An investigation into behaviour of electroactive polymers as mechanical sensors

We present our experimental investigation into 'mechanochemoelectrica' behavior of tri-layer polypyrrole (PPy) -type conducting polymer sensors. One end of the polymer strip is clamped and the other-free end-is excited through a mechanical lever system, which provides sinusoidal displacement inputs. The voltage generated and current passing between the two outer PPy layers as a result of the displacement input is measured to model the output/input behaviour of the sensors through their experimental current/displacement and voltage/displacement frequency responses. We specifically targeted the low frequency behaviour of the sensor as it is a relatively slow system. Experimental transfer function models are generated for three sensors with the dimensions of (7.5 mm times 1 mm times 0.17 mm), (10 mm times 1 mm times 0.17 mm), and (12.5 mm times 1 mm times 0.17 mm). These models are for use in understanding the dynamic behaviour and sensing ability of the polymers as mechanical sensors. The effect of the active sensor length on the voltage and current outputs are investigated that the shorter is the sensor length, the higher are the voltage output and the current passed. Also, their current and voltage responses under an impulse stimulus (i.e. displacement) are experimentally measured to show their dynamic sensing response.