical prototype. The resulting models describe waterbomb base behavior and provide an engineering tool for application development.

Carbon nanotubes (CNTs) can be grown in dense lithographically patterned forests to form framework structures that can be filled in via chemical vapor deposition to form solid structures. These solid structures can then be used in microelectromechanical systems (MEMS) applications. Initial testing with these structures suggests that when these frameworks are filled with carbon, the resulting material exhibits favorable properties for use in compliant MEMS. To better understand this material's properties, we conducted tests to measure its Young's modulus, failure stress, and stress relaxation in the direction perpendicular to the CNT growth, as well as the modulus and stress in the direction parallel to the CNTs. To determine the properties in the transverse direction, we applied vertical loads to the tips of simple cantilever beam samples, and recorded the force and deflection until failure. The results showed failure strain up to 2.48%. Cantilever samples prepared from the same pattern were also used to measure the stress relaxation of the material. The first test for each sample showed an average force relaxation of 3.72%, while successive tests only produced 1.23% after 24 h. To determine the properties in the direction parallel to the CNTs, we prepared simple rectangular beams and subjected them to 3-point bending tests. The average strain calculated in the parallel direction was 8.17%.[2013-0121] Index Terms-Micromechanical devices, carbon nanotubes, material properties.

Carbon nanotubes can be grown vertically from a substrate to form dense forests hundreds of microns tall. The space between the nanotubes can then be filled with carbon using chemical vapor deposition to create solid structures. These infiltrated structures can be detached from the substrate and operated as single-piece MEMS. To facilitate the design of compliant microdevices using this process, we explored the influence of two fabrication parameters—iron layer thickness and infiltration time—on the material’s mechanical properties, using the fracture strain to judge suitability for compliance. We prepared samples of a simple meso-scale cantilever beam pattern at various levels of these parameters, applied vertical loads to the tips of the beams, and recorded the forces and deflections at brittle failure. These data were then used in conjunction with a nonlinear FEA model of the beams to determine Young’s modulus and fracture stress for each experimental setting. From these data the fracture strains were obtained. The highest fracture strain observed was 2.48%, which is approximately 3.5 times that of polycrystalline silicon. This was obtained using an iron layer thickness of 10 nm and an infiltration time of 30 minutes. We used a test device—a compliant gripper mechanism for holding mammalian egg cells—to demonstrate the use of this material in compliant MEMS design.

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