A team of researchers from the Korean Institute of Science and Technology has created a soft octopus-inspired robot.
According to its developers, the aptly named OCTOID is a soft robot that leverages cholesteric liquid crystal elastomers (CLCEs) to achieve dynamic color-changing camouflage with programmable and reversible shapeshifting, all on one platform.
Source: Advanced Functional Materials
The team designed two complementary layers — one a tunable optical active layer and the other a mechanically distinct passive layer — to create modular actuators capable of achieving diverse motions, from directional movement to secure object gripping.
While similar octopus-inspired robot designs have previously struggled to achieve camouflage, locomotion and gripping in one robot design as current materials tend to lack coordinated optical and mechanical integration, LCEs, particularly cholesteric LCEs (CLCEs), have offered a solution. The team explained that their anisotropic molecular structure allowed for precise shape changes and structural color changes under mechanical deformation.
The researchers built on these properties to create OCTOID, which combines shape morphing and dynamic color modulation thanks to its bilayer design that features an active layer capable of changing shape and color and a passive layer that offers stiffness and optical transparency. Together, the layers allow for reversible, programmable movements and adaptive camouflage in a single, integrated system.
The team built active (AL) and passive layers (PL) from CLCEs using a bottom-up self-assembly of reactive mesogens, crosslinkers and chain extenders to create OCTOID’s modular actuating legs. ALs, featuring lower crosslinker and cRM concentrations, were reportedly soft and displayed visible structural colors, while PLs, featuring higher concentrations, were stiff and transparent. The researchers covalently bonded these bilayers using secondary UV curing, thus ensuring strong interfacial adhesion and stability over 100 actuation cycles.
Further, the camouflaging legs used two ALs featuring embedded Nichrome wires for Joule heating. Once electrical power was applied, it induced contraction, which shifted colors from blue to red in under 40 seconds. The team explained that the contraction ratio correlated with temperature, reaching 29.8% at 4 W, and was stable over repeated cycles.
Meanwhile, the moving legs combined AL and PL asymmetrically, thus producing bending through differential thermal expansion. For instance, optimal bending required an AL:PL thickness ratio of 8:1, which allowed for controlled directional motion. During trials, OCTOID traveled 20 mm at 0.45 mm/s under 4 W, with reversible bending maintained over 100 cycles.
The team noted that OCTOID’s grabbing legs combined AL contraction with PL bending to wrap and lift objects weighing up to 6 g — which is 30 times the leg’s weight — with 90% performance retained after 100 cycles. During trials, OCTOID reportedly manipulated objects of assorted shapes and materials, while simultaneously camouflaging its legs and adapting colors to match complex environments.
The team detailed their work in the article, “OCTOID: A Soft Robotic System Featuring Programmable Shape Morphing and Dynamic Structural Coloration,” which appears in the journal Advanced Functional Materials.
