The needle method measures dynamic contact angle on an optical tensiometer by using an automated dispenser to grow and shrink a drop on a surface, capturing the advancing and receding angles as the contact line moves.
The needle method is a common way to measure dynamic contact angle since it doesn't require any additional accessories apart from an automated dispenser. The software records and analyzes the contact angle automatically, giving repeatable, operator-independent results.
Dynamic contact angles provide information about contact angle hysteresis, which originates from surface properties that differ from the ideal case. The dynamic contact angle measurement can indicate chemical and topographical heterogeneity of a surface, with the advancing and receding values representing the extremes of the possible contact angle range.
How the measurement works
The measurement itself is done by placing a thin needle close to the sample surface, thin enough that it doesn't distort the drop shape and affect the contact angle being measured. Water is typically used as the test liquid. A recipe defines the dispensing time and rate for the advancing contact angle measurement, and the measurement starts when the play button is pressed. Dispensing continues for the time defined in the recipe, after which the receding measurement starts automatically and continues for its own defined time.
The software records contact angle as a function of baseline, giving a plot over time: a plateau during dispensing gives the advancing angle, and a plateau during withdrawal gives the receding angle. Contact angle hysteresis is then calculated as the difference between the two — advancing angle minus receding angle.
How does the needle method compare to other dynamic contact angle methods?
The needle method is one of two established ways to get dynamic contact angle from an optical tensiometer. The tilting method is the other: instead of dispensing and withdrawing liquid through a needle, the sample is tilted until the drop starts to move, giving the advancing and receding angles at the point of movement, along with the roll-off angle. The needle method tends to be preferred on superhydrophobic surfaces specifically, since their very low roll-off angle can make it hard to capture a clean advancing/receding measurement before the drop rolls away during tilting.
It's also worth knowing where dynamic contact angle sits relative to force tensiometry. A force tensiometer can measure dynamic contact angle too, via the Wilhelmy plate method — but only for samples with a regular, homogeneous shape. See Optical vs. Force Tensiometer: How to Choose the Right Instrument for the fuller comparison.
For a broader comparison across contact angle methods generally, including static measurements and the Wilhelmy plate and Washburn methods, see our article on 7 Ways to Measure Contact Angle.
To learn more about dynamic contact angle and its measurement methods, join our free webinar on November 12th, 2026. The session looks at what dynamic contact angle data can tell you about a surface, and how automated needle and tilting methods make it fast and easy to generate reliable results.
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