Electrostatic Actuators

Strong Reliable Electrostatic Actuation Based on Self-Clearing Using a Thin Conductive Layer

  • An enough thin conductive layer (e.g., < 7 μm for copper)
  • It can improve the maximum available voltage by 260% and the maximum electrostatic adhesive force by 276%.
  • The robustness and repeatability of the self-clearing mechanism are validated by surviving consecutive breakdowns and self-clearing of 173 times during 65 min.

Electrostatic Adhesion Clutch with Superhigh Force Density Achieved by MXene-Poly (Vinylidene Fluoride-Trifluoroethylene-Chlorotrifluoroethylene) Composites

  • Nanocomposite films with high dielectric constant ( > 2300) and low loss tangent.
  • Superhigh shear stress (85.61 N cm-2), 408% higher than the previous maximum value.
  • One of the EA clutches fabricated in this study is only 160 μm thin and 0.4 g heavy.
  • It can hold a 2.5 kg weight by only 0.32 cm2 area and support an adult (45 kg).

So-EAGlove: VR Haptic Glove Rendering Softness Sensation with Force-tunable Electrostatic Adhesive Brakes

  • Haptic gloves allow the players to feel the virtual world more realistically by providing force feedback.
  • we designed a haptic glove (So-EAGlove) integrating a flexible electrostatic adhesive brake to resist human fingers with a tunable braking force and render a softness sensation.
  • This glove weighs only 51 g but is capable of simulating objects in a large range of Young's modulus from 540 Pa to 5.4 MPa.
  • Experimental results show that this glove can generate an accurate force to follow the force-displacement profile of the corresponding real objects.

A multifunctional robotic system toward moveable sensing and energy harvesting

  • Moveable sensing and energy harvesting are enabled by the integrated multifunctional robotic system.
  • Triboelectric nanogenerator and electrostatic robot are combined together utilizing a similar electrostatic field.
  • The integrated system is lightweight, flexible, and compact.
  • It is promising in vast applications such as structural health monitoring, environmental surveillance, and rescue.

Biologically Inspired Electrostatic Artificial Muscles for Insect-sized Robots

  • Millimeter-sized electrostatic film actuators, inspired by the efficient spatial arrangement of insect muscles, achieve a muscle-like power density (61 W kg-1) and enable robotic applications in which agility is needed in confined spaces.
  • A typical actuator can achieve 85 mN of force with a 15 mm stroke, with a size of 28 x 5.7 x 0.3 mm3 and mass of 92 mg.
  • The earthworm robot undertakes inspection tasks: the navigation of a 5 mm channel and a 19 mm square tube while carrying an on-board camera.
  • The surgical tool, which conforms to the surface of the distal end of an endoscope, similar to the thin, smooth muscle that covers the intestine, completes tissue cutting and penetrating tasks.

Modeling and Optimization of Electrostatic Film Actuators

  • We build a mathematical model based on the method of moments by assuming that each electrode consists of a large number of line charges.
  • This model can directly deduce fluctuation in thrust and adhesive forces during actuator movement, as well as the distribution of electric potential and field strength, for analysis and optimization.
  • Based on this model, we generate numerous values of actuator output force for different structural parameters.
  • By analyzing the tendency, we summarize a parameter optimization workflow and write an open-sourced program as an example to facilitate the parameter selection for actuator design starting from scratch.
  • With the concern on the electrical breakdown, this work is a preliminary attempt to analyze the maximum force and critical voltages for different specifications using the method of moments with line-charges.
  • To achieve a higher maximum force, balancing the breakdown in the vertical gap and the horizontal gap is one of the primary concerns in the design.
  • The theoretical maximum force for electrostatic film actuators can be achieved by different parameter sets: a large insulation layer and electrode space (high critical voltage) or a thin insulation layer and electrode space (low critical voltage).
  • Based on this knowledge, we designed and fabricated an electrostatic film actuator with a force density of 126.5 N/m2, 35% larger than the previous actuators at the same condition.

Analyses and Solutions for the Buckling of Thin and Flexible Electrostatic Inchworm Climbing Robots

  • As the body of the robot has only 2.5 mm of thickness, it is more prone to buckling than any other flexible robots, making it the best example for the buckling problem.
  • Based on the analyses, the paper proposes a buckling-free control strategy for the electrostatic robots.
  • A prototype of climbing robot was developed to verify the analyses and solutions, weighing merely 29 g (excluding battery and control circuits). It successfully climbed up a vertical wall without buckling, carrying the payload of 0.4 N.

Soft Robotics

Three-Dimensional Sensing Microchannels

  • The innervation of sensing microchannel networks into elastic matrices to mimic the exteroception and proprioception of the human bodies is employed.
  • A soft cubic sensor containing 3D microchannels (diameter: 400 µm) is capable of identifying 3D external stimuli, including force types (pressing, squeezing, shearing, and twisting)

Origami Anisotropic Stiffness Structure

  • The combined softness-rigidity hybrid property of desert iguanas' skin.
  • This anisotropic stiffness structure comprises a silicone-paper composite with multiple superimposed origami patterns and has high stiffness and softness properties.

Flow Casting Soft Shells

  • A facile, robust, and scalable manufacturing technique, named flow casting, to create soft shells with complex geometries and multifunctionalities is proposed.
  • A one-dimensional soft shell is first made with controllable thicknesses (100-400 µm) and fabricated various soft shells of intricate geometries, including three-branched, circular-shaped, and exquisite microstructures such as papillae and microgrooves on curved surfaces, with the resolution of feature sizes on the order of 100 µm.

Origami-Inspired Soft Twisting Actuator

  • Origami-inspired soft pneumatic actuators (OSPAs) made from silicone enlargeing working space and increasing degrees of freedom.
  • Output a rotation of more than one revolution (up to 435°), more significant than its counterparts.
  • Its rotation ratio ( = rotation angle/aspect ratio) is more than 136°, about twice the largest one in other literature.

Self-shrinking soft demoulding for complex high-aspect-ratio microchannels

  • A simple and solvent-free fabrication method capable of producing monolithic microchannels with complex 3D structures, long length, and small diameter.
  • In combination with thermal drawing technology, microchannels with a small diameter (10 µm), a high aspect ratio (6000, length-to-diameter), and intricate 3D geometries are generated.
  • the vast applicability and significant impact of this technology in multiple scenarios, including soft robotics, wearable sensors, soft antennas, and artificial vessels.

Micro Robotics

SimoBot: An Underactuated Miniature Robot Driven by A Single Motor

  • A simple-structured, low-cost miniature robot is highly desired for swarm robotics research.
  • This robot has only five simple components--a vibration motor, a button cell, a microcontroller board, four-pin legs (one of which is shorter than the others), and sensors.
  • The prototype weighs only 4.76 g, costs 4.7 dollars, and is 20 mm in diameter and 18 mm in height.
  • Since it has only one motor but needs to travel on the 2D ground, the design, moving mechanism, and control are all challenging.