Way back in 2010, Rob Cockerham of the Cockeyed blog was obsessed with his then-new Eyeclops Bionic Eye Camera, a sort of toy microscope that hooks up to a television set, providing extreme 200x macro images. He turned the Eyeclops onto the seals of Ziploc-style sandwich bags to reveal what those closures look like up close.
With the naked eye, this is about the best you can see:
Using the Eyeclops, Cockerham reveals the female side:
Next, a dual seal bag:
And one of those bags with the separate zipper pull:
"This is the view of the bag seal magnified by 200 times," Cockerham writes. "The connection is an incredibly tight handshake between the two channels. This looks like a waterproof seal!"
"Not impressed? Compare it to this shot of half of the standard double zipper. Notice all the open space around the connecting hooks... how shoddy!"
Also check out Cockerham's Eyeclops explorations of Velcro and yarn.