The Engineering of a Disposable Diaper

Bill reveals the stunning engineering underlying the design of a diaper. He describes the five layers of a diaper, including the superabsorbent polymer in the diaper's core. He illustrates the action of this polymer with a stunning demonstration using a single bead of polymer: it soaks up enough water to grow from a diameter of 4 mm to nearly a half inch.

You can bundle watch Bill's videos using this playlist:
If you are interested in mechanical computers you'll likely enjoy his series on Albert Michelson's Harmonic Analyzer -- a 19th century machine that calculates Fourier transforms:

Creative Commons Images Used in Video
First cotton image is by dotlizard

The cotton candy image is from Stefano Mortellaro

[PracticalEngineeringChannel]

This is fascinating. Excellent job covering a tricky topic with professionalism ;) In civil engineering we have woven and non-woven geotextiles that serve different purposes as well. Great work as always.

[FilmmakerIQ]

Not sure if this is my number 1 favorite video on diapers.... or number 2.

[katetranscribes]

It just struck me that almost none of the mechanics of these diapers rely on gravity, meaning that no matter what the position of the baby (laying down, on an angle) the diaper will be equally effective.

[holtek]

I have been working in this industry for over 30 years so I do get to see the machines that make diapers and similar disposable products every day. When I started, 400 products per minute was considered fast and everything was driven by a lineshaft and belts. Now it's hundreds of servo motors synchronized together with incredible precision and well over 1000 products per minute is a reality. Thanks for explaining the product so well, we do kind of take all this for granted but there is quite a bit of engineering that goes into it!

[BluDog]

"Stagnant Pool Of Evacuated Urine" The name of my new metal band.

[MonMalthias]

I wonder what the guy at the patent office thought when he read the sentence, "explosive liquified bowel movements".

[stevesynan]

I went in thinking 'what could possibly be that interesting about a diaper?' and now I'm completely blown away by materials science and need to learn more! Great job as always!

[klorn]

I just discovered Bill and his channel. I could listen to him talk all day. Great voice and presentation.

[Getyurfactsstrait]

I used to work on diaper machines and what you said at the end is so true. I was amazed at how fast these machines would run. We were a smaller company and the machines ran at 650 dpm. Even at that speed it's was really something to watch.
Everything had to be synced up perfectly for the machine to operate properly. One of the most interesting parts of the machine was the vision system which would reject any diaper was out of spec while running at full speed.

[wheeman]

So glad you're making videos again.

[itcamefromabox]

Listen Bill, I don't want to freak you out but we fall asleep to the sound of your voice at night. I'm not saying you're boring because we love your content, i'm just saying you have a soothing voice. KEEP UP THE AWESOME WORK :D

[nickkillian]

You know, as a first time father (7 month old child), I have wondered just how the basis of disposable diapers worked. I knew it had to be something far more than meets the eye.
Now I know, thank you.

[DanBillings]

I'm a UIUC engineering alumnus and these videos make me very proud. Always incredibly informative and the production is airtight. Thanks to Bill and your team!

[peterlinddk]

I love videos like this one and the one about aluminum cans - stuff that we think of as simple "throw-away" items, but in fact contain a lot of ingenious engineering solutions!
A shame that we can't get to see the manufacturing process.

[skyfeelan]

not planning to have a kid in the near future, but I really love the engineering principle behind it!

[rym]

I don't even know what's happening in half of his videos, but it's very soothing and interesting to watch/listen to so I get completely lost learning about diapers and coffeemakers ...

[harrisonbalduf]

This man could narrate anything and I'd watch it.

[SubhomMitra]

This is just so impossibly fascinating! Thanks for making such great content; can't wait for the videos on Faraday.

[tommythai]

3:04 Shouldn't the labels for 1mm and 1.5 mm be swapped?

[DIYTyler]

My mind just exploded! Need to make that many a minute to keep the cost be a neat place to work.