Metamaterial is an engineered material whose electromagnetic properties can be determined by the unit structure. Lithography is one of main methods to fabricate metamaterials for fine patterning which has limitations in large-area fabrication. We present a direct fabrication method for metamaterial using the electrohydrodynamic jet printing. An electrical pulse was controlled to make drop-on-demand operation, through which flexible high refractive-index metamaterial could be fabricated in the form of I-shaped silver electrodes with 10-μm widths and 5-μm gaps on polyimide substrate. The peak value of the refractive index was 18.4 at a frequency of around 0.48 THz.

Electrohydrodynamic (EHD) jet printing technology is an attractive method for micro-scale electronic device fabrication. The primary advantage of EHD jet printing compared with conventional inkjet printing is the capability to print at resolutions below 10 µm and to eject high-viscosity ink. In this study, by using drop-on-demand (DOD) jetting, we printed silver (Ag) dots onto a silicon (Si)-wafer and evaluated the dot uniformity. Furthermore, we investigated the effects of substrate surface energy and substrate temperature on the dot morphology. We also investigated the effects of overprinting on the dot morphologies. Our results show that we successfully created uniform dot patterns under 10 µm by using EHD jet printing. In addition the dot diameter approached 14 µm while the substrate was heated up to 40 °C. We also found that on the hydrophobic Si-wafer, increasing the substrate temperature and the number of overprinting could be used as an alternative method for increasing the aspect ratio of dot and suppressing the coffee-stain effect.

The inkjet-printing technique is regarded as an efficient method to fabricate microlens arrays used in digital cameras, medical endoscopes, displays, optical communication, and light source devices. The diameter, height, and aspect ratio of the microlens are the major contributors to these optical properties. Hence, the optical characteristics of the microlens array can vary with the type of inkjet-printing method. In this study, by employing electrohydrodynamic (EHD) jet printing with the drop-on-demand strategy, we fabricated microlenses and microlens arrays using a UV-curable photopolymer liquid on flexible poly(3,4-ethylene­dioxythiophene):polystyrene­sulfonate-coated poly(ethylene terephthalate). By controlling the number of printing drops, which is regarded as an efficient approach to control the dimension of the microlens, lenses with diameters of 11.9 ± 0.2 and 24.4 ± 0.5 μm and aspect ratio ranging from 0.22 to 0.33 were constructed. It was found that the focal length (15.44–26.79 μm), numerical aperture (0.39–0.46), and f-number (1.3–1.1) varied with the number of printing drops. The results demonstrate that the EHD-printed microlenses have a much shorter focal length, higher numerical aperture, and smaller f-number than the previously reported printed lenses. Hence, the EHD-printed microlens can be utilized to produce wide-angle-of-view applications and capture accurate images with insufficient light intensity. In addition, the proposed EHD-printing method may provide a cost-effective and simple route for manufacturing microlens arrays.