After watching Wall-E, I become very intrigued by a number of technologies portrayed in the movie. In particular, I find those contactless joints or contactless limbs of EVE, a character in the movie, fascinating. EVE is an elongated-egg-shaped robot whose arms and head are not physically joined to her body. Nevertheless, there appears to be an invisible force that binds her limbs and her body together. She is also able to move them around without physical contact. This raises some questions:
1) Is there an existing effort to create such a technology?
2) If there is, what is it called, and how is it done?
3) If there isn't, can it be feasibly developed using existing means (never mind if extra research is needed)?
4) If it can be developed, what does it entail?
5) If it can't be developed, what are the reasons, and what conceivable but as-yet-unattainable technologies are needed?
To create a contactless joint/limb, we need to solve several problems:
1) Make the limb float.
2) Make the limb attracted to the body.
3) Move the limb without physical contact with the body.
Of course, in all 3 cases, we must ensure the forces are always in a stable equilibrium. If stability is not possible, then we should look at feedback control systems.
My puny mind, as far as its imagination can be stretched, gives me several ideas.
1) acoustic pressure.
2) electromagnet array/matrix.
3) ionized air and electromagnets.
1) Acoustic pressure. We can use ultrasound transducers to create a pressure field, so to speak, that provides counter-act forces to the limb's weight. This solves problem 1. To solve problem 2, we again use acoustic pressure to push the limb towards the body. We must balance the limb based on its center of mass. To solve problem 3, we vary the energy density of the ultrasound waves to give varying forces along the limb. At places where the force of the transducers exceed the gravitational force at that point, it gets pushed up. We get the opposite effect if we reduce the energy density.
2) Electromagnet matrix. Along the limb is a matrix of electromagnets. On the matrix are small magnetic cells. We can use Halbach arrays to change the magnetization vector of each cell. We vary the magnetic force to ensure the limb stays at one position, or move to whatever position we want. If done correctly, we can solve all 3 problems at once.
3) Ionized air and electromagnets. We use UV rays to ionize the air surrounding the limb. We set up a potential through the ionized air, so that there is a current, and hence magnetic field. The limb itself controls it electromagnets' direction and magnitude to balance itself within this column of air. Again it solves all 3 problems at once. Note this is not unlike the technology we believe will be used in future hover-boards.
All the above solutions require tremendous amount of energy just to balance the limb. For example, by my rough estimated calculations, an ultrasound transducer used in solution 1 must have output upwards of 34 kilowatts. Unless we can create a stable equilibrium force, the above solutions might not seem viable.