Toward Self‐Sustained Soft Robotics: Triboelectric Nanogenerator–Dielectric Elastomer Actuator Hybrids

For people in life, the existence of triboelectrification usually is a kind of negative effect, especially in winter. However, the team of professor Zhong Lin Wang of Georgia Institute of Technology in the United states invented Triboelectric nanogenerator (TENG) to fully utilize this kind of effect. TENG can convert mechanical energy in the environment into electrical energy, which based on the principle of triboelectrification and charge induction, such as waves, sounds, muscle contractions, mechanical vibrations, etc. The charge separation between the two layers of polymer films will lead to the formation of potential difference. In addition, not only the fabrication process of TENG is simple and low cost, it also can be used in large-scale production. At the same time, it has excellent durability and plasticity, so TENG can be easily combined with other devices. Therefore, TENG and its applications are an important research direction of nanoenergy. Here we have designed TENG for different applications. Listed below is two applications in electrostatic manipulations based on TENG: 1. Integrate a TENG with electrostatic actuation system (EAS) to manipulate the movement of micro-droplets and fine solids. The mechanical triggering of the TENG produces a very high electrostatic field inside the electrostatic actuator, producing a Coulomb force that drives tiny objects (liquid or solid) in the electrostatic actuator. Therefore, the tribomotion of TENG can be used as a driving source and control signals of electrostatic actuators.2. Based on dielectric elastomer actuator (DEA), tunable optical gratings (TOGs) and TENG combined so that the grating period can be controlled by dielectric elastomer actuator. Therefore, a self-powered TOGs system can be implemented, with TENG as the power and control module for its system. In combination with unique output performance of the TENG, three different TOGs systems were designed and used to compress or expand the spacing of the grating array by driving the dielectric elastomer actuator.

TENG-Bot: Triboelectric nanogenerator powered soft robot made of uni-directional dielectric elastomer

Soft actuators have attracted significant attention owing to their unique characteristics and potential for various applications. A dielectric elastomer actuator (DEA) is a type of soft actuator driven by electric voltage and has superior characteristics, such as a fast response, light weight, and simple structure. Several studies have been conducted to analyze the static and dynamic characteristics of a DEA to control its displacements. However, a theoretical analysis of dynamic characteristics of balloon-type DEA including their drive system has not yet been performed. In this study, we analyzed the dynamic characteristics of a balloon-type DEA pre-stretched with water pressure. To this end, we fabricated a DEA using poly (dimethylsiloxane) (PDMS) as an elastomer film and carbon grease as an electrode. We constructed a physical model of the balloon-type DEA pre-stretched with water pressure based on a water oscillation model in an experimental system. Further, we derived an analytical solution for the equation of motion of the system and evaluated the frequency and dynamic responses of the DEA. The theoretical values calculated by the model are in good agreement with the experimental values. Furthermore, we attempted an open-loop control for the displacements of the DEA using the constructed model and successfully achieved it for various input signals. Finally, we demonstrated an application of the balloon-type DEA pre-stretched with water pressure as a membrane pump, which can help generate various pressure waves that are important for artificial hearts or microfluidic cell culture systems.

Triboelectric nanogenerator powered dielectric elastomer: Mechanism and applications

Triboelectric nanogenerators (TENGs) have proven to be a robust power source for efficiently converting environmental mechanical energy into electricity. Triboelectric technology experienced substantial growth in the past few years, especially in the field of green wearable power sources as the Internet of Things develops. However, it is still difficult to overcome some remaining bottlenecks for wearable TENGs, such as limited choice of materials, unsafe metal electrodes, complex structures, and finally an insufficient electrical output. In this work, we present a simply structured wearable TENG that delivers usable electric power based on human motion. The form of TENG, which combines a friction material of silk and an electrode material of carbon nanotube (CNT) in liquid phase to achieve a biodegradable conductive mixing friction layer is new and unique. A series of delicate investigative experiments were conducted to clarify the impacts of various parameters and their optimal values in the fabrication. Then the special mixing layer was attached to a glove and tested with various daily actions, showing high potential as a power source for wearable electronics and as a motion sensor itself. This new form of CNT-silk TENG will push the field’s development toward actual use, with lower cost and less burden for both of production and usage, with the advanced features of high softness, high sensibility, light weight, and simple structure.

