Optimization of Phase-Change Material–Elastomer Composite and Integration in Kirigami-Inspired Voxel-Based Actuators

Abstract

Phase-change material–elastomer composite (PCMEC) actuators are composed of a soft elastomer matrix embedding a phase-change fluid, typically ethanol, in microbubbles. When increasing the temperature, the phase change in each bubble induces a macroscopic expansion of the matrix. This class of actuators is promising for soft robotic applications because of their high energy density and actuation strain, and their low cost and easy manufacturing. However, several limitations must be addressed, such as the high actuation temperature and slow actuation speed. Moreover, the lack of a consistent design approach limits the possibility to build PCMEC-based soft robots able to achieve complex tasks. In this work, a new approach to manufacture PCMEC actuators with different fluid–elastomer combinations without altering the quality of the samples is proposed. The influence of the phase-change fluid and the elastomer on free elongation and bending is investigated. We demonstrate that choosing an appropriate fluid increases the actuation strain and speed, and decreases the actuation temperature compared with ethanol, allowing PCMECs to be used in close contact with the human body. Similarly, by using different elastomer materials, the actuator stiffness can be modified, and the experimental results showed that the curvature is roughly proportional to the inverse of Young’s modulus of the pure matrix. To demonstrate the potential of the optimized PCMECs, a kirigami-inspired voxel-based design approach is proposed. PCMEC cubes are molded and reinforced externally by paper. Cuts in the paper induce anisotropy into the structure. Elementary voxels deforming according to the basic kinematics (bending, torsion, elongation, compression and shear) are presented. The combination of these voxels into modular and reconfigurable structures could open new possibilities towards the design of flexible robots able to perform complex tasks.

Utilizing the Peltier effect for actuation of thermo-active soft robots

“…This low conductivity resulted in the heating of the soft actuator to be heavily concentrated at the contact surface of the Peltier, which causes localized expansion at the Peltier junction interface. Previous studies utilizing resistive heating [29,42] experience this problem on a smaller level, as the soft body is built around the axis of an inner coil, and the heating/expansion occurs radially. This finding led to much lower aspect ratios with relation to the Peltier surface for the application design.…”

“…However, the use of fluorocarbons has become limited due to their adverse impact on the ozone layer. In order to address this issue, Novec-7000, an engineering fluid with a vaporization temperature of 34 • C, has emerged as a promising alternative [41,42]. Novec-7000 has been found to be effective in managing thermal systems while being environmentally friendly.…”

A Voxel‐Based Approach for the Generation of Advanced Kinematics at the Microscale

“…[ 10,12 ] In our previous work, we showed that shear could also be obtained at the centimeter scale using an isotropically expansive transducer. [ 13 ] Advanced modular robots have been engineered using similar voxel‐based approaches, with either predefined bending or twisting modules [ 14 ] or reprogramable voxels which can bend, contract, and stiffen. [ 15 ] Both solutions rely on pneumatic actuation and are implemented at the centimeter scale.…”

“…[10,12] In our previous work, we showed that shear could also be obtained at the centimeter scale using an isotropically expansive transducer. [13] Advanced modular robots have been engineered using similar voxel-based approaches, with either predefined bending or twisting modules [14] or reprogramable DOI: 10.1002/aisy.202200394…”

Research on the Use of Silicon-Ethanol Composite in Actuators

“…In the literature, composite-based actuators in which the bending movement is performed are also proposed and described in [ 16 , 17 ]. So far, designers of these solutions are looking for applications in the field of flexible robots, called soft robots.…”