Aspects of the invention include determining, by a first AFM tip, a first snap-off force of a solid surface immersed in a first fluid, determining, by a second AFM tip, a second snap-off force, determining, by a third AFM tip, a third snap-off force, determining, by the first AFM tip, a fourth snap-off force of a droplet of the first fluid immersed in the second fluid on the solid surface, determining, by the second AFM tip, a fifth snap-off force, determining, by the third AFM tip, a sixth snap-off force, determining a first capillary force for first AFM tip and first droplet based on first snap-off force and fourth snap-off force, determining a second capillary force for second AFM tip and first droplet and a third capillary force for third AFM tip and first droplet, and determining interfacial tension between first fluid and second fluid based on the capillary forces.