Physics Mystery Behind “Coffee Ring” Formation Uncovered

Coffee Rings

Researchers developed a mathematical model that predicts when a coffee ring might form in systems of hard spherical particles.

An international research team, led by Monash University, has discovered for the first time the mystery behind the formation of ‘coffee rings’ by examining the contact angle of droplets onto a surface, and how they dry.  

The research collaboration involving Monash University and Cambridge University also developed a mathematical model that is capable of predicting when a coffee ring could be observed in hard spherical particle systems.

Professor Gil Garnier, Director of BioPRIA (Bioresource Processing Research Institute of Australia) in the Department of Chemical Engineering at Monash University, led an international team to explore how patterns formed from evaporating droplets – a phenomenon that has mystified physicists for years.

Professor Garnier said this discovery, created by Dr. Michael Hertaeg from BioPRIA, could open up doors in the blood diagnostics arena, especially for the discovery of treatments for anemia and other blood diseases.

Coffee Rings Physics

A new study has discovered the mystery behind ‘coffee rings’ and how it could advance research in blood diagnostics. Credit: Monash University

Pattern formation is a common occurrence in drying colloidal liquids, such as milk, coffee, paint, aerosols, and blood.

Most common in droplets is a ring distribution where the liquid particles have relocated to the edge, which is referred to as a coffee ring, when drying. This deposit is unfavorable in many manufacturing processes and is of fundamental interest to experts in the building, medical, and engineering professions.

They concluded that the contact angles at which a droplet is placed on a wetted surface determines the prevalence of coffee angles. When the droplet is placed at a high contact angle, no coffee rings are present.

“Our research identified the contact angle formed by the suspension of droplets on the surface and its solids content as the two important governing variables to coffee ring formation,” Professor Garnier said.

“Although successful modeling has been achieved previously, we show here for the first time that for each contact angle, there is a critical initial colloid volume fraction over which no ring-like pattern will be formed.

“Essentially, the lower the contact angle, the higher likelihood that ring profiles will be found.”

When a droplet is placed on a surface, it quickly reaches an apparent equilibrium position that can, for small droplets, be defined solely by contact angle and radius.

The rate of evaporation and the variation of mass fluidity on the drop’s surface is dependent on many factors, including the vapor pressure of the fluid, the geometry of the droplet’s surface as well as the velocity and partial pressure of the surrounding atmosphere.

Drying experiments were conducted by placing a 6µL droplet of solution onto a substrate with an Eppendorf pipette. The droplet was left to dry in a humidity and temperature-controlled room held at 23°C (73°F) and 50 percent relative humidity.

“We showed that the presence or absence of a coffee ring can be solely predicted by the initial volume fraction of particles in a suspension and the contact angle formed by the suspension on the surface of interest,” Dr. Garnier said.

“Using this finding, we were then able to calculate a model to predict coffee ring formation from contact angles using a number of liquid droplets.

“This modeling technique and its resulting insights are new powerful tools to optimize manufacturing and diagnostic techniques.”

Reference: “Predicting coffee ring formation upon drying in droplets of particle suspensions” by Michael J. Hertaeg, Clare Rees-Zimmerman, Rico F. Tabor, Alexander F. Routh and Gil Garnier, 1 February 2021, Journal of Colloid and Interface Science.
DOI: 10.1016/j.jcis.2021.01.092

This work was funded by the Australian Research Council with Haemokinesis and an Australian Government Research Training Program Scholarship.

105 Comments on "Physics Mystery Behind “Coffee Ring” Formation Uncovered"

  1. This is the biggest load of crap I have ever heard. Did these yahoo’s actually get paid to spend time on this? With the problems facing humanity…..This is why we are doomed. Idiot savants, all of you.

    • A new study has discovered the mystery behind ‘coffee rings’ and how it could advance research in blood diagnostics.

    • Professor Garnier said this discovery, created by Dr. Michael Hertaeg from BioPRIA, could open up doors in the blood diagnostics arena, especially for the discovery of treatments for anemia and other blood diseases.

    • It’s one thing to read and learn information. It’s an entirely different animal applying that information to the real world. Take a breath, read more books, no one is as smart as they think they are.

  2. … okay,
    I just wonder who was making so much coffee and coffee rings…

  3. Jock Campbell | April 4, 2021 at 11:20 am | Reply

    I think this article was supposed to have been published 4 days ago…

  4. So I suppose it’s potential application in blood diagnostics isn’t enough for you? You might remember how dismisive you were should you ever need urgent care for a blood disorder in the future.