The integration of triboelectric nanogenerators (TENGs) into soft robotic systems marks a significant advancement toward autonomous, self-powered, and environmentally responsive machines. TENGs offer lightweight, flexible structures capable of efficiently converting mechanical energy into electricity, supporting both on-board power generation and active sensing. This review provides a comprehensive overview of recent progress in TENG-powered soft robotics, emphasizing developments in actuation, sensing, locomotion, and intelligent interaction. Notable systems include freestanding-mode TENG-Bots, tribo-piezoelectric soft grippers, somatosensory fingers, light-responsive actuators, and electrohydrodynamic pumps each demonstrating TENGs' dual role as energy sources and control elements. Bioinspired designs, such as leech-like and star-nosed mole-inspired robots, further illustrate their potential in adaptive locomotion and nonvisual spatial perception. The integration of TENGs with soft materials and intelligent feedback architectures enables untethered, multifunctional robotic platforms with applications ranging from wearable electronics and human-machine interfaces to environmental exploration. This review also discusses current limitations, including low energy output, durability challenges, and system-level integration, while outlining future research directions in material optimization, energy storage, wireless control, and machine learning-enhanced perception. Collectively, these developments underscore the transformative impact of TENGs on the future of intelligent soft robotics.

By integrating a triboelectric nanogenerator (TENG) and a thin film dielectric elastomer actuator (DEA), the DEA can be directly powered and controlled by the output of the TENG, which demonstrates a self-powered actuation system toward various practical applications in the fields of electronic skin and soft robotics. This paper describes a method to construct a physical model for this integrated TENG-DEA system on the basis of nonequilibrium thermodynamics and electrostatics induction theory. The model can precisely simulate the influences from both the viscoelasticity and current leakage to the output performance of the TENG, which can help us to better understand the interaction between TENG and DEA devices. Accordingly, the established electric field, the deformation strain of the DEA, and the output current from the TENG are systemically analyzed by using this model. A comparison between real measurements and simulation results confirms that the proposed model can predict the dynamic response of the DEA driven by contact-electrification and can also quantitatively analyze the relaxation of the tribo-induced strain due to the leakage behavior. Hence, the proposed model in this work could serve as a guidance for optimizing the devices in the future studies.

Hybrid Energy-Harvesting Systems Based on Triboelectric Nanogenerators

Dielectric elastomers are a type of actuator materials that exhibit excellent performance as artificial muscles, but a high driving voltage is required for their operation. By using the amazingly high output voltage generated from a triboelectric nanogenerator (TENG), a thin film dielectric elastomer actuator (DEA) can be directly driven by the contact‐separation motion of TENG, demonstrating a self‐powered actuation system. A TENG with a tribo surface area of 100 cm2 can induce an expansion strain of 14.5% for the DEA samples (electrode diameter of 0.6 cm) when the system works stably within the contact‐separation velocity ranging from 0.1 to 10 cm s−1. Finally, two simple prototypes of an intelligent switch and a self‐powered clamper based on the TENG and DEA are demonstrated. These results prove that the dielectric elastomer is an ideal material to work together with TENG and thereby the fabricated actuation system can potentially be applied to the field of electronic skin and soft robotics.

Fluid-driven and smart material-driven research for soft body robots

In recent years, dielectric elastomer actuators (DEA) have been investigated as artificial muscle for soft robots, thanks to their light weight, high energy density, and silent operation. Moreover, the low stiffness of the dielectric elastomer (DE) material allows DEA to exhibit large actuation strain. On the other hand, the intrinsic softness of DEA limits their blocking and holding force. Therefore, incorporating variable stiffness structures into DEA is necessary to leverage both large actuation strain, and large holding force from such actuators. This work describes the modeling, fabrication, and characterization of a variable-stiffness DEA (VSDEA) based on interlaminar electrostatic chucking. The VSDEA consists of a multitude of stacked multilayer unimorph DEA units, where each unit consists of a passive layer and one or more active DE layers whose expansion under applied voltage induces bending of the DEA unit. Adhesion between the DEA units is mediated by electrostatic attraction caused by opposite charges accumulating on the interfacial surfaces between each unit. The bending stiffness of the VSDEA is controlled by increasing or decreasing the charge on the interfacial surfaces; large deformation can be achieved when the unit interfaces are allowed to freely slip, and a large increase in stiffness is realized when electrostatic chucking is applied.

