Application Cases

Experiment Name: Research on Leech-Inspired Soft Robots Made of Dielectric Elastomer Muscles

Research Direction:Leeches exhibit a unique mode of locomotion characterized by the alternating attachment of suckers and body contraction, providing high adaptability and stability on complex terrains. Here, for the first time, a leech-inspired triboelectric soft robot capable of amphibious movement, climbing, and load-bearing crawling is proposed. A high-performance triboelectric bionic robotic system for driving and controlling electro-responsive soft robots has been developed. Crawler robots have garnered significant attention due to their special adaptability to different environments and have found applications in environmental monitoring, exploration, biomedicine, and equipment inspection. Although many rigid crawler robots, including wheeled, tracked, and legged variants, can provide precise control and high payload capacity for fine operations or heavy lifting, their dependence on complex mechanisms composed of rigid joints limits their ability to traverse complex terrains. Compared to rigid robots, soft robots are lightweight, deformable, low-cost, and material-flexible, with excellent mechanical flexibility. This enables them to imitate invertebrates such as octopuses, caterpillars, and snakes crawling in complex environments, including uneven or rough surfaces and narrow tunnels.

Currently, soft crawler robots can be classified based on their actuation mechanisms, including electrical, magnetic, chemical, thermal, optical, pneumatic, and humidity. They are further divided into tethered and untethered robots based on their connection to an external power source or control system. Untethered robots are renowned for their high mobility and operational flexibility and are widely used for exploring inaccessible areas, performing remote sensing, or executing complex tasks. The recently proposed triboelectric soft robots effectively address issues brought by high-voltage power supply circuit failures. By leveraging the high-voltage and high-impedance characteristics of triboelectric nanogenerators (TENGs), these systems can easily generate thousands of volts with low output current (≈μA) without additional circuits, ensuring the stable operation of electro-responsive soft robots. TENGs have been proven to drive electro-responsive materials, such as liquid crystals, electrorheological fluids, and dielectric elastomers, demonstrating the potential of TENGs to power soft robots. Moreover, due to the small amount of charge transfer, using TENGs to drive materials like dielectric elastomers reduces the risk of thin-film breakdown under high electric fields, making them an ideal power source for soft robots.

Experiment Objective:To compare the high-voltage power supply (Aigtek, ATA-7100, 100W) with the HDC-TENG (high-density channel triboelectric nanogenerator) by evaluating the mechanical properties of two key components, DM and TES (enabled by force sensors), to assess the ability to drive electro-responsive soft robots, providing arguments and groundwork for subsequent experiments.

Testing Equipment:ATA-7100 High-Voltage Amplifier, Signal Generator, Oscilloscope, Digital Source Meter, Ceramic Resistor, Uniaxial Force Sensor, Laser Distance Sensor, High-Speed Camera, Host Computer

Experiment Process:The study utilized deformable muscles and triboelectric suckers. Materials for fabricating deformable muscles included dielectric elastomers, carbon grease, and PET films. An electrometer, ceramic resistors (1MQ~50GΩ), and a resistor-capacitor voltage divider were used to measure the open-circuit voltage and power curves of the HDC-TENG. The short-circuit current and transferred charge were directly measured using a digital multimeter. Scanning electron microscopy was employed to capture microscopic images of the triboelectric materials. The high-voltage power supply (Aigtek, ATA-67110, 100W) and signal generator powered the DM for comparison with the HDC-TENG. The PET for DM was processed at a precision metal laser cutting workstation. A uniaxial force sensor measured the blocking force of the DM and the adhesion force of the TES. The protrusion length of the DM was measured using a laser distance sensor. The capacitance values of the DM and TES were determined using a digital source meter. A camera continuously recorded the crawling speed of the LSR, calculating the distance crawled per unit time. Data processing and plotting were performed using MATLAB and Origin.

Figure 1: Block Diagram of the Experiment on Leech-Inspired Soft Robots Made of Dielectric Elastomer Muscles

Experiment Results:The driving performance of the HDC-TENG for soft actuators can be evaluated by measuring the voltage applied to the DM by the HDC-TENG during various charging cycles (see Figure 2B). A soft actuator with one segment of DM reaches the maximum saturation voltage within 1 second; two segments in 1.5 seconds; and three segments in 2.5 seconds. Since the capacitance values of the muscle segments 1, 2, and 3 are 298.49pF, 556.38pF, and 674.91pF respectively, the increase in the number of DM segments enhances the capacitance value of the soft actuator (due to parallel connection), requiring more charge from the HDC-TENG to reach the saturation voltage. When the HDC-TENG rotates at different speeds, the voltage applied to soft actuator configurations with 1, 2, and 3 muscle segments (3-second charging cycle) varies. The voltage increase is due to the enhanced electrical output of the HDC-TENG at higher rotation speeds (see Figure 2B, C), which affects the voltage and charge delivered to the soft actuator. Figures 2C and D show the variations in blocking force and protrusion length of the soft actuator with 1, 2, and 3 segments of DM (3-second charging cycle) when the HDC-TENG operates at different rotation speeds. At a rotation speed of 240rpm and a 3-second charging cycle, the soft actuator with three segments, two segments, and one segment of DM generates blocking forces and displacements of 83.3mN/11.88mm, 60.5mN/8.57mm, and 35mN/4.32mm, respectively. Both the blocking force and displacement of the soft actuator increase with the addition of deformable muscle segments. Figures 2E and F show the variations in blocking force and protrusion length of the soft actuator (with three segments of DM) during a 3-second charging cycle when the HDC-TENG operates at a rotation speed of 240rpm. The soft actuator with three segments of DM generates maximum blocking force and displacement during the 0.5-3-second charging cycle, as shown: 83.3mN/11.88mm, 10.59mN/8.57mm, 79.8mN/9.71mm, 78.06mN/8.24mm, 60.06mN/5.38mm, and 33.7mN/1.57mm. The performance (blocking force and protrusion length) of the soft actuator significantly improves within a 1-second charging cycle. As the charging cycle extends, this performance enhancement stabilizes, consistent with the voltage growth curve of the soft actuator (see Figure 2B), highlighting that the output charge of the HDC-TENG and the capacitance value of the soft actuator are decisive factors for the rapid deformation of the DM.

Figure 2: Characterization of the Actuation Voltage, Blocking Force, and Protrusion Length of the Bio-Inspired Deformable Actuator. A) Schematic illustration of the blocking force and displacement generated by the actuator. During the measurement, one end of the soft actuator is fixed to the substrate, while the blocking force and displacement at the other end are measured using force and laser sensors. B) Voltage across the DM (1, 2, and 3 segments) during different charging cycles. C, D) Blocking force and protrusion length generated by the soft actuator (1, 2, and 3 segments of DM, 3-second charging cycle) at different rotation speeds of the HDC-TENG. E, F) Blocking force and protrusion length generated by three segments of DM during different charging cycles.

Figure: ATA-7100 High-Voltage Amplifier Specifications

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