Phosphorene is a promising candidate for flexible nano systems due to its ultra-thin nature with ideal electrostatic control and superior mechanical flexibility. Researchers have demonstrated the flexible transistors, circuits and [https://www.youtube.com/watch?v=Sd6JGbKmvUY AM demodulator] based on few-layer phosphorus, showing enhanced am bipolar transport with high room temperature carrier mobility as high as ~310 cm/Vs and strong current saturation. Fundamental circuit units including digital inverter, voltage amplifier and frequency doubler have been realized. Radio frequency (RF) transistors with highest intrinsic cutoff frequency of 20 GHz has been realized for potential applications in high frequency flexible smart nano systems.