Reliability and efficiency of tele-micromanipulation systems with haptic feedback over the Internet face to strong problems due to the nonlinear nature of microenvironment and time-varying delays in communication lines. In this paper, a bilateral controller for a micro-teleoperation system is presented using passivity approaches. We showed that the application of wave variable formalism allows the passivity of the system in spite of external perturbations. Mainly, the communication varying delays between the master and the slave and the specific scale factors modeling the interaction between the slave and the environment (structural and surface interactions) are considered. A design framework demonstrates regions where scaling factors keep the passivity of the overall micro-teleoperation system. Finally, the validity of the proposed method is demonstrated by simulations for a pick-and-place micromanipulation task with constant and variable time-delay.