Smart materials are materials that respond to external stimuli such as temperature, light, pressure, and electric or magnetic fields. By reacting to these environmental changes, they can modify their size, stiffness, shape, or other physical properties, enabling the development of innovative and dynamic products.
In the medical field, for example, smart materials are used to develop implantable devices such as pacemakers and joint prostheses that can interact with the human body and adapt their behavior to physiological stimuli. Another area of growing interest is that of smart hydrogels—materials capable of changing their structure or volume in response to external stimuli, such as variations in temperature, pH, or electric fields. This property enables the controlled and targeted release of drugs.
The ENEA–CNR team, led by Giuseppe Nenna for ENEA and Lucia Petti for CNR-ISASI, focused on a particular class of smart materials known as Photomobile Polymers (PMPs). These materials represent a new category of actuators-optical actuators-thanks to their ability to respond to light stimuli by generating precise movements.
“These are stimulus-responsive materials capable of converting light energy into mechanical work. When exposed to specific wavelengths of light, they undergo controlled and reversible deformations. These materials offer a wide range of potential applications, spanning from optoelectronics and microengineering to the biomedical field and environmental sciences,” explains Giuseppe Nenna, an ENEA researcher at the Laboratory for Intelligent Components and Systems for Manufacturing within the Department for Sustainability.
A key feature of these materials is the incorporation of azobenzene units, which serve as the primary driving force behind their motion. With the goal of improving the performance of photomobile polymers, the research team investigated their photomechanical response, focusing in particular on bending angles and actuation speed under different experimental conditions.
For example, the researchers explored various strategies to optimize heat distribution, including laminating PMP films with a copper layer, which enables the material to withstand higher levels of irradiation without compromising its performance. In addition, different types of nanoparticles-such as carbon black, zinc oxide, and silver nanocuboids-were incorporated into the polymer matrix. These nanoparticles indirectly activate the azobenzene units, thereby increasing the efficiency of the material’s movement while reducing response times.
“At the recent International Conference on Materials Science and Nanotechnology in Barcelona, we presented new strategies that broaden the range of wavelengths that can be used to activate photomobile polymers. This makes them suitable for operation under solar radiation as well, offering a scalable solution for applications in soft robotics and adaptive systems,” Nenna concludes.
More info:
Lucia Petti, CNR lucia.petti@isasi.cnr.it
Gianluigi Torchiani, ENEA gianluigi.torchiani@enea.it