With Davis now back and relegating Lewis to the bench, Town boss Joe Royle has let his Welsh Under 21 goalkeeper out on loan to gain some further first team experience.
Speaking to the Official Club Website, Royle confirmed: "It's the next step forward for Lewis and we have been actively trying to loan him out for much of the season.
"We couldn't let him go when Kelvin was injured but now he's back and with Shane Supple here as well, we are in a position where Lewis can go out and gain some more first-team experience.
"He will join up with Cambridge this week but part of the deal means we can bring him back immediately if anything happens to Kelvin."