Chiroptical 3D Actuators for Smart Sensors

Abstract

Examples of anisotropic movement paired with helical geometry abound in the animal and plant kingdoms are used for a variety of reasons, such as diverse social signaling directed at conspecifics or camouflage to avoid predation. Inspired by these natural phenomena, a smart sensor is developed with a chiroptical 3D actuator that can fold, bend, and twist in response to external stimuli, reflecting light of specific wavelengths, and possessing circular polarization properties. Chirophotonic crystal actuators are constructed with an asymmetric Janus structure and are fabricated by self‐assembly, screen printing, and in situ photopolymerization. The optically active layer consists of cholesteric liquid crystal polymer, and the mechanically active layer is composed of a polymeric gel thin film. The programmed in‐planar and out‐of‐planar asymmetric Janus structures control the directionality of various shapes morphing from 2D to 3D. Finite element simulations allow to predict the shape changes associated with these chirophotonic crystal actuators: flower blooming, tendril climbing, eagle hunting, ant lifting, and inchworm moving motions. By utilizing the chirophotonic crystal actuator, a reusable and portable methanol‐laced water identifier is developed.

Stimuli‐responsive photonic actuators for integrated biomimetic and intelligent systems

“…Another example is reported by Kim et al, who developed a photonic actuator for methanol-laced water recognition. [90] As shown in Figure 19b, the photonic actuator-based methanol-laced water identifier (MLWID) employed alternating RGB color Crosslinked liquid crystal polymer layers and black polymeric gel film (PGTF) layers, thereby displaying bright structure colors under daylight. The MLWID strip was immersed in a suspicious solution, and it underwent different degrees of bending corresponding to the concentration of methanol in the solution, thus showing different color codes.…”

Rapid-Responsive Hydrogel Actuators with Hierarchical Structures: Strategies and Applications

“…Nevertheless, under the general physical framework of eq , two directions to accelerate the response rate of hydrogel actuators can be proposed: one is to decrease the size of the hydrogel; the other is to promote the diffusion of molecules. Since a hydrogel with a large size takes a longer time to reach a swelling/shrinking equilibrium, the response times of macroscopic hydrogel actuators can reach minutes or even several hours. − The current investigated strategies that enhance the response rate are divided into four categories: (1) increase the intensity of stimuli, , (2) fabricate microscopic hydrogel actuators, (3) adopt air or liquid as the driving force, − and (4) design special internal structures. Since the intensity of stimuli cannot be increased unlimitedly, the applications of microscopic hydrogel actuators at the macroscale are restricted, and pneumatic/hydraulic hydrogel actuators require additional catheter devices.…”