In recent studies, optical forces have been exploited to guide particles along waveguides and to trap particles near
refractive index sensors. But the ability of photonic devices to bind a freely flowing particle from an adjacent
microfluidic channel has yet to be fully characterized. In order to determine the ability of a given device to trap an
arbitrary particle, we develop a method to numerically calculate the trajectory of a particle flowing near a model system.
We determine the trajectories of 50 nm radius particles in a fluid flowing at an average velocity of 1 cm/s near a
photonic crystal resonator pumped at 1 W. The finite element method is used to calculate the force of the fluid on the
particles and finite-difference time-domain simulations are used to calculate optical forces. The particle equation of
motion is solved using the adaptive Runge-Kutta method.