Photomechanical Actuators Based on Azobenzene Units and Possible Improvement Strategies in Solar Applications

Photomobile polymers (PMPs), which deform in response to light stimuli, have attracted increasing interest because of their potential in soft robotics, adaptive structures, and energy-harvesting systems. In this work, we made an in-depth exploration of various strategies aimed at applying such materials as sunlight-responsive actuators. A breakthrough in our study was the enhancement of the polymer actuation efficiency. By incorporating carbon black nanoparticles into the PMP matrix, we succeeded in broadening its optical absorption spectrum, enabling more effective light harvesting across a wider range of wavelengths. This addition led to an improvement in actuation efficiency of up to 35% compared to the pristine polymer. Furthermore, to overcome thermal limitations and enable operation under more intense irradiation conditions, we introduced a thin copper film into the system. This layer functions both as a heat sink ensuring a uniform spatial distribution of temperature across the entire surface of the PMP-based film and preventing material degradation and as a structural skeleton for the bilayer. As a result, higher light intensities can be actuated, and the overall performance of the PMP-based actuator is improved beyond the capabilities of the PMP film, representing a significant advancement in the light-driven actuation systems. Finally, we achieved a significant extension of the functional capabilities of PMPs, adopting innovative methodologies, and ensuring that the material can lift weights (until about 0.62 g, namely, 14 times its weight) through the bending process. These approaches opened promising routes for their practical integration into real-world applications, particularly in solar-powered devices, where autonomous and wireless actuation is highly desirable.