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Chih-Ming Ho, Xiaoying Shen, and Tak-Sing Wong show how world's smallest 'coffee ring' may help biosensors detect disease

May 6, 2010

Chih-Ming Ho, Xiaoying Shen, and Tak-Sing Wong show how world's smallest 'coffee ring' may help biosensors detect disease

Coffee rings.

By Matthew Chin

The field of biosensing has recently found an unlikely partner in the quest for increased sensitivity: coffee rings. The next time you spill your coffee on a table, look at the spot left after the liquid has evaporated, and you'll notice it has a darker ring around its perimeter that contains a much higher concentration of particles than the center.  
 
Because this "coffee ring" phenomenon occurs with many liquids after they have evaporated, scientists have suggested that such rings can be used for examining blood or other fluids for disease markers by using biosensing devices. But a better understanding of how these rings behave at the micro- and nano-scale would probably be needed for practical bionsensors.
 
"Understanding micro- and nano-particle transportation within evaporating liquid droplets has great potential for several technological applications, including nanostructure self-assembly, lithography patterning, particle coating, and biomolecule concentration and separation," said Chih-Ming Ho, the Ben Rich–Lockheed Martin Professor at the UCLA Henry Samueli School of Engineering and Applied Science and director of the UCLA Center for Cell Control. "However, before we can engineer biosensing devices to do these applications, we need to know the definitive limits of this phenomenon. So our research turned to physical chemistry to find the lowest limits of coffee-ring formation."
 
A research group led by Ho, a member of the National Academy of Engineering, has now found the definitive microscopic minimal threshold of coffee-ring formation, which can be used to set standards for biosensor devices for multiple disease detection, as well as other uses. The research appears in the current issue of the Journal of Physical Chemistry B and is available online.
 
"If we consider human blood, or saliva, it has a lot of micro- and nano-scale molecules or particles that carry important health information," said Tak-Sing Wong, one of the researchers and a postdoctoral scholar in UCLA Engineering's department of mechanical and aerospace engineering. "If you put this blood or saliva on a surface, and then it dries, these particles will be collected in a very small region in the ring. By doing so, we can quantify these biomarkers by various sensing techniques, even if they are very small and in a small amount in the droplets."
 
As water evaporates from a droplet, particles that are suspended inside the liquid move to the droplet's edges. Once all the water has evaporated, the particles are concentrated in a ring around the stain that is left behind. However, if a droplet is small enough, the water will evaporate faster than the particles move. Rather than a ring, there will be a relatively uniform concentration in the stain, as the particles have not had enough time to move to the edges while still in the liquid.
 
"It is the competition between the timescale of the evaporation of the droplet and the timescale of the movement of the particles that dictates coffee-ring formation," said Xiaoying Shen, the paper's lead author and a senior microelectronics major at Peking University in China, who worked on these experiments while at the UCLA Cross Disciplinary Scholars in Science and Technology (CSST) program last summer.
 
To determine the smallest droplet size that would still show a coffee ring after evaporation, the research team manufactured a special surface coated in a checkerboard pattern that featured alternating hydrophilic, or water-loving, material and hydrophobic, or water-repelling, material.
 
The group then placed latex particles, ranging in size from 100 nanometers to 20 nanometers, in water. The particles were similar in size to disease-marker proteins that biosensors would look for.
 
The group washed the new surface with the particle-infused water. The remaining water lined up as droplets on the hydrophilic spots, much like checkers on a checkerboard. The group repeated the experiments with smaller grid patterns until the coffee-ring phenomenon was no longer evident. For the 100-nanometer sized particles, this occurred at a droplet diameter of approximately 10 micrometers, or about 10 times smaller than the width of a human hair. At this point, the water evaporated before the particles had enough time to move to the perimeter.
 
"Knowing the minimum size of this so-called coffee ring will guide us in making the smallest biosensors possible," Wong said. "This means that we can pack thousands, even millions, of small micro-biosensors onto a lab-on-a-chip, allowing one to perform a large number of medical diagnostics on a single chip. This may also open the doors to potentially detecting multiple diseases in one sitting."
 
"There's another important advantage — this whole process is very natural, it's just evaporation," Wong added. "We don't need to use additional devices, such as an electrical power source or other sophisticated instruments to move the particles. Evaporation provides a very simple way of concentrating particles and has potential in medical diagnosis. For example, researchers at Vanderbilt University were recently awarded a Gates Foundation Research Fund for proposing the use of the coffee-ring phenomenon for malaria detection in developing countries."
 
