Development of 4D-printed shape memory polymer large-stroke XY micropositioning stages

Abstract

This paper presents two novel large-stroke XY micropositioning stages that are fabricated completely using four-dimensional (4D) printed polylactic acid (PLA). The proposed designs do not require manual training to perform actuation. Instead, printing speed is used to achieve shape programming and manipulate the deformation and shrinking levels of the PLA microactuators that control the microstage. A relationship between the printing speed, number of layers, and deformation value is formulated to model the performance of the microactuators based on these variables. The same approach is then used to develop the two proposed designs in this work. One-way actuations in the x- and y-axes are achieved using PLA actuators that are printed at speeds in the range of 40-80 mm s-1, while the rest of the structure (passive part) is printed at a speed of 10 mm s-1 to minimize unwanted deformations. The microactuators are activated by immersing the designs in hot water at 85 °C. The maximum values of the x- and y-actuations are achieved when using the highest printing speed for the microactuators. Design 1 offers actuation values of 1.99 and 1.40 mm along the x- and y-axes, respectively, while these values are 1.76 and 2.30 mm when using Design 2. The proposed designs offer a cost-effective batch fabrication solution for micropositioning applications, where the weight of the PLA required for Design 1 and Design 2 is 48.37 g and 12.61 g, respectively, which respectively costs $0.65 and $0.17. The performance of the x- and y-axes actuations show repeatable results with standard deviation values of 0.062 and 0.050 for Designs 1, and 0.054 and 0.047 for Design 2, respectively. Moreover, the standard deviation of the reproducibility of the x- and y-axes actuations are 0.064 and 0.051 for Designs 1, and 0.054 and 0.048 for Design 2, respectively. In addition, the designs offer a promising performance compared to the currently available large-stroke micropositioning stages in terms of the simplicity of the fabrication process and the area ratio.