Research progress in laser direct writing of flexible circuit

At present, the flexible electronics industry is in an important transitional period, and various flexible electronic devices with novel properties and enhanced functions are constantly emerging, from limited flexibility to flexible electronic devices with shape adaptability and ductility. This has greatly stimulated demand for flexible electronic devices. The development of manufacturing technologies for flexible circuits with smaller feature sizes and better performance on larger-format substrates at lower costs has attracted increasing attention. Among various technologies, laser direct writing has proven to be an efficient and flexible manufacturing method that can produce large-area flexible electronic circuits. As a nonlithographic, nonvacuum, and online processing technology, laser direct writing has received considerable attention. It can be employed in the production of circuit electrodes of various substrates, including heat-sensitive flexible substrates, and it has huge application prospects in the production of flexible electronic and energy storage devices, sensors, and wearable electronic devices. On this basis, this article summarizes the latest development in the laser direct writing of flexible circuit (LDWFC) technology for manufacturing flexible circuits. It focuses on the material types and characteristics of the conductive inks suitable for LDWFC in the production of flexible circuits. The LDWFC processing technology is introduced in detail from four aspects: laser sintering technology, laser reduction technology, laser-induced modification technology, and laser auxiliary circuit manufacturing technology. In addition, the application of LDWFC in flexible energy storage devices, tenderness sensors, and flexible displays is introduced, and the development prospects of LDWFC technology in flexible circuit manufacturing are highlighted.