  5. Wonder how much government grant money went into figuring this useless bs out.

  6. Marshall Whitehurst | April 5, 2021 at 5:55 am | Reply

    Future politicians in training!

  7. Obviously, other comments failed to even understand the topic being discussed – this is NOT about actual coffee-cup-ring-stains. It is about individual droplets that form stains in ring patterns, which can be a huge problem in many important processes.
    TBF, the headline and main photo of the article is misleading clickbaity nonsense, and the author does not make a point up front of explaining the analogy, so a lot of the blame is on bad writing & editing in an otherwise sound description of an important discovery.

  8. Who cares what this is about. Hell if it did not cost any money the cost in time is a disgrace. With all the BS going on in the USA and the rest of the world this and all the crap like it (in the name of science) is such a waste. If money for this type of things was used for the homeless or hundreds of other worthwhile endeavors or hell even the national debt it would be better spent.

  9. Initially i was wondered why anyone would waste their time on such a things, but there is value for this in medicine is invaluable.
    There was a man who spent most of his university studying dyes. It seemed like a waste to his peers and his professors. However, his research was invaluable in medicine as certain dyes acted as a transport of medicines to specific organs.

  10. This is what you get when people who know alot of really stupid sh*t just think they know

  11. Michael Pomeroy | April 5, 2021 at 7:57 am | Reply

    I believe the practical applications of this basic research are endless. In this era of anti-Science, I give my heartfelt thanks!

  12. “The 10th Man” = crapbot.

  13. The title and thumbnail are quite misleading since the article itself does not really imply they were studying actual coffee rings but rather trying to solve an age old phenomenon that has many applications in the medical field.

    However many people are just taking it at face value without understanding the actual intent of the study and that’s why they are saying it’s a waste of money


  15. It’s the aliens writing in the movie arrival.

  16. People in this comment section need to understand that the people who did research on this actually helped society more than the people who just scrolls on their phone all day and starts a fight on every comment section they see. what a hypocrtitical society we have. that’s why you study and don’t just skip school then pretend that you know a lot to judge such a helpful research 🙂 yes, there’s a pandemic but that doesn’t mean that other scientists who doesn’t even study viruses aren’t able to share such researches.

  17. Garry Pavlovic | April 6, 2021 at 7:41 am | Reply

    No matter the subject at least this person tried to resolve an unknown issue. And was willing share his finding for humanity.
    Hat Off to those that think of ways to further our knowledge to life’s problems.

  18. Hey 10th Man, you’re the problem facing humanity.

  19. coffee rings on the table always remind me it’s time to drink another cup of coffee. If taxpayers funded this study, there better be a cure for cancer in it!

  20. These comments are what happens when you take an important piece of scientific research and try to dumb it down with a moronic analogy. Armchair blowhards who know nothing about the physics problem under investigation, nor its practical implications for manufacturing, medicine, etc, all chiming in with opinions about “wasted resources”.

    Maybe they should switch to decaf.

  21. Invaluable medical research or not .. I hope you all die

  22. Seriously? Most people with experience in the painting industry “automotive painting” have know this ever since metalics and pearls have been used. Infact they are way ahead of this study. Come on people this is old news. Just ask any chemical engineer at 3M. I’m sure they have done studies in this area. Lol

  23. I agree what is wrong with the idiots to get money for this type of study is assigned to say the least

  24. Y’all talking about national debt yada yada. This was in Australia you moron

  25. What a waste of time, intelligence, and money.

  26. Did they use our tax dollars for this? For some coffee stains? Instead for fighting the nations problems they want to study coffee stains?

  27. couldn’t agree with you more Layman.. if 10th man is so smart he should be writing his own article of his recent groundbreaking scientific break threw .. but instead just being a troll . good thing none of us needed to hear what a guy that most likely works as a janitor at a gas station thinks .. why do the dumbest people think they understand all life’s secrets and think they are so much smarter then scientist that dedicate their life to they trade lol ..

  28. Whoa Nelly. I hope they can cure diabetes…

  29. There will always be those without the ability to see how something can have innumerable applications…those are the unimaginative ones.

  30. You can tell the Trump supporters came in the comments

  31. And they could have been studying how to cure cancer. I often wonder why we give any money to scientific exploration with stupid scientists thinking about things that don’t really matter in the world

  32. What’s worse, educated idiots or the educated idiots who waste money backing them. Too many hungry children in THIS country to be impressed by this.

  33. The comment section is as always is full of crap. There are people who aren’t interested in science and yet they read the title of an article and then sh*t on it in comment section. What is wrong with you people. If you don’t like a topic you don’t have to read it.

  34. when you dumb down an article, expect dumb responses.

