Agree with all that! If the cube can be made big enough, and...

Agree with all that! If the cube can be made big enough, and durable enough, ink-powered bulldozers might yet be feasible!
But I have one or two reservations:
The 4 to 5 cms includes a sheet of protective glass on the front and a protective sheet of something else on the back.
(The actual solar material is a lot thinner than the 5cm assembled panel.)
Presumably something as fragile as a spaced stack of (flexible?) sheets only 200 microns thick would also need
at least as much protection, back and front, as the solar panel. What I also wonder about is the minimum air gap without losing
efficiency, but most importantly how they propose to PROTECT such thin, flimsy layers, while also leaving the sides of the cube
open enough for the humidity to get in? And out in whatever form, if necessary?
(Would the cubes need to be "super-charged" with a fan blowing wet air through them in a closed system?
Would the fan and humidifier use more or less energy than the ink films were producing?)

What happens if the cube gets jarred, jolted, or subjected to even minor repetitive vibration?
Do these factors place an upper limit on the area of the sheets that can be supported, and kept separate, only along the edges?
Or, can they use wider sheets by putting supporting posts up through the middle of the cube with spaced support
for each sheet? Imagine the micro-engineering to do that, and then the sheet-by-sheet assembly of the cube!
More intricate things have certainly been done, but they also required a whole new precision engineering technology
to do them. Certainly worth the development cost for anything that took on in a really BIG way... eg., silicon microchips,
or filament light bulbs. But (chicken and egg) will these cube thingies take off in a big enough way to cover the cost
of developing the technology to build them? The possibilites are enormous - IF they can do it... but can they?
Will there be sufficient up-take of demonstrated applications to cover the cost of developing the technology?
And which comes first?

Some disruptive new technologies come over the horizon at the speed of sound. CDs replaced LP records in the space of
about eighteen months, and suddenly hi-fi record players all over the world were redundant and obsolete. The advent of
commercial passenger jets killed the cross-Atlantic steamer trade in about the same amount of time. Suddenly, 40,000 ton
steamships (which were built for speed, not comfort and cruising) were being sold for scrap metal because there weren't enough
passengers to cover the cost of keeping them in service. It will be very nice if this technology takes off like that.
But Parker were still selling fountain pens THIRTY YEARS after the introduction of ballpoint pens!
And Gene van Grecken's very slick hydrogen powered sports car - cheap, clean, stylish, zero-pollution transportation -
just faded away without ever getting into production.

P.