Image-based feedback in microfluidics

Microfluidics is the manipulation of fluids on the micron scale which allows for cell-sized units of liquid to be generated, manipulated and analysed. While the small scale provides many benefits in terms of the precision and sample volumes required, it also makes accurate manipulation difficult. By combining microfluidics with high resolution microscopy and real-time computer analysis, image-based feedback can be used to benefit a range of microfluidic techniques, including microdroplet production, the analysis of microdroplet contents and cell sorting.

One rapidly growing technique is microdroplet production which encapsulates aqueous solutions within immiscible oil phases to create up to billions of individual reaction vessels known as microdroplets. By developing imaged-based feedback and using fast pressure driven pumping, new levels of control over microdroplet volume for a prolonged period of time has been demonstrated. The use of fast-response, pressure driven pumps allows the microfluidic flows to be accurately and quickly changed to account for changes in microdroplet volume leading to a large increase in the mono-dispersity of microdroplets produced over long periods.

The pressure pump feedback has been further extended to allow the control and manipulation of individual cells within a microfluidic device to sort them into one of two outlets. The cell is imaged in flow and categorised into one of two classes; cell type A or cell type B. A signal is then fed to the feedback loop which controls the pressures at the various outlets, guiding the cell down the correct channel and into the appropriate sub-population.