Direct Printing of Flexible Multilayer Composite Electrodes Based on Electrohydrodynamic Printing

With the development of electronic devices toward thinner, lighter, and more flexible, the preparation of transparent electrodes for device assembly has garnered significant attention. Traditional transparent electrodes of indium tin oxides are brittle and difficult to adapt to deformations such as bending and stretching of flexible substrates. Flexible electrodes based on two-dimensional microstructures have become viable alternatives; however, the current electrode fabrication methods are complex, typically requiring the involvement of multiple machining equipment and the combination of multiple fabrication processes for machining and fabrication, and the simple, direct, and efficient integrated fabrication of electrodes is still a great challenge. Herein, an integrated manufacturing strategy for directly printing flexible multilayer composite electrodes based on an electrohydrodynamic printing process is proposed. The printing experimental system was designed. A finite element model was developed to make a preliminary selection of the parameters and the range of values affecting printing. Experiments were designed to analyze the combination of printing parameters to determine the range of applicability. The line width prediction model was used to predict the printing of structures with superior finish quality. Different printing modes were selected for different mesh electrode layers, electrode reinforcement layers, and encapsulation layers of the composite electrodes. Surface modification treatment was combined with direct printing for the direct assembly of electrodes. The electrode of finalized size 20 mm × 20 mm has good light transmission, conductivity, deformation, and mechanical stability; current efficiency and light-emitting diode (LED) light brightness before and after deformation are basically unchanged. The electrode in different bending diameters after 1000 cycles of resistance change is small and lightweight and has stable performance under different working conditions, good environmental adaptability, and excellent overall performance. The potential of composite electrodes for a wide range of applications in emerging wearable multifunctional electronic devices is shown by fabricating wearable strain sensors and heated films based on this electrode. This method can be used to manufacture simple, low-cost, high-performance, and high-efficiency electrodes.