  35. Evan Schwader | April 8, 2021 at 2:50 pm | Reply

    Any Joe Blow that has ever ran a paint gun could tell you the same thing. Hell even the juvenile delinquents spray painting graffiti could tell you this.

  36. interesting how the topic of coffee rings overshadowed the larger issue of potential applications in blood disorder diagnostics. Many people once thought we had more pressing issues than putting a man on the moon but, all the technologies developed for space exploration have given us things like radial tires, plexiglass. carbon fiber and glass fiber technology that we take for granted in our daily lives

  37. Kar ugh el el egrek | April 8, 2021 at 10:43 pm | Reply

    It’s a shame that they chose to be misleading with the title and clickbait image to rile people up!!

    Read the full article before you comment angrily – people are so forthright and don’t have a clue what they are getting mad about 🙄

  38. Lol 10th man. I was just wondering the same thing.

  39. If you’ve nothing nice to say! Say nothing at all.(some people really need a hug or something.)

  40. Trust the australians to research this nonsense,

  41. 1,1,2,3,5,8,13,21,34....... | April 9, 2021 at 2:52 am | Reply

    The majority of everyone in this comment section smart or not are narcissistic brain suckers.. Those who know more should explain it or shut up. Instead you insult peoples intelligence for being ignorant of implications of the study…. and those who don’t know or care and think its dumb and a waste of time should go save the world themselves or get involved in politics

  42. Very Slow Dishwasher | April 9, 2021 at 4:06 am | Reply

    I admire and commisserate with the inquisitive minds that find mysteries like this all around us to solve. Let us not lose our fascination with everyday phenomena. Obtaining an advantage in an industrial process means making money. Real poverty is starvation while surrounded by abundance.

  43. Is this real life?

    What a stupid article about nothing. What was this a recommendation in my news feed of all things!?

  44. This has nothing to do with coffee cups … it’s a discription relating to the drying of liquid droplets and presumably this discovery has a medical application Read the article to the end ……

  45. I would like a venti non-fat extra hot no whip no coffee ring mocha please.

  46. You can tell how read the article and who didnt lol

  47. … yeah, I heard about it…

  48. Jonathan Revis | April 9, 2021 at 11:17 am | Reply

    This is important research in both manufacturing in health care. The dispersion of solids in a liquid and how they dry could bring about many advances in several industries and and medical technology.

  49. Seriously? All the things we need to research and/or put money towards and this is what was chosen? Coffee rings? Ridiculous

  50. She takes my coffee and runs, she don’t love me anymore, she leaves me as empty as my cup, but wait,I read the coffee rings as though they were tarot cards, and then it all comes together,a warm breeze,a whisper in the wind saying she’ll be back again if only for a night, and then she’ll steal my coffee again in the morning light.

  51. You morons who dont understand science and how research is made… dont you have a beer can to smash on your forehead or something? Leave science for the big boys.

  52. What a joke no wonder tuition is so expensive. To support bs studies like this .. people go into lifetime debt to get a good education then the same institution forks out millions to study coffee rings ! Man what a f*cked up time we live in ..

  53. itt: idiots who have no idea how academic research works and jump to click bait titles, and actual academics. one unfortunately outweighing the other

  54. Very Slow Dishwasher | April 9, 2021 at 7:34 pm | Reply

    We search for techy, sciencey stuff on the Internet, we click on sciencey, techy stuff on the headlines of our browsers, we build a digital profile, and this article pops up. We didn’t resist the urge to click, and this is why we are here. There are ads that need to be seen, and article writers that need to be paid by the ad companies. It looks to me like a well-oiled machine. Like this article or not, we are part of the machine! Thanks very much for clicking.
    By the way, Morning star, cool song!

  55. Maybe they can study tea leaves I’m sure they can find some useful info other than reading them

  56. I want to know. WHO the heck paid for this stupid study.

    And why?

  57. So Monash University & Cambridge University teamed up to work on this “problem project” for over 12 months. They have spent over $15 MILLION USD on this joint project. It begs the question of, “Why?” Were these people so bored in their lives since the Covid-19 pandemic that they decided the world needed to know about the true nature of coffee rings!!! ☕☕☕

    I can think of a few thousand organizations, foundations and/or charities that that money could have been better allocated too.

