Fig. 3: b-FDM 3D printed functional gradients.

a Design of a tensile test specimen with PLA (illustrated in red) and PETG (illustrated in light gray). The relative distance from the center is represented as x, ranging from 0 to 1. b Printed tensile test specimens with different material gradients at the interface. Printing direction was perpendicular to the longitudinal axis. c Fracture stresses and the corresponding locations of fracture from the specimens with different material gradient designs across the interface. The blue lines indicate the mean value of the fracture stresses. d Printed DM filament for full color 3D printing. e b-FDM printed planar object (inset) with 36 colors. The upper half of the object shows graded colors between any two of the primary colors (cyan, magenta, and yellow). The lower half shows the printed colors with increased brightness. f Resulting color spectrum mapped on CIE diagram. The black dotted triangle indicates the standard RGB (sRGB) gamut. g Schematic of a multimaterial device programmed with different levels of electrical resistance. h b-FDM printed result (inset) and an infrared photograph which reveals each letter with thermal gradient.