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|2018 US News and World Report Top Twenty Best Colleges|
Here in the United States, and perhaps this is also true in most countries around the world, a good college education is not only the most costly purchase in the first quarter century of one's life, but also one of the most researched. Among the tools available to college-bound high school students in the US is US News and World Report Annual College Rankings.1 It's the gold standard for college rankings. Reams of data are collected via annual surveys and hundreds of data points are measured.
Student retention is weighed the heaviest - the six-year graduation rate and first-year student retention. Peer and guidance counselor assessments weigh in the score, too. Class size, faculty salary, the percentage of faculty who are full-time, student test scores, financial resources, graduation rate, and alumni giving are also elements of the ranking process.
Here at ramé-hart we like to watch this annual ranking. In the main National Universities rankings, the overwhelming majority of these schools are our customers. All but a few that are in the top 100 have one or more of our goniometers. In fact, we have at least 38 instruments installed in all 20 of the top 20 in this list. The table below details the top 20 National Universities and their 2018 US News & World Report Rank along with the number of ramé-hart instruments installed at each school. Note that with one exception (Georgetown) we have only counted the instruments sold in the past dozen years. Since we've been making contact angle tools for over 50 years, there are undoubtedly a number of legacy systems in use at these schools that are not included in the tally.
As you can see from the above list, MIT is one of our better customers with at least (7) of our instruments installed in various labs on campus. We love MIT. If you are a researcher at any of the schools in the US News Rankings, or really anywhere in the world, we value your business and would like to add you to our list of prestigious colleges that use our surface science tools.
|Fifty Shades of Wetting|
By way of review, the lower case theta
symbol, θ, is used to represent the contact angle formed by placing
a small sessile drop on a solid surface. When wetting is perfect and
complete, θ = 0. When wetting is less than complete, the contact
angle can be measured. The actual contact angle measured by a
goniometer determines the measure of wettability of the surface by
When the wetting is good and the contact angle measures less than 90°, the surface is said to be wettable and if the test liquid is water, the surface is described as being hydrophilic. When this condition exists, solid surface free energy (aka, surface energy) is high and adhesiveness is said to be good.
When the contact angle is greater than 90°, wetting is poor. When water is the test liquid, the surface is called hydrophobic. Surface energy is low and adhesiveness is poor. The surface can be described as non-wetting. See graphic below.
When the contact angle exceeds 150°, the surface is considered superhydrophobic. These surfaces exhibit the "Lotus effect" named after the superhydrophobic lotus leaf found in nature and the model for hierarchical nanostructures which exhibit roughness at both the micro and nano scale. We are not aware of any surface that exhibits superhydrophobic behavior without having degree of surface roughness or nanoscopic topology.
Since contamination can greatly affect wetting, contact angle is often used to determine relative cleanliness. Contaminants will increase the contact angle; that is, wetting is poorer as seen in the graphic above. In the fabrication of semiconductors, for example, our Model 400 is used to measure contact angle which in turn is used to used to characterize the wettability of the wafer in an effort to characterize the efficacy of production processes and surface modifications such as etching, passivation, ultrasonic agitation, and cleaning processes.
If you have a need to measure contact angle for any application, please contact us for a no-obligation price quotation and to find answers to any questions you may have.