The researchers are currently optimizing the ring formation parameters and will then explore the application of this approach toward biosensing technologies that are being developed in Ho's laboratory.
 
The research was supported by the Center for Cell Control through the National Institutes of Health's Roadmap for Nanomedicine and by the Center for Scalable and Integrated Nanomanufacturing through the National Science Foundation. Shen received financial support from UCLA's Cross Disciplinary Scholars in Science and Technology (CSST) program.

 

Media Coverage
67 international news/media outlets, including media outlets in Germany, Japan, Australia, United Kingdom, India, Africa, and United States.  More than 20 websites are listed as Top Global 15,000 Websites by Quantcast 2010.
    
1.    Spektrumdirekt (by Scientific America)
            http://www.wissenschaft-online.de/artikel/1031336

2.    “Coffee Ring may help detect disease”, The Times of India (India), May 6, 2010.  Available online at: http://timesofindia.indiatimes.com/life/health-fitness/health/Coffee-ring-may-help-detect-disease/articleshow/5898449.cms
[Founded in 1838, TOI is the #1 largest-selling English newspaper in the World with >3.14 millions circulation per day.  TOI online is the world’s most-visited newspaper website with 159 million page views in May 2009 according to ComScore].  

3.    “Coffee Ring may help biosensors detect disease”, Yahoo! India News (India), May 6, 2010.  Available online at: http://in.news.yahoo.com/139/20100506/981/tsc-coffee-ring-may-help-biosensors-dete_1.html

4.    “Coffee ring may help biosensors detect disease”, Ethiopian Review (Africa), May 5, 2010.  Available online at: http://www.ethiopianreview.com/news/97663  
[The largest and the most visited Ethiopian news website with daily readership of 15,000 – 20,000]  

5.    “How World’s Smallest ‘Coffee Ring’ May Help Biosensors Detect Disease”, Science Daily (United States), May 5, 2010.  Available online at: http://www.sciencedaily.com/releases/2010/05/100505143128.htm  
[Listed by Quantcast 2010 as one of the Top 1000 Global Websites, Science Daily is one of the most popular online science website with > 3 millions monthly visitors worldwide]  

6.    “Coffee ring may help biosensors detect disease”, Thaindian News (India), May 6, 2010.  Available online at: http://www.thaindian.com/newsportal/health/coffee-ring-may-help-biosensors-detect-disease_100359391.html
[Listed by Quantcast 2010 as one of the Top 1000 Global Websites, with ~ 3 millions monthly visitors worldwide]  

7.    “Coffee ring may help biosensors detect disease”, AllVoices.com, May 6, 2010.  Available online at: http://www.allvoices.com/news/5764973-coffee-ring-may-help-biosensors-detect-disease [Listed by Quantcast 2010 as one of the Top 2000 Global Websites, with > 3.5 million monthly visitors worldwide]

8.    “How World’s Smallest ‘Coffee Ring’ Detect Disease”, Medical News Today (United Kingdom), May 6, 2010.  Available online at http://www.medicalnewstoday.com/articles/187925.php
[Listed by Quantcast 2010 as one of the Top 2000 Global Websites, with > 1.8 million monthly visitors worldwide]  

9.      “How world’s smallest ‘coffee ring’ may help biosensors detect disease”, PhysOrg.com (United Kingdom), May 5, 2010.  Available online at: http://www.physorg.com/news192288241.html
[Listed by Quantcast 2010 as one of the Top 2000 Global Websites, with 1.75 million monthly visitors worldwide]  

10.    “Coffee Ring may help biosensors detect disease”, TopNews.in (India), May 6, 2010.  Available online at http://www.topnews.in/health/coffee-ring-may-help-biosensors-detect-disease-27179
[Listed by Quantcast 2010 as one of the Top 2000 Global Websites, with > 1.4 million monthly visitors worldwide]
 
11.     “UCLA researchers show how world’s smallest ‘coffee ring’ may help biosensors detect disease”, UCLA Newsroom, May 5, 2010.  Available online at: http://newsroom.ucla.edu/portal/ucla/ucla-engineering-researchers-identify-157602.aspx
[Listed by Quantcast 2010 as one of the Top 2000 Global Websites, with > 1 million monthly visitors worldwide]  

12.    “Coffee ring may help biosensors detect disease”, Taragana.com, May 6, 2010.  Available online at: http://blog.taragana.com/science/2010/05/06/coffee-ring-may-help-biosensors-detect-disease-12406/
[Listed by Quantcast 2010 as one of the Top 2000 Global Websites, Science Daily is one of the most popular online science website with >1 millions monthly visitors in the United States]

