Wavelength-influenced electrical performance of laser-written flexible copper-based structures.

One-step direct laser writing process has been an efficient route for constructing flexible metal structures. However, the effect of laser wavelength on the structuring process remains unclear, thus limiting the universal manufacturing process development. In this work, the feasibility of one-step writing flexible Cu structures with different wavelength continuous diode lasers has been verified. Here, photothermal reaction dominate in the decomposition of the reducing agent to form copper structures. Difference in the wavelength mainly affect the photothermal reaction amplitude for structuring, resulting in a variation in the formation of Cu structures. At our processing conditions, the photothermal reaction induced by 532 nm laser is higher than 808 nm laser, a higher reducing-joining degree of Cu structure can be achieved by 532 nm laser. This results in a superior conductivity, adhesion, and bendability of Cu structures fabricated by 532 nm laser than that of 808 nm laser. Further, strain sensor that can detect different bending angles and bending frequencies have been fabricated by 532 nm laser-written structures to demonstrate their practical application.