Full transcript
0:00Hanging on your bathroom wall right now
0:02is the last piece of 19 th-century
0:03technology . That you still use every
0:06single day . It costs America millions
0:09of trees every year . It clogs the pipes
0:12under your street , and fundamentally ,
0:14it has barely changed since 1857 . But
0:18in a lab in Indiana , a team of
0:19engineers just built a small device
0:22that cleans more thoroughly than any
0:24paper ever could , using nothing more
0:26than sound and a mist you can barely
0:28feel . If this catches on at scale , the
0:32roll on your wall will become about as
0:34obsolete as the outhouse it once
0:35replaced . This is by no means just a
0:39gimmick ; it is a genuine breakthrough
0:41in fluid dynamics . And the truly
0:44strange thing is that the people who
0:46developed it never intended to reinvent
0:49the bathroom . That is a detail worth
0:52acknowledging , because such
0:53coincidences occur surprisingly often
0:55in the history of technology . They were
0:58trying to solve a completely different
1:01problem in hospitals , and what they
1:03found by accident could end up
1:04replacing a product that almost every
1:06American household buys every single
1:08week without ever questioning it . The
1:11technology in this device is
1:13surprisingly based on something quite
1:15simple : an effect scientists discovered
1:18back in the 1890s while investigating
1:20why ships were destroying their own
1:22propellers for over 100 years . This
1:25effect remained trapped in industrial
1:28machinery for an entire century because
1:30one persistent technical problem
1:32prevented it from ever growing beyond
1:34that . The team in Indiana finally
1:36solved that exact problem . And once
1:39they succeeded , they realized they
1:41hadn't just built a better cleaning
1:43device , but an entirely new way to
1:45clean anything at all . But before you
1:48understand why the roll in your
1:50bathroom is suddenly on borrowed time ,
1:52you first have to understand what this
1:54roll actually is and what it really
1:56costs . Almost everything else in your
1:58bathroom has long been modernized . The
2:00lights are now smart . The scale talks
2:02to your phone . The toothbrush has a
2:04timer , a pressure sensor , and its own
2:06app . In some homes , even the mirror
2:08displays the weather , and then there is
2:10the paper . Toilet paper as a commercial
2:14product dates back to 1857 , when a man
2:17named Joseph Gayet in New York began
2:20selling flat , medicated sheets . The
2:23roll format was only added a few
2:25decades later . In the 1930s of the 20th
2:28. Century , a well-known manufacturer
2:30was even proud that its product was
2:32finally splinter-free , which reveals
2:34quite a bit about how the product must
2:36have been before then . Since then , all
2:39changes have been purely cosmetic : more
2:41layers , softer texture , embossed
2:43patterns , elaborate packaging . The
2:46actual core concept hasn't moved a
2:48single step forward in over 150 years .
2:51What this core concept actually demands
2:53is the following . You take a tree ,
2:55usually softwood , often from northern
2:57forests , sometimes from forests that
2:59have taken decades or even centuries to
3:01grow that large , and you cut it down .
3:04Americans consume more of this product
3:06per capita than almost any other nation
3:08in the world . About 140 rolls per
3:10person per year . A number that has
3:12hardly changed , even though virtually
3:14every other consumer good has shifted
3:15toward sustainability in that same time
3:17. Environmental organizations
3:19investigating forestry supply chains
3:21have been pointing out for years that a
3:23large portion of the pulp for
3:25high-quality toilet paper comes from
3:27old boreal forests and that it is a
3:29particularly bad trade-off to turn a
3:31centuries-old tree into something that
3:33is flushed away within seconds of its
3:35production . The production of a single
3:38roll alone consumes several dozen
3:40liters of water before it even arrives
3:42at your home . Then there is the second
3:44side of the costs , the one nobody sees
3:46because it only emerges after flushing .
3:49Municipal sewage systems in the United
3:51States spend several hundred million
3:53dollars each year dealing with what
3:55actually gets flushed down . Paper
3:58products , wet wipes advertised as
4:00supposedly flushable , grease , and
4:01everything else clump together in the
4:03pipes into dense , hardened masses that
4:05maintenance teams then have to
4:07laboriously cut open by hand . A task
4:09that has even developed its own
4:11informal name in sewage industry job
4:14titles because it happens so frequently
4:16. Cities have pulled blockages out of
4:19their sewers that were heavier than an
4:21entire car , and every single one of
4:23these removal operations is paid for
4:25with public funds , which ultimately
4:27means you are paying for it yourself .
