Photochemically Induced Propulsion of a 4D Printed Liquid Crystal Elastomer Biomimetic Swimmer

• Published in: Advanced science Vol. 11; no. 25; pp. e2308561 - n/a
• Main Authors: Sartori, Paolo, Yadav, Rahul Singh, Barrio, Jesús, DeSimone, Antonio, Sánchez‐Somolinos, Carlos
• Format: Journal Article
• Language: English
• Published: Germany John Wiley & Sons, Inc 01.07.2024; John Wiley and Sons Inc; Wiley
• Subjects: 4D printing; azobenzene; biomimetic swimmers; Deformation; Heat; Lasers; liquid crystal elastomers; Morphology; Organisms; Phase transitions; photochemical actuation; Robots; Swimming; Temperature; Vortices; azobenzene; biomimetic swimmers; 4D printing; liquid crystal elastomers; photochemical actuation
• ISSN: 2198-3844; 2198-3844
• DOI: 10.1002/advs.202308561

Underwater organisms exhibit sophisticated propulsion mechanisms, enabling them to navigate fluid environments with exceptional dexterity. Recently, substantial efforts have focused on integrating these movements into soft robots using smart shape‐changing materials, particularly by using light for their propulsion and control. Nonetheless, challenges persist, including slow response times and the need of powerful light beams to actuate the robot. This last can result in unintended sample heating and potentially necessitate tracking specific actuation spots on the swimmer. To tackle these challenges, new azobenzene‐containing photopolymerizable inks are introduced, which can be processed by extrusion printing into liquid crystalline elastomer (LCE) elements of precise shape and morphology. These LCEs exhibit rapid and significant photomechanical response underwater, driven by moderate‐intensity ultraviolet (UV) and green light, being the actuation mechanism predominantly photochemical. Inspired by nature, a biomimetic four‐lapped ephyra‐like LCE swimmer is printed. The periodically illumination of the entire swimmer with moderate‐intensity UV and green light, induces synchronous lappet bending toward the light source and swimmer propulsion away from the light. The platform eliminates the need of localized laser beams and tracking systems to monitor the swimmer's motion through the fluid, making it a versatile tool for creating light‐fueled robotic LCE free‐swimmers. 4D printing of azobenzene‐containing liquid crystal elastomers (LCEs) actuating at low temperatures close to room temperature is demonstrated. Elastomer irradiation with moderate‐intensity ultraviolet light leads to fast photodeformation underwater indicating predominant photochemical response. Periodic illumination of a 4D printed biomimetic four‐lapped ephyra‐like LCE swimmer, with moderate‐intensity UV and green light, covering the entire sample, propels the swimmer away the light source.