13.    “Coffee-ring formation can be used to set standards for biosensor devices: UCLA researchers”, The Medical News (Australia), May 7, 2010.  Available online at: http://www.news-medical.net/news/20100507/Coffee-ring-formation-can-be-used-to-set-standards-for-biosensor-devices-UCLA-researchers.aspx
[Listed by Quantcast 2010 as one of the Top 7000 Global Websites, with ~ 1 million monthly visitors worldwide]  

14.    “Coffee Rings May Hold Secret for Nanofabrication Processes”, AZoMaterials (Australia), May 6, 2010.  Available online at: http://www.azom.com/news.asp?NewsID=21475
[One of the most popular nanotechnology website, with ~ 1 million monthly visitors worldwide according to Quantcast 2010]  

15.     “Micro- and Nano-scale Research on Coffee Ring Leads Way to More Biosensor Applications”, AZoNanotechnology, May 6, 2010.  Available online at: http://www.azonano.com/news.asp?newsID=17403
[One of the most popular nanotechnology website, with ~ 1 million monthly visitors worldwide according to Quantcast 2010]  

16.    “Coffee Ring may help biosensors detect disease”, OneIndia (India), May 6, 2010.  Available online at: http://news.oneindia.in/2010/05/06/coffeering-may-help-biosensors-detectdisease.html
[Listed by Quantcast 2010 as one of the Top 7000 Global Websites, with ~ 730,000 monthly visitors worldwide]  

17.    “Study Says Coffee Ring may Help Biosensors Detect Disease”, Med India (India), May 7, 2010.  Available online at: http://www.medindia.net/news/Study-Says-Coffee-Ring-may-Help-Biosensors-Detect-Disease-68649-1.htm
[Listed by Quantcast 2010 as one of the Top 7000 Global Websites, with ~ 700,000 monthly visitors worldwide]  

18.    “Coffee-ring formation can be used to set standards for biosensor devices: UCLA researchers”, Biotechnology News Today, EIN News, May 7, 2010.  Available online at: http://biotech.einnews.com/news/biosensors
[Listed by Quantcast 2010 as one of the Top 10,000 Global Websites, with > 330,000 monthly visitors in the United States]

19.    “UCLA researchers show how world’s smallest ‘coffee ring’ may help biosensors detect disease”, EurekAlert! (United States), May 5, 2010.  Available online at: http://www.eurekalert.org/pub_releases/2010-05/uoc--urs050510.php
[Listed by Quantcast 2010 as one of the Top 10,000 Global Websites, with > 250,000 monthly visitors worldwide]  

20.    “UCLA researchers show how world’s smallest ‘coffee ring’ may help biosensors detect disease”, ScienceBlog, May 5, 2010.  Available online at: http://www.scienceblog.com/cms/ucla-researchers-show-how-worlds-smallest-coffee-ring-may-help-biosensors-detect-disease.html
[Listed by Quantcast 2010 as one of the Top 15,000 Global Websites, with ~ 240,000 monthly visitors worldwide]

21.     “How World’s Smallest ‘Coffee Ring’ Detect Disease”, MediLexicon (United Kingdom), May 6, 2010.  Available online at http://www.medilexicon.com/medicalnews.php?newsid=187925
[Listed by Quantcast 2010 as one of the Top 15,000 Global Websites, with ~ 180,000 monthly visitors worldwide]
    
22.    “UCLA Researchers Show How Nanoscale ‘Coffee Ring’ May Help Biosensors Detect Disease”, Before It’s News, May 5, 2010.  Available online at: http://beforeitsnews.com/news/40/105/UCLA_Researchers_Show_How_Nanoscale_Coffee_Ring_May_Help_Biosensors_Detect_Disease.html [Listed by Quantcast 2010 as one of the Top 15,000 Global Websites, with ~ 178,000 monthly visitors in the United States]
    
23.    “World’s smallest ‘coffee ring’ may help biosensors detect disease”, R&D Magazine (United States), May 5, 2010.  Available online at: http://www.rdmag.com/News/2010/05/Life-Sciences-Nanotechnology-Worlds-Smallest-Coffee-Ring-May-Help-Biosensors-Detect-Disease/
[Founded in 1959, R&D Magazine is circulated >72,000 readers]  

24.     “Coffee rings & biosensing”, University of California Health, May 5, 2010.  Available online at: http://universityofcalifornia.edu/sites/uchealth/2010/05/05/coffee-rings-biosensing/ [Listed by Quantcast 2010 as one of the Top 15,000 Global Websites, with ~160,000 monthly visitors worldwide]