4:29So , you have produced a product from
4:31slow-growing trees , bleached with
4:33chemicals , transported it across an
4:35entire continent , used it for 3 seconds
4:38, and then flushed it into a system
4:40that has to spend public money all over
4:42again to remove it . And it doesn't even
4:44clean very well in the process . Paper
4:46doesn't actually dissolve anything at
4:47all . It just moves things from one
4:49place to another . Anyone who has ever
4:52tried to wipe their plate with a dry
4:54napkin knows this physical principle
4:56from their own experience . For almost
4:59an entire century , water has been the
5:01only serious alternative to this .
5:03Bidets have been around since the 18th .
5:06Century , and they are standard
5:07equipment in large parts of the world .
5:10They clean better , but American homes
5:12were simply not designed for them . A
5:15subsequent installation means
5:16additional cold water lines , additional
5:18pressure lines , and space that most
5:20bathrooms simply do not have . And 100
5:23million people didn't want to renovate
5:25their entire home because of it , even
5:27if they theoretically knew the
5:28alternative would be more hygienic . So
5:31the roll stayed on the wall , not
5:32because it was good , but because
5:34nothing better would simply fit through
5:35the door . That was exactly the problem
5:38a group of engineers in Indiana began
5:40to look into , though with no intention
5:42of actually solving it . They were
5:44trying to solve something completely
5:46different in a hospital , and the answer
5:48they found came from a phenomenon that
5:50engineers had spent a whole century
5:52desperately trying to get rid of . In
5:55the 1890s , the British Royal Navy faced
5:58an expensive mystery . Their newest ,
6:00fastest ships were destroying their own
6:02propellers , not slowly , not just
6:04through rust , but rapidly , with the
6:06metal looking eaten away and scarred ,
6:09as if something had been gnawing at it .
6:12It was a mystery that left naval
6:14engineers of the time baffled , because
6:16it contradicted all previous experience
6:18with metal wear . A naval engineer named
6:21John Thornycraft was commissioned to
6:23investigate , and what he and his
6:25colleagues eventually identified later
6:27became known as cavitation . Here is the
6:31logic : if a propeller blade moves
6:33through water fast enough , the pressure
6:36on one side of the blade drops so much
6:38that the water begins to boil for a
6:40tiny moment , even at normal
6:42temperatures . Tiny vapor bubbles form ,
6:45which shortly thereafter reach areas of
6:47higher pressure and collapse inward .
6:50And when one of these bubbles collapses
6:52, it doesn't just pop . It implodes
6:55quite violently , shooting out a
6:57microscopic jet of liquid at enormous
7:00speed . A single bubble is meaningless ,
7:03but billions of them , over and over
7:05again , will eventually punch holes even
7:08in solid steel . For decades , cavitation
7:11was considered exclusively an enemy . It
7:14ruined propellers , pumps , and turbines .
7:16Entire careers were dedicated to
7:18fighting it . But eventually , in the mid
7:20- 20th century , someone simply turned
7:22the obvious question around . If these
7:26collapsing bubbles are strong enough to
7:28destroy metal , what happens if you aim
7:30them at dirt instead ? Exactly that
7:32question led to the ultrasonic cleaner ,
7:34which you might have seen at a
7:36jeweler's or an optician's . It is a
7:39small stainless steel container full of
7:41water , with an oscillating element at
7:42the bottom that vibrates thousands of
7:44times per second , creating pressure
7:46waves that cause microscopic bubbles to
7:48form and collapse throughout the liquid
7:50. If you place a dirty ring or glasses
7:53in this tank , every single particle of
7:56dirt dissolves within a few seconds ,
7:58even from grooves and crevices that no
8:01cloth could ever reach . It works
8:03because there is no scrubbing involved
8:04at all . It’s not chemistry either ,
8:07but simply millions of microscopic
8:09pressure events that occur every single
8:11second . Each one is essentially a tiny
8:13hammer blow that strikes exactly where
8:15the surface is located . Think about a
8:18stain on a shirt . If you rub it with a
8:20dry cloth , you’re just moving it
8:22around ; if you soak and scrub it ,
8:24you’re using force and friction that
8:26also damages the fabric itself . But if
8:28you could hit that stain with a million
8:31invisible little hammers per second —
8:33small enough to never harm the fabric ,
8:35but powerful enough to loosen every
8:37single particle — you wouldn't have to
8:39rub anything at all . That is exactly
8:42what cavitation cleaning is :
8:43simultaneously the gentlest and the
8:45most aggressive method of all , which
8:47sounds like a contradiction at first ,
8:49until you understand the scale at which
8:51it actually happens . Hospitals adopted
8:54this process for surgical instruments ,
8:56semiconductor factories for silicon
8:58wafers , and aerospace workshops for
9:00components with internal channels that
9:03no brush would ever fit into . It became
9:05the gold standard for everything that
9:07must be absolutely clean , yet for 70
9:09years , it never found its way into the
9:12bathroom , the kitchen , or any normal
9:14home . The reason for this was the water
9:16tank itself . Cavitation , as understood
9:18until now , functioned exclusively
9:20within a liquid . The object had to be
9:23completely submerged because the
9:25bubbles needed a continuous body of
9:27liquid in which they could form and
9:28collapse . If you took the object out of
9:31the water , the effect vanished
9:33instantly , and that one single
9:34requirement kept the technology locked
9:36inside industrial machines forever . You
9:39can’t submerge a wound . You can’t
9:41submerge a countertop . And you
9:43certainly can’t submerge an entire
9:44human being . Engineers tried for
9:46decades to bypass this obstacle . They
9:49sprayed cavitating water through
9:51nozzles . But the effect died the moment
9:54the jet left the nozzle . They tried it
9:56with foam , they tried it with gel .
