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

Abstract

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.

A self-sustained soft actuator able to rock and roll

“…The light triggered bending actuation of LCNs doped with such photothermal azobenzenes as dye 3 has been elucidated in previous work. 32 To demonstrate this additional rolling action, during the rocking motion, a triangular LCN is exposed to a collimated (455 nm, corresponding to the absorption of the azobenzene, Fig. S5, ESI †) light emitting diode (LED) positioned at an oblique angle.…”

Brush‐Paintable, Temperature and Light Responsive Triple Shape‐Memory Photonic Coatings Based on Micrometer‐Sized Cholesteric Liquid Crystal Polymer Particles

“…To prepare the light and temperature responsive shape memory photonic paints, we synthesized cholesteric polymer particle pigments exhibiting blue, green, and red structural colors, respectively, by suspension polymerization of a CLC mixture containing a light‐responsive azobenzene dye [ 33,34 ] (Figure S1, Supporting Information). [ 25 ] Bisphenol‐A based ethoxylate diacrylate (Figure S1, Supporting Information) was used as the binder because it has a high refractive index ( n ≈ 1.53) similar to that of the particles ( n ≈ 1.6) and a glass transition temperature ( T g ) after polymerization around 38 °C which is lower than that of the particles ( T g,particles ≈ 67 °C) and higher than room temperature (Figure S2, Supporting Information).…”

An Untethered Magnetic‐ and Light‐Responsive Rotary Gripper: Shedding Light on Photoresponsive Liquid Crystal Actuators

“…As the magnetic PDMS is coated solely on the middle section of the LCN, it is not directly exposed to incident light used for opening/closing of the soft robot and hence does not influence the light‐responsive behavior. Full coverage of the LCN by a PDMS layer has consequences for the photo actuation of the material, for a detailed study we refer to our other work in this issue …”