Design and fabrication of novel discrete actuators for microrobotic tasks

Abstract

This paper presents a compliant monolithic multistable actuator which is able to switch its moving part between several stable positions linearly in one dimensional direction. The number of stable positions can be increased by extending the range of displacement of the moving part. The transition in each step of displacement is made to the nearest stable position in the direction of motion. Upward and downward steps are made by a specific sequence of moving, using a bistable module, opening and closing two internal clamps which are actuated by U-shaped electrothermal actuator using three subsystems. The principle and the design of each subsystem in the discrete acruator, fabrication process and experimental results are presented. The fabricated prototypes of the discrete actuator showed a proper functioning. The mean achieved displacement is 120.67±0.08 µm over 12 upward steps with a mean step of 10.06 µm, which is very close to the designed performance.

Analytical Study of the Snap-Through and Bistability of Beams With Arbitrarily Initial Shape

“…Introducing the different coefficients and constants, the snap-through solution (18) and snapping force expressions ((24), (25), (34)) are obtained. Afterwards, the different snapping points ((29), (32), (33), (38), (39)) and the conditions for reaching different levels of axial compression (28) and for bistability (41) are determined. These steps are summarized in Table 1.…”

“…Bistable beams exhibit additional advantages, such as their simplicity, passive holding, low actuation energy, small footprint, large stroke with small restoring forces, and negative stiffness zone. These advantages make bistable beams suitable for an increasing number of applications at different scales, such as space applications [1], biomedical [2], energy harvesting [3,4], resonators [5], actuators [6] accelerometers [7], shock sensors [8], gas sensors [9], pressure sensors [10], flow sensors [11], grippers [12], mechanisms with large displacement and small actuation stroke [13], switches [14], relays [15], memory devices [16], logics [17], lamina emergent frustrum [18], statically-balanced mechanisms [19], soft robotics [20], constant force mechanisms [21,22], bistable positioning [23][24][25][26], and multistable devices [27][28][29][30][31][32].…”

Repeatability and Reproducibility Analysis of a Multistable Module Devoted to Digital Microrobotics

“…Instead of using multiple bistables, this compact structure is based on three subsystems allowing to generate several stable positions. Figure 1 shows the architecture of the multistable module described in our previous work [16], [17]. It consists of three subsystems acting on a moving part.…”

“…As described in [16], the multistable module was fabricated using a single-crystalline silicon-on-insulator (SOI) wafer. As shown in Fig.…”

“…Nevertheless, this option increases the size of the actuator and its microfabrication becomes ever more complex and non-intuitive. To tackle this limitation, a new multistable module has been developed to reach several stable positions within a miniaturized structure [16]. This new architecture allows switching linearly a moving part between several stable positions in one dimensional direction.…”