Sequential droplet manipulation via vibrating ratcheted microchannels

This work reports on a simple scheme for transport and sequential manipulation of droplets using ratchet-shaped microchannels. Once subjected to lateral vibration through a sinusoidal shaker with a controllable frequency and amplitude, droplets move along the direction of least resistance with velocities depending on vibration parameters (amplitude and frequency), channel geometry and material properties, and the angle between the channel and vibration direction (lateral offset angle). Using channels having different lateral offset angles, we achieved a controllable time delay between the transports of various droplets. Based on the same principal, we also designed a multi-functional droplet manipulation platform with the capability to transport, collect, mix, and discharge several droplets.