Development of self-powered strain sensor using mechano-luminescent ZnS:Cu and mechano-optoelectronic P3HT

Aerospace structural systems are prone to structural damage during their use by vibration, impact, material degradation, and other factors. Due to the harsh environments in which aerospace structures operate, aerospace structures are susceptible to various types of damage and often their structural integrity is jeopardized unless damage onset is detected in timely manner. Yet, current state-of-the-art sensor technologies are still limited for structural health monitoring (SHM) of aerospace structures due to their high power consumption, need for large form factor design, and manageable integration into aerospace structures. This study proposes a design of multilayered self-powered strain sensor by coupling mechano-luminescent (ML) property of copper-doped zinc sulfide (ZnS:Cu) and mechano-optoelectronic (MO) property of poly(3-hexylthiophene) (P3HT). One functional layer of the self-powered strain sensor is ZnS:Cu-based elastomeric composites that emit light in response to mechanical deformation. Another functional layer is P3HT-based thin films that generate direct current (DC) under light illumination and DC magnitude changes with applied strain. First, ML light emission characteristics of ZnS:Cu-based composites are studied under cyclic tensile strain with two various maximum strain up to 10% and 15% at various loading frequencies from 5 Hz to 20 Hz. Second, piezo-optical properties of P3HT-based thin films are investigated by acquiring light absorption of the thin films at various strains from 0% to 2% tensile strain. Last, micro-mechanical properties of the P3HT-based thin films are characterized using nanoindentation.