9:59Every single attempt failed against the
10:01same wall : that the liquid itself was
10:03the real bottleneck . A circumstance
10:05that runs like a common thread through
10:07decades of failed patents . The
10:09technology worked wonderfully , but only
10:11if you brought the object to the water .
10:14A team in Indiana therefore asked a
10:15completely different question . What if
10:18you don't need a continuous body of
10:20water at all ? What if you could simply
10:22carry cavitation with you through the
10:23air ? At a fluid dynamics laboratory in
10:26West Lafayette , Indiana , a small group
10:28of engineers had been tasked with
10:30working on a wound care problem .
10:33Cleaning an open wound is one of the
10:35more brutal routines in medicine . It
10:37mostly consists of saline solution ,
10:39gauze pads , and physical wiping , which
10:42is painful , damages healing tissue , and
10:44is genuinely feared by patients . The
10:47team was asked if ultrasonic cleaning
10:49could be adapted for this , and the
10:51initially obvious answer was , of course
10:53: No , you can't exactly put a burn
10:55victim into a tank . The lead
10:57researchers behind this work , which was
11:00later published in a journal for fluid
11:02physics in 2020 , arrived at a
11:04refreshingly simple realization . They
11:08stopped viewing the water as one single
11:11large tank and instead began treating
11:13every individual water droplet as its
11:16own tiny tank . The underlying idea can
11:19be described as follows . If you create
11:22a mist of water droplets in a very
11:24specific size range , about 40
11:26micrometers , thinner than a human hair ,
11:29and send an ultrasonic field through
11:31this mist while the droplets are still
11:33in the air , each individual drop can
11:36harbor cavitation within itself . You
11:38don't need a tank at all anymore . Each
11:41drop is already its own tank . Billions
11:44of tiny tanks floating through the air
11:46together . Each one with its own
11:48collapsing bubble and its own
11:50microscopic hammer blow that lands on
11:52the surface at the exact moment of
11:54impact . They called this effect an
11:57aerosol cavitation field . Getting there
12:00, however , was anything but easy .
12:03Droplets that are too large simply fall
12:06down as ordinary spray , and the
12:08cavitation collapses before it even
12:10hits the surface . Droplets that are too
12:13small evaporate before they reach their
12:14target . The team had to find that
12:17narrow range where a drop actually
12:18survives the flight , stores the
12:20acoustic energy , and delivers the
12:22collapse exactly upon contact . They
12:25spent months tuning nozzle geometry ,
12:27ultrasonic frequency , and droplet size
12:29spectrum , photographing the results
12:30with high-speed cameras at hundreds of
12:32thousands of frames per second . When
12:36they finally got it right , the results
12:38were , by their own admission , even
12:40better than with the classic tank . The
12:42mist cleaned skin more thoroughly than
12:44simple wiping . And it did so completely
12:46contactless , without friction , without
12:48abrasion , without pressure .
12:50Contaminants adhering to the skin ,
12:52including oils and biological residues ,
12:54were lifted and carried away by the
12:57very droplets that had acted upon them .
12:59Because the cleaning took place at a
13:01microscopic level , it even reached
13:03textures and wrinkles that a flat sheet
13:05of paper could never physically touch .
13:08An aspect that makes a decisive
13:10difference , especially for sensitive ,
13:12wrinkled , or injured skin . And all this
13:15was achieved with an astonishingly
13:16small amount of water because there was
13:18no longer any need to fill a tank .
13:20According to estimates from this work ,
13:22a complete cleaning cycle uses only a
13:24fraction of a cup of water . Less water
13:28than is used to produce a single sheet
13:30of the paper it is meant to replace .