    
        B. Other International News/Online Media:

25.    “University of California, Los Angeles (UCLA) Researchers Show How World’s Smallest ‘Coffee Ring’ May Help Biosensors Detect Disease”, BioSpace, May 5, 2010.  Available online at: http://www.biospace.com/news_story.aspx?StoryID=179466&full=1
[Listed by Quantcast 2010 as one of the Top 30,000 Global Websites, with ~ 106,000 monthly visitors in the United States]

26.    “Coffee ring may help biosensors detect disease”, WebIndia123.com, May 6, 2010.  Available online at: http://news.webindia123.com/news/articles/India/20100506/1499762.html
[Listed by Quantcast 2010 as one of the Top 30,000 Global Websites, with ~ 91,800 monthly visitors in the United States]

27.    “Coffee ring may help biosensors detect disease”, BigNews Network.com, May 6, 2010.  Available online at: http://feeds.bignewsnetwork.com/?sid=631792
[Listed by Quantcast 2010 as one of the Top 30,000 Global Websites, with ~ 80,000 monthly visitors in the United States]

28.    “The world’s smallest ‘coffee ring’ may help biosensors detect disease”, Nanowerk, May 5, 2010.  Available online at: http://www.nanowerk.com/news/newsid=16157.php
[Listed by Quantcast 2010 as one of the Top 50,000 Global Websites, with ~ 80,000 monthly visitors worldwide]

29.    “UCLA researchers show how world’s smallest ‘coffee ring’ may help biosensors detect disease”, Innovations Report, May 6, 2010.  Available online at: http://www.innovations-report.com/html/reports/life_sciences/ucla_researchers_show_world_039_s_smallest_039_154246.html  
[Listed by Quantcast 2010 as one of the Top 50,000 Global Websites, with ~ 44,000 monthly visitors in the United States]

30.    “Coffee Ring may help biosensors detect disease”, Sindh Today News (India), May 6, 2010.  Available online at http://www.sindhtoday.net/news/2/135196.htm
[Listed by Quantcast 2010 as one of the Top 50,000 Global Websites, with ~ 43,000 monthly visitors worldwide]

31.     “UCLA researchers show how world’s smallest ‘coffee ring’ may help biosensors detect disease”, FirstScience News, May 5, 2010.  Available online at: http://www.firstscience.com/home/news/breaking-news-all-topics/ucla-researchers-show-how-world-s-smallest-coffee-ring-may-help-biosensors-detect-disease_83706.html [Listed by Quantcast 2010 as one of the Top 50,000 Global Websites, with ~ 43,000 monthly visitors in the United States]

32.     “UCLA researchers show how world’s smallest ‘coffee ring’ may help biosensors detect disease”, e! Science News (United States), May 5, 2010.  Available online at: http://esciencenews.com/articles/2010/05/05/ucla.researchers.show.how.worlds.smallest.coffee.ring.may.help.biosensors.detect.disease
[Listed by Quantcast 2010 as one of the Top 50,000 Global Websites, with ~ 32,000 monthly visitors worldwide]  

33.    “UCLA researchers show how world’s smallest ‘coffee ring’ may help biosensors detect disease”, Bio-Medicine, May 5, 2010.  Available online at: http://www.bio-medicine.org/biology-news-1/UCLA-researchers-show-how-worlds-smallest-coffee-ring-may-help-biosensors-detect-disease-13291-1/
[Listed by Quantcast 2010 as one of the Top 50,000 Global Websites, with ~ 22,000 monthly visitors in the United States]

34.    “UCLA researchers show how world’s smallest ‘coffee ring’ may help biosensors detect disease”, Science Codex, May 5, 2010.  Available online at: http://www.sciencecodex.com/ucla_researchers_show_how_worlds_smallest_coffee_ring_may_help_biosensors_detect_disease
[~ 30,000 monthly visitors worldwide according to Quantcast 2010]

35.     “Coffee Ring may help biosensors detect disease”, India Vision (India), May 6, 2010.  Available online at: http://www.indiavision.com/news/article/scitech/52286/
[~20,000 monthly visitors worldwide according to Quantcast 2010]  

36.    “Coffee ring may help biosensors detect disease”, Article Ant, May 5, 2010.  Available online at: http://www.articleant.com/gen/78052-coffee-ring--may-help-biosensors-detect-disease.html
    [~17,300 monthly visitors in the United States according to Quantcast 2010]

37.    “UCLA Researchers Show How World’s Smallest ‘coffee Ring’ May Help Biosensors Detect Disease”, BioCompare, May 6, 2010.  Available online at: http://www.biocompare.com/News/NewsStory/324011/NewsStory.html
    [~16,600 monthly visitors in the United States according to Quantcast 2010]

