Speaker 1: Welcome to brain Stuff production of iHeart Radio. Hey brain Stuff,
Speaker 1: Lauren bog Obam. Here. If you're a human who grows
Speaker 1: hair and occasionally attempts to remove some of it, there's
Speaker 1: a decent chance that you've stood over the bathroom sink
Speaker 1: or in the shower and wondered, how is it possible
Speaker 1: that your hair can dull a razor blade. Hair is
Speaker 1: notoriously strong for its thickness, but come on, it's a
Speaker 1: stainless steel razor blade. That's gotta be stronger than a
Speaker 1: little old strand of hair, right. It turns out scientists
Speaker 1: have wondered the same thing, and now we've got an answer,
Speaker 1: and that answer is heterogeneity, of which is when an
Speaker 1: object's composition isn't completely uniform. But let's back up. So
Speaker 1: hair is indeed softer than steel. You might have noticed
Speaker 1: this yourself. It's about fifty times softer than the stainless
Speaker 1: steel used in razor blades, and yet the race or
Speaker 1: blades we used for shaving get dull fairly quickly. A
Speaker 1: team of scientists at m I t S Department of
Speaker 1: Material Signs and Engineering wanted to find out why, and
Speaker 1: their results were published in August and the journal Science.
Speaker 1: Researcher Jean Luca Or Sholey started by shaving his own
Speaker 1: facial hair with disposable razors and taking those blades into
Speaker 1: the lab to be examined with a scanning electron microscope.
Speaker 1: He found that the edges of the metal weren't rounding
Speaker 1: or being worn down as you might expect. Rather, they
Speaker 1: were chipping and cracking. So he created a mechanized shaving
Speaker 1: apparatus in the lab for a more controlled testing, and
Speaker 1: he built it to fit inside that electron microscope. He
Speaker 1: used hair from himself and his lab mats, and blades
Speaker 1: from commercially available razors. What were Sholey and his co
Speaker 1: authors on the study found was that chips were more
Speaker 1: likely to occur in the blade's edge when the hair
Speaker 1: was able to bend before being cut by the blade.
Speaker 1: So the team went even further to create computer simulations
Speaker 1: with more variations different hair, different cutting angles, different directions
Speaker 1: of force being applied, and different materials used in the blade.
Speaker 1: They found that the chips appeared under three conditions, when
Speaker 1: the blade approached to the hair at an angle, when
Speaker 1: the blade was heterogeneous in composition, and when the hair
Speaker 1: met the blade at a week point. Heterogeneous means that
Speaker 1: the blades material is not perfectly uniform. Thus, there are
Speaker 1: microscopic imperfections in the steel that allowed chips to happen
Speaker 1: when it comes into contact with something, even something as
Speaker 1: relatively soft as a hair. The presence of those tiny
Speaker 1: cracks in the material increases stress to the rest of
Speaker 1: the material, meaning that when there's one chip, there will
Speaker 1: be more chips breaking apart that fine edge and resulting
Speaker 1: in a dull blade. The researchers are now working on
Speaker 1: creating a more homogeneous or uniform steel material for sharper,
Speaker 1: longer lasting blades. Today's episode was written by Kristen hall
Speaker 1: Geisler and produced by Tyler Clang. For more on this
Speaker 1: and lots of other sharp topics, visit how stuff works
Speaker 1: dot com. Brain Stuff is production of iHeart Radio or
Speaker 1: more podcasts. My heart Radio visit the iHeart Radio app,
Speaker 1: Apple Podcasts, or wherever you listen to your favorite shows.