13:34They then added the second half of the
13:36device : a directed warm air stage that
13:38runs immediately after the mist and
13:41evaporates the last remaining moisture
13:43within a few seconds . Clean , dry , done .
13:47Nothing to wipe , nothing to rinse ,
13:49nothing you’d need to buy again next
13:51week . And that’s exactly where
13:53someone in the lab voiced the obvious
13:56thought . If this can clean a wound
13:58without even touching it , then why do
14:00you actually still need the paper ? The
14:03demo unit they eventually built is
14:05small , about the size of a thick book ,
14:07mounts to existing fixtures , and only
14:09needs a standard water connection and a
14:12power outlet . No plumbing modifications
14:15, no hot water heater , no pressure
14:17nozzle . From the outside , almost
14:19nothing dramatic seems to happen . You
14:21feel a slight cool breeze for a few
14:23seconds , then warm air , and it's
14:25already over . The real difference
14:28compared to a classic bidet is that
14:29water isn't used as a solvent here , but
14:31merely as a medium for acoustic energy .
14:34The actual amount of water becomes
14:36almost insignificant , which is why the
14:38whole device works with a mere trickle
14:40instead of a high-pressure line . And
14:42that is precisely why the plumbing
14:44renovations that kept bidets out of
14:46American homes for a full century are
14:48unnecessary . But the moment the mist
14:52proved functional , the team realized
14:54they had built something far greater
14:56than just a bathroom fixture . Because
15:00if you can transport cavitation through
15:02the air , you can essentially aim it at
15:03literally anything . The original
15:06application in wound care didn't become
15:08less , but even more promising . Cleaning
15:11a burn or ulcer without touching it
15:14removes by far the most painful part of
15:16the entire process while eliminating
15:19the risk of spreading bacteria across
15:21healing tissue . One of the true causes
15:24of hospital-acquired infections . This
15:27very application is currently receiving
15:29the most clinical attention , but the
15:31list by no means ends there . Long-term
15:33care facilities showed immediate
15:34interest , though for reasons that have
15:36nothing at all to do with the
15:38technology itself . A huge portion of
15:40care work in nursing homes is personal
15:43hygiene , and that is what patients
15:45usually find most humiliating and
15:47caregivers find most physically taxing .
15:49A device that allows someone to do that
15:51independently is thus far more than
15:53just a convenience . For many people , it
15:56simply means dignity , and that very
15:57aspect is mentioned surprisingly rarely
15:59in public discussions about new medical
16:01technology , even though it often weighs
16:03more heavily for those affected than
16:05any mere increase in efficiency . Food
16:08processing plants showed interest
16:10because washing fruits and vegetables
16:13has meant massive baths of chlorinated
16:15water , and a mist that cleans without
16:18submersion would drastically reduce
16:20water consumption while reaching
16:22surfaces a bath simply cannot .
16:25Semiconductor manufacturers showed
16:27interest because cleaning wafers is a
16:29constant battle against contamination
16:31on a scale where a single particle can
16:34ruin an entire chip , and directed
16:36aerosol gravity can be focused
16:38precisely on a specific area of a wafer
16:40instead of flooding the entire
16:42component . Space engineers showed
16:45interest for perhaps the most extreme
16:47reason of all . On board a spacecraft ,
16:49water is precious and free-floating
16:51liquid is dangerous . A cleaning system
16:53that makes do with a fraction of a cup
16:55and evaporates on contact solves a
16:57hygiene problem that has accompanied
16:59manned spaceflight since its inception .
17:02After all , a crew on the way to Mars
17:04cannot possibly carry three years ’
17:06worth of paper products , and they can
17:08afford to waste water just as little .
17:10What started as a project intended only
17:12to make wound cleaning less painful has
17:14thus become a universal method for
17:16cleaning virtually anything anywhere ,
17:18without touching it and without needing
17:21a basin . This brings us to the part
17:22where reality comes into play , because
17:24one should be honest about where this
17:26technology actually stands . What exists
17:29today is a laboratory demonstrator and
17:31a series of published results . There is
17:33no product on the shelf , no announced
17:36release date , and no manufacturer that
17:38has publicly committed to a consumer
17:40version . Everything beyond the
17:42laboratory remains a projection for now
17:43. The first obstacle is the cost .
17:46Ultrasonic transducers that can run
17:48continuously at the required frequency
17:49and power are not particularly
17:51expensive when considered individually .
17:53However , building them into a sealed ,
17:55waterproof consumer fixture that must
17:57survive a full decade of daily use in a
18:00humid room is a completely different
18:02engineering problem . One that falls
18:04more into the realm of materials
18:06science and manufacturing technology
18:07than into actual fundamental physics .
