Agar and PDMS mazes


I was wondering if anyone is currently doing or did in the past experiments involving using a PDMS maze in which the C. Elegan travelled.
I cannot seem to keep the worm inside the channel. Since the PDMs is hydrophillic and the agar is constantly wet the seal is just not tight enough and the worm escapes. I tried increasing the concentration of agar slightly (from the original NGM agar recipe) but the worm still managed to crawl out. Can someone please suggest a good agar concentration or an alternate method of using a maze for the C. elegan to travel in?

Thank you for all of your help.