Online monitoring of shape memory polymers with a material integrated flexible interdigital sensor

Thermoset thermoplastic mixtures can be used to fabricate shape memory polymer actuators. For most applications, the current state of an actuator during operation must be known e.g. for movement control. In this work, we present a miniaturized dielectric sensor, which enables online monitoring of the different states of a thermoset thermoplastic actuator. The impedance of the sensor strongly correlates with the internal structure of the shape memory polymer and, thus, can be used for the determination of the current switching state of the material. Additionally, impedance measurements give insights on the internal reorientation mechanisms and processes of the polymer. The dielectric sensor has great potential to be used for continuous monitoring of shape memory polymers during actuation and, therefore, could largely promote industrial applications.