Killing the Clank: How MIT Researchers are Enabling Motorless Humanoids

In this talk

1. 0:00

   Muscles distributed through the robot

   The researchers describe McKibben actuators about 1.5 mm across, arranged as fibers that can be woven, bundled, and routed through a robot. This approach distributes actuation through the robot’s body, unlike a failed motor or gearbox that can disable an entire joint.

2. 10:34

   Why fluidic muscles need a new pump

   McKibben actuators are inexpensive and scalable, but friction causes hysteresis and nonlinear pressure-to-stroke behavior. Traditional pneumatic and hydraulic systems also depend on bulky, noisy compressors or reservoirs, which limit portability. The researchers integrate slender electrohydrodynamic pumps that move dielectric liquid using an electric field and have no moving mechanical parts.

3. 16:35

   A closed circuit that avoids pump breakdown

   An open circuit draws liquid from an exposed reservoir, which can spill or evaporate. To make the system self-contained, the researchers pair actuators and use bias pressure to keep the pump inlet above the fluid’s vapor-pressure threshold, avoiding bubbles that can cause electrical breakdown. The pressure also lets them operate at a higher electric field and use the actuator in an antagonistic pair.

4. 26:10

   Modular designs balance speed and force

   The model helps tune performance by changing how pumps and actuators are arranged. More pumps in parallel increase flow and response speed; more actuator cross-section increases force. One demonstration lifts 4 kg with an 8-actuator bundle weighing 16 g when filled, while another configuration launches an object in 100 milliseconds.

5. 35:01

   Remaining engineering challenges

   The researchers identify low electrohydrodynamic pump efficiency, material fatigue, friction, and hysteresis as priorities for further work. They also want to reduce operating voltage so the system can use smaller power electronics. The compliant muscles are backdrivable and can be stretched while active or at rest, which the researchers describe as useful for human interaction.