Sensing a contact between two point

Hello \

I am brainstorming about a project that involves a statistical count to calculate the number pi. The problem is consisted of a flat surface with 2 very thin parallel lines separated from each other distance "s". I now release a matchstick like piece on this surface that also has length "s". All I need to be able to do is to detect a hit if the matchstick is in contact with one of the lines on this surface.

I though of a simple switch as the surface could be differently charged than the parallel lines and the stick could be simply wire acting as a conductor, however, As the medium is water or oil the conduction property will fail...

I am open to any suggestions from image processing to capacitor/resistance sensors. really anything that is out there that can help.

Thank you in advance!

I d appreciate any help/ pointers on this.

How would the medium being oil be any different from the case of air?

Put an light beam down each line at the surface level.

For a beam generator, use an LED that shines through 2 collimated holes, each the approximate size of the diameter of the object. You'll need two of these, one for each line Use 2 photo transistors at the other end of each line behind a screen to detect the beams. The screen will have the same holes as the collimator. Laser LEDs would work best. See the attached drawing.

detector.JPG