  58. Waiting for the study of how donut crumbs fall and lay on the saucer around the coffee rings.

  59. Douglas I Vargas | April 10, 2021 at 3:16 am | Reply

    It’s interesting that color dye can depict where the pills go, kinda like the chakras in our bodies, makes sense sortve but it could help to determine viscous and I guess a not so viscous flow, to keep things like residue out of their veins maybe if there is, from medications bursting into action kinda thing? But if I ever mis a beat, I guess I can count on the flow of the vessels should not ever burst for some reason or another but hey whatever right, now back to you bob

  60. It’s ok they are probably also environmental scientists, so we can trust they have thoroughly thought this out, and have been paid accordingly.

  61. A caffeinated scientist | April 10, 2021 at 8:52 am | Reply

    How can I cross check the work here? I don’t see a single reference credit of info from the scientific Institute of Dunkin Donuts. Did someone actually pay money into this research?

  62. I’m surprised that this wasn’t discovered yet. The mathematical description is great but can we please see the detailed equations step by step?

  63. Now can the science tell us how to make them disappear?

  64. DEBORAH KIENBAUM | April 10, 2021 at 9:58 am | Reply

    There is our hard earned dollars at work. Seriously WTH are we doing? I know just last week I was wondering what’s up with the coffee rings. I think the government should take back these colleges tuitions and put it toward the US debt instead.

  65. Waste of cash,as usual. People aren’t going to need blood in the future dumbazzes…

    • The actual truth | April 11, 2021 at 2:11 am | Reply

      I cant tell if this is satire or you’re just plain stupid. Either way, scientific advancement has a long way to go before we could even devise a functioning prototype for anything with this effect.

  66. To the people complaining about “wasted money”, they just developed a mathematical model and probably made a few simulations. You don’t need that big of a research grant to buy whiteboard markers and run a pc for a few days unlike grants needed to perform high precision experiments. Not to mention, fluid mechanics is a very complex field that is mostly not very well understood and any mathematical advancements are welcome and will most likely find more applications outside of their initial scenarios. Such as the ones mentioned in this article (blood diagnostics).

    Please stop being morons, it’s 2021 for god’s sake. Scientists know what they’re doing and if you’re not involved in the field you have no right to complain

  67. I can’t wait for the sequel..
    ‘Why and how do donuts crumble around the coffee rings’ 🤯🤔..
    But like they say, sequels are never better than the first part.
    “Back to the future 2 and Deadpool 2 might be an exception..”

  68. “A new study has discovered the mystery behind ‘coffee rings’ and how it could advance research in blood diagnostics.”

    Ok, how? Every single surface type, liquid carrier and the infinite number of things in colloidal suspension make this “discovery” seem pretty much useless. And talking about magic blood tests – sounds like the old Theranos crew found a home in whatever this ‘research’ is

  69. What the hell are you all blabbering about?
    Now, Give me a triple shot and I will spill it.
    I Will read uour coffee rings for lates.

  70. Cheryl Bridges | April 10, 2021 at 12:59 pm | Reply

    I had to look up “coffee rings” and then read the article a second time before it made sense.

  71. Dan’s the man! But some don’t understand. They call them coffee rings as a real world example of the liquid droplet phenomenon.

    “Most common in droplets is a ring distribution where the liquid particles have relocated to the edge, which is referred to as a coffee ring, when drying.”

    All the trolls might relate better to a meniscus; they are a real world example of surface tension that you can see in your full glass of whine.

  72. You idiots going on about it being a waste of funds don’t even realize this was done in f**king Australia.

  73. Stephen Swanson | April 10, 2021 at 2:11 pm | Reply

    Fake News!

  74. Michael Fever | April 10, 2021 at 2:33 pm | Reply

    How many of the idiot commenters actually read the article?? SMH… 🙁

  75. I was wondering what coffee rings had to do with anything pertinent in todays economy..blood analyses makes sense..

  76. To any and all people bashing this because “why is this important” or “fake news” or anything like that, are ANY of you physicists? No, you’re not, because if you were you wouldnt be reading this article. Just because you’re sitting in your bed alone right now doesnt make you the smartest person in the room.

  77. To The 10th Man: Not to mention all the tax money they have wasted on “arts” or alleged “arts”. Considering that, there should be absolutely no objections in congress to giving as many (phoney baloney virus) stimulus checks as are necessary to get every citizen of the United States out of debt. And anyone who worked between 1975 and 2013 should receive three times as much as the rest for two good reasons:

    A. During the time when we needed our money the most to get a good start in life and support our families, we were forced to finance the oil companies by paying ridiculously high gas prices. Meanwhile, congress did nothing to regulate those prices. Now, with the advent of fracking, later generations get to enjoy the lowest gas prices in at least 35, maybe 40, years. But WE paid the price!

