Figure 1 (see Figure S1, Supporting Information) demonstrates the fabrication of a highly stretchable supercapacitor. A carbon nanotube (CNT) array was first synthesized from ethylene at 740 C by chemical vapor deposition.[15, 16] The CNTs were then coaxially re-grown with N-doped layers from acetonitrile also by chemical vapor deposition but at a higher temperature of 1060 C.[17–20] Polyurethane (PU) was coated onto the resulting NCNT array to prepare an NCNT/PU film, followed by deposition of polyvinyl alcohol (PVA) gel electrolyte. Two NCNT/PU films were attached face to face with the PVA gel electrolyte sandwiched between them to produce the desired supercapacitor.