Development and prototyping of SMA-metamaterial biaxial composite actuators

Abstract

Shape memory alloys (SMA) are excellent candidates for implementation in actuator systems due to their ability to recover their original shape after high-strain loading through a thermally-induced phase transition. In this work, we propose and develop a novel SMA-metamaterial actuator which is capable of exhibiting a reversible, global elongation in multiple directions induced by the unidirectional contraction upon heating of a single SMA component. This actuator consists of i) an SMA component, ii) a bias component and iii) the metamaterial geometry, with each component having a distinct function: i) actuation activation, ii) reversibility of actuation upon deactivation and iii) amplifying and re-directing the uni-directional SMA actuation globally throughout the actuator, respectively. A prototype actuator was designed and tested in various configurations over multiple activation/deactivation cycles in order to demonstrate the functionality and reusability of this system. Furthermore, a theoretical model which predicts the actuation stroke of the system on the basis of the material properties of the SMA and bias components as well as the geometry of the metamaterial system was developed and validated. The findings of this work demonstrate the considerable potential of SMA-metamaterial actuators for implementation in systems requiring a multi-axial actuation output.

Design of auxetic cellular structures for in-plane response through out-of-plane actuation of stimuli-responsive bridge films

“…Consequently, one could consider the use of pin-joints to couple the bridge film to the unit cell. Such joints have been used in fabricating stimuli-responsive metamaterials [48]. The torsional stiffness of such couplings are negligible and τ will tend to 0.…”

“…This design allows for a greater macroscopic inplane negative expansion range while maintaining high relative stiffness. A similar strategy has been employed in-plane by instead using shrinking shape memory alloys (SMA) [47,48] as actuators to induce expansion in cellular structures [48]. However, in contrast to these designs, the actuation mechanism of the bi-material bridge film proposed in the current work is out-of-plane and only its projection into the plane governs the in-plane response, expanding the design space significantly.…”

“…However, in contrast to these designs, the actuation mechanism of the bi-material bridge film proposed in the current work is out-of-plane and only its projection into the plane governs the in-plane response, expanding the design space significantly. Additionally, SMA actuators are generally one-way actuators and require a bias component to be designed into the system to impart reusability [48][49][50][51]. This also implies that they can generally be designed to only shrink with either a positive or negative stimulus.…”

A differentiable actuator extends potential configurations of modular robots

“…There are some knowledge gaps in designing differentiable actuators and composing as many potential robot configurations as possible. First, smart materials and mechanical structures [39][40][41][42][43][44] are needed to provide multidimensional and efficient motion. Proper mechanical design enables actuators to respond to mechanical preloading and differentiate like MSCs.…”

Transmission efficiency of one tooth difference sine tooth profile planetary reducer

“…For it, various actuators based on functional materials have been developed, including memory alloy actuators [ 30 , 31 ], piezoelectric actuators [ 32 , 33 ], and dielectric elastomer actuators [ 34 ], greatly simplifying the driver structure and reducing the driver size. However, this type of driver has relatively small driving capacity and is mainly used in micro robots and micro electromechanical systems.…”