The link has a step-by-step guide to how they were made and as the pylons were resin casts it's also a neat introduction to casting. I really like acrylic force fields but having cut clear acrylic sheet in the past I know how hard that can be to get a nice edge. Still with saving time on the casting process you can spend a little more for the tidy finish. Alternatively you could look at transparent polypropylene folders and use them for the force field. Easier to cut, perhaps a little less durable but you could make them a little oversized for the gap and that way they could curve to fit between the pylons. You could even use the plastic from a 7Up or Sprite bottle - pre-curved and coloured!
But it's a really cool idea by Spyrle and very much reminds me of the Webway Gates and Energy shields from Dawn of War:
Also, specifically check out page 2 or Spyrle's step-by-step guide as it includes some links to other Xenos Defence Lines, including Grubnards that prompted Spyrle's comment [thanks again for contributing].