First high speed simultaneous force feedback for multi-trap optical tweezers

Optical tweezers use a tightly focused laser beam to trap dielectric micro-object. Haptic optical tweezers integrate a robotic haptic device into the system to control trap positions and in the meantime feedback forces. This technique opens a broad reaching applications by providing direct and intuitive interactions during micromanipulation. However, 1 kHz sampling rate is required to ensure a reliable tactile sensation. A system satisfying this requirement has been presented in our previous work. This paper goes one big step further to perform real-time high speed haptic feedback on multi-trap optical tweezers. The goal of the system is to enable users to touch the microscale object the same way as using their fingers. The used force sensor is a novel event-based vision sensor that transmits output as a stream of asynchronous timestamped events that eliminates internally the redundant static information. The associated event based algorithm can thus be able to track the positions of two spheres up to 1 kHz. A contact experiment is performed demonstrating the feasibility and the efficiency of the presented method. To our knowledge, this is the first time high speed haptic feedback is performed on multiple microspheres simultaneously in a contact scenario.