Highly flexible liquid metal composite electrodes through direct laser patterning

A highly flexible electrode was fabricated using eutectic gallium–indium (eGaIn) liquid metal combined with an ultraviolet (UV)-curable polyurethane acrylate (PUA) polymer. The eGaIn liquid metal electrodes prepared by a negative-type direct patterning technique using a UV pulse laser can eliminate the need for complex photolithography masks. The optimal UV pulsed laser peak fluence was ∼1.43 J/cm² to pattern and sinter the eGaIn/PUA composite electrode simultaneously. The laser-patterned eGaIn/PUA composite electrode under optimal laser conditions exhibited a remarkable electrical conductivity of 6.33 × 10⁵ S/m with a patterning resolution of ∼40 μm. Moreover, the resistance of the electrode deteriorated by only 0.95% after 50 000 cycles of severe cyclic folding at a peak strain of 2.5% with a bending radius of 1 mm, demonstrating its exceptional flexibility and durability. These easily patterned eGaIn flexible electrodes through direct laser patterning techniques hold great promise for applications in wearable and flexible electronic devices that require extreme flexibility.