Droplets transport in a microfluidic chip for in vitro compartmentalisation

In vitro compartmentalisation is an emerging technology for protein evolution and selection. In this presentation, we will report the development of a microdrop-based microfluidic platform for in vitro enzyme evolution and selection applications. A microfluidic chip has been developed and fabricated using the standard photolithography method in conjunction with electroplating and hot embossing techniques. A cross channel geometry was used to focus liquid flows for droplet generation. To realize on-chip compartmentalised bio-reactions, two droplet generators were fabricated on the same chip. Experiments have been carried out to measure droplet size, generation rate and speed using a photographic technique. Droplet size was found to be decreasing with increasing focusing oil flow rate for a given aqueous phase flow rate. When two droplet generators are used in the same chip, the droplets may be generated asynchronously due to different flow conditions. If the droplets were significantly smaller than channel size, the faster moving droplets could pass the slower moving droplets with little coalescence. If the droplets were of the channel size, the faster moving droplets would break or fuse with the slow droplets. To achieve high rate of droplet fusion, active control should be in place for synchronous generation and fusion.