Question

reread the sentences from the passage. a drop of water sliding across a surface coated with two different materials would generate enough friction to create an electrical charge. so if metal wires are placed on that surface, and water droplets touch them as they move, harvesting electricity should be possible, ma reasoned... and it worked. in fact, mas researchers lit up 15 led light bulbs with a single moving water droplet. what this new method of forming water droplets this new method of making metal wires this new method of generating electricity this new method of coating surfaces and worked.

Explanation:

The passage describes a process where a water drop sliding on a surface with two materials creates friction - generated electrical charge. Metal wires are placed on the surface, and when water droplets touch them as they move, electricity is harvested. The key action is generating electricity, not just forming water droplets (no mention of a new way to form them in the context of "it worked"), making metal wires (the wires are just used for harvesting, not made in a new way here), or coating surfaces (coating is part of the setup but the main success is electricity generation).

Answer:

this new method of generating electricity