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ramé-hart Newsletter

                    

June 2025
 
Can You Guess the Contact Angle?

Fasten your seatbelts. This month we're going to play a game more fun than Jeopardy and more challenging than The Price is Right. The game is called Can You Guess the Contact Angle?. And here's how it works, below I will ask you to guess the contact angle for 15 different solid/liquid combinations. Don't cheat and look ahead from the answers. Once you've made your guesses, you can scroll down and see how close you are. So, here goes. Guess the contact angle for each of the liquid/solid pair and if it falls within the published range, you earn a point for each.

1. Water on Clean Glass

2. Water on Teflon (PTFE)

3 Diiodomethane on Stainless Steel

4. Water on Polystyrene

5. Glycerol on Glass

6. Mercury on Glass

7. Water on Silicon Wafer

8. Water on Superhydrophobic Coating

9. Ethanol on Teflon PTFE

10. Olive Oil on Stainless Steel

11. Water on PDMS

12. Hexadecane on Glass

13. Water on Gold

14. Water on Aluminum

15. Water on Paraffin Wax

 
Product of the Month - Model 90 Pro

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ramé-hart Model 90 Pro shown with optional Fiber Optic Illuminator Upgrade Kit

To learn more about Model 90, please visit this page. If you would like a quotation for Model 90 Pro or the more basic Model 90 CA Edition, contact us today for a no-obligation quotation.
 
Answer Key to Quiz
No.

Liquid

Solid

Contact Angle (°)

What Drives It?
1

Water

 Clean Glass 20–30° High surface energy of glass promotes strong adhesion with polar water molecules, lowering contact angle.
2 Water Teflon (PTFE) 108–112° Teflon’s extremely low surface energy resists wetting, leading to a high contact angle.
3 Diiodomethane Stainless Steel 40–50° Diiodomethane’s non-polar nature interacts moderately with high-energy steel surfaces.
4 Water Polystyrene 80–90° Polystyrene is moderately hydrophobic due to its non-polar aromatic groups.
5 Glycerol Glass 30–40° Glycerol’s high polarity and hydrogen bonding affinity encourage spreading on polar surfaces like glass.
6 Mercury Glass 130–140° Mercury’s high surface tension resists spreading, even on high-energy surfaces.
7 Water Silicon Wafer (native oxide) 40–50° Oxide layer increases surface energy and enhances hydrophilicity.
8 Water Superhydrophobic Coating (fluorinated silica nanoparticles) 155–165° Micro/nano-roughness traps air beneath the drop, dramatically lowering solid-liquid contact area (Cassie-Baxter regime).
9 Ethanol Teflon 20–30° Ethanol’s low surface tension allows it to wet low-energy surfaces more easily than water.
10 Olive Oil Stainless Steel 30–40° Moderate polarity and lower surface tension relative to water allow partial wetting.
11 Water Polydimethylsiloxane (PDMS) 105–110° PDMS is inherently hydrophobic due to its methyl-terminated siloxane chains.
12 Hexadecane Glass 10–20° Very low surface tension hydrocarbon spreads easily on high-energy surfaces like glass.
13 Water Gold (clean) 70–80° Gold is relatively inert, but cleaned surfaces have moderate surface energy promoting partial wetting.
14 Water Aluminum (polished) 65–75° Oxidized aluminum surface is moderately hydrophilic due to native oxide formation.
15 Water Paraffin Wax 105–115° Hydrocarbon-rich surface with very low surface energy discourages wetting.

For each combination that you guessed correctly within the ranges listed above, give yourself one point. Add up you points and see where you fit in the following ranking

14-15 Correct = Congratulations. You are a true surface scientist of high esteem.

11-13 Correct = Good job, you know your stuff. Keep up the good work.

9-12 Correct = Valiant effort. You may be a neophyte, but you're on the right track.

4-8 Correct = You did better than the average college freshman. You have a future in surface science - with a little work.

0-3 Correct = You guessed, didn't you?

So, how did you do? And thanks for playing.

 
Regards,

Carl Clegg
Director of Sales
Phone 973-448-0305
www.ramehart.com
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