[mindcruzer]

Actually, I'm not sure it is. Not for an energy related reason anyway. I'd wager the main reason the the glucose is present is due to osmolarity when the CSF is being created from the blood. Also realize that the CSF has a high turnover rate, something like 3-4 times per day, so that glucose is being replenished readily. I doubt this chip uses much glucose in comparison (plus, they've probably thought of this).

[carbocation]

Usually glucose is transported, as it doesn't freely pass through membranes. I believe the same is true for the glucose in the csf.

[mindcruzer]

Yup, my point was that the glucose may be moved into the CSF in order to favor the movement of water in that direction.