With the rapid development of wearable and portable electronics, the demand for all-solid-state flexible energy storage devices with high performance, long-term cycling stability and bending stability has been aroused. Physical and chemical method for preparing thin-film materials has enabled planar flexible supercapacitors (SCs) to be fabricated for a variety of applications. In this work, we report on the facile fabrication of an all-solid-state flexible interdigitated supercapacitor with a convenient and efficient two-step method. 3-D nanostructured alpha-MnO2 has been prepared on the surface of interdigitated Pt metal pattern on polyethylene terephthalate (PET) substrate as high-performance electrode material via in-situ catalytic solution route without any assistance of template or surfactant. The SCs are fabricated with PVA/H3PO4 as solid-state electrolyte, which exhibited good electrochemical performance with areal capacitance as much as 20 mF cm(-2) at a scan rate of 10 mV s(-1), relatively high energy density (3.6 x 10(-7) Wh cm(-2)-1.9 x 10(-6) Wh cm(-2)) and power density (9 x 10(-5) W cm(-2)-1.6 x 10(-4) W cm(-2)), and excellent long-term cycling stability with capacitance retention of 82.2% (10,000 times charge and discharge), and bending stability with capacitance retention of 89.6%. (C) 2016 Elsevier B.V. All rights reserved.