Fig. 2. Ink Design for Direct Ink Writing (DIW).

a Schematic illustration of the multi-material printing process for fabricating an EL device, which consisted of two ion conducting elastomer (ICE) layers and one electroluminescent elastomer (ELE) layer. The addition of SiO₂ nanoparticles in the inks leads to physically-crosslinked gels, which are fluidized by the shearing force during ink extrusion and can be recovered to the gel state right after printing. Further UV-initiated polymerization of DMAPS/PEGDA or TEAc/PEGDA leads to the formation of an intact network structure. b Images of the 3DP EL devices under mechanical deformation (i.e., twisting and bending), which are powered with an alternating current. Scale bar: 5 mm. c Shear storage moduli (G') and loss moduli (G'') of the ICE, ELE, and IDE inks as a function of shear stress at 25 ^∘C, measured under an oscillatory mode at a frequency of 1 Hz. d Apparent viscosity of the optimized ICE, ELE, and IDE inks as a function of shear rate at 25 ^∘C. e Images of the high-fidelity electroluminescent prints of the ELE patterns. f Summary of the physical parameters (i.e., modulus (E), strength (S), elongation at break (λ) and conductivity (σ)) of the ICE samples fabricated from both molding and the 3D printing techniques. g Plotting of the luminance intensity of the 3DP ELE patterns using inks with or without SiO₂ NPs against the applied voltage per thickness (E) (thickness of ELE layer was 150 μm, frequency of the applied voltage was 500 Hz). h Plotting of the luminance intensity of the 3DP ELE patterns against the applied voltage per thickness (E) at various frequencies of the applied voltage. Data in f, g, and h are means ± S.D., n = 3 independent samples.