Photographs showing the structure of FICs. (a) Photograph of a FIC with exclusive-or circuits on the fibre surface (scale bar: 200 μm) and enlarged views (scale bars: 40 μm). (1), (2) and (3) show the uniformity of the circuits in the FIC. (b) Reconstructed three-dimensional fluorescence photomicrograph showing the connectivity of the microdevices in a FIC. The circuit can be distributed 360° around the fibre circumference. (c) Fluorescence photomicrograph showing an active driving circuit unit inside a FIC, suggesting that a wide variety of devices can be integrated into the fibre. Scale bar: 40 μm. (d) Photograph of FICs being produced at a large scale. The enlarged photograph shows the continuity of circuits in the FICs. Scale bars: 1 cm (left); 1 mm (right). (e) Photograph of a FIC being knotted and placed on a thumb, exhibiting the flexibility and structural integrity of the FIC. Scale bar: 2 mm. Reproduced with permission from Ref. [5].