Magnetism

Electro-Magnetic Soft Actuators

Over the past five years, we worked on initial prototypes that demonstrated multi-functionality in soft robots. We developed Wormbot, a soft robot that uses voice coils for actuation (locomotion) and communication. We particularly focused on fully-integrated systems in which all components resided within the soft body, as opposed to soft robots in which control elements are external to the robot.

  • Using Voice Coils to Actuate Modular Soft Robots: Wormbot, an Example
    M.P. Nemitz, P. Mihaylov, T.W. Barraclough, D. Ross, A.A. Stokes
    Soft Robotics, 3(4), 198-204
  • Linbots: Soft Modular Robots Utilizing Voice Coils
    R.M. McKenzie, M.E. Sayed, M.P. Nemitz, B.W. Flynn, A.A. Stokes
    Soft Robotics, 6(2), 195-94

Figure 1. Sequential actuation of electro-magnetic soft actuators. A series of frames showing one cycle of sequential expansion and attraction of modules, the robot moves from left (a) to right (f).

Electro-Magnetic Swarm Robots

We also developed the HoverBot system, a swarm robotic platform that uses planar coils for actuation. In this work, we allowed robots to hover on a specialized platform and interact (via their planar coils) with permanent magnets that were embedded into the platform. Our approach led to a robot swarm in which robots did not possess mechanical parts, but were comprised of circuit boards only. We also started integrating Hall-effect sensors onto our robots and using magnetic field readings to improve the perception of robots. HoverBots were able to detect collisions, movements (odometry), and rotations by analyzing its measurements of magnetic fields.

  • HoverBots: Precise Locomotion Using Robots That Are Designed for Manufacturability
    M.P. Nemitz, M.E. Sayed, J. Mamish, G. Ferrer, L. Teng, R.M. McKenzie, A.O. Hero, E. Olson, A.A. Stokes
    Frontiers in Robotics and AI, 4, 55
  • Multi-Functional Sensing for Swarm Robots Using Time Sequence Classification: HoverBot, an Example
    M.P. Nemitz, R.J. Marcotte, M.E. Sayed, G. Ferrer, A.O. Hero, E. Olson, A.A. Stokes
    Frontiers in Robotics and AI, 5, 55

Figure 2. A HoverBot. The bottom layer of the HoverBot consists of an array of five planar actuation coils. Its top layer is populated with Hall-effect and infrared sensors and a low-power (SAMD21E) microcontroller. The battery of a HoverBot is detached in this figure.

Electro-Magnetic Soft Sensors

Electro-magnetism and elastomeric polymers can also be effectively used for the development of sensor systems. We integrated soft channels (which we subsequently filled with liquid metal) and a RFID chip into an elastomeric polymer. This device is a wireless stretch sensor in which the soft channels act as antennas. Stretch leads to a change in resistance (of the antenna), which leads to a shift in resonance frequency of the RFID circuit. Our system does not require external power, which makes it extremely suitable for the development of smart clothing.

  • Soft Radio-Frequency Identification Sensors: Wireless Long-Range Strain Sensors Using Radio-Frequency Identification
    L. Teng, K. Pan, M.P. Nemitz, R. Song, A.A. Stokes
    Soft Robotics, 6(1), 82-94
  • Integrating Soft Sensor Systems Using Conductive Ink
    L. Teng, K. Jeronimo, T. Wei, M.P. Nemitz, G. Lyu, A.A. Stokes
    Journal of Micromechanics and Microengineering, 28(5), 054001

Figure 3. Soft robot with embedded RFID sensors. Each leg (pneunet) of the fluidically-driven soft robot contains a microfluidic strain sensor: a RFID antenna and a RFID chip. These sensors do not require an external power supply. A change in strain leads to a change in resonance frequency.

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