| Abstract Scope |
Direct writing of metal features on flexible substrates with additive manufacturing (AM) is challenging due to polymer heat sensitivity. Traditional AM, like laser selective melting with continuous wavelength laser, isn't viable for flexible electronics due to large heat affected zones. Current techniques, like flash light and intense pulsed light sintering, yield low electrical conductivity. Here, we introduce femtosecond selective laser sintering (fs-SLS) for directional metal film writing on flexible substrates under ambient conditions. Femtosecond lasers have small heat affected zones but cause metal particle ablations due to hot electron effects. Fs-SLS uses double-pulse femtosecond lasers to sinter metal nanoparticles, eliminating hot electron effects and reducing the heat affected zone. Another advantage is preventing metal particle oxidation even under ambient conditions. A continuous copper film was sintered onto a polyimide substrate without observing damage. Bending tests showed no cracking after 2000 cycles, with higher electrical conductivity than films from other techniques. |