Electrical potential from the hair movement stimulates cells of the outer layer to rapidly pump hydrogen ions into the cell walls. This creates an acidic condition that activates enzymes which loosen fibers in the cell walls, weakening them. High osmotic pressure inside the cells causes them to absorb water and rapidly increase in size while the inner layer doesnt. This snaps the leaf closed.
The insect is held in place by sticky substances until the leaf can respond to the electrical signal in a manner similar to an animal nerve cell.
Potassium and hydrogen ions are pumped across the cell membrane, resulting in a rapid increase in water from osmosis. The leaf snaps shut with the increase in turgor pressure.
"Motor cells" increase their permeablilty to potassium ions, water flows by osmosis, and the cell shrinks as water is lost from the leaflets and petiole, and they wilt rapidly.