Haptic Manipulation of Microspheres Using Optical Tweezers

We report the manipulation of glass microspheres having a diameter of 3-10 μm using optical tweezers and with haptic feedback. We detect the position of a microsphere manipulated in a fluid bed using a CCD camera and calculate the forces acting on it due to the optical trap and viscous drag. We calculate the optical forces between the laser beam and the manipulated particle using a mass-spring-damper model. For this purpose, we calibrated the optical trap and used image processing and curve fitting techniques to evaluate the coefficients of the mass-spring-damper model. The drag force is calculated using the velocity of the sphere and the viscous damping coefficient of the fluid. We then use a potential field approach to generate a collision-free path for the manipulated microsphere among other spheres and display the optical trapping and drag forces and the forces due the artificial potential field to a user of the system via a haptic device for better manipulation and steering. We have observed performance improvements over manual control in our preliminary manipulation experiments.