Science Buddies: "Ask an Expert"

I am doing my experiment on the effects of caffeine on C. elegans and I have a couple of questions. Essentially I plan to place the worms in the middle of an agar test plate and place a solution with the drug on one side and place nothing on the other side. I also plan to pre-expose the worms to different concentrations of caffeine, and then observe their behavior towards the drug.
1. How can I divide the test plate such that I will be able to create these two "chambers"?
2. If I put the caffeine solution on the agar, how can I ensure that it won't be absorbed into the agar?
3. Is there a chance that the worms will move randomly as they are not aware of which side contains the drug and which does not? If so, how can I prevent this?

Thanks in advance!!!

You may be able to spread a thin film of solution on half the way you would plate bacteria (https://www.youtube.com/watch?v=Rye6DfMv66Q) but with tape stopping you from crossing the side. I do not think it is a problem if some drug is absorbed by the gel; it will basically still be divided by the line you create.
If the worms do not respond with any preference for the drug in any condition, that may be your real result! Not all experiments demonstrate the results you expect, and it's important to let the scientific method work. You wouldn't 'prevent' anything. If you have doubts about the validity of your experiment you can try a different method, but you should report all of your results, not just the ones you expect.