Fig 1.
Displacement-driven compliant mechanisms exhibit a unique trait of scalability that unlocks potential for novel mechanical designs to operate at various scales.
(A) Three sizes of a parallel-guided mechanism. (B) Three sizes of a one-piece, fully compliant projectile launcher, with a person for scale. (C) Three sizes of a monolithic chair. The individual in this figure has given written informed consent (as outlined in PLOS consent form) to have their image appear in this paper.
Fig 2.
A compliant parallel-guiding mechanism as an example of a scalable compliant mechanism.
(A) A compliant parallel-guiding mechanism with a specified applied force, F, (shown undeflected). (B) The same device shown as a displacement-driven compliant mechanism which has undergone a specified displacement, δ. (C) The mechanism illustrated in an isometric view, with geometric parameters shown. (D) A prediction of stress for the parallel-guided mechanism (size A.1 from Fig 3) using finite element analysis software.
Table 1.
The result of scaling the geometry of the mechanism in Fig 2 by a factor of C on different mechanical behaviors.
Note that the maximum deflection ratio before failure remains constant regardless of scaling the geometry.
Table 2.
Values for and
as functions of
. This table is adapted from [36].
Fig 3.
Compliant parallel-guiding mechanisms are shown at various scales.
(A-B) Three parallel guiding mechanisms with increasing values of the scaling factor, C, (from left to right: C = 1, C = 2, C = 5). (C) Three parallel guiding mechanisms with increasing values of the scaling factor for the width b (from left to right: C = 1, C = 2, C = 4). (D) The dimensions of A.1, A.2, A.5, B.1, B.2, and B.4 are illustrated (not to scale). All dimensions are in units of millimeters. For both Series A and B, the number in the label represents the relative scaling factor from the first mechanism in the series.
Fig 4.
Finite element analyses of strain in three scales of a compliant parallel-guided mechanism.
Finite element simulations of each parallel-guided mechanism scale shown in Fig 3A and 3B. The observed strain values aligned with the experimental data shown in Fig 6.
Fig 5.
The testing setup for compliant parallel-guided mechanism data collection.
(A-B) Two views of the testing setup used for both the force/displacement and strain tests are illustrated here. (C) High-precision strain gauges on flexible beams of three geometric scales of a compliant parallel-guided mechanism. Strain gauges were adhered to the Series-A parallel guided mechanisms. The smallest specimen, A.1, has a strain gauge touching the end of the flexible member—the point of maximum bending stress. To make an approximate comparison between scales, the center of the wire grid for each strain gauge is located at the same relative distance along the length of the flexure for each specimen.
Fig 6.
Strain and force data is collected for various scales of compliant parallel-guiding mechanisms.
Top: The measured strain (𝜖) for the displacement-driven compliant mechanism at different scales. Bottom: The reaction force (F) over the width b for three different scales of b from a specified input displacement range of 0.0 to 0.30 .
Fig 7.
A toy dart launcher as a demonstrative compliant mechanism.
(A) A disassembled commercially available foam dart launcher illustrating that over eighty parts are used to construct the device. (B) An assembled foam dart launcher. (C) A monolithic compliant mechanism version of the launcher made from a single 3-D printed piece. (D) The compliant launcher at 100% of the scale of the original launcher (C = 1), at one-tenth scale (C = 0.1), one-hundredth scale (C = 0.01), and 725% of the original (C = 7.25) with a person for reference. The individual in this figure has given written informed consent (as outlined in PLOS consent form) to have their image appear in this paper.
Fig 8.
A monolithic chair folded from a single piece of material.
(A) A lamina emergent torsional (LET) joint as a unit cell used in the array. (B) A single piece of fluorescent acrylic with cuts made to create arrays of LET joints in select locations. (C) The 1.22 m by 1.83 m acrylic sheet folded into a chair. (D) Three sizes of the chair including a doll-house chair (C = 1/3), a child-size chair (C = 1/2), and an adult-size chair (C = 1).