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June 2016

  The Receding Contact Angle
  Bonnie and Clyde, Jack and Jill, Bert and Ernie, Tom and Jerry, Advancing and Receding. Some duos seem inseparable. Today, however, we're going to leave advancing behind and discuss the receding contact angle.

Traditionally, the static contact angle measured at the three-phase line of a sessile drop of liquid on a given surface is used to describe the wetting properties of the solid/liquid pair. This single measurement is somewhat one-dimensional. A more comprehensive characterization can be achieved by measuring the maximum and minimum contact angles. The receding contact angle represents the smallest possible contact angle for a particular solid/liquid combination. There are a number of ways to measure the receding contact angle.

One of the most common ways is using the Tilting Plate Method. The left and right contact angles are repeatedly measured while the contact angle tool is being tilted from from 0° to 180°. The receding contact angle is measured from the side which is diminishing in value as the tilt angle is increased. This type of measurement requires a tilting base. A manual tilting base (such as ramé-hart p/n 100-25-M) can be used but a more automated measurement can be taken using a motor-controlled and software-driven tilting base (such as the ramé-hart Automated Tilting Base p/n 100-25-A). If the drop rolls off while tilting, then the last prior measurement prior to the drop releasing is used. If the drop stays on to a tilt angle of 90°, then the smallest contact angle measurement (which is also usually the final measurement on the downhill side) is used to determine the receding contact angle. This method is volume dependant as a larger drop is more inclined to roll off at a given tilt angle than a drop with smaller volume.

The Tilting Plate Method using a ramé-hart Automated Tilting Base.

The Add/Remove Volume Method is another popular method. A tip or needle is embedded in a sessile drop and the contact angle is measured while volume is retracted from the drop. The receding contact angle is reached when the minimum contact angle can be measured and prior to dewetting which results in the contraction of the three-phase line.

The Add/Remove Volume Method for measuring the receding contact angle.

While this measurement can be taken using a manual microsyringe, it's more automated and repeatable when using an Automated Dispensing System. The main disadvantage to this method is the disturbance of drop geometry by the needle itself. Some researchers have determined that for polymer solids, the discrepancy can be as much as 30%.1

The Add/Remove Volume Method using the ramé-hart Automated Dispensing System.

The Evaporation Method1 requires no special accessory but only works with water and aqueous liquids that actually evaporate over time. It can also be a very time consuming measurement. The main advantage is that the drop volume can be reduced without disturbing the drop geometry. And unlike the other methods, the evaporation method can only capture the receding contact angle and not the advancing. On some surfaces, especially where surface roughness is pronounced, the drop will never dewet; it stays pinned all the way to the disappearance of the drop.2 In those cases, the evaporation method is not so useful. Likewise, this method is not very well suited for hydrophobic and superhydrophobic surfaces.

The method selected is often a function of the equipment that is available. However, for superhydrophobic surfaces, the add/remove volume method can be done reliably using large drops with a small gauge needle.3  

Researchers in Italy have determined that receding contact angle can predict rebound behavior of dynamic drops on hydrophobic surfaces.4 Their studies indicate that rebound only occurs when the receding contact angle is greater than 100°.


  • The receding contact angle cannot be larger than the advancing contact angle.
  • The receding contact angle is typically smaller than both the static contact angle and the advancing contact angle.
  • There are a number of ways to measure the receding contact angle.
  • The tilting plate and add/remove volume methods are the two most common.
  • The tilting plate method is more sensitive to drop volume and works well for many types of surfaces. However, it requires tilting hardware.
  • The add/remove volume method does better with advancing than receding contact angle measurements due to the perturbation caused by the needle and works better on hydrophobic and superhydrophobic surfaces than hydrophilic surfaces.
  • The evaporation method is very time consuming, does not work for many types of surfaces, but requires the least additional testing hardware.
  • The receding contact angle is used to determine the contact angle hysteresis (when subtracted from the advancing contact angle).
  • When the contact angle hysteresis is small, the surface is highly homogenous relative to both chemical composition and structure (roughness).
  • In most cases, roughness is the biggest driver of contact angle hysteresis.
  • When measuring receding contact angle using the add/remove volume method with DROPimage, you should use the Line method. For advancing, use the circle method.

1 Determination of the Receding Contact Angle of Sessile Drops on Polymer Surfaces by Evaporation H. Yildirim Erbil,*,†, G. McHale,‡, S. M. Rowan,‡ and, and M. I. Newton‡ Langmuir 1999 15 (21), 7378-7385 DOI: 10.1021/la9900831
2 On the Uniqueness of the Receding Contact Angle: Effects of Substrate Roughness and Humidity on Evaporation of Water Drops Paola G. Pittoni, Chia-Hui Lin, Teng-Shiang Yu, and Shi-Yow Lin Langmuir 2014 30 (31), 9346-9354 DOI: 10.1021/la501455d
3 Reliable Measurement of the Receding Contact Angle Juuso T. Korhonen, Tommi Huhtamäki, Olli Ikkala, and Robin H. A. Ras Langmuir 2013 29 (12), 3858-3863 DOI: 10.1021/la400009m
4 Drop Rebound after Impact: The Role of the Receding Contact Angle  C. Antonini, F. Villa, I. Bernagozzi, A. Amirfazli, and M. Marengo Langmuir 2013 29 (52), 16045-16050 DOI: 10.1021/la4012372

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