Mechanical design of support structure for chips embedded in a convex-deformable mobile device

Abstract

Recently, the authors developed and fabricated specimens of a monolithic three-dimensionally (3D) printed convex-deformable polymer sandwich plate composed of two-dimensional (2D) auxetic face sheets and a double-pyramid truss core. The detailed dimensions of the specimens were determined through precise mechanical design, and the specimens exhibited satisfactory behavior under tensile and bending loads. However, as a more realistic mainframe of a mobile device that can be carried comfortably in the back pocket, these sandwich plates should be convex-deformable and possess appropriate flexural rigidity, even when many solid chips of different dimensions are embedded in its core. In this study, we design a support structure called the buffer to keep the embedded chips in place to minimize their interference effect on the overall convex deformation. Specimens with chips embedded in their cores were fabricated monolithically by means of 3D printing, and their mechanical behaviors under tensile and bending loads were observed. As a result, the Poisson's ratio v, flexural rigidity D, and curvature ratio of the optimally designed specimen with chips embedded in its core were −0.614, 0.0522 Nm2, and 0.591, respectively, which were satisfactory in view of the number of embedded chips.