We show a new instability in sessile water droplets when a particle is trapped close to the edge interface of air and water by optical tweezers when the light beam heats up the glass substrate and generate thermophoretic forces that direct the particle outward from the tweezers trap. There is competition between the optical trapping and the thermophoretic forces which direct the particle away from the trap to generate this instability. © COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.