Triply Periodic Channels Enable Soft Pneumatic Linear Actuator With Single Material and Scalability

Abstract

In this letter, we propose a new class of soft pneumatic linear actuators with single-material, uniaxial deformation, high energy density, and scalability, purely based on periodic curved air channels. The shape of channels is implicitly parameterized by modified triply periodic minimal surfaces (mTPMS) that partition the space into two intertwined sub-domains of open-cell topology. The period ratio of mTPMS that controls the stiffness along primary directions is identified as a key design variable, by tuning which the actuator may deliver linear, areal, and volumetric actuation modes. This letter mainly investigates the linear motion mode. The actuator&#x2019;s deformation behavior and energy density have no scale effect when the gravity is ignored, and thus the optimal design is readily scalable. Based on a unit cell with periodic boundary conditions, we develop a finite element model to predict the effect of the period ratio and the thickness-related isovalue on the actuator&#x2019;s deformation behavior, and further perform parametric optimization. The mTPMS-based actuators of complex geometry are 3D printed and exhibit linear motions up to nominal strain of 48.6&#x0025;, blocking force of 45.9 N, and energy density of 1.25 kJ/m<inline-formula><tex-math notation="LaTeX">$^3$</tex-math></inline-formula>. We demonstrate an application of the linear actuators as artificial muscles by an antagonistic arrangement. This letter explores the geometry-actuation integrated design of pneumatic metamaterials, and represents an important step toward the blueprint of &#x201C;materials as machines&#x201D; for applications envisioned across different scales.