Fast and Multifunctional Optically‐Driven Actuators based on Stable, Efficient, and Superhydrophobic Photothermal Paper Films

Abstract

By applying external energy such as electrical, magnetic, and light, the actuators can be manipulated to move or perform designed actions. [2,5,6] Electrically-driven actuators require a wired connection, and magnetically-driven actuation requires strong magnets or a short distance between the magnet and the actuator. [7][8][9] Compared to their electric and magnetic counterparts, opticallydriven actuators are wireless and can be controlled remotely. Various propulsion strategies such as photochemical reactions, photoelectric effect, self-thermophoresis, and Marangoni effect have been developed to realize the optically induced actuation. [10][11][12][13][14] Among these strategies, driving the actuators via the photothermally-promoted Marangoni propulsion has been found to be an efficient and facile method. [15,16] Marangoni propulsion relies on the heat generated by photothermal conversion on the actuator to form a temperature gradient on a liquid surface. Due to the Marangoni effect, the temperature gradient will induce a surface tension gradient of the liquid and produce microscopic Marangoni flows. [2,[15][16][17][18][19] The Marangoni flow propels the actuator to complete the macroscopic actuation behavior on the liquid surface. There are two essential features for an efficient opticallydriven actuation on the water surface. It should primarily have efficient photothermal conversion characteristics to rapidly form temperature and surface tension gradients on the water surface. Additionally, the drag force should be minimized when the Marangoni flow propels the actuator. Materials with high absorption can be used for efficient photothermal conversion and reduce drag by fabricating the superhydrophobic surface. [15,20] However, several challenges limit the wide application of optically-driven actuators with the Marangoni effect. Preparation methods for actuators based on superhydrophobic photothermal materials are usually complicated and fluorinecontaining reagents used for superhydrophobic chemical modification are environmentally harmful. [21][22][23] The fabrication of actuators based on superhydrophobic photothermal materials synthesized in an environmentally friendly way is crucial for Remotely controlled self-propelled optically-driven actuators are increasingly attractive for sensing and robotic applications. However, complexities in material synthesis, multifunctionality, dynamic response, and the response rate limit their use for wide-ranging application. This work uses a simple and efficient spraying method to prepare optically-driven actuators based on TiN@PDMS-PVDF (TiN@polydimethylsiloxane-polyvinylidene difluoride) papers. The actuator exhibits stable superhydrophobicity for photothermal heating and corrosive solutions with a contact angle and sliding angle of 169.9° and 2.3°, respectively. The superhydrophobic actuators exhibit an efficient photothermal conversion aided by a very high optical absorption of the material approaching 97%. The optically-driven actuator based on the TiN@PDMS-PVDF pap...

Multifunctional actuators integrated with the function of self-powered temperature sensing made with Ti3C2Tx–bamboo nanofiber composites

“…Thus, the temperature gradient on the liquid surface is utilized to generate a surface tension gradient that triggers the Marangoni flow, inducing a difference in the surface tension of the liquid and triggering the actuator to move. 57 The actuator based on the Marangoni effect can move on the liquid–gas interface and perform a series of tasks (such as forward, turn, or rotation) on the liquid surface as needed. 58 As shown in Fig.…”

“…When one side of the triangular actuator is irradiated, the torque formed by the superposition of the Marangoni force and actuator force drives the actuator to complete circular and turning movements. 57 The demonstration videos of the Ti 3 C 2 T x -bamboo nanofiber/ PI light-driven floating actuator for the circular motion and going through the maze are presented in Videos S1 and S2, † respectively.…”

Design and mechanism of photothermal soft actuators and their applications

“…94–96 To achieve multifunctionality, photothermal actuators can be designed by integrating self-healing and superhydrophobic properties. 33,34,97 Photothermal actuators have shown fast response and outstanding performance in oil-spill recovery, 98 microplastic collection from water, 99 switches, 100 cargo delivery, 101 nanogenerators, 102 and sensors. 103 Recently a US patent was registered in 2021 for photothermal actuators; they have dip coated nylon fibers with graphene flakes that revealed bending under laser light irradiation.…”

“…With rapid response and low energy input, they can be activated from a distance using light sources like lasers, LEDs, or natural sunlight and nd applications in robotics, optical devices, and microuidic systems. Based on light manipulation, researchers have proposed three types of actuations using photoresponsive materials based on photochemical, 29,30 photoelectrical, 31,32 and photothermal 33,34 effects.…”

Editorial for the Special Issue on Flexible Sensors and Actuators for Biomedicine

“…In such cases, soft actuators are often capable of producing motion [29] or deformation [30] under various stimuli such as mechanical input, laser irradiation, electric and magnetic fields, temperature variation, etc. [31][32][33]. These actuators are generally small, possess flexibility similar to biological tissues, and thus enable precise targeting and intervention in biomedical applications.…”