Sadly there is precious little info on these machines, which appear in the novel Rainbows End.
A character who works on a transport tray for shop class comments on "solid-state robots" while looking through a parts catalog- I'm guessing these are machines that somehow do mechanical work without moving parts. In chapter 8 they apparently 'sound like ceramics when under stress' and mention something about microgrooves being the part that interacts with other objects.
How do they work? Are there any real-life equivalents?