Fabricating the Skin
The skin is made of a highly elastic silicone rubber and is designed to fit over the mechanics in a way that maximizes the realism of motion. To create the organic look and feel of this synthetic flesh, the exterior of the skin was first carefully sculpted in clay and then a four-part, lightweight syntactic mold with a plastic inner core was created. Pre-colored silicone and other additives to create the correct elasticity and opacity was then injected into the cavity between the mold and the core and allowed to cure. Finally the skin was trimmed, patched, and painted. This process is shown in the movie.
Mechanical Design
The public anemone robot has 13 degrees of freedom: 8 body stages and 5 tentacles. Each body stage is rotated 90 degrees relative to the stage below. Servomotors at each stage allow us to fit all of the mechanical parts within the robot itself, avoiding problems of friction, control lags, and elasticity that would be introduced with external control. This gives the robot a broad range of motion with the ability to precisely control each stage. To avoid the effects of cumulative backlash from the planetary gearboxes at each stage, torsional springs preload each gearbox against one side of the backlash region. This permits a smooth quality of motion as shown in the movie.
Motor Controllers
Modified commercial servo controllers, using optical encoders to measure finger positions, control each of the finger motors. The eight stages of the robot's body are controlled using a custom high-density motor control platform currently under development for use in robots with many degrees of freedom. The body motors are equipped with a combination of optical encoders and potentiometers, enabling both precise control and absolute position sensing.