On Untethered, Dual Magneto‐ and Photoresponsive Liquid Crystal Bilayer Actuators Showing Bending and Rotating Motion

• Published in: Advanced optical materials 2019-04, Vol.7 (7), p.n/a
• Main Authors: Pilz da Cunha, Marina, Foelen, Yari, Engels, Tom A. P., Papamichou, Kleopatra, Hagenbeek, Michiel, Debije, Michael G., Schenning, Albert P. H. J.
• Format: Article
• Language: English
• Subjects: Actuation; Actuators; Amplitudes; Deformation; Liquid crystals; magnetic response; Materials science; Optics; photoresponse; Polydimethylsiloxane; Product design; Silicone resins; Stiffness; Stimuli; stimuli‐responsive materials; Synchronism
• ISSN: 2195-1071; 2195-1071
• DOI: 10.1002/adom.201801604

The integration of untethered, multi‐stimuli responsive actuation into soft microrobotic devices is a goal in the development of “smart” materials. This manuscript reports on a dual‐stimuli responsive bilayer actuator consisting of a light responsive liquid crystal network (LCN) and a magnetic responsive polydimethylsiloxane (PDMS) composite. This design is of facile fabrication with ample design freedom, using no additional adhesion layers. Untethered control of the bilayer permits motions including bending and rotation, steered individually or in synchronization. Through a systematic study the direct impact of the PDMS layer was elucidated on the light triggered rate of actuation and maximum deformation amplitude of the LCN film. The alignment (homeotropic or planar) of the LCN has a profound effect on the resulting bilayer actuation. It is demonstrated, both experimentally and theoretically, that the rates of sample heating and actuation are directly correlated and highlight the critical role of the PDMS as a heat sink. The maximum amplitude of displacement of the bilayer is tied to the stiffness, being inversely correlated to the PDMS thickness to the third power. These results give insights and provide straightforward design rules to fabricate bilayer actuators with programmed multi‐responsive properties. Bilayers are a popular choice towards the design of untethered multi‐stimuli responsive materials. Doping the rubbery polydimethylsiloxane (PDMS) matrix of a liquid crystal/PDMS bilayer, allows for additional stimuli‐triggered actuation such as magnetic response. A detailed study of the photo‐responsive actuation of liquid crystal/PDMS bilayers provides theoretical insight and a design toolbox towards bilayer actuators with programmed multi‐responsive properties.