Electrohydrodynamic lithography of metallic mesh for optically transparent flexible and conformal antennas

Abstract

The optically transparent antenna is becoming a very attractive proposition for various applications, such as wearable devices and vehicle radars. The fabrication of transparent flexible/conformal antennas is a long-lasting interest in academia and industry. However, the preparation of radio-frequency radiators with excellent conductivity and optical transmittance is still quite challenging. Herein, we introduce a facile approach to directly fabricate optically transparent flexible and conformal coplanar waveguide-fed antennas using programmable electrohydrodynamic lithography. Metallic meshes with transmittance above 90% have been successfully created based on the conformal electrohydrodynamic printing of high-viscosity photoresist masks, and the corresponding sheet resistance can be tuned down to ∼2 Ω/□. Then, the geometrical structure of the proposed transparent antenna has been systematically optimized because of the basic radio frequency components, including the radiator, feeder line, ground plane, and size of metallic meshes. Optically transparent flexible and conformal antennas are finally obtained, presenting an optical transmittance of 92% and 55%, respectively. The simulated and measured results demonstrate that the transparent antennas with a good optoelectronic performance indeed exhibit a nice electromagnetic behavior. We believe that this newly developed conformal electrohydrodynamic lithography method can be utilized to fabricate a variety of other transparent electronic devices, such as transparent electromagnetic shielding meshes on aircraft canopies, in the future.