Self-Sensing Photoactive Thin Films for Monitoring Space Structures

Reusable and on-orbit space structures endure harsh operating conditions and can sustain damage due to impact by micrometeoroids and orbital debris. Thus, it is necessary to develop and implement suitable sensing technologies for monitoring space structure performance, detecting damage, and preventing catastrophic failure from occurring. The challenge however is to tailor these sensors for operating in such unique environments and constraints. One such limitation is the amount of energy available for powering onboard sensing systems. Thus, the objective of this study is to design and characterize the properties of a novel self-sensing photoactive thin film. Self-sensing is encoded by designing the films to generate a photocurrent in response to illuminated light so that no electrical energy is needed for powering the sensor, and photocurrent generated varies with applied strain. First, the self-sensing thin films were fabricated using poly(3-hexylthiophene) (P3HT) and double-walled carbon nanotubes (DWNT). Two different sets of films, ones with and without DWNTs, were fabricated. Second, photocurrent generation was validated. Then, tensile tests were conducted for characterizing their strain sensing performance. Lastly, current-voltage measurements were also obtained for characterizing thin film shunt and series resistance relationships to applied strains. The results showed that photocurrent varied linearly with applied tensile strains, and this was mainly due to the effects of P3HT alignment and shunt resistance changes of the photoactive thin films.