Flexible Structural Color Films Based on Electro-Hydrodynamic Inkjet Printing

Abstract

Structural coloration based on nanostructures is one of the alternatives that can prevent environmental pollution compared to the use of chemically synthesized materials. This technique has attracted considerable attention for various applications, including displays and sensors. In this study, a photonic crystal structure based on spherical silica was formed to provide structural color using an electro-hydrodynamic (EHD) equipment, a printed electronic system attracting considerable interest. The EHD inkjet printing equipment could print micro- and nanostructures using the voltage applied between the nozzle and substrate. Silica-based ink samples were prepared for use in the EHD equipment. Appropriate printing parameters for the EHD inkjet printing were set using the prepared sample. Spherical silica was printed on a polyimide (PI) film layer. The spherical silica nanoparticles discharged during the EHD inkjet printing were not deformed by the EHD process. A photonic crystal structure was formed on a polydimethylsiloxane (PDMS) layer by EHD printing by covering the PDMS layer on the PI film. The spherical-silica-based photonic crystal structure formed on the PDMS layer with elasticity and flexibility exhibited a color change with bending loads.