Time-multiplexed droplet manipulation via vibrating ratcheted micro-channels

In this paper, we demonstrate time-multiplexed movement of droplets confined in asymmetrically ratcheted SU8 channels on top of a silanized glass or silicon surface actuated through an external sinusoidal vibrating shaker. We show the motion of droplets (5~8mul) and characterize its dependence on shaking (amplitude and frequency) and channel (height and direction with respect to the vibrating angle) parameters. A maximum droplet moving speed of 100 mm/s is achieved with a vibration frequency and amplitude of 50 Hz and 3.5 mm, respectively. Due to the limited engagement force, under the testing conditions mentioned above, the droplets did not move in the channels with a height of less than 100 mum.