Multi-Functional Actuators Made with Biomass-Based Graphene-Polymer Films for Intelligent Gesture Recognition and Multi-Mode Self-Powered Sensing.

Multi-functional actuation systems involve the mechanical integration of multiple actuation and sensor devices with external energy sources. The intricate combination makes it difficult to meet the requirements of lightweight. Hence, polypyrrole@graphene-bacterial cellulose (PPy@G-BC) films are proposed to construct multi-responsive and bilayer actuators integrated with multi-mode self-powered sensing function. The PPy@G-BC film not only exhibits good photo-thermoelectric (PTE) properties but also possesses good hydrophilicity and high Young's modulus. Thus, the PPy@G-BC films are used as active layers in multi-responsive bilayer actuators integrated with self-powered sensing functions. Here, two types of multi-functional actuators integrated with self-powered sensing functions is designed. One is a light-driven actuator that realizes the self-powered temperature sensing function through the PTE effect. Assisted by a machine learning algorithm, the self-powered bionic hand can realize intelligent gesture recognition with an accuracy rate of 96.8%. The other is humidity-driven actuators integrated a zinc-air battery, which can realize self-powered humidity sensing. Based on the above advantages, these two multi-functional actuators are ingeniously integrated into a single device, which can simultaneously perform self-powered temperature/humidity sensing while grasping objects. The highly integrated design enables the efficient utilization of environmental energy sources and complementary synergistic monitoring of multiple physical properties without increasing system complexity.

A multi-functional light-driven actuator with an integrated temperature-sensing function based on a carbon nanotube composite.

Actuators play an important role in the fields of intelligent robots and wearable electronics. Temperature has a great impact on the performances of many actuators. However, most of the traditional actuators only have an actuating function, failing to monitor and send real-time feedback of the temperature of the actuator. To solve the existing problem and break the single-function limit of traditional actuators, we propose a multi-functional light-driven actuator integrated with a temperature-sensing function, which is based on a carbon nanotube (CNT) and methylcellulose (MC) composite. When the CNT-MC film is assembled with biaxially oriented polypropylene (BOPP) to form a bilayer structure, the CNT-MC/BOPP actuator can be driven by near-infrared (NIR) light. Its morphing is based on thermal expansion differences between two layers and shrinkage of MC induced by water loss. The maximal bending curvature is up to 1.03 cm-1. Meanwhile, the resistance of the actuator can change by about 10%, which realizes real-time temperature monitoring and feedback. Furthermore, we demonstrate two practical applications. First, the CNT-MC film can work as a temperature sensor, as its resistance changes with the temperature in real time. Second, we design an intelligent gripper, which can monitor the temperature during the entire working process. This multi-functional CNT-based device is expected to have a broad application prospect in artificial muscles, soft robotics and wearable electronics.

Humidity- and light-driven actuators based on carbon nanotube-coated paper and polymer composite.

Multi-responsive actuators driven by different stimuli (e.g. light, humidity, electricity) have attracted intense attention recently for the advantages of being used in various environments and show enormous actuation. In this work, we propose humidity- and light-driven actuators based on carbon nanotube (CNT)-coated paper and a biaxially oriented polypropylene (BOPP) composite. The CNT-paper/BOPP actuator shows large bending actuation when driven by humidity change (curvature of 1.2 cm-1) and near infrared (NIR) light irradiation (curvature up to 1.6 cm-1). The great actuation performances outperform most other paper-based actuators. Finally, a smart gripper, of which the initial opening width can be enlarged, is fabricated on the basis of the CNT-paper/BOPP actuators. By utilizing the bidirectional bending motion of the actuator, the opening width of the gripper can increase to a width that is 4 times larger than its initial width, so as to grasp a large object. The gripper is also able to raise and move an object that is 20 times heavier than one actuator of the gripper. We assume that this new type of actuator has great potential in artificial muscle, soft robotics and biomimetic applications.

Multi-responsive actuators based on a graphene oxide composite: intelligent robot and bioinspired applications.

Carbon-based electrothermal or photothermal actuators have attracted intense attention recently. They can directly convert electrical or light energy into thermal energy and exhibit obvious deformations. However, if the actuation mechanism is only limited to thermal expansion, the deformation amplitude is difficult to increase further. Moreover, complex shape-deformation is still challenging. Although a few materials were reported to realize twisting or untwisting actuation by cutting the samples into strips along different orientations, each single strip could perform only one shape-deformation mode. In this work, we propose multi-responsive actuators based on a graphene oxide (GO) and biaxially oriented polypropylene (BOPP) composite, which are designed with different shapes (strip-shape and helical-shape). The strip-shape GO/BOPP actuator shows great bending actuations when driven by humidity (curvature of up to 3.1 cm-1). Due to a developed dual-mode actuation mechanism, the actuator shows a bending curvature of 2.8 cm-1 when driven by near infrared (NIR) light. The great actuation outperforms most other carbon-based actuators. Then, an intelligent robot based on the GO/BOPP composite is fabricated, which can switch between the protection mode and weightlifting mode with different external stimuli. Inspired from plant tendrils, a bioinspired helical GO/BOPP actuator is further realized to show both twisting and untwisting actuations in a single actuator, fully mimicking the deformation of plant tendrils. Finally, a robot arm consisting of strip-shape and helical GO/BOPP actuators can grasp an object that is 2.9 times heavier than itself, demonstrating promising bioinspired applications.