I wonder which IR proximity sensor they used. I'm currently using the OSRAM SFH7773 in my projects — it's the cheapest one I could find, but it is still quite expensive ($1.20 at qty 25 from RS/Allied). They are using 64 of them.

I also wonder how they deal with interference. Each sensor emits IR pulses and measures the light that bounced back. On the SFH7773 at least, there is no way to synchronize the pulses to an external source. Which means you will get light bleeding inbetween sensors.

Sadly, the publication is not (yet) available.

On a side note: I noticed that ETH Zurich seems to be doing a lot of groundbreaking work recently in electronics and robotics related fields.