38.    “UCLA researchers show how world’s smallest ‘coffee ring’ may help biosensors detect disease”, Science Centric, May 6, 2010.  Available online at: http://www.sciencecentric.com/news/article.php?q=10050608-ucla-researchers-show-how-world-smallest-coffee-ring-may-help-biosensors-detect-disease
[~11,000 monthly visitors in the United States according to Quantcast 2010]  

39.    “UCLA researchers show how world’s smallest ‘coffee ring’ may help biosensors detect disease”, Microbe World, May 5, 2010.  Available online at: http://www.microbeworld.org/index.php?option=com_jlibrary&view=article&id=3564  [~11,000 monthly visitors in the United States according to Quantcast 2010]

40.    “UCLA Researchers Show How World’s Smallest ‘Coffee Ring’ May Help Biosensors Detect Disease”, Insciences Organization, May 5, 2010.  Available online at: http://insciences.org/article.php?article_id=8918
    [~9200 monthly visitors in the United States according to Quantcast 2010]

41.    “Smallest Coffee Ring Detects Disease”, Laboratory Equipment, May 6, 2010.  Available online at: http://www.laboratoryequipment.com/News-smallest-coffee-ring-detects-disease-050610.aspx?xmlmenuid=51
    [~5800 monthly visitors in the United States according to Quantcast 2010]

42.    “UCLA researchers show how world’s smallest ‘coffee ring’ may help biosensors detect disease”, HealthCanal.com, May 5, 2010.  Available online at: http://www.healthcanal.com/medical-breakthroughs/7616-UCLA-researchers-show-how-worlds-smallest-coffee-ring-may-help-biosensors-detect-disease.html
    [~2400 monthly visitors in the United States according to Quantcast 2010]

43.    “Chih-Ming Ho, Xiaoying Shen, and Tak-Sing Wong show how world’s smallest ‘coffee ring’ may help biosensors detect disease”, UCLA Mechanical and Aerospace Engineering Department News, May 6, 2010.  Available online at: http://www.mae.ucla.edu/news/news-archive/2010/ucla-researchers-show-how-worlds-smallest-coffee-ring-may-help-biosensors-detect-disease

44.    “Coffee Ring may help biosensors detect disease”, India Talkies (India), May 6, 2010.  Available online at: http://www.indiatalkies.com/2010/05/coffee-ring-biosensors-detect-disease.html

45.    “Coffee Ring may help biosensors detect disease”, DailyIndia.com (India), May 6, 2010. Available online at: http://www.dailyindia.com/show/373596.php

46.     “How world’s smallest ‘coffee ring’ may help biosensors detect disease”, Quantum Times, May 6, 2010.  Available online at: http://www.quantumtimes.com/nano-physics-news/cluster554985/

47.    “How World’s Smallest ‘Coffee Ring’ May Help Biosensors Detect Disease”, Pan Globus Medical Device Industry News, May 6, 2010.  Available online at: http://www.panglobus.com/medical-devices-news/2206/how-worlds-smallest-coffee-ring-may-help-biosensors-detect-disease/

48.    “Coffee ring may help biosensors detect disease”, Newspolitan, May 6, 2010.  Available online at: http://www.newspolitan.com/india/sci-tech/2010/05/06/Yahoo--Coffee-ring--may-help-biosensors-detect-disease

49.    “Coffee ring may biosensors detect disease”, newKerala.com, May 6, 2010.  Available online at: http://www.newkerala.com/news/fullnews-102954.html

50.    “How world’s smallest ‘coffee ring’ may help biosensors detect disease”, Medical Device Guru, May 6, 2010.   Available online at: http://www.medicaldeviceguru.com/showthread.php?p=14475

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53.    “UCLA Researchers Show How World’s Smallest ‘Coffee Ring’ May Help Biosensors Detect Disease”, ChemInfo, May 6, 2010.  Available online at: http://www.chem.info/News/Feeds/2010/05/topics-plant-operations-ucla-researchers-show-how-worlds-smallest-coffee-r/

54.    “Coffee Ring may help biosensors detect disease”, NetIndia123.com, May 6, 2010.  Available online at: http://www.netindia123.com/showdetails.asp?id=1499762&cat=India&head=%27Coffee+ring%27+may+help+biosensors+detect+disease

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56.    “How world’s smallest ‘coffee ring’ may help biosensors detect disease”, Physics News, May 5, 2010.  Available online at: http://www.physnews.com/bio-medicine-news/cluster73147023/

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