Electronic skin (e-skin) with skin-like flexibility and tactile sensation will promote the great advancements in the fields of wearable equipment. Thus, the multifunction and high robustness are two important requirements for sensing capability of the e-skin. Here, a fully organic self-powered e-skin (FOSE-skin) based on the triboelectric nanogenerator (TENG) is developed. FOSE-skin based on TENG can be fully self-healed within 10 hours after being sheared by employing the self-healing polymer as a triboelectric layer and ionic liquid with the temperature sensitivity as an electrode. FOSE-skin based on TENG has the multifunctional and highly robust sensing capability and can sense the pressure and temperature simultaneously. The sensing capability of the FOSE-skin based on TENG can be highly robust with no changes after self-healing. FOSE-skin based on TENG can be employed to detect the arm swing, the temperature change of flowing water, and the motion trajectory. This work provides a new idea for solving the issues of monofunctional and low robust sensing capability for FOSE-skin based on TENG, which can further promote the application of wearable electronics in soft robotics and bionic prosthetics.

With the development of the Internet of Things and intelligent robots, there is an increasing demand for distributed flexible sensor networks and portable power devices. As a self-powered sensor and micro/nano powering supplier, triboelectric nanogenerator (TENG) that can convert the irregular and ubiquitous mechanical energy into electrical energy demonstrates promising applications in human-machine interaction, soft robotics, wearable healthcare, etc. However, achieving ultrahigh current density and water resistance in TENGs remains challenging, mainly due to the non-utilization of the electrons in the interior of triboelectric layers. Herein, it is proposed that linking the electron cloud potential wells (ECPWs) of triboelectric materials can lead to a huge increase in the output current of TENGs. This hypothesis is verified by embedding a conductive network of reduced graphene oxide (rGO) into the triboelectric layers of ethyl cellulose (EC) and polydimethylsiloxane (PDMS). The TENG based on this model demonstrates a record-high current density of ≈3533mAm-2 among the TENGs working in contact-separation mode. In addition, this TENG shows excellent endurance in high-humidity and even rainy environments. This work provides a novel and promising strategy for fabricating TENGs with ultrahigh output current and water resistance, largely expanding their practical applications in many fields.

In recent years, soft pipeline robot, as a new concept, is proposed to adapt to tunnel. The soft pipeline robots are made of soft materials such as rubber or silicone. These materials have good elasticity, which enhance the adaptability of the soft pipeline robot. Therefore, the soft pipeline robot has better performance on deformability than rigid robot. However, the structure of tunnel is complex and varied that brought challenges on design structure of soft pipeline robot. In this paper, we propose soft pipeline robot with simple structure and easy fabrication, which can be realized straight, turning motion in a variety of tunnels with different diameters. The soft pipeline robot composed of two types of structure, which are expansion part and deformation part. Front and rear deformation part for bending and position fixation, and middle expansion part for elongation, so the pipeline soft robot can be moved in various structures of tunnels. Moreover, the locomotion ability and adaptability in tunnel are verified by simulating on software. The structure of chamber proposed in this paper can guide the design method of soft pipeline robot.

Soft robots are receiving increasing attention and have great potential in the fields of health care, education, service, rescue, exploration, detection, and wearable devices owing to their inherent high flexibility, good compliance, excellent adaptability, and safe interactivity. Soft pneumatic robots are a well-known type of soft robot with characteristics such as light weight, high performance, pollution-free operation, and strong environmental adaptability. In recent decades, the development of soft pneumatic robots is closely related to the application of new materials, novel designs, and new manufacturing processes. In this study, the literature review and main advances in soft pneumatic robots’ design and fabrication technology are reviewed. In addition, the trends of multifunctionalization, modularization, and the bionic design of soft pneumatic robots are analyzed and discussed. Furthermore, the problems and challenges associated with soft pneumatic robots’ system reliability, air supply, and motion control are analyzed. Finally, the future development outlook and significance of soft pneumatic robots are summarized.