Fig. 2: Characterization of LM microstructures with a single gallium layer.

a Evolution of an LM microstructure as the evaporated mass of gallium increases. Schematic illustrations and SEM images are presented for deposited gallium mass per unit area: λ_Ga = 0 mg cm⁻², λ_Ga = 0.043 mg cm⁻², λ_Ga = 0.22 mg cm⁻², and λ_Ga = 0.86 mg cm⁻² from left to right (scale bars: 2, 2, 5, and 20 µm from left to right). An indium layer with a thickness of 150 nm was deposited onto a PDMS substrate prior to the gallium evaporation. A uniform, entire coverage of gallium on the film is achieved only with λ_Ga = 0.22 mg cm⁻² (1 × LBL). b–d Relative resistance responses of the LM microstructures of λ_Ga = 0.043 mg cm⁻² (b), λ_Ga = 0.22 mg cm⁻² (c), λ_Ga = 0.86 mg cm⁻² (d). Resistance values were measured during ten cycles of 50% tensile strain with the samples pre-strained up to 50% before the measurement. e–g SEM images and energy dispersive spectroscopy (EDS) mappings of the LM microstructures of λ_Ga = 0.043 mg cm⁻² (e), λ_Ga = 0.22 mg cm⁻² (f), λ_Ga = 0.86 mg cm⁻² (g) under 50% tensile strain; gallium (red) and indium (yellow) are the evaporated metals; silicon (green) represents the underlying PDMS substrate (scale bars: 10 µm; inset image scale bars: 2 µm).