1. θ/2Method (Arc Approximation)

Assuming the droplet is spherical in shape and has a circular arc contour. Formula:��=2arctan⁡(ℎ��)θ=2arctan(rh).

Small droplets（Bo<0.1）Superhydrophobic surface

Fast calculation, no need for complex equipment

Neglecting gravity and droplet deformation results in low accuracy

Adamson《Physical Chemistry of Surfaces

2. How to translate

Elliptical fitting methodFitting deformed droplets through elliptic equations (such as approaching contact angles)0°or

180°）Calculate the long and short axes or eccentricity.hydrophilic

/

Hydrophobic wetting surface

Dealing with large deformationsRelying on the ideal ellipse assumption, accuracy is limited

3. Butt & Kappl

Adv. Colloid Interface Sci.

Tangent method

Draw a tangent line manually or using image method at the three-phase contact point for direct measurement.

Laboratory static droplets, high-resolution images

Intuitive and simpleLarge subjective error, not suitable for dynamic scenes

4. DrelichLangmuirpolynomial

/Spline drafting is legalFit the contour of the droplet with a high-order function and obtain the slope of the tangent by taking the derivative. Formula:��=arctan⁡(��������)θ=arctan(dxdy

)

.

Non ideal contour droplet

Strong flexibility, suitable for non spherical dropletsRisk of overfitting, parameters need to be optimized

StalderRev. Sci. Instrum.

5. TrueDrop®technologySegmented calculation of asymmetric droplet profileIterative optimization of high fitting factor models, supporting progress

/

Backward angle and rolling angle measurement.

Industrial testing, dynamic wetting process (such as rolling angle)

Non axisymmetric modeling, supporting complex parameters2006Dependent on algorithm convergence, calibration is required

局限性literature

Select PlanelawBondNumber of（����2=Δ������

��

）

Static droplets, unified scale modeling

Avoiding dimensional interference and simplifying multi-scale simulationsDependent on empirical parameters, not applicable to dynamic scenariosRotenberg1983J. Colloid Interface Sci.

（）

Sessile Dropiterative methodDroplet height

/Diameter ratio or inclination angleGentle gravity field（

Bo<1

）

Clear physical meaning, moderate accuracyLong iteration time, relatively few selected points, low accuracy, and low sensitivityHansen1999Colloids Surf. A
（）BIHAI SONG AND JURGEN SPRINGER,1996Colloids Surf. A

/

source

ADSA®-P

Axial symmetric droplets, high-precision static measurement

No need for empirical parameters, direct physical modelingOnly supports axial symmetryNeumann2002Adv. Colloid Interface Sci.

（

）ADSA®-RealDrop®tilt

/

Non axisymmetric droplets, multiple physical fields

Eliminate symmetry assumption and support dynamic wetting

High computational complexity, requiring high-performance hardware2010High sensitivity and high testing accuracy

advantage

business source

TrueDrop®

Geometric segmentation optimization

Industrial online detection (rolling angle, dynamic wetting)2006Asymmetric modeling, efficient algorithm

Shanghai Solon Technology（

）ADSA®-RealDrop®Dimensional

Young-Laplace

equation

High precision measurement for scientific research (non axisymmetric droplets)2010Physically rigorous, supporting complex field coupling