We are interested in dispensing single cells into individual wells of a multi-well plate for single cell gene expression analysis using qRT-PCR (Taqman Low Density Arrays).
In a system where cell travel across a T-intersection (from left to right in the top left figure), a pressure pulse can eject a droplet containing a single cell as it passes the nozzle. Backpressure is supplied by a nitrogen tank, and the pressure pulse is provided by quickly opening and closing a solenoid valve. The ejected droplet is placed above a 2D computer controlled stage to position the multi-well plate below the nozzle. The figures show the design and constructed device.
Recent work with microfluidic cell dispensing includes integration of cell detection electrodes, fabrication in PDMS, and redesigning the geometry to include an extended ejection channel. Our newest iteration, pictured here, uses the same pressure pulse method for cell dispensing while modifying the T-intersection design to allow for a higher probability of dispensing a cell. A lock-in amplifier is connected to the device to make a real-time AC impedance measurement to determine cell position.