18:10Early estimates place the price of a
18:12consumer device significantly above
18:14what most households would spend on a
18:16bathroom fixture , and far above the
18:17ongoing costs of the paper it is meant
18:19to replace . If something costs several
18:22hundred dollars upfront to displace a
18:24product that costs only a few dollars a
18:26week , most people do a quick
18:27calculation and simply keep buying
18:29paper . The second obstacle is energy
18:31consumption . Creating a controlled mist
18:35, sending an acoustic field through it ,
18:37and then running a warm air cycle uses
18:39real electricity — not much per use .
18:42But it turns a product with zero energy
18:44costs at the point of use into one that
18:46draws power every single time . Whether
18:50the overall balance ends up being
18:52better depends on how you weigh forest ,
18:54water , and sewage disposal against
18:56domestic electricity consumption , and
18:58quite frankly , no one has yet published
19:00a complete life-cycle comparison . The
19:03third obstacle is water quality . Hard
19:05water is the natural enemy of anything
19:08with a fine nozzle . Mineral deposits
19:10would clog a 40 - micrometer droplet
19:12generator faster than almost any other
19:14household appliance , which means
19:16filtering , maintenance , and spare parts
19:18. that consumers should actually be
19:20concerned about . The fourth obstacle is
19:23validation . Cleaning a surgical
19:25instrument can be measured in a lab .
19:27But cleaning a human being is measured
19:29by a habit practiced since childhood ,
19:32which can hardly be changed by a
19:34technical claim alone . Any company
19:36wanting to bring something like this to
19:38market must prove it not just once , but
19:41continuously to regulators and a public
19:43that is understandably very reserved on
19:45this exact topic . And the fifth
19:47obstacle is the strangest of them all .
19:50It is not a technical question at all ,
19:52but simply the fact that people dislike
19:54talking about it . An invention that
19:56solves a problem no one likes to talk
19:59about faces a marketing problem that no
20:01engineering team can solve . Bidets have
20:04been superior to paper for 200 years ,
20:06yet that has never really mattered . But
20:09every one of these obstacles is
20:11ultimately a cost or habit problem .
20:14None of them are physical problems
20:16anymore . The physics has already been
20:18solved , and that is exactly the part
20:19that has truly changed . For 70 years ,
20:22this technology remained trapped in
20:24industrial tanks because a hard
20:26scientific limit existed . And that
20:28exact limit no longer exists . That is
20:31how things like this practically always
20:33go . The first computers filled entire
20:35rooms and cost millions . The first
20:37solar cells were calculated for
20:39satellites , not for rooftops . And the
20:41same story later repeated itself with
20:43flat screens , lithium batteries , and
20:46LED bulbs , whose prices fell by more
20:48than 90 % over decades without any
20:50changes to the underlying physics at
20:52all . A technology never comes into the
20:55world finished . It arrives at first
20:57expensive , cumbersome , and obviously
20:59impractical . And then a decade of
21:01engineers works silently to drive the
21:03price down , until one day everyone
21:05simply owns the thing . It is a strange
21:08thought that one should ponder for a
21:09moment . The roll on the wall behind you
21:12is a Victorian product made from trees
21:15that were alive before your
21:16grandparents were born , used for 3
21:18seconds , and then flushed into a system
21:21that has to spend public money again to
21:23get it back out . It survived , not
21:25because it was good , but because the
21:27alternatives never fit through the door
21:29. And now a small team in Indiana ,
21:32which was actually working on a
21:34completely different problem , has
21:36figured out how to carry a 100 - year-old
21:38physical effect through the open air in
21:40a mist you can barely feel . Such
21:43technologies rarely appear all at once .
21:45They first appear in technical papers
21:47that hardly anyone reads , years before
21:49they end up in a store . And once
21:50they've become completely normal ,
21:52everyone will have long forgotten that
21:54anything else ever existed . But one day
21:57, the last analog product in your
21:59household might finally disappear .
22:00Replaced by a few seconds of sound and
22:02a mist that dissolves before it has
22:04even truly settled . If this story
22:07surprised you as much as it did me ,
22:09feel free to leave a like , subscribe to
22:11Secret Globe , and hit the bell so you
22:13don't miss the next video , because a
22:15lot of real work goes into every one of
22:17these investigations . And now I’m
22:20genuinely curious : which everyday
22:22product in your own home do you think
22:24could be the next to quietly disappear ?
22:27Feel free to write your answer in the
22:28comments . I really do read every single
22:30one of them . Yeah .