    B. Congress allowed their friends to treasonously lay off workers and move their factories to other countries and did nothing to stop them.
    The excuse was that the workers here didn’t want to do those jobs. But they left off the rest of that sentence. It should have been that we didn’t want to do those jobs for wages below poverty level while the business execs and their (Wall Street) investors lived better than kings and just got richer and richer. We could not do that and pay the inflated prices of necessities in those days while supporting our families.

    Therefore, this generation should receive extra stimulus as compensation for these injustices.

    • An actual sociologist | April 11, 2021 at 2:26 am | Reply

      You think this is a solution but in reality (cool place) this would create more injustice, (the thing you were talking about) and you would never be satisfied anyway. You shouldn’t hold a younger generation accountable for what the older generation did. (No one can affect the world before they exist) this would make the younger generation the ones being injusticed. (The thing you’re complaining about)

  78. Although the applications of this are far more significant than I’d thought they’d be… I was really hoping to find out how the stains were coffee colored when no actual coffee gets out of the cup. I even get coffee colored stains when there’s a lid on the cup. It blows my mind

  79. Neal Winningham | April 10, 2021 at 9:05 pm | Reply

    Too many people comment in an emotional manner without using the few brain cells they possess, and usually to say how stupid an intellectual is.

  80. Talk about a waste of time and money. Wow I could tell you how a coffee ring forms and not go through all that sh*t

  81. Just some random human | April 11, 2021 at 2:00 am | Reply

    This isn’t new information. We’ve known this for years. If it can be applied in new ways that’s great, but don’t phrase it like the main subject has just recently been uncovered.
    Also, all of you in the comments complaining about other people complaining should know that that is a good way to achieve nothing and cause further disputes.

  82. Wahyu Indrasto | April 11, 2021 at 2:39 am | Reply

    Besides being useful for chains like Starbucks what real-world benefits does research like this bring to our lives?

  83. I think what makes people upset is there is no scientific explanation on how this information is useful in manufacturing or “diagnostic analysis” are there currently issues with blood analysis for anemia? We have the why… No we need the “what for” maybe just on example for each?

  84. Rogue Commenter | April 11, 2021 at 4:47 am | Reply

    Sorry guys but this person has reached a status of God to me. They are now able to determine when a droplet will leave a ring. It is truly amazing. Well done and it will have worldly applications and is important. Anyone claiming anything less, go hang out with your wife or girlfriend named Karen and go yell at someone at your local food court.

    On a side not and for humor, I am never buying pledge again.

    All the best and please keep using more than 10% of that brain, add value to society and don’t just consume from Youtube.

  85. Biggest mistery still not solved why is there a ring o. My left finger 😐

  86. Biggest mistery still not solved why is there a ring on my left hand 😐

  87. The comments are intriguing. Why is such a simple study being done, when the manufacturing industry-apparently-has been dealing with this issue for decades? Why is this article here? Why do they bother putting it in my Google news feed?

    I think that this article is interesting. One of my theories is that people with the right software can expose a bunch of users, millions of them, to a topic, and then A.I. can comb through the data in order to get results. It’s like mental group-funding or brain car-sharing… Brain sharing.

    When everything is said and done, a bunch of new, groundbreaking ideas will probably turn out to come from comments from people on platforms like reddit. A person reads a comment (input), then writes a comment (output). With a little social engineering, one can “program” this system to work on any problem that he wants. It’s a human super-computer.

    …articles like this serve as input to point our thinking in the right direction. The goal isn’t to get us to think about coffee rings, but reading about coffee rings will either give us some knowledge that we need to tackle a larger, more obscure problem, or is strictly just putting us in a mindset that is useful.

    … That’s what I think this article is about. Maybe I’m the only one who saw this on my Google news feed, but data mining and social engineering (advertising) are there thing.

  88. Doesn’t this article belong in The Onion?

  89. elon musk yada yada, if ur the ridiculously wealthy elon how bout u and many many more super rich ppl do humanity some real good and share ur wealth with ppl who r very unfortunate. (not including me) have u ever thought about making that type of difference? ur kind of ppl make me sick. when I c u on tv I can’t help but to look away, u know like when one of those ASPCA commercials come on.

  90. Man science divulgation is terrible… Scientists use a term like “coffee-ring” do describe a physical phenomenon – and the authors of this article try to pretend they’re talking about actual coffee rings because it has a human interest hook. They’re right, I expect: this article probably got more hits – but why the hell do they do this with their lives? To get hits, or actually convery to people who are curious or interested some of the interesting things going on in the world of science. It is a choice – but the hit-seeking actually distorts information to the point where what you’re doing is the exact opposite: disinforming.

Leave a comment

Email address is optional. If provided, your email will not be published or shared.