(a) Schematic representation of a transistor wrapped round a human hair. (b) Scanning electron microscopy picture of transistors wrapped around three fragments of human hairs placed on a glass support. The thin membrane ensures high flexibility and conformability and it wraps around the hairs, which have a radius of ~50 μm (tensile strain, ε=0.4%) (scale bar, 200 μm). (c) Optical microscope picture of the area highlighted by the white box in b (scale bar, 200 μm). (d) Optical microscope picture of a non-transparent TFT (Ti/Au metallization) whose channel is bent around a hair (scale bar, 100 μm). (e) Transfer (VDS=0.1, 5 V) and output (VGS=3.5, 4, 4.5, 5 V) characteristics of a non-transparent TFT (W/L=280 μm/80 μm) bent around a hair. The device shows a threshold voltage, VTH, of about 3.4 V, a mobility, μ, of about 26 cm2 V−1s−1, a Ion/Ioff ratio greater than 106 and a gate leakage current, IG, smaller than 10 pA for full range of operations. The relatively high threshold voltage is due to the fact that this device is not passivated. (f) Transparent TFT whose channel region is bent around a hair (scale bar, 100 μm). (g) Transparent TFT (W/L=280 μm per 80 μm), when bent around a hair, shows a threshold voltage of 0.17 V and an effective mobility of 11 